/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Copyright by The HDF Group. * * Copyright by the Board of Trustees of the University of Illinois. * * All rights reserved. * * * * This file is part of HDF5. The full HDF5 copyright notice, including * * terms governing use, modification, and redistribution, is contained in * * the files COPYING and Copyright.html. COPYING can be found at the root * * of the source code distribution tree; Copyright.html can be found at the * * root level of an installed copy of the electronic HDF5 document set and * * is linked from the top-level documents page. It can also be found at * * http://hdfgroup.org/HDF5/doc/Copyright.html. If you do not have * * access to either file, you may request a copy from help@hdfgroup.org. * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ #include "h5repack.h" #include "h5tools.h" #include "h5tools_utils.h" /* number of members in an array */ #ifndef NELMTS # define NELMTS(X) (sizeof(X)/sizeof(X[0])) #endif static int verify_layout(hid_t pid, pack_info_t *obj); static int verify_filters(hid_t pid, hid_t tid, int nfilters, filter_info_t *filter); /*------------------------------------------------------------------------- * Function: h5repack_verify * * Purpose: verify if filters and layout in the input file match the output file * * Return: * 1 match * 0 do not match * -1 error * * Programmer: Pedro Vicente, pvn@hdfgroup.org * * Date: December 19, 2003 * Modified: December, 19, 2007 (exactly 4 years later :-) ) * Separate into 3 cases * 1) no filter input, get all datasets and compare DCPLs. TO DO * 2) filter input on selected datasets, get each one trough OBJ and match * 3) filter input on all datasets, get all objects and match * *------------------------------------------------------------------------- */ int h5repack_verify(const char *in_fname, const char *out_fname, pack_opt_t *options) { hid_t fidin; /* file ID for input file*/ hid_t fidout; /* file ID for output file*/ hid_t did; /* dataset ID */ hid_t pid; /* dataset creation property list ID */ hid_t sid; /* space ID */ hid_t tid; /* type ID */ unsigned int i; trav_table_t *travt = NULL; int ok = 1; hid_t fcpl_in; /* file creation property for input file */ hid_t fcpl_out; /* file creation property for output file */ H5F_file_space_type_t in_strat, out_strat; /* file space handling strategy for in/output file */ hsize_t in_thresh, out_thresh; /* free space section threshold for in/output file */ /* open the output file */ if((fidout = H5Fopen(out_fname, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0 ) return -1; for(i = 0; i < options->op_tbl->nelems; i++) { char* name = options->op_tbl->objs[i].path; pack_info_t *obj = &options->op_tbl->objs[i]; /*------------------------------------------------------------------------- * open *------------------------------------------------------------------------- */ if((did = H5Dopen2(fidout, name, H5P_DEFAULT)) < 0) goto error; if((sid = H5Dget_space(did)) < 0) goto error; if((pid = H5Dget_create_plist(did)) < 0) goto error; if((tid = H5Dget_type(did)) < 0) goto error; /*------------------------------------------------------------------------- * filter check *------------------------------------------------------------------------- */ if(verify_filters(pid, tid, obj->nfilters, obj->filter) <= 0) ok = 0; /*------------------------------------------------------------------------- * layout check *------------------------------------------------------------------------- */ if((obj->layout != -1) && (verify_layout(pid, obj) == 0)) ok = 0; /*------------------------------------------------------------------------- * close *------------------------------------------------------------------------- */ if(H5Pclose(pid) < 0) goto error; if (H5Sclose(sid) < 0) goto error; if (H5Dclose(did) < 0) goto error; if (H5Tclose(tid) < 0) goto error; } /*------------------------------------------------------------------------- * check for the "all" objects option *------------------------------------------------------------------------- */ if(options->all_filter == 1 || options->all_layout == 1) { /* init table */ trav_table_init(&travt); /* get the list of objects in the file */ if(h5trav_gettable(fidout, travt) < 0) goto error; for(i = 0; i < travt->nobjs; i++) { char *name = travt->objs[i].name; if(travt->objs[i].type == H5TRAV_TYPE_DATASET) { /*------------------------------------------------------------------------- * open *------------------------------------------------------------------------- */ if((did = H5Dopen2(fidout, name, H5P_DEFAULT)) < 0) goto error; if((sid = H5Dget_space(did)) < 0) goto error; if((pid = H5Dget_create_plist(did)) < 0) goto error; if((tid = H5Dget_type(did)) < 0) goto error; /*------------------------------------------------------------------------- * filter check *------------------------------------------------------------------------- */ if(options->all_filter == 1) { if(verify_filters(pid, tid, options->n_filter_g, options->filter_g) <= 0) ok = 0; } /*------------------------------------------------------------------------- * layout check *------------------------------------------------------------------------- */ if(options->all_layout == 1) { pack_info_t pack; init_packobject(&pack); pack.layout = options->layout_g; pack.chunk = options->chunk_g; if(verify_layout(pid, &pack) == 0) ok = 0; } /*------------------------------------------------------------------------- * close *------------------------------------------------------------------------- */ if (H5Pclose(pid) < 0) goto error; if (H5Sclose(sid) < 0) goto error; if (H5Dclose(did) < 0) goto error; if (H5Tclose(tid) < 0) goto error; } /* if */ } /* i */ /* free table */ trav_table_free(travt); } /*------------------------------------------------------------------------- * Verify that file space strategy and free space threshold * are set as expected *------------------------------------------------------------------------- */ /* open the input file */ if((fidin = H5Fopen(in_fname, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0 ) goto error; /* Get file creation property list for input file */ if((fcpl_in = H5Fget_create_plist(fidin)) < 0) { error_msg("failed to retrieve file creation property list\n"); goto error; } /* Get file space management info for input file */ if(H5Pget_file_space(fcpl_in, &in_strat, &in_thresh) < 0) { error_msg("failed to retrieve file space strategy & threshold\n"); goto error; } /* Output file is already opened */ /* Get file creation property list for output file */ if((fcpl_out = H5Fget_create_plist(fidout)) < 0) { error_msg("failed to retrieve file creation property list\n"); goto error; } /* Get file space management info for output file */ if(H5Pget_file_space(fcpl_out, &out_strat, &out_thresh) < 0) { error_msg("failed to retrieve file space strategy & threshold\n"); goto error; } /* * If the strategy option is not set, * file space handling strategy should be the same for both * input & output files. * If the strategy option is set, * the output file's file space handling strategy should be the same * as what is set via the strategy option */ if(!options->fs_strategy && out_strat != in_strat) { error_msg("file space strategy not set as unexpected\n"); goto error; } else if(options->fs_strategy && out_strat!= options->fs_strategy) { error_msg("file space strategy not set as unexpectec\n"); goto error; } /* * If the threshold option is not set, * the free space section threshold should be the same for both * input & output files. * If the threshold option is set, * the output file's free space section threshold should be the same * as what is set via the threshold option. */ if(!options->fs_threshold && out_thresh != in_thresh) { error_msg("free space threshold not set as unexpected\n"); goto error; } else if(options->fs_threshold && out_thresh != options->fs_threshold) { error_msg("free space threshold not set as unexpectec\n"); goto error; } /* Closing */ if (H5Pclose(fcpl_in) < 0) goto error; if (H5Pclose(fcpl_out) < 0) goto error; if (H5Fclose(fidin) < 0) goto error; if (H5Fclose(fidout) < 0) goto error; return ok; error: H5E_BEGIN_TRY { H5Pclose(fcpl_in); H5Pclose(fcpl_out); H5Pclose(pid); H5Sclose(sid); H5Dclose(did); H5Fclose(fidin); H5Fclose(fidout); if (travt) trav_table_free(travt); } H5E_END_TRY; return -1; } /* h5repack_verify() */ /*------------------------------------------------------------------------- * Function: verify_layout * * Purpose: verify which layout is present in the property list DCPL_ID * * H5D_COMPACT = 0 * H5D_CONTIGUOUS = 1 * H5D_CHUNKED = 2 * * Return: 1 has, 0 does not, -1 error * * Programmer: Pedro Vicente, pvn@ncsa.uiuc.edu * * Date: December 30, 2003 * *------------------------------------------------------------------------- */ int verify_layout(hid_t pid, pack_info_t *obj) { hsize_t chsize[64]; /* chunk size in elements */ H5D_layout_t layout; /* layout */ int nfilters; /* number of filters */ int rank; /* rank */ int i; /* index */ /* check if we have filters in the input object */ if ((nfilters = H5Pget_nfilters(pid)) < 0) return -1; /* a non chunked layout was requested on a filtered object */ if (nfilters && obj->layout!