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-rw-r--r--generic/tkImgGIF.c50
1 files changed, 34 insertions, 16 deletions
diff --git a/generic/tkImgGIF.c b/generic/tkImgGIF.c
index b6fec53..f1fc25a 100644
--- a/generic/tkImgGIF.c
+++ b/generic/tkImgGIF.c
@@ -29,7 +29,7 @@
* | provided "as is" without express or implied warranty. |
* +-------------------------------------------------------------------+
*
- * RCS: @(#) $Id: tkImgGIF.c,v 1.12 2000/02/10 08:52:33 hobbs Exp $
+ * RCS: @(#) $Id: tkImgGIF.c,v 1.13 2000/02/26 00:51:17 ericm Exp $
*/
/*
@@ -63,6 +63,22 @@ typedef struct mFile {
#include "tkPort.h"
/*
+ * Non-ASCII encoding support:
+ * Most data in a GIF image is binary and is treated as such. However,
+ * a few key bits are stashed in ASCII. If we try to compare those pieces
+ * to the char they represent, it will fail on any non-ASCII (eg, EBCDIC)
+ * system. To accomodate these systems, we test against the numeric value
+ * of the ASCII characters instead of the characters themselves. This is
+ * encoding independant.
+ */
+
+# define GIF87a "\x47\x49\x46\x38\x37\x61" /* ASCII GIF87a */
+# define GIF89a "\x47\x49\x46\x38\x39\x61" /* ASCII GIF89a */
+# define GIF_TERMINATOR 0x3b /* ASCII ; */
+# define GIF_EXTENSION 0x21 /* ASCII ! */
+# define GIF_START 0x2c /* ASCII , */
+
+/*
* HACK ALERT!! HACK ALERT!! HACK ALERT!!
* This code is hard-wired for reading from files. In order to read
* from a data stream, we'll trick fread so we can reuse the same code.
@@ -311,7 +327,7 @@ FileReadGIF(interp, chan, fileName, format, imageHandle, destX, destY,
break;
}
- if (buf[0] == ';') {
+ if (buf[0] == GIF_TERMINATOR) {
/*
* GIF terminator.
*/
@@ -321,7 +337,7 @@ FileReadGIF(interp, chan, fileName, format, imageHandle, destX, destY,
goto error;
}
- if (buf[0] == '!') {
+ if (buf[0] == GIF_EXTENSION) {
/*
* This is a GIF extension.
*/
@@ -340,7 +356,7 @@ FileReadGIF(interp, chan, fileName, format, imageHandle, destX, destY,
continue;
}
- if (buf[0] != ',') {
+ if (buf[0] != GIF_START) {
/*
* Not a valid start character; ignore it.
*/
@@ -509,14 +525,14 @@ StringMatchGIF(dataObj, format, widthPtr, heightPtr, interp)
/* Check whether the data is Base64 encoded */
- if ((strncmp("\107\111\106\70\67\141", (char *) data, 6) != 0) &&
- (strncmp("\107\111\106\70\71\141", (char *) data, 6) != 0)) {
+ if ((strncmp(GIF87a, (char *) data, 6) != 0) &&
+ (strncmp(GIF89a, (char *) data, 6) != 0)) {
/* Try interpreting the data as Base64 encoded */
mInit((unsigned char *) data, &handle);
got = Mread(header, 10, 1, &handle);
if (got != 10
- || ((strncmp("\107\111\106\70\67\141", (char *) header, 6) != 0)
- && (strncmp("\107\111\106\70\71\141", (char *) header, 6) != 0))) {
+ || ((strncmp(GIF87a, (char *) header, 6) != 0)
+ && (strncmp(GIF89a, (char *) header, 6) != 0))) {
return 0;
}
} else {
@@ -570,8 +586,8 @@ StringReadGIF(interp, dataObj, format, imageHandle,
* Check whether the data is Base64 encoded
*/
data = (char *) Tcl_GetByteArrayFromObj(dataObj, NULL);
- if ((strncmp("\107\111\106\70\67\141", data, 6) != 0) &&
- (strncmp("\107\111\106\70\71\141", data, 6) != 0)) {
+ if ((strncmp(GIF87a, data, 6) != 0) &&
+ (strncmp(GIF89a, data, 6) != 0)) {
mInit((unsigned char *)data, &handle);
tsdPtr->fromData = 1;
dataSrc = (Tcl_Channel) &handle;
@@ -615,8 +631,8 @@ ReadGIFHeader(chan, widthPtr, heightPtr)
unsigned char buf[7];
if ((Fread(buf, 1, 6, chan) != 6)
- || ((strncmp("\107\111\106\70\67\141", (char *) buf, 6) != 0)
- && (strncmp("\107\111\106\70\71\141", (char *) buf, 6) != 0))) {
+ || ((strncmp(GIF87a, (char *) buf, 6) != 0)
+ && (strncmp(GIF89a, (char *) buf, 6) != 0))) {
return 0;
}
@@ -1381,7 +1397,7 @@ CommonWriteGIF(interp, handle, format, blockPtr)
alphaOffset = 0;
}
- Tcl_Write(handle, (char *) (alphaOffset ? "GIF89a":"GIF87a"), 6);
+ Tcl_Write(handle, (char *) (alphaOffset ? GIF89a : GIF87a), 6);
for (x=0;x<MAXCOLORMAPSIZE;x++) {
mapa[x][CM_RED] = 255;
@@ -1437,10 +1453,12 @@ CommonWriteGIF(interp, handle, format, blockPtr)
*/
if (alphaOffset) {
- Tcl_Write(handle, "!\371\4\1\0\0\0", 8);
+ c = GIF_EXTENSION;
+ Mputc(c, handle);
+ Tcl_Write(handle, "\371\4\1\0\0\0", 7);
}
- c = ',';
+ c = GIF_START;
Mputc(c,handle);
c=LSB(top);
Mputc(c,handle);
@@ -1472,7 +1490,7 @@ CommonWriteGIF(interp, handle, format, blockPtr)
c = 0;
Mputc(c,handle);
- c = ';';
+ c = GIF_TERMINATOR;
Mputc(c,handle);
return TCL_OK;