summaryrefslogtreecommitdiffstats
path: root/ast/zoommap.c
blob: 44177d15f4e9ede7987f8fcfc72933462fbd4021 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
/*
*class++
*  Name:
*     ZoomMap

*  Purpose:
*     Zoom coordinates about the origin.

*  Constructor Function:
c     astZoomMap
f     AST_ZOOMMAP

*  Description:
*     The ZoomMap class implements a Mapping which performs a "zoom"
*     transformation by multiplying all coordinate values by the same
*     scale factor (the inverse transformation is performed by
*     dividing by this scale factor). The number of coordinate values
*     representing each point is unchanged.

*  Inheritance:
*     The ZoomMap class inherits from the Mapping class.

*  Attributes:
*     In addition to those attributes common to all Mappings, every
*     ZoomMap also has the following attributes:
*
*     - Zoom: ZoomMap scale factor

*  Functions:
c     The ZoomMap class does not define any new functions beyond those
f     The ZoomMap class does not define any new routines beyond those
*     which are applicable to all Mappings.

*  Copyright:
*     Copyright (C) 1997-2006 Council for the Central Laboratory of the
*     Research Councils

*  Licence:
*     This program is free software: you can redistribute it and/or
*     modify it under the terms of the GNU Lesser General Public
*     License as published by the Free Software Foundation, either
*     version 3 of the License, or (at your option) any later
*     version.
*
*     This program is distributed in the hope that it will be useful,
*     but WITHOUT ANY WARRANTY; without even the implied warranty of
*     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*     GNU Lesser General Public License for more details.
*
*     You should have received a copy of the GNU Lesser General
*     License along with this program.  If not, see
*     <http://www.gnu.org/licenses/>.

*  Authors:
*     RFWS: R.F. Warren-Smith (Starlink)
*     DSB: David S. Berry (Starlink)

*  History:
*     1-FEB-1996 (RFWS):
*        Original version.
*     18-JUL-1996 (RFWS):
*        Updated to support attributes and an external interface.
*     10-SEP-1996 (RFWS):
*        Added I/O facilities.
*     4-JUN-1997 (RFWS):
*        Over-ride the MapMerge method to provide ZoomMap
*        simplification facilities.
*     8-JAN-2003 (DSB):
*        Changed private InitVtab method to protected astInitZoomMapVtab
*        method.
*     10-MAY-2006 (DSB):
*        Override astEqual.
*class--
*/

/* Module Macros. */
/* ============== */
/* Set the name of the class we are implementing. This indicates to
   the header files that define class interfaces that they should make
   "protected" symbols available. */
#define astCLASS ZoomMap

/* Include files. */
/* ============== */
/* Interface definitions. */
/* ---------------------- */

#include "globals.h"             /* Thread-safe global data access */
#include "error.h"               /* Error reporting facilities */
#include "memory.h"              /* Memory allocation facilities */
#include "globals.h"             /* Thread-safe global data access */
#include "object.h"              /* Base Object class */
#include "pointset.h"            /* Sets of points/coordinates */
#include "mapping.h"             /* Coordinate mappings (parent class) */
#include "channel.h"             /* I/O channels */
#include "unitmap.h"             /* Unit Mappings */
#include "matrixmap.h"           /* Matrix Mappings */
#include "zoommap.h"             /* Interface definition for this class */

/* Error code definitions. */
/* ----------------------- */
#include "ast_err.h"             /* AST error codes */

/* C header files. */
/* --------------- */
#include <float.h>
#include <math.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>

/* Module Variables. */
/* ================= */

/* Address of this static variable is used as a unique identifier for
   member of this class. */
static int class_check;

/* Pointers to parent class methods which are extended by this class. */
static AstPointSet *(* parent_transform)( AstMapping *, AstPointSet *, int, AstPointSet *, int * );
static const char *(* parent_getattrib)( AstObject *, const char *, int * );
static int (* parent_testattrib)( AstObject *, const char *, int * );
static void (* parent_clearattrib)( AstObject *, const char *, int * );
static void (* parent_setattrib)( AstObject *, const char *, int * );

/* Define macros for accessing each item of thread specific global data. */
#ifdef THREAD_SAFE

/* Define how to initialise thread-specific globals. */
#define GLOBAL_inits \
   globals->Class_Init = 0; \
   globals->GetAttrib_Buff[ 0 ] = 0;

/* Create the function that initialises global data for this module. */
astMAKE_INITGLOBALS(ZoomMap)

/* Define macros for accessing each item of thread specific global data. */
#define class_init astGLOBAL(ZoomMap,Class_Init)
#define class_vtab astGLOBAL(ZoomMap,Class_Vtab)
#define getattrib_buff astGLOBAL(ZoomMap,GetAttrib_Buff)



/* If thread safety is not needed, declare and initialise globals at static
   variables. */
#else

static char getattrib_buff[ 101 ];


/* Define the class virtual function table and its initialisation flag
   as static variables. */
static AstZoomMapVtab class_vtab;   /* Virtual function table */
static int class_init = 0;       /* Virtual function table initialised? */

#endif

/* External Interface Function Prototypes. */
/* ======================================= */
/* The following functions have public prototypes only (i.e. no
   protected prototypes), so we must provide local prototypes for use
   within this module. */
AstZoomMap *astZoomMapId_( int, double, const char *, ... );

/* Prototypes for Private Member Functions. */
/* ======================================== */
static AstPointSet *Transform( AstMapping *, AstPointSet *, int, AstPointSet *, int * );
static const char *GetAttrib( AstObject *, const char *, int * );static double GetZoom( AstZoomMap *, int * );
static double Rate( AstMapping *, double *, int, int, int * );
static int *MapSplit( AstMapping *, int, const int *, AstMapping **, int * );
static int Equal( AstObject *, AstObject *, int * );
static int GetIsLinear( AstMapping *, int * );
static int MapMerge( AstMapping *, int, int, int *, AstMapping ***, int **, int * );
static int TestAttrib( AstObject *, const char *, int * );
static int TestZoom( AstZoomMap *, int * );
static void ClearAttrib( AstObject *, const char *, int * );
static void ClearZoom( AstZoomMap *, int * );
static void Dump( AstObject *, AstChannel *, int * );
static void SetAttrib( AstObject *, const char *, int * );
static void SetZoom( AstZoomMap *, double, int * );

/* Member functions. */
/* ================= */
static void ClearAttrib( AstObject *this_object, const char *attrib, int *status ) {
/*
*  Name:
*     ClearAttrib

*  Purpose:
*     Clear an attribute value for a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     void ClearAttrib( AstObject *this, const char *attrib, int *status )

*  Class Membership:
*     ZoomMap member function (over-rides the astClearAttrib protected
*     method inherited from the Mapping class).

*  Description:
*     This function clears the value of a specified attribute for a
*     ZoomMap, so that the default value will subsequently be used.

*  Parameters:
*     this
*        Pointer to the ZoomMap.
*     attrib
*        Pointer to a null-terminated string specifying the attribute
*        name.  This should be in lower case with no surrounding white
*        space.
*     status
*        Pointer to the inherited status variable.
*/

/* Local Variables: */
   AstZoomMap *this;             /* Pointer to the ZoomMap structure */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain a pointer to the ZoomMap structure. */
   this = (AstZoomMap *) this_object;

/* Check the attribute name and clear the appropriate attribute. */

/* Zoom. */
/* ----- */
   if ( !strcmp( attrib, "zoom" ) ) {
      astClearZoom( this );

/* If the attribute is still not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      (*parent_clearattrib)( this_object, attrib, status );
   }
}

static int Equal( AstObject *this_object, AstObject *that_object, int *status ) {
/*
*  Name:
*     Equal

*  Purpose:
*     Test if two ZoomMaps are equivalent.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     int Equal( AstObject *this, AstObject *that, int *status )

*  Class Membership:
*     ZoomMap member function (over-rides the astEqual protected
*     method inherited from the astMapping class).