=H5D_CHUNKED) return 0; /* get layout */ if ((layout = H5Pget_layout(pid)) < 0) return -1; if (obj->layout != layout) return 0; if (layout==H5D_CHUNKED) { if ((rank = H5Pget_chunk(pid,NELMTS(chsize),chsize/*out*/)) < 0) return -1; if (obj->chunk.rank != rank) return 0; for ( i=0; ichunk.chunk_lengths[i]) return 0; } return 1; } /*------------------------------------------------------------------------- * Function: h5repack_cmp_pl * * Purpose: compare 2 files for identical property lists of all objects * * Return: 1=identical, 0=not identical, -1=error * * Programmer: Pedro Vicente, pvn@ncsa.uiuc.edu * * Date: December 31, 2003 * *------------------------------------------------------------------------- */ int h5repack_cmp_pl(const char *fname1, const char *fname2) { hid_t fid1=-1; /* file ID */ hid_t fid2=-1; /* file ID */ hid_t dset1=-1; /* dataset ID */ hid_t dset2=-1; /* dataset ID */ hid_t gid=-1; /* group ID */ hid_t dcpl1=-1; /* dataset creation property list ID */ hid_t dcpl2=-1; /* dataset creation property list ID */ hid_t gcplid=-1; /* group creation property list */ unsigned crt_order_flag1; /* group creation order flag */ unsigned crt_order_flag2; /* group creation order flag */ trav_table_t *trav=NULL; int ret=1; unsigned int i; /*------------------------------------------------------------------------- * open the files *------------------------------------------------------------------------- */ /* disable error reporting */ H5E_BEGIN_TRY { /* Open the files */ if ((fid1=H5Fopen(fname1,H5F_ACC_RDONLY,H5P_DEFAULT)) < 0 ) { error_msg("<%s>: %s\n", fname1, H5FOPENERROR ); return -1; } if ((fid2=H5Fopen(fname2,H5F_ACC_RDONLY,H5P_DEFAULT)) < 0 ) { error_msg("<%s>: %s\n", fname2, H5FOPENERROR ); H5Fclose(fid1); return -1; } /* enable error reporting */ } H5E_END_TRY; /*------------------------------------------------------------------------- * get file table list of objects *------------------------------------------------------------------------- */ trav_table_init(&trav); if(h5trav_gettable(fid1, trav) < 0) goto error; /*------------------------------------------------------------------------- * traverse the suppplied object list *------------------------------------------------------------------------- */ for(i = 0; i < trav->nobjs; i++) { if(trav->objs[i].type == H5TRAV_TYPE_GROUP) { if ((gid = H5Gopen2(fid1, trav->objs[i].name, H5P_DEFAULT)) < 0) goto error; if ((gcplid = H5Gget_create_plist(gid)) < 0) goto error; if (H5Pget_link_creation_order(gcplid, &crt_order_flag1) < 0) goto error; if (H5Pclose(gcplid) < 0) goto error; if (H5Gclose(gid) < 0) goto error; if ((gid = H5Gopen2(fid2, trav->objs[i].name, H5P_DEFAULT)) < 0) goto error; if ((gcplid = H5Gget_create_plist(gid)) < 0) goto error; if (H5Pget_link_creation_order(gcplid, &crt_order_flag2) < 0) goto error; if (H5Pclose(gcplid) < 0) goto error; if (H5Gclose(gid) < 0) goto error; if ( crt_order_flag1 != crt_order_flag2 ) { error_msg("property lists for <%s> are different\n",trav->objs[i].name); goto error; } } else if(trav->objs[i].type == H5TRAV_TYPE_DATASET) { if((dset1 = H5Dopen2(fid1, trav->objs[i].name, H5P_DEFAULT)) < 0) goto error; if((dset2 = H5Dopen2(fid2, trav->objs[i].name, H5P_DEFAULT)) < 0) goto error; if((dcpl1 = H5Dget_create_plist(dset1)) < 0) goto error; if((dcpl2 = H5Dget_create_plist(dset2)) < 0) goto error; /*------------------------------------------------------------------------- * compare the property lists *------------------------------------------------------------------------- */ if((ret = H5Pequal(dcpl1, dcpl2)) < 0) goto error; if(ret == 0) { error_msg("property lists for <%s> are different\n",trav->objs[i].name); goto error; } /*------------------------------------------------------------------------- * close *------------------------------------------------------------------------- */ if(H5Pclose(dcpl1) < 