*  Description:
*     This function returns a boolean result (0 or 1) to indicate whether
*     two ZoomMaps are equivalent.

*  Parameters:
*     this
*        Pointer to the first Object (a ZoomMap).
*     that
*        Pointer to the second Object.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     One if the ZoomMaps are equivalent, zero otherwise.

*  Notes:
*     - A value of zero will be returned if this function is invoked
*     with the global status set, or if it should fail for any reason.
*/

/* Local Variables: */
   AstZoomMap *that;
   AstZoomMap *this;
   int nin;
   int nout;
   int result;

/* Initialise. */
   result = 0;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Obtain pointers to the two ZoomMap structures. */
   this = (AstZoomMap *) this_object;
   that = (AstZoomMap *) that_object;

/* Check the second object is a ZoomMap. We know the first is a
   ZoomMap since we have arrived at this implementation of the virtual
   function. */
   if( astIsAZoomMap( that ) ) {

/* Get the number of inputs and outputs and check they are the same for both. */
      nin = astGetNin( this );
      nout = astGetNout( this );
      if( astGetNin( that ) == nin && astGetNout( that ) == nout ) {

/* If the Invert flags for the two ZoomMaps differ, it may still be possible
   for them to be equivalent. First compare the ZoomMaps if their Invert
   flags are the same. In this case all the attributes of the two ZoomMaps
   must be identical. */
         if( astGetInvert( this ) == astGetInvert( that ) ) {
            result = ( astEQUAL( this->zoom, that->zoom ) );

/* If the Invert flags for the two ZoomMaps differ, the attributes of the two
   ZoomMaps must be inversely related to each other. */
         } else {
            result = ( astEQUAL( this->zoom, 1.0/that->zoom ) );

         }
      }
   }

/* If an error occurred, clear the result value. */
   if ( !astOK ) result = 0;

/* Return the result, */
   return result;
}

static const char *GetAttrib( AstObject *this_object, const char *attrib, int *status ) {
/*
*  Name:
*     GetAttrib

*  Purpose:
*     Get the value of a specified attribute for a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     const char *GetAttrib( AstObject *this, const char *attrib, int *status )

*  Class Membership:
*     ZoomMap member function (over-rides the protected astGetAttrib
*     method inherited from the Mapping class).

*  Description:
*     This function returns a pointer to the value of a specified
*     attribute for a ZoomMap, formatted as a character string.

*  Parameters:
*     this
*        Pointer to the ZoomMap.
*     attrib
*        Pointer to a null-terminated string containing the name of
*        the attribute whose value is required. This name should be in
*        lower case, with all white space removed.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     - Pointer to a null-terminated string containing the attribute
*     value.

*  Notes:
*     - The returned string pointer may point at memory allocated
*     within the ZoomMap, or at static memory. The contents of the
*     string may be over-written or the pointer may become invalid
*     following a further invocation of the same function or any
*     modification of the ZoomMap. A copy of the string should
*     therefore be made if necessary.
*     - A NULL pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*/

/* Local Variables: */
   astDECLARE_GLOBALS           /* Pointer to thread-specific global data */
   AstZoomMap *this;             /* Pointer to the ZoomMap structure */
   const char *result;           /* Pointer value to return */
   double zoom;                  /* Zoom attribute value */

/* Initialise. */
   result = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(this_object);

/* Obtain a pointer to the ZoomMap structure. */
   this = (AstZoomMap *) this_object;

/* Compare "attrib" with each recognised attribute name in turn,
   obtaining the value of the required attribute. If necessary, write
   the value into "getattrib_buff" as a null-terminated string in an appropriate
   format.  Set "result" to point at the result string. */

/* Zoom. */
/* ----- */
   if ( !strcmp( attrib, "zoom" ) ) {
      zoom = astGetZoom( this );
      if ( astOK ) {
         (void) sprintf( getattrib_buff, "%.*g", DBL_DIG, zoom );
         result = getattrib_buff;
      }

/* If the attribute name was not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      result = (*parent_getattrib)( this_object, attrib, status );
   }

/* Return the result. */
   return result;
}

static int GetIsLinear( AstMapping *this_mapping, int *status ){
/*
*  Name:
*     GetIsLinear

*  Purpose:
*     Return the value of the IsLinear attribute for a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "mapping.h"
*     void GetIsLinear( AstMapping *this, int *status )

*  Class Membership:
*     ZoomMap member function (over-rides the protected astGetIsLinear
*     method inherited from the Mapping class).

*  Description:
*     This function returns the value of the IsLinear attribute for a
*     Frame, which is always one.

*  Parameters:
*     this
*        Pointer to the ZoomMap.
*     status
*        Pointer to the inherited status variable.
*/
   return 1;
}

void astInitZoomMapVtab_(  AstZoomMapVtab *vtab, const char *name, int *status ) {
/*
*+
*  Name:
*     astInitZoomMapVtab

*  Purpose:
*     Initialise a virtual function table for a ZoomMap.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "zoommap.h"
*     void astInitZoomMapVtab( AstZoomMapVtab *vtab, const char *name )

*  Class Membership:
*     ZoomMap vtab initialiser.

*  Description:
*     This function initialises the component of a virtual function
*     table which is used by the ZoomMap class.

*  Parameters:
*     vtab
*        Pointer to the virtual function table. The components used by
*        all ancestral classes will be initialised if they have not already
*        been initialised.
*     name
*        Pointer to a constant null-terminated character string which contains
*        the name of the class to which the virtual function table belongs (it
*        is this pointer value that will subsequently be returned by the Object
*        astClass function).
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstObjectVtab *object;        /* Pointer to Object component of Vtab */
   AstMappingVtab *mapping;      /* Pointer to Mapping component of Vtab */

/* Check the local error status. */
   if ( !astOK ) return;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Initialize the component of the virtual function table used by the
   parent class. */
   astInitMappingVtab( (AstMappingVtab *) vtab, name );

/* Store a unique "magic" value in the virtual function table. This
   will be used (by astIsAZoomMap) to determine if an object belongs
   to this class.  We can conveniently use the address of the (static)
   class_check variable to generate this unique value. */
   vtab->id.check = &class_check;
   vtab->id.parent = &(((AstMappingVtab *) vtab)->id);

/* Initialise member function pointers. */
/* ------------------------------------ */
/* Store pointers to the member functions (implemented here) that provide
   virtual methods for this class. */
   vtab->ClearZoom = ClearZoom;
   vtab->GetZoom = GetZoom;
   vtab->SetZoom = SetZoom;
   vtab->TestZoom = TestZoom;

/* Save the inherited pointers to methods that will be extended, and
   replace them with pointers to the new member functions. */
   object = (AstObjectVtab *) vtab;
   mapping = (AstMappingVtab *) vtab;

   parent_clearattrib = object->ClearAttrib;
   object->ClearAttrib = ClearAttrib;
   parent_getattrib = object->GetAttrib;
   object->GetAttrib = GetAttrib;
   parent_setattrib = object->SetAttrib;
   object->SetAttrib = SetAttrib;
   parent_testattrib = object->TestAttrib;
   object->TestAttrib = TestAttrib;

   parent_transform = mapping->Transform;
   mapping->Transform = Transform;

/* Store replacement pointers for methods which will be over-ridden by
   new member functions implemented here. */
   object->Equal = Equal;
   mapping->MapMerge = MapMerge;
   mapping->MapSplit = MapSplit;
   mapping->Rate = Rate;
   mapping->GetIsLinear = GetIsLinear;

/* Declare the class dump function. There is no copy constructor or
   destructor. */
   astSetDump( vtab, Dump, "ZoomMap", "Zoom about the origin" );

/* If we have just initialised the vtab for the current class, indicate
   that the vtab is now initialised, and store a pointer to the class
   identifier in the base "object" level of the vtab. */
   if( vtab == &class_vtab ) {
      class_init = 1;
      astSetVtabClassIdentifier( vtab, &(vtab->id) );
   }
}

static int MapMerge( AstMapping *this, int where, int series, int *nmap,
                     AstMapping ***map_list, int **invert_list, int *status ) {
/*
*  Name:
*     MapMerge

*  Purpose:
*     Simplify a sequence of Mappings containing a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "mapping.h"
*     int MapMerge( AstMapping *this, int where, int series, int *nmap,
*                   AstMapping ***map_list, int **invert_list, int *status )

*  Class Membership:
*     ZoomMap method (over-rides the protected astMapMerge method
*     inherited from the Mapping class).

*  Description:
*     This function attempts to simplify a sequence of Mappings by
*     merging a nominated ZoomMap in the sequence with its neighbours,
*     so as to shorten the sequence if possible.
*
*     In many cases, simplification will not be possible and the
*     function will return -1 to indicate this, without further
*     action.
*
*     In most cases of interest, however, this function will either
*     attempt to replace the nominated ZoomMap with one which it
*     considers simpler, or to merge it with the Mappings which
*     immediately precede it or follow it in the sequence (both will
*     normally be considered). This is sufficient to ensure the
*     eventual simplification of most Mapping sequences by repeated
*     application of this function.
*
*     In some cases, the function may attempt more elaborate
*     simplification, involving any number of other Mappings in the
*     sequence. It is not restricted in the type or scope of
*     simplification it may perform, but will normally only attempt
*     elaborate simplification in cases where a more straightforward
*     approach is not adequate.

*  Parameters:
*     this
*        Pointer to the nominated ZoomMap which is to be merged with
*        its neighbours. This should be a cloned copy of the ZoomMap
*        pointer contained in the array element "(*map_list)[where]"
*        (see below). This pointer will not be annulled, and the
*        ZoomMap it identifies will not be modified by this function.
*     where
*        Index in the "*map_list" array (below) at which the pointer
*        to the nominated ZoomMap resides.
*     series
*        A non-zero value indicates that the sequence of Mappings to
*        be simplified will be applied in series (i.e. one after the
*        other), whereas a zero value indicates that they will be
*        applied in parallel (i.e. on successive sub-sets of the
*        input/output coordinates).
*     nmap
*        Address of an int which counts the number of Mappings in the
*        sequence. On entry this should be set to the initial number
*        of Mappings. On exit it will be updated to record the number
*        of Mappings remaining after simplification.
*     map_list
*        Address of a pointer to a dynamically allocated array of
*        Mapping pointers (produced, for example, by the astMapList
*        method) which identifies the sequence of Mappings. On entry,
*        the initial sequence of Mappings to be simplified should be
*        supplied.
*
*        On exit, the contents of this array will be modified to
*        reflect any simplification carried out. Any form of
*        simplification may be performed. This may involve any of: (a)
*        removing Mappings by annulling any of the pointers supplied,
*        (b) replacing them with pointers to new Mappings, (c)
*        inserting additional Mappings and (d) changing their order.
*
*        The intention is to reduce the number of Mappings in the
*        sequence, if possible, and any reduction will be reflected in
*        the value of "*nmap" returned. However, simplifications which
*        do not reduce the length of the sequence (but improve its
*        execution time, for example) may also be performed, and the
*        sequence might conceivably increase in length (but normally
*        only in order to split up a Mapping into pieces that can be
*        more easily merged with their neighbours on subsequent
*        invocations of this function).
*
*        If Mappings are removed from the sequence, any gaps that
*        remain will be closed up, by moving subsequent Mapping
*        pointers along in the array, so that vacated elements occur
*        at the end. If the sequence increases in length, the array
*        will be extended (and its pointer updated) if necessary to
*        accommodate any new elements.
*
*        Note that any (or all) of the Mapping pointers supplied in
*        this array may be annulled by this function, but the Mappings
*        to which they refer are not modified in any way (although
*        they may, of course, be deleted if the annulled pointer is
*        the final one).
*     invert_list
*        Address of a pointer to a dynamically allocated array which,
*        on entry, should contain values to be assigned to the Invert
*        attributes of the Mappings identified in the "*map_list"
*        array before they are applied (this array might have been
*        produced, for example, by the astMapList method). These
*        values will be used by this function instead of the actual
*        Invert attributes of the Mappings supplied, which are
*        ignored.
*
*        On exit, the contents of this array will be updated to
*        correspond with the possibly modified contents of the
*        "*map_list" array.  If the Mapping sequence increases in
*        length, the "*invert_list" array will be extended (and its
*        pointer updated) if necessary to accommodate any new
*        elements.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     If simplification was possible, the function returns the index
*     in the "map_list" array of the first element which was
*     modified. Otherwise, it returns -1 (and makes no changes to the
*     arrays supplied).

*  Notes:
*     - A value of -1 will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*/

/* Local Variables: */
   AstMapping *map;              /* Pointer to Mapping */
   AstMapping *new;              /* Pointer to replacement Mapping */
   const char *class;            /* Pointer to Mapping class string */
   double *zooms;                /* Pointer to zoom factor array */
   double maxzoom;               /* Maximum zoom factor */
   double minzoom;               /* Minimum zoom factor */
   double zoom;                  /* Zoom factor */
   int coord;                    /* Loop counter for coordinates */
   int imap1;                    /* Index of first ZoomMap */
   int imap2;                    /* Index of last ZoomMap */
   int imap;                     /* Loop counter for Mappings */
   int ncoord;                   /* Number of input/output coordinates */
   int ngone;                    /* Number of Mappings eliminated */
   int nin;                      /* Total number of input coordinates */
   int nzoom;                    /* Number of zoom factors */
   int result;                   /* Result value to return */
   int simpler;                  /* Mapping(s) simplified? */
   int single;                   /* Replacement is a single ZoomMap? */
   int unit;                     /* Replacement Mapping is a UnitMap? */

/* Initialise the returned result. */
   result = -1;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Further initialisation. */
   new = NULL;
   ngone = 0;
   simpler = 0;

/* In series. */
/* ---------- */
/* Handle the case where the Mappings are connected in series. */
   if ( series ) {

/* Obtain the effective zoom factor of the nominated Mapping (which is
   a ZoomMap) when its Invert attribute is set to the value given. */
      zoom = astGetZoom( ( *map_list )[ where ] );
      if ( ( *invert_list )[ where ] ) zoom = 1.0 / zoom;

/* Search adjacent lower-numbered Mappings and identify the class to
   which they belong. */
      imap1 = where;
      while ( astOK && ( ( imap1 - 1 ) >= 0 ) ) {
         map = ( *map_list )[ imap1 - 1 ];
         class = astGetClass( map );
         if ( astOK ) {

/* For each ZoomMap found, obtain the effective zoom factor (taking
   account of the associated invert flag value), and accumulate the
   overall zoom factor to be used for the simplified Mapping. */
            if ( !strcmp( class, "ZoomMap" ) ) {
               if ( ( *invert_list )[ imap1 - 1 ] ) {
                  zoom /= astGetZoom( map );
               } else {
                  zoom *= astGetZoom( map );
               }

/* UnitMaps have an effective zoom factor of unity, so we include them
   but they so have no effect. Quit looping when the first Mapping is
   found which is not a ZoomMap or a UnitMap. */
            } else if ( strcmp( class, "UnitMap" ) ) {
               break;
            }
            imap1--;
         }
      }

/* Similarly search adjacent higher-numbered ZoomMaps and UnitMaps and
   accumulate their effective zoom factors. */
      imap2 = where;
      while ( astOK && ( ( imap2 + 1 ) < *nmap ) ) {
         map = ( *map_list )[ imap2 + 1 ];
         class = astGetClass( map );
         if ( astOK ) {
            if ( !strcmp( class, "ZoomMap" ) ) {
               if ( ( *invert_list )[ imap2 + 1 ] ) {
                  zoom /= astGetZoom( map );
               } else {
                  zoom *= astGetZoom( map );
               }
            } else if ( strcmp( class, "UnitMap" ) ) {
               break;
            }
            imap2++;
         }
      }