0) goto error; if(H5Pclose(dcpl2) < 0) goto error; if(H5Dclose(dset1) < 0) goto error; if(H5Dclose(dset2) < 0) goto error; } /*if*/ } /*i*/ /*------------------------------------------------------------------------- * free *------------------------------------------------------------------------- */ trav_table_free(trav); /*------------------------------------------------------------------------- * close *------------------------------------------------------------------------- */ H5Fclose(fid1); H5Fclose(fid2); return ret; /*------------------------------------------------------------------------- * error *------------------------------------------------------------------------- */ error: H5E_BEGIN_TRY { H5Pclose(dcpl1); H5Pclose(dcpl2); H5Dclose(dset1); H5Dclose(dset2); H5Fclose(fid1); H5Fclose(fid2); H5Pclose(gcplid); H5Gclose(gid); trav_table_free(trav); } H5E_END_TRY; return -1; } /*------------------------------------------------------------------------- * Function: verify_filters * * Purpose: verify if all requested filters in the array FILTER obtained * from user input are present in the property list PID obtained from * the output file * * Return: * 1 match * 0 do not match * -1 error * * Programmer: Pedro Vicente, pvn@hdfgroup.org * * Date: December 21, 2007 * *------------------------------------------------------------------------- */ static int verify_filters(hid_t pid, hid_t tid, int nfilters, filter_info_t *filter) { int nfilters_dcpl; /* number of filters in DCPL*/ unsigned filt_flags; /* filter flags */ H5Z_filter_t filtn; /* filter identification number */ unsigned cd_values[20]; /* filter client data values */ size_t cd_nelmts; /* filter client number of values */ char f_name[256]; /* filter name */ size_t size; /* type size */ int i; /* index */ unsigned j; /* index */ /* get information about filters */ if((nfilters_dcpl = H5Pget_nfilters(pid)) < 0) return -1; /* if we do not have filters and the requested filter is NONE, return 1 */ if(!nfilters_dcpl && nfilters == 1 && filter[0].filtn == H5Z_FILTER_NONE ) return 1; /* else the numbers of filters must match */ if (nfilters_dcpl != nfilters ) return 0; /*------------------------------------------------------------------------- * build a list with DCPL filters *------------------------------------------------------------------------- */ for( i = 0; i < nfilters_dcpl; i++) { cd_nelmts = NELMTS(cd_values); filtn = H5Pget_filter2(pid, (unsigned)i, &filt_flags, &cd_nelmts, cd_values, sizeof(f_name), f_name, NULL); /* filter ID */ if (filtn != filter[i].filtn) return 0; /* compare client data values. some filters do return local values */ switch (filtn) { case H5Z_FILTER_NONE: break; case H5Z_FILTER_SHUFFLE: /* 1 private client value is returned by DCPL */ if ( cd_nelmts != H5Z_SHUFFLE_TOTAL_NPARMS && filter[i].cd_nelmts != H5Z_SHUFFLE_USER_NPARMS ) return 0; /* get dataset's type size */ if((size = H5Tget_size(tid)) <= 0) return -1; /* the private client value holds the dataset's type size */ if ( size != cd_values[0] ) return 0; break; case H5Z_FILTER_SZIP: /* 4 private client values are returned by DCPL */ if ( cd_nelmts != H5Z_SZIP_TOTAL_NPARMS && filter[i].cd_nelmts != H5Z_SZIP_USER_NPARMS ) return 0; /* "User" parameter for pixels-per-block (index 1) */ if ( cd_values[H5Z_SZIP_PARM_PPB] != filter[i].cd_values[H5Z_SZIP_PARM_PPB] ) return 0; break; case H5Z_FILTER_NBIT: /* only client data values number of values checked */ if ( H5Z_NBIT_USER_NPARMS != filter[i].cd_nelmts) return 0; break; case H5Z_FILTER_SCALEOFFSET: /* only client data values checked */ for( j = 0; j < H5Z_SCALEOFFSET_USER_NPARMS; j++) { if (cd_values[j] != filter[i].cd_values[j]) { return 0; } } break; /* for these filters values must match, no local values set in DCPL */ case H5Z_FILTER_FLETCHER32: case H5Z_FILTER_DEFLATE: if ( cd_nelmts != filter[i].cd_nelmts) return 0; for( j = 0; j < cd_nelmts; j++) { if (cd_values[j] != filter[i].cd_values[j]) { return 0; } } break; default: if ( cd_nelmts != filter[i].cd_nelmts) return 0; for( j = 0; j < cd_nelmts; j++) { if (cd_values[j] != filter[i].cd_values[j]) { return 0; } } break; } /* switch */ } return 1; } on value='dkf_quieter_compiles'>dkf_quieter_compiles Tcl is a high-level, general-purpose, interpreted, dynamic programming language. It was designed with the goal of being very simple but powerful.