/* Determine how many Mappings can be eliminated by condensing those
   found above into a single Mapping. */
      ngone = imap2 - imap1;

/* Determine if the replacement Mapping can be a UnitMap. This will be
   the case only if the accumulated zoom factor is unity (within some
   tolerable error). */
      unit = ( fabs( zoom - 1.0 ) <= ( 8.0 * DBL_EPSILON ) );

/* Determine if simplification is possible. This will be so if (a)
   Mappings can be eliminated ("ngone" is non-zero), or (b) the
   replacement can be a UnitMap, or (c) where there was initially only
   one ZoomMap, its invert flag was set (it will always be cleared in
   the replacement Mapping). */
      simpler = ngone || unit || ( *invert_list )[ where ];

/* Do nothing more unless simplification is possible. */
      if ( simpler ) {

/* Obtain the number of input/output coordinates for the replacement
   Mapping and create the appropriate replacement. */
         nin = astGetNin( ( *map_list )[ where ] );
         if ( unit ) {
            new = (AstMapping *) astUnitMap( nin, "", status );
         } else {
            new = (AstMapping *) astZoomMap( nin, zoom, "", status );
         }
      }

/* In parallel. */
/* ------------ */
/* Handle the case where the Mappings are connected in parallel. */
   } else {

/* Obtain the number of input/output coordinates for the nominated Mapping. */
      nin = astGetNin( ( *map_list )[ where ] );

/* Search adjacent lower-numbered Mappings and identify the class to
   which they belong. */
      imap1 = where;
      while ( astOK && ( ( imap1 - 1 ) >= 0 ) ) {
         map = ( *map_list )[ imap1 - 1 ];
         class = astGetClass( map );
         if ( astOK ) {

/* Quit looping when the first Mapping is found which is not a ZoomMap
   or a UnitMap. */
            if ( strcmp( class, "ZoomMap" ) &&
                 strcmp( class, "UnitMap" ) ) break;

/* Accumulate the total number of input/output coordinates for each
   adjacent ZoomMap and UnitMap found. */
            nin += astGetNin( map );
            imap1--;
         }
      }

/* Similarly search adjacent higher-numbered Mappings and accumulate
   the number of input/output coordinates.*/
      imap2 = where;
      while ( astOK && ( ( imap2 + 1 ) < *nmap ) ) {
         map = ( *map_list )[ imap2 + 1 ];
         class = astGetClass( map );
         if ( astOK ) {
            if ( strcmp( class, "ZoomMap" ) &&
                 strcmp( class, "UnitMap" ) ) break;
            nin += astGetNin( map );
            imap2++;
         }
      }

/* Allocate memory for an array of zoom factors, one for each
   input/output coordinate in the replacement Mapping. */
      zooms = astMalloc( sizeof( double ) * (size_t) nin );
      if ( astOK ) {

/* Initialise. */
         nzoom = 0;
         minzoom = DBL_MAX;
         maxzoom = -DBL_MAX;

/* Loop through all the ZoomMaps and UnitMaps being merged and again
   identify the class to which they belong. */
         for ( imap = imap1; astOK && ( imap <= imap2 ); imap++ ) {
            map = ( *map_list )[ imap ];
            class = astGetClass( map );
            if ( astOK ) {

/* Set a default zoom factor of unity (for UnitMaps). If the Mapping
   is a ZoomMap, replace this with the effective zoom factor, taking
   account of the associated invert flag. */
               zoom = 1.0;
               if ( !strcmp( class, "ZoomMap" ) ) {
                  if ( ( *invert_list )[ imap ] ) {
                     zoom = 1.0 / astGetZoom( map );
                  } else {
                     zoom = astGetZoom( map );
                  }
               }

/* Replicate the zoom factor in the zoom factor array, once for each
   input/output coordinate associated with the current Mapping. */
               ncoord = astGetNin( map );
               for ( coord = 0; coord < ncoord; coord++ ) {
                  zooms[ nzoom++ ] = zoom;
               }

/* Store the minimum and maximum zoom factors encountered. */
               if ( zoom < minzoom ) minzoom = zoom;
               if ( zoom > maxzoom ) maxzoom = zoom;
            }
         }

/* Determine how many Mappings can be eliminated by condensing those
   found above into a single Mapping. */
         ngone = imap2 - imap1;

/* Determine whether the replacement Mapping can be a single
   ZoomMap. This will be so if all the effective zoom factors were the
   same. */
         single = ( minzoom == maxzoom );

/* Determine if the replacement Mapping can be a UnitMap. This will be
   so if all the effective zoom factors were equal to unity. */
         unit = single && ( minzoom == 1.0 );

/* Determine if simplification is possible. This will be so if (a)
   Mappings can be eliminated ("ngone" is non-zero), or (b) the
   replacement can be a UnitMap, or (c) where there was initially only
   one ZoomMap, its invert flag was set (it will always be cleared in
   the replacement Mapping). */
         simpler = ngone || unit || ( *invert_list )[ where ];

/* Do nothing more unless simplification is possible. */
         if ( simpler ) {

/* Create a replacement UnitMap or ZoomMap if appropriate. */
            if ( unit ) {
               new = (AstMapping *) astUnitMap( nin, "", status );
            } else if ( single ) {
               new = (AstMapping *) astZoomMap( nin, minzoom, "", status );

/* Otherwise, replace the original ZoomMaps and UnitMaps with a
   diagonal MatrixMap containing the zoom factors as its diagonal
   elements. */
            } else {
               new = (AstMapping *) astMatrixMap( nin, nin, 1, zooms, "", status );
            }
         }
      }

/* Free the array of zoom factors. */
      zooms = astFree( zooms );
   }

/* If OK, and simplification is possible, we now have a replacement
   Mapping and can insert it into the Mapping list. */
   if ( astOK ) {
      if ( simpler ) {

/* Annul the pointers to all the ZoomMaps that are being replaced. */
         for ( imap = imap1; imap <= imap2; imap++ ) {
            ( *map_list )[ imap ] = astAnnul( ( *map_list )[ imap ] );
         }

/* Insert the new pointer and the associated invert flag. */
         ( *map_list )[ imap1 ] = new;
         ( *invert_list )[ imap1 ] = 0;

/* Loop to close the resulting gap by moving subsequent elements down
   in the arrays. */
         for ( imap = imap2 + 1; imap < *nmap; imap++ ) {
            ( *map_list )[ imap - ngone ] = ( *map_list )[ imap ];
            ( *invert_list )[ imap - ngone ] = ( *invert_list )[ imap ];
         }

/* Clear the vacated elements at the end. */
         for ( imap = *nmap - ngone; imap < *nmap; imap++ ) {
            ( *map_list )[ imap ] = NULL;
            ( *invert_list )[ imap ] = 0;
         }

/* Decrement the Mapping count and return the index of the first
   modified element. */
         ( *nmap ) -= ngone;
         result = imap1;
      }

/* If an error occurred, but a new Mapping has been created, then
   annul it. */
   } else {
      if ( new ) new = astAnnul( new );
   }

/* If an error occurred, clear the returned result. */
   if ( !astOK ) result = -1;

/* Return the result. */
   return result;
}

static int *MapSplit( AstMapping *this_map, int nin, const int *in, AstMapping **map, int *status ){
/*
*  Name:
*     MapSplit

*  Purpose:
*     Create a Mapping representing a subset of the inputs of an existing
*     ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     int *MapSplit( AstMapping *this, int nin, const int *in, AstMapping **map, int *status )

*  Class Membership:
*     ZoomMap method (over-rides the protected astMapSplit method
*     inherited from the Mapping class).

*  Description:
*     This function creates a new Mapping by picking specified inputs from
*     an existing ZoomMap. This is only possible if the specified inputs
*     correspond to some subset of the ZoomMap outputs. That is, there
*     must exist a subset of the ZoomMap outputs for which each output
*     depends only on the selected ZoomMap inputs, and not on any of the
*     inputs which have not been selected. If this condition is not met
*     by the supplied ZoomMap, then a NULL Mapping is returned.

*  Parameters:
*     this
*        Pointer to the ZoomMap to be split (the ZoomMap is not actually
*        modified by this function).
*     nin
*        The number of inputs to pick from "this".
*     in
*        Pointer to an array of indices (zero based) for the inputs which
*        are to be picked. This array should have "nin" elements. If "Nin"
*        is the number of inputs of the supplied ZoomMap, then each element
*        should have a value in the range zero to Nin-1.
*     map
*        Address of a location at which to return a pointer to the new
*        Mapping. This Mapping will have "nin" inputs (the number of
*        outputs may be different to "nin"). A NULL pointer will be
*        returned if the supplied ZoomMap has no subset of outputs which
*        depend only on the selected inputs.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     A pointer to a dynamically allocated array of ints. The number of
*     elements in this array will equal the number of outputs for the
*     returned Mapping. Each element will hold the index of the
*     corresponding output in the supplied ZoomMap. The array should be
*     freed using astFree when no longer needed. A NULL pointer will
*     be returned if no output Mapping can be created.

*  Notes:
*     - If this function is invoked with the global error status set,
*     or if it should fail for any reason, then NULL values will be
*     returned as the function value and for the "map" pointer.
*/

/* Local Variables: */
   AstZoomMap *this;          /* Pointer to ZoomMap structure */
   int *result;               /* Pointer to returned array */
   int i;                     /* Loop count */
   int iin;                   /* Mapping input index */
   int mnin;                  /* No. of Mapping inputs */
   int ok;                    /* Are input indices OK? */

/* Initialise */
   result = NULL;
   *map = NULL;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Get a pointer to the ZoomMap structure. */
   this = (AstZoomMap *) this_map;

/* Allocate memory for the returned array and create a ZoomMap with the
   required number of axes. */
   result = astMalloc( sizeof( int )*(size_t) nin );
   *map = (AstMapping *) astZoomMap( nin, astGetZoom( this ), "", status );

/* Set its Invert attribute to be like the supplied ZoomMap. */
   astSetInvert( *map, astGetInvert( this ) );

/* Check pointers can be used safely. */
   if( astOK ) {

/* Store the required output axis indices. At the same time check that each
   axis is valid. */
      mnin = astGetNin( this );
      ok = 1;
      for( i = 0; i < nin; i++ ) {
         iin = in[ i ];
         if( iin >= 0 && iin < mnin ) {
            result[ i ] = iin;
         } else {
            ok = 0;
            break;
         }
      }

/* If the "in" array contained any invalid values, free the returned
   resources. */
      if( !ok ) {
         result = astFree( result );
         *map = astAnnul( *map );
      }
   }

/* Free returned resources if an error has occurred. */
   if( !astOK ) {
      result = astFree( result );
      *map = astAnnul( *map );
   }

/* Return the list of output indices. */
   return result;
}

static double Rate( AstMapping *this, double *at, int ax1, int ax2, int *status ){
/*
*  Name:
*     Rate

*  Purpose:
*     Calculate the rate of change of a Mapping output.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     result = Rate( AstMapping *this, double *at, int ax1, int ax2, int *status )

*  Class Membership:
*     ZoomMap member function (overrides the astRate method inherited
*     from the Mapping class ).

*  Description:
*     This function returns the rate of change of a specified output of
*     the supplied Mapping with respect to a specified input, at a
*     specified input position.

*  Parameters:
*     this
*        Pointer to the Mapping to be applied.
*     at
*        The address of an array holding the axis values at the position
*        at which the rate of change is to be evaluated. The number of
*        elements in this array should equal the number of inputs to the
*        Mapping.
*     ax1
*        The index of the Mapping output for which the rate of change is to
*        be found (output numbering starts at 0 for the first output).
*     ax2
*        The index of the Mapping input which is to be varied in order to
*        find the rate of change (input numbering starts at 0 for the first
*        input).
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     The rate of change of Mapping output "ax1" with respect to input
*     "ax2", evaluated at "at", or AST__BAD if the value cannot be
*     calculated.

*/

/* Local Variables: */
   double result;

/* Check inherited status */
   if( !astOK ) return AST__BAD;

/* Result is zero if the axes differ */
   if( ax1 != ax2 ) {
      result = 0.0;

/* Otherwise, get the zoom factor. */
   } else {
      result = astGetZoom( (AstZoomMap *) this );

/* If the ZoomMap has been inverted, return the reciprocal of the zoom
   factor. */
      if ( astGetInvert( this ) ) {
         if( result != AST__BAD && result != 0.0 ) {
            result = 1.0/result;
         } else {
            result = AST__BAD;
         }
      }
   }

/* Return the result. */
   return result;
}

static void SetAttrib( AstObject *this_object, const char *setting, int *status ) {
/*
*  Name:
*     SetAttrib

*  Purpose:
*     Set an attribute value for a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     void SetAttrib( AstObject *this, const char *setting )

*  Class Membership:
*     ZoomMap member function (over-rides the astSetAttrib protected
*     method inherited from the Mapping class).

*  Description:
*     This function assigns an attribute value for a ZoomMap, the
*     attribute and its value being specified by means of a string of
*     the form:
*
*        "attribute= value "
*
*     Here, "attribute" specifies the attribute name and should be in
*     lower case with no white space present. The value to the right
*     of the "=" should be a suitable textual representation of the
*     value to be assigned and this will be interpreted according to
*     the attribute's data type.  White space surrounding the value is
*     only significant for string attributes.

*  Parameters:
*     this
*        Pointer to the ZoomMap.
*     setting
*        Pointer to a null-terminated string specifying the new attribute
*        value.
*/

/* Local Variables: */
   AstZoomMap *this;             /* Pointer to the ZoomMap structure */
   double zoom;                  /* Zoom attribute value */
   int len;                      /* Length of setting string */
   int nc;                       /* Number of characters read by astSscanf */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain a pointer to the ZoomMap structure. */
   this = (AstZoomMap *) this_object;

/* Obtain the length of the setting string. */
   len = (int) strlen( setting );

/* Test for each recognised attribute in turn, using "astSscanf" to parse
   the setting string and extract the attribute value (or an offset to
   it in the case of string values). In each case, use the value set
   in "nc" to check that the entire string was matched. Once a value
   has been obtained, use the appropriate method to set it. */

/* Zoom. */
/* ----- */
   if ( nc = 0,
        ( 1 == astSscanf( setting, "zoom= %lf %n", &zoom, &nc ) )
        && ( nc >= len ) ) {
      astSetZoom( this, zoom );

/* If the attribute is still not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      (*parent_setattrib)( this_object, setting, status );
   }
}

static int TestAttrib( AstObject *this_object, const char *attrib, int *status ) {
/*
*  Name:
*     TestAttrib

*  Purpose:
*     Test if a specified attribute value is set for a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     int TestAttrib( AstObject *this, const char *attrib, int *status )

*  Class Membership:
*     ZoomMap member function (over-rides the astTestAttrib protected
*     method inherited from the Mapping class).

*  Description:
*     This function returns a boolean result (0 or 1) to indicate whether
*     a value has been set for one of a ZoomMap's attributes.

*  Parameters:
*     this
*        Pointer to the ZoomMap.
*     attrib
*        Pointer to a null-terminated string specifying the attribute
*        name.  This should be in lower case with no surrounding white
*        space.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     One if a value has been set, otherwise zero.