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'\"
'\" Copyright (c) 1989-1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: TraceVar.3,v 1.19 2007/12/13 15:22:32 dgp Exp $
'\" 
.so man.macros
.TH Tcl_TraceVar 3 7.4 Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_TraceVar, Tcl_TraceVar2, Tcl_UntraceVar, Tcl_UntraceVar2, Tcl_VarTraceInfo, Tcl_VarTraceInfo2 \- monitor accesses to a variable
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
int
\fBTcl_TraceVar(\fIinterp, varName, flags, proc, clientData\fB)\fR
.sp
int
\fBTcl_TraceVar2(\fIinterp, name1, name2, flags, proc, clientData\fB)\fR
.sp
\fBTcl_UntraceVar(\fIinterp, varName, flags, proc, clientData\fB)\fR
.sp
\fBTcl_UntraceVar2(\fIinterp, name1, name2, flags, proc, clientData\fB)\fR
.sp
ClientData
\fBTcl_VarTraceInfo(\fIinterp, varName, flags, proc, prevClientData\fB)\fR
.sp
ClientData
\fBTcl_VarTraceInfo2(\fIinterp, name1, name2, flags, proc, prevClientData\fB)\fR
.SH ARGUMENTS
.AS Tcl_VarTraceProc prevClientData
.AP Tcl_Interp *interp in
Interpreter containing variable.
.AP "const char" *varName in
Name of variable.  May refer to a scalar variable, to
an array variable with no index, or to an array variable
with a parenthesized index.
.AP int flags in
OR-ed combination of the values \fBTCL_TRACE_READS\fR,
\fBTCL_TRACE_WRITES\fR, \fBTCL_TRACE_UNSETS\fR, \fBTCL_TRACE_ARRAY\fR,
\fBTCL_GLOBAL_ONLY\fR, \fBTCL_NAMESPACE_ONLY\fR,
\fBTCL_TRACE_RESULT_DYNAMIC\fR and \fBTCL_TRACE_RESULT_OBJECT\fR.
Not all flags are used by all
procedures.  See below for more information.
.AP Tcl_VarTraceProc *proc in
Procedure to invoke whenever one of the traced operations occurs.
.AP ClientData clientData in
Arbitrary one-word value to pass to \fIproc\fR.
.AP "const char" *name1 in
Name of scalar or array variable (without array index).
.AP "const char" *name2 in
For a trace on an element of an array, gives the index of the
element.  For traces on scalar variables or on whole arrays,
is NULL.
.AP ClientData prevClientData in
If non-NULL, gives last value returned by \fBTcl_VarTraceInfo\fR or
\fBTcl_VarTraceInfo2\fR, so this call will return information about
next trace.  If NULL, this call will return information about first
trace.
.BE
.SH DESCRIPTION
.PP
\fBTcl_TraceVar\fR allows a C procedure to monitor and control
access to a Tcl variable, so that the C procedure is invoked
whenever the variable is read or written or unset.
If the trace is created successfully then \fBTcl_TraceVar\fR returns
\fBTCL_OK\fR.  If an error occurred (e.g. \fIvarName\fR specifies an element
of an array, but the actual variable is not an array) then \fBTCL_ERROR\fR
is returned and an error message is left in the interpreter's result.
.PP
The \fIflags\fR argument to \fBTcl_TraceVar\fR indicates when the
trace procedure is to be invoked and provides information
for setting up the trace.  It consists of an OR-ed combination
of any of the following values:
.TP
\fBTCL_GLOBAL_ONLY\fR
Normally, the variable will be looked up at the current level of
procedure call;  if this bit is set then the variable will be looked
up at global level, ignoring any active procedures.
.TP
\fBTCL_NAMESPACE_ONLY\fR
Normally, the variable will be looked up at the current level of
procedure call;  if this bit is set then the variable will be looked
up in the current namespace, ignoring any active procedures.
.TP
\fBTCL_TRACE_READS\fR
Invoke \fIproc\fR whenever an attempt is made to read the variable.