*  Notes:
*     - A value of zero will be returned if this function is invoked
*     with the global status set, or if it should fail for any reason.
*/

/* Local Variables: */
   AstZoomMap *this;             /* Pointer to the ZoomMap structure */
   int result;                   /* Result value to return */

/* Initialise. */
   result = 0;

/* Check the global error status. */
   if ( !astOK ) return result;

/* Obtain a pointer to the ZoomMap structure. */
   this = (AstZoomMap *) this_object;

/* Check the attribute name and test the appropriate attribute. */

/* Zoom. */
/* ----- */
   if ( !strcmp( attrib, "zoom" ) ) {
      result = astTestZoom( this );

/* If the attribute is still not recognised, pass it on to the parent
   method for further interpretation. */
   } else {
      result = (*parent_testattrib)( this_object, attrib, status );
   }

/* Return the result, */
   return result;
}

static AstPointSet *Transform( AstMapping *this, AstPointSet *in,
                               int forward, AstPointSet *out, int *status ) {
/*
*  Name:
*     Transform

*  Purpose:
*     Apply a ZoomMap to transform a set of points.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     AstPointSet *Transform( AstMapping *this, AstPointSet *in,
*                             int forward, AstPointSet *out, int *status )

*  Class Membership:
*     ZoomMap member function (over-rides the astTransform protected
*     method inherited from the Mapping class).

*  Description:
*     This function takes a ZoomMap and a set of points encapsulated in a
*     PointSet and transforms the points so as to apply the required zoom
*     factor.

*  Parameters:
*     this
*        Pointer to the ZoomMap.
*     in
*        Pointer to the PointSet holding the input coordinate data.
*     forward
*        A non-zero value indicates that the forward coordinate transformation
*        should be applied, while a zero value requests the inverse
*        transformation.
*     out
*        Pointer to a PointSet which will hold the transformed (output)
*        coordinate values. A NULL value may also be given, in which case a
*        new PointSet will be created by this function.
*     status
*        Pointer to the inherited status variable.

*  Returned Value:
*     Pointer to the output (possibly new) PointSet.

*  Notes:
*     -  A null pointer will be returned if this function is invoked with the
*     global error status set, or if it should fail for any reason.
*     -  The number of coordinate values per point in the input PointSet must
*     match the number of coordinates for the ZoomMap being applied.
*     -  If an output PointSet is supplied, it must have space for sufficient
*     number of points and coordinate values per point to accommodate the
*     result. Any excess space will be ignored.
*/

/* Local Variables: */
   AstPointSet *result;          /* Pointer to output PointSet */
   AstZoomMap *map;              /* Pointer to ZoomMap to be applied */
   double **ptr_in;              /* Pointer to input coordinate data */
   double **ptr_out;             /* Pointer to output coordinate data */
   double scale;                 /* Scale factor to implement zoom */
   int coord;                    /* Loop counter for coordinates */
   int ncoord_in;                /* Number of coordinates per input point */
   int npoint;                   /* Number of points */
   int point;                    /* Loop counter for points */

/* Check the global error status. */
   if ( !astOK ) return NULL;

/* Obtain a pointer to the ZoomMap. */
   map = (AstZoomMap *) this;

/* Apply the parent mapping using the stored pointer to the Transform member
   function inherited from the parent Mapping class. This function validates
   all arguments and generates an output PointSet if necessary, but does not
   actually transform any coordinate values. */
   result = (*parent_transform)( this, in, forward, out, status );

/* We will now extend the parent astTransform method by performing the
   calculations needed to generate the output coordinate values. */

/* Determine the numbers of points and coordinates per point from the input
   PointSet and obtain pointers for accessing the input and output coordinate
   values. */
   ncoord_in = astGetNcoord( in );
   npoint = astGetNpoint( in );
   ptr_in = astGetPoints( in );
   ptr_out = astGetPoints( result );

/* Determine whether to apply the forward or inverse mapping, according to the
   direction specified and whether the mapping has been inverted. */
   if ( astGetInvert( map ) ) forward = !forward;

/* Perform coordinate arithmetic. */
/* ------------------------------ */
/* Generate the coordinate scale factor, according to the direction
   of mapping required. */
   scale = astGetZoom( map );
   if ( !forward && astOK ) scale = 1.0 / scale;

/* Loop to apply the scale factor to all the coordinate values, checking for
   (and propagating) bad values in the process. */
   if ( astOK ) {
      for ( coord = 0; coord < ncoord_in; coord++ ) {
         for ( point = 0; point < npoint; point++ ) {
            if ( ptr_in[ coord ][ point ] == AST__BAD ) {
               ptr_out[ coord ][ point ] = AST__BAD;
            } else {
               ptr_out[ coord ][ point ] = ptr_in[ coord ][ point ] * scale;
            }
         }
      }
   }

/* Return a pointer to the output PointSet. */
   return result;
}

/* Functions which access class attributes. */
/* ---------------------------------------- */
/* Implement member functions to access the attributes associated with
   this class using the macros defined for this purpose in the
   "object.h" file. For a description of each attribute, see the class
   interface (in the associated .h file). */

/*
*att++
*  Name:
*     Zoom

*  Purpose:
*     ZoomMap scale factor.

*  Type:
*     Public attribute.

*  Synopsis:
*     Double precision.

*  Description:
*     This attribute holds the ZoomMap scale factor, by which
*     coordinate values are multiplied (by the forward transformation)
*     or divided (by the inverse transformation). The default value
*     is unity.
*
c     Note that if a ZoomMap is inverted (e.g. by using astInvert),
f     Note that if a ZoomMap is inverted (e.g. by using AST_INVERT),
*     then the reciprocal of this zoom factor will, in effect, be
*     used.
*
*     In general, Mapping attributes cannot be changed after the Mapping
*     has been created (the exception to this is the Invert attribute,
*     which can be changed at any time). However, several of the oldest
*     Mapping classes - including the ZoomMap class - were introduced
*     into the AST library before this restriction was enforced. To
*     reduce the chances of breaking existing software, the attributes of
*     such Mappings may still be changed, but only for Mapping instances
*     that have exactly one active reference. In other words, an error will
*     be reported if an attempt is made to set or clear an attribute of a
*     Mapping (other than the Invert attribute) if that Mapping has been
*     cloned. Mappings are cloned when they are incorporated into another
*     object such as a CmpMap or FrameSet, or when the
c     astClone
f     AST_CLONE
*     function is used.

*  Applicability:
*     ZoomMap
*        All ZoomMaps have this attribute.

*  Notes:
*     - The Zoom attribute may not be set to zero.
*att--
*/
/* This ia a double value with a value of 0.0 when undefined but
   yielding a default of 1.0. Setting it explicitly to 0.0 is not
   permitted except via astClearZoom. */
astMAKE_CLEAR1(ZoomMap,Zoom,zoom,0.0)
astMAKE_GET(ZoomMap,Zoom,double,1.0,( ( this->zoom == 0.0 ) ?
                                      1.0 : this->zoom ))

/* Check for an attempt to set a value of zero and report an error if
   necessary (leaving the Zoom value unchanged). */
astMAKE_SET1(ZoomMap,Zoom,double,zoom,(
            ( value != 0.0 ) ?
            value :
            ( astError( AST__ZOOMI,
                       "astSetZoom(%s): A zoom factor of zero is not allowed.", status,
                        astGetClass( this ) ),
              this->zoom ) ))
astMAKE_TEST(ZoomMap,Zoom,( this->zoom != 0.0 ))

/* Copy constructor. */
/* ----------------- */
/* No copy constructor is needed, as a byte-by-byte copy suffices. */

/* Destructor. */
/* ----------- */
/* No destructor is needed as no memory, etc. needs freeing. */

/* Dump function. */
/* -------------- */
static void Dump( AstObject *this_object, AstChannel *channel, int *status ) {
/*
*  Name:
*     Dump

*  Purpose:
*     Dump function for ZoomMap objects.

*  Type:
*     Private function.

*  Synopsis:
*     void Dump( AstObject *this, AstChannel *channel, int *status )

*  Description:
*     This function implements the Dump function which writes out data
*     for the ZoomMap class to an output Channel.