.TP
\fBTCL_TRACE_WRITES\fR
Invoke \fIproc\fR whenever an attempt is made to modify the variable.
.TP
\fBTCL_TRACE_UNSETS\fR
Invoke \fIproc\fR whenever the variable is unset.
A variable may be unset either explicitly by an \fBunset\fR command,
or implicitly when a procedure returns (its local variables are
automatically unset) or when the interpreter is deleted (all
variables are automatically unset).
.TP
\fBTCL_TRACE_ARRAY\fR
Invoke \fIproc\fR whenever the array command is invoked.
This gives the trace procedure a chance to update the array before
array names or array get is called.  Note that this is called
before an array set, but that will trigger write traces.
.TP
\fBTCL_TRACE_RESULT_DYNAMIC\fR
The result of invoking the \fIproc\fR is a dynamically allocated
string that will be released by the Tcl library via a call to
\fBckfree\fR.  Must not be specified at the same time as
\fBTCL_TRACE_RESULT_OBJECT\fR.
.TP
\fBTCL_TRACE_RESULT_OBJECT\fR
The result of invoking the \fIproc\fR is a Tcl_Obj* (cast to a char*)
with a reference count of at least one.  The ownership of that
reference will be transferred to the Tcl core for release (when the
core has finished with it) via a call to \fBTcl_DecrRefCount\fR.  Must
not be specified at the same time as \fBTCL_TRACE_RESULT_DYNAMIC\fR.
.PP
Whenever one of the specified operations occurs on the variable,
\fIproc\fR will be invoked.
It should have arguments and result that match the type
\fBTcl_VarTraceProc\fR:
.CS
typedef char *Tcl_VarTraceProc(
        ClientData \fIclientData\fR,
        Tcl_Interp *\fIinterp\fR,
        char *\fIname1\fR,
        char *\fIname2\fR,
        int \fIflags\fR);
.CE
The \fIclientData\fR and \fIinterp\fR parameters will
have the same values as those passed to \fBTcl_TraceVar\fR when the
trace was created.
\fIClientData\fR typically points to an application-specific
data structure that describes what to do when \fIproc\fR
is invoked.
\fIName1\fR and \fIname2\fR give the name of the traced variable
in the normal two-part form (see the description of \fBTcl_TraceVar2\fR
below for details).
\fIFlags\fR is an OR-ed combination of bits providing several
pieces of information.
One of the bits \fBTCL_TRACE_READS\fR, \fBTCL_TRACE_WRITES\fR,
\fBTCL_TRACE_ARRAY\fR, or \fBTCL_TRACE_UNSETS\fR
will be set in \fIflags\fR to indicate which operation is being performed
on the variable.
The bit \fBTCL_GLOBAL_ONLY\fR will be set whenever the variable being
accessed is a global one not accessible from the current level of
procedure call:  the trace procedure will need to pass this flag
back to variable-related procedures like \fBTcl_GetVar\fR if it
attempts to access the variable.
The bit \fBTCL_NAMESPACE_ONLY\fR will be set whenever the variable being
accessed is a namespace one not accessible from the current level of
procedure call:  the trace procedure will need to pass this flag
back to variable-related procedures like \fBTcl_GetVar\fR if it
attempts to access the variable.
The bit \fBTCL_TRACE_DESTROYED\fR will be set in \fIflags\fR if the trace is
about to be destroyed;  this information may be useful to \fIproc\fR
so that it can clean up its own internal data structures (see
the section \fBTCL_TRACE_DESTROYED\fR below for more details).
Lastly, the bit \fBTCL_INTERP_DESTROYED\fR will be set if the entire
interpreter is being destroyed.
When this bit is set, \fIproc\fR must be especially careful in
the things it does (see the section \fBTCL_INTERP_DESTROYED\fR below).
The trace procedure's return value should normally be NULL;  see
\fBERROR RETURNS\fR below for information on other possibilities.
.PP
\fBTcl_UntraceVar\fR may be used to remove a trace.
If the variable specified by \fIinterp\fR, \fIvarName\fR, and \fIflags\fR
has a trace set with \fIflags\fR, \fIproc\fR, and
\fIclientData\fR, then the corresponding trace is removed.
If no such trace exists, then the call to \fBTcl_UntraceVar\fR
has no effect.
The same bits are valid for \fIflags\fR as for calls to \fBTcl_TraceVar\fR.
.PP
\fBTcl_VarTraceInfo\fR may be used to retrieve information about
traces set on a given variable.