*  Parameters:
*     this
*        Pointer to the ZoomMap whose data are being written.
*     channel
*        Pointer to the Channel to which the data are being written.
*     status
*        Pointer to the inherited status variable.
*/

/* Local Variables: */
   AstZoomMap *this;             /* Pointer to the ZoomMap structure */
   double dval;                  /* Double value */
   int set;                      /* Attribute value set? */

/* Check the global error status. */
   if ( !astOK ) return;

/* Obtain a pointer to the ZoomMap structure. */
   this = (AstZoomMap *) this_object;

/* Write out values representing the instance variables for the
   ZoomMap class.  Accompany these with appropriate comment strings,
   possibly depending on the values being written.*/

/* In the case of attributes, we first use the appropriate (private)
   Test...  member function to see if they are set. If so, we then use
   the (private) Get... function to obtain the value to be written
   out.

   For attributes which are not set, we use the astGet... method to
   obtain the value instead. This will supply a default value
   (possibly provided by a derived class which over-rides this method)
   which is more useful to a human reader as it corresponds to the
   actual default attribute value.  Since "set" will be zero, these
   values are for information only and will not be read back. */

/* Zoom. */
/* ----- */
   set = TestZoom( this, status );
   dval = set ? GetZoom( this, status ) : astGetZoom( this );
   astWriteDouble( channel, "Zoom", set, 1, dval, "Zoom factor" );
}

/* Standard class functions. */
/* ========================= */
/* Implement the astIsAZoomMap and astCheckZoomMap functions using the macros
   defined for this purpose in the "object.h" header file. */
astMAKE_ISA(ZoomMap,Mapping)
astMAKE_CHECK(ZoomMap)

AstZoomMap *astZoomMap_( int ncoord, double zoom, const char *options, int *status, ...) {
/*
*++
*  Name:
c     astZoomMap
f     AST_ZOOMMAP

*  Purpose:
*     Create a ZoomMap.

*  Type:
*     Public function.

*  Synopsis:
c     #include "zoommap.h"
c     AstZoomMap *astZoomMap( int ncoord, double zoom,
c                             const char *options, ... )
f     RESULT = AST_ZOOMMAP( NCOORD, ZOOM, OPTIONS, STATUS )

*  Class Membership:
*     ZoomMap constructor.

*  Description:
*     This function creates a new ZoomMap and optionally initialises its
*     attributes.
*
*     A ZoomMap is a Mapping which "zooms" a set of points about the
*     origin by multiplying all coordinate values by the same scale
*     factor (the inverse transformation is performed by dividing by
*     this scale factor).

*  Parameters:
c     ncoord
f     NCOORD = INTEGER (Given)
*        The number of coordinate values for each point to be
*        transformed (i.e. the number of dimensions of the space in
*        which the points will reside). The same number is applicable
*        to both input and output points.
c     zoom
f     ZOOM = DOUBLE PRECISION (Given)
*        Initial scale factor by which coordinate values should be
*        multiplied (by the forward transformation) or divided (by the
*        inverse transformation). This factor may subsequently be
*        changed via the ZoomMap's Zoom attribute. It may be positive
*        or negative, but should not be zero.
c     options
f     OPTIONS = CHARACTER * ( * ) (Given)
c        Pointer to a null-terminated string containing an optional
c        comma-separated list of attribute assignments to be used for
c        initialising the new ZoomMap. The syntax used is identical to
c        that for the astSet function and may include "printf" format
c        specifiers identified by "%" symbols in the normal way.
f        A character string containing an optional comma-separated
f        list of attribute assignments to be used for initialising the
f        new ZoomMap. The syntax used is identical to that for the
f        AST_SET routine.
c     ...
c        If the "options" string contains "%" format specifiers, then
c        an optional list of additional arguments may follow it in
c        order to supply values to be substituted for these
c        specifiers. The rules for supplying these are identical to
c        those for the astSet function (and for the C "printf"
c        function).
f     STATUS = INTEGER (Given and Returned)
f        The global status.

*  Returned Value:
c     astZoomMap()
f     AST_ZOOMMAP = INTEGER
*        A pointer to the new ZoomMap.

*  Notes:
*     - A null Object pointer (AST__NULL) will be returned if this
c     function is invoked with the AST error status set, or if it
f     function is invoked with STATUS set to an error value, or if it
*     should fail for any reason.

*  Status Handling:
*     The protected interface to this function includes an extra
*     parameter at the end of the parameter list descirbed above. This
*     parameter is a pointer to the integer inherited status
*     variable: "int *status".

*--
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstZoomMap *new;              /* Pointer to new ZoomMap */
   va_list args;                 /* Variable argument list */

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Check the global status. */
   if ( !astOK ) return NULL;

/* Initialise the ZoomMap, allocating memory and initialising the
   virtual function table as well if necessary. */
   new = astInitZoomMap( NULL, sizeof( AstZoomMap ), !class_init, &class_vtab,
                         "ZoomMap", ncoord, zoom );

/* If successful, note that the virtual function table has been
   initialised. */
   if ( astOK ) {
      class_init = 1;

/* Obtain the variable argument list and pass it along with the options string
   to the astVSet method to initialise the new ZoomMap's attributes. */
      va_start( args, status );
      astVSet( new, options, NULL, args );
      va_end( args );

/* If an error occurred, clean up by deleting the new object. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return a pointer to the new ZoomMap. */
   return new;
}

AstZoomMap *astZoomMapId_( int ncoord, double zoom,
                           const char *options, ... ) {
/*
*  Name:
*     astZoomMapId_

*  Purpose:
*     Create a ZoomMap.

*  Type:
*     Private function.

*  Synopsis:
*     #include "zoommap.h"
*     AstZoomMap *astZoomMapId_( int ncoord, double zoom,
*                                const char *options, ... )

*  Class Membership:
*     ZoomMap constructor.

*  Description:
*     This function implements the external (public) interface to the
*     astZoomMap constructor function. It returns an ID value (instead
*     of a true C pointer) to external users, and must be provided
*     because astZoomMap_ has a variable argument list which cannot be
*     encapsulated in a macro (where this conversion would otherwise
*     occur).
*
*     The variable argument list also prevents this function from
*     invoking astZoomMap_ directly, so it must be a re-implementation
*     of it in all respects, except for the final conversion of the
*     result to an ID value.

*  Parameters:
*     As for astZoomMap_.

*  Returned Value:
*     The ID value associated with the new ZoomMap.
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstZoomMap *new;              /* Pointer to new ZoomMap */
   va_list args;                 /* Variable argument list */

   int *status;                  /* Pointer to inherited status value */

/* Get a pointer to the inherited status value. */
   status = astGetStatusPtr;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(NULL);

/* Check the global status. */
   if ( !astOK ) return NULL;

/* Initialise the ZoomMap, allocating memory and initialising the
   virtual function table as well if necessary. */
   new = astInitZoomMap( NULL, sizeof( AstZoomMap ), !class_init, &class_vtab,
                         "ZoomMap", ncoord, zoom );

/* If successful, note that the virtual function table has been
   initialised. */
   if ( astOK ) {
      class_init = 1;

/* Obtain the variable argument list and pass it along with the options string
   to the astVSet method to initialise the new ZoomMap's attributes. */
      va_start( args, options );
      astVSet( new, options, NULL, args );
      va_end( args );

/* If an error occurred, clean up by deleting the new object. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return an ID value for the new ZoomMap. */
   return astMakeId( new );
}

AstZoomMap *astInitZoomMap_( void *mem, size_t size, int init,
                             AstZoomMapVtab *vtab, const char *name,
                             int ncoord, double zoom, int *status ) {
/*
*+
*  Name:
*     astInitZoomMap

*  Purpose:
*     Initialise a ZoomMap.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "zoommap.h"
*     AstZoomMap *astInitZoomMap( void *mem, size_t size, int init,
*                                 AstZoomMapVtab *vtab, const char *name,
*                                 int ncoord, double zoom )

*  Class Membership:
*     ZoomMap initialiser.

*  Description:
*     This function is provided for use by class implementations to initialise
*     a new ZoomMap object. It allocates memory (if necessary) to accommodate
*     the ZoomMap plus any additional data associated with the derived class.
*     It then initialises a ZoomMap structure at the start of this memory. If
*     the "init" flag is set, it also initialises the contents of a virtual
*     function table for a ZoomMap at the start of the memory passed via the
*     "vtab" parameter.