The return value from \fBTcl_VarTraceInfo\fR is the \fIclientData\fR
associated with a particular trace.
The trace must be on the variable specified by the \fIinterp\fR,
\fIvarName\fR, and \fIflags\fR arguments (only the \fBTCL_GLOBAL_ONLY\fR and
\fBTCL_NAMESPACE_ONLY\fR bits from \fIflags\fR is used;  other bits are
ignored) and its trace procedure must the same as the \fIproc\fR
argument.
If the \fIprevClientData\fR argument is NULL then the return
value corresponds to the first (most recently created) matching
trace, or NULL if there are no matching traces.
If the \fIprevClientData\fR argument is not NULL, then it should
be the return value from a previous call to \fBTcl_VarTraceInfo\fR.
In this case, the new return value will correspond to the next
matching trace after the one whose \fIclientData\fR matches
\fIprevClientData\fR, or NULL if no trace matches \fIprevClientData\fR
or if there are no more matching traces after it.
This mechanism makes it possible to step through all of the
traces for a given variable that have the same \fIproc\fR.
.SH "TWO-PART NAMES"
.PP
The procedures \fBTcl_TraceVar2\fR, \fBTcl_UntraceVar2\fR, and
\fBTcl_VarTraceInfo2\fR are identical to \fBTcl_TraceVar\fR,
\fBTcl_UntraceVar\fR, and \fBTcl_VarTraceInfo\fR, respectively,
except that the name of the variable consists of two parts.
\fIName1\fR gives the name of a scalar variable or array,
and \fIname2\fR gives the name of an element within an array.
When \fIname2\fR is NULL, 
\fIname1\fR may contain both an array and an element name:
if the name contains an open parenthesis and ends with a
close parenthesis, then the value between the parentheses is
treated as an element name (which can have any string value) and
the characters before the first open
parenthesis are treated as the name of an array variable.
If \fIname2\fR is NULL and \fIname1\fR does not refer
to an array element it means that either the variable is
a scalar or the trace is to be set on the entire array rather
than an individual element (see WHOLE-ARRAY TRACES below for
more information). 
.SH "ACCESSING VARIABLES DURING TRACES"
.PP
During read, write, and array traces, the
trace procedure can read, write, or unset the traced
variable using \fBTcl_GetVar2\fR, \fBTcl_SetVar2\fR, and
other procedures.
While \fIproc\fR is executing, traces are temporarily disabled
for the variable, so that calls to \fBTcl_GetVar2\fR and
\fBTcl_SetVar2\fR will not cause \fIproc\fR or other trace procedures
to be invoked again.
Disabling only occurs for the variable whose trace procedure
is active;  accesses to other variables will still be traced.
However, if a variable is unset during a read or write trace then unset
traces will be invoked.
.PP
During unset traces the variable has already been completely
expunged.
It is possible for the trace procedure to read or write the
variable, but this will be a new version of the variable.
Traces are not disabled during unset traces as they are for
read and write traces, but existing traces have been removed
from the variable before any trace procedures are invoked.
If new traces are set by unset trace procedures, these traces
will be invoked on accesses to the variable by the trace
procedures.
.SH "CALLBACK TIMING"
.PP
When read tracing has been specified for a variable, the trace
procedure will be invoked whenever the variable's value is
read.  This includes \fBset\fR Tcl commands, \fB$\fR-notation
in Tcl commands, and invocations of the \fBTcl_GetVar\fR
and \fBTcl_GetVar2\fR procedures.
\fIProc\fR is invoked just before the variable's value is
returned.
It may modify the value of the variable to affect what
is returned by the traced access.
If it unsets the variable then the access will return an error
just as if the variable never existed.
.PP
When write tracing has been specified for a variable, the
trace procedure will be invoked whenever the variable's value
is modified.  This includes \fBset\fR commands,
commands that modify variables as side effects (such as
\fBcatch\fR and \fBscan\fR), and calls to the \fBTcl_SetVar\fR
and \fBTcl_SetVar2\fR procedures).
\fIProc\fR will be invoked after the variable's value has been
modified, but before the new value of the variable has been
returned.
It may modify the value of the variable to override the change
and to determine the value actually returned by the traced
access.
If it deletes the variable then the traced access will return
an empty string.
.PP
When array tracing has been specified, the trace procedure
will be invoked at the beginning of the array command implementation,
before any of the operations like get, set, or names have been invoked.
The trace procedure can modify the array elements with \fBTcl_SetVar\fR
and \fBTcl_SetVar2\fR.
.PP
When unset tracing has been specified, the trace procedure
will be invoked whenever the variable is destroyed.
The traces will be called after the variable has been
completely unset.
.SH "WHOLE-ARRAY TRACES"
.PP
If a call to \fBTcl_TraceVar\fR or \fBTcl_TraceVar2\fR specifies
the name of an array variable without an index into the array,
then the trace will be set on the array as a whole.
This means that \fIproc\fR will be invoked whenever any
element of the array is accessed in the ways specified by
\fIflags\fR.
When an array is unset, a whole-array trace will be invoked
just once, with \fIname1\fR equal to the name of the array
and \fIname2\fR NULL;  it will not be invoked once for each
element.
.SH "MULTIPLE TRACES"
.PP
It is possible for multiple traces to exist on the same variable.
When this happens, all of the trace procedures will be invoked on each
access, in order from most-recently-created to least-recently-created.
When there exist whole-array traces for an array as well as
traces on individual elements, the whole-array traces are invoked
before the individual-element traces.
If a read or write trace unsets the variable then all of the unset
traces will be invoked but the remainder of the read and write traces
will be skipped.
.SH "ERROR RETURNS"
.PP
Under normal conditions trace procedures should return NULL, indicating
successful completion.
If \fIproc\fR returns a non-NULL value it signifies that an
error occurred.
The return value must be a pointer to a static character string
containing an error message,
unless (\fIexactly\fR one of) the \fBTCL_TRACE_RESULT_DYNAMIC\fR and
\fBTCL_TRACE_RESULT_OBJECT\fR flags is set, which specify that the result is
either a dynamic string (to be released with \fBckfree\fR) or a
Tcl_Obj* (cast to char* and to be released with
\fBTcl_DecrRefCount\fR) containing the error message.
If a trace procedure returns an error, no further traces are
invoked for the access and the traced access aborts with the
given message.
Trace procedures can use this facility to make variables
read-only, for example (but note that the value of the variable
will already have been modified before the trace procedure is
called, so the trace procedure will have to restore the correct
value).
.PP
The return value from \fIproc\fR is only used during read and
write tracing.
During unset traces, the return value is ignored and all relevant
trace procedures will always be invoked.
.SH "RESTRICTIONS"
.PP
A trace procedure can be called at any time, even when there
is a partially formed result in the interpreter's result area.  If
the trace procedure does anything that could damage this result (such
as calling \fBTcl_Eval\fR) then it must save the original values of
the interpreter's \fBresult\fR and \fBfreeProc\fR fields and restore
them before it returns.
.SH "UNDEFINED VARIABLES"
.PP
It is legal to set a trace on an undefined variable.
The variable will still appear to be undefined until the
first time its value is set.
If an undefined variable is traced and then unset, the unset will fail
with an error
.PQ "no such variable" "" ,
but the trace procedure will still be invoked.
.SH "TCL_TRACE_DESTROYED FLAG"
.PP
In an unset callback to \fIproc\fR, the \fBTCL_TRACE_DESTROYED\fR bit
is set in \fIflags\fR if the trace is being removed as part
of the deletion.
Traces on a variable are always removed whenever the variable
is deleted;  the only time \fBTCL_TRACE_DESTROYED\fR is not set is for
a whole-array trace invoked when only a single element of an
array is unset.
.SH "TCL_INTERP_DESTROYED"
.PP
When an interpreter is destroyed, unset traces are called for
all of its variables.
The \fBTCL_INTERP_DESTROYED\fR bit will be set in the \fIflags\fR
argument passed to the trace procedures.
Trace procedures must be extremely careful in what they do if
the \fBTCL_INTERP_DESTROYED\fR bit is set.
It is not safe for the procedures to invoke any Tcl procedures
on the interpreter, since its state is partially deleted.
All that trace procedures should do under these circumstances is
to clean up and free their own internal data structures.
.SH BUGS
.PP
Tcl does not do any error checking to prevent trace procedures
from misusing the interpreter during traces with \fBTCL_INTERP_DESTROYED\fR
set.
.PP
Array traces are not yet integrated with the Tcl \fBinfo exists\fR command,
nor is there Tcl-level access to array traces.
.SH KEYWORDS
clientData, trace, variable
generated by cgit v0.12 at 2024-10-12 09:56:32 (GMT)