*  Parameters:
*     mem
*        A pointer to the memory in which the ZoomMap is to be initialised.
*        This must be of sufficient size to accommodate the ZoomMap data
*        (sizeof(ZoomMap)) plus any data used by the derived class. If a value
*        of NULL is given, this function will allocate the memory itself using
*        the "size" parameter to determine its size.
*     size
*        The amount of memory used by the ZoomMap (plus derived class data).
*        This will be used to allocate memory if a value of NULL is given for
*        the "mem" parameter. This value is also stored in the ZoomMap
*        structure, so a valid value must be supplied even if not required for
*        allocating memory.
*     init
*        A logical flag indicating if the ZoomMap's virtual function table is
*        to be initialised. If this value is non-zero, the virtual function
*        table will be initialised by this function.
*     vtab
*        Pointer to the start of the virtual function table to be associated
*        with the new ZoomMap.
*     name
*        Pointer to a constant null-terminated character string which contains
*        the name of the class to which the new object belongs (it is this
*        pointer value that will subsequently be returned by the astGetClass
*        method).
*     ncoord
*        The number of coordinate values per point.
*     zoom
*        The scale factor by which coordinate values are multiplied (by the
*        forward mapping) or divided (by the inverse mapping). This factor may
*        not be zero.

*  Returned Value:
*     A pointer to the new ZoomMap.

*  Notes:
*     -  A null pointer will be returned if this function is invoked with the
*     global error status set, or if it should fail for any reason.
*-
*/

/* Local Variables: */
   AstZoomMap *new;              /* Pointer to new ZoomMap */

/* Check the global status. */
   if ( !astOK ) return NULL;

/* If necessary, initialise the virtual function table. */
   if ( init ) astInitZoomMapVtab( vtab, name );

/* Initialise. */
   new = NULL;

/* Check the initialisation value(s) for validity, reporting an error if
   necessary. Prefix the error report with the name of the function and the
   class of object being processed. */
   if ( zoom == 0.0 ) {
      astError( AST__ZOOMI, "astInitZoomMap(%s): A zoom factor of zero is not "
                "allowed.", status, name );
   } else {

/* Initialise a Mapping structure (the parent class) as the first component
   within the ZoomMap structure, allocating memory if necessary. Specify that
   the Mapping should be defined in both the forward and inverse directions. */
      new = (AstZoomMap *) astInitMapping( mem, size, 0,
                                           (AstMappingVtab *) vtab, name,
                                           ncoord, ncoord, 1, 1 );

      if ( astOK ) {

/* Initialise the ZoomMap data. */
/* ---------------------------- */
/* Store the zoom factor. */
         new->zoom = zoom;

/* If an error occurred, clean up by deleting the new ZoomMap. */
         if ( !astOK ) new = astDelete( new );
      }
   }

/* Return a pointer to the new ZoomMap. */
   return new;
}

AstZoomMap *astLoadZoomMap_( void *mem, size_t size,
                             AstZoomMapVtab *vtab, const char *name,
                             AstChannel *channel, int *status ) {
/*
*+
*  Name:
*     astLoadZoomMap

*  Purpose:
*     Load a ZoomMap.

*  Type:
*     Protected function.

*  Synopsis:
*     #include "zoommap.h"
*     AstZoomMap *astLoadZoomMap( void *mem, size_t size,
*                                 AstZoomMapVtab *vtab, const char *name,
*                                 AstChannel *channel )

*  Class Membership:
*     ZoomMap loader.

*  Description:
*     This function is provided to load a new ZoomMap using data read
*     from a Channel. It first loads the data used by the parent class
*     (which allocates memory if necessary) and then initialises a
*     ZoomMap structure in this memory, using data read from the input
*     Channel.
*
*     If the "init" flag is set, it also initialises the contents of a
*     virtual function table for a ZoomMap at the start of the memory
*     passed via the "vtab" parameter.


*  Parameters:
*     mem
*        A pointer to the memory into which the ZoomMap is to be
*        loaded.  This must be of sufficient size to accommodate the
*        ZoomMap data (sizeof(ZoomMap)) plus any data used by derived
*        classes. If a value of NULL is given, this function will
*        allocate the memory itself using the "size" parameter to
*        determine its size.
*     size
*        The amount of memory used by the ZoomMap (plus derived class
*        data).  This will be used to allocate memory if a value of
*        NULL is given for the "mem" parameter. This value is also
*        stored in the ZoomMap structure, so a valid value must be
*        supplied even if not required for allocating memory.
*
*        If the "vtab" parameter is NULL, the "size" value is ignored
*        and sizeof(AstZoomMap) is used instead.
*     vtab
*        Pointer to the start of the virtual function table to be
*        associated with the new ZoomMap. If this is NULL, a pointer
*        to the (static) virtual function table for the ZoomMap class
*        is used instead.
*     name
*        Pointer to a constant null-terminated character string which
*        contains the name of the class to which the new object
*        belongs (it is this pointer value that will subsequently be
*        returned by the astGetClass method).
*
*        If the "vtab" parameter is NULL, the "name" value is ignored
*        and a pointer to the string "ZoomMap" is used instead.

*  Returned Value:
*     A pointer to the new ZoomMap.

*  Notes:
*     - A null pointer will be returned if this function is invoked
*     with the global error status set, or if it should fail for any
*     reason.
*-
*/

/* Local Variables: */
   astDECLARE_GLOBALS            /* Pointer to thread-specific global data */
   AstZoomMap *new;              /* Pointer to the new ZoomMap */

/* Initialise. */
   new = NULL;

/* Check the global error status. */
   if ( !astOK ) return new;

/* Get a pointer to the thread specific global data structure. */
   astGET_GLOBALS(channel);

/* If a NULL virtual function table has been supplied, then this is
   the first loader to be invoked for this ZoomMap. In this case the
   ZoomMap belongs to this class, so supply appropriate values to be
   passed to the parent class loader (and its parent, etc.). */
   if ( !vtab ) {
      size = sizeof( AstZoomMap );
      vtab = &class_vtab;
      name = "ZoomMap";

/* If required, initialise the virtual function table for this class. */
      if ( !class_init ) {
         astInitZoomMapVtab( vtab, name );
         class_init = 1;
      }
   }

/* Invoke the parent class loader to load data for all the ancestral
   classes of the current one, returning a pointer to the resulting
   partly-built ZoomMap. */
   new = astLoadMapping( mem, size, (AstMappingVtab *) vtab, name,
                         channel );

   if ( astOK ) {

/* Read input data. */
/* ================ */
/* Request the input Channel to read all the input data appropriate to
   this class into the internal "values list". */
      astReadClassData( channel, "ZoomMap" );

/* Now read each individual data item from this list and use it to
   initialise the appropriate instance variable(s) for this class. */

/* In the case of attributes, we first read the "raw" input value,
   supplying the "unset" value as the default. If a "set" value is
   obtained, we then use the appropriate (private) Set... member
   function to validate and set the value properly. */

/* Zoom. */
/* ----- */
      new->zoom = astReadDouble( channel, "zoom", 0.0 );
      if ( TestZoom( new, status ) ) SetZoom( new, new->zoom, status );

/* If an error occurred, clean up by deleting the new ZoomMap. */
      if ( !astOK ) new = astDelete( new );
   }

/* Return the new ZoomMap pointer. */
   return new;
}

/* Virtual function interfaces. */
/* ============================ */
/* These provide the external interface to the virtual functions defined by
   this class. Each simply checks the global error status and then locates and
   executes the appropriate member function, using the function pointer stored
   in the object's virtual function table (this pointer is located using the
   astMEMBER macro defined in "object.h").

   Note that the member function may not be the one defined here, as it may
   have been over-ridden by a derived class. However, it should still have the
   same interface. */