[gimp] Issue #4210 - GIMP reports errors on scanning ...

[Ell <ell src gnome org>]

commit 9a1d43c978131293276ff226268cdd1f56cbd3ed
Author: Ell <ell_se yahoo com>
Date:   Wed Jun 3 16:44:44 2020 +0300

    Issue #4210 - GIMP reports errors on scanning ...
    
    ... since GEGLification of the twain plug-in (2.10.14 and later
    versions)
    
    In the data-transfer functions, allocate a temporary buffer for the
    converted data on each call using the current chunk size, instead
    of reusing the buffer allocated on the first chunk.  This allows
    for different chunks sizes across calls.

 plug-ins/twain/twain.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)
---
diff --git a/plug-ins/twain/twain.c b/plug-ins/twain/twain.c
index 47060ac2ec..e8f3ae4b13 100644
--- a/plug-ins/twain/twain.c
+++ b/plug-ins/twain/twain.c
@@ -109,7 +109,6 @@
 /* Global variables */
 pTW_SESSION twSession = NULL;
 
-static char *destBuf = NULL;
 #ifdef _DEBUG
 static int twain_run_mode = RUN_STANDARD;
 #endif
@@ -651,13 +650,13 @@ bitTransferCallback (pTW_IMAGEINFO     imageInfo,
 {
   int   row, col, offset;
   char *srcBuf;
+  char *destBuf;
   int   rows = imageMemXfer->Rows;
   int   cols = imageMemXfer->Columns;
   pClientDataStruct theClientData = (pClientDataStruct) clientData;
 
   /* Allocate a buffer as necessary */
-  if (! destBuf)
-    destBuf = g_new (char, rows * cols);
+  destBuf = gegl_scratch_new (char, rows * cols);
 
   /* Unpack the image data from bits into bytes */
   srcBuf = (char *) imageMemXfer->Memory.TheMem;
@@ -678,6 +677,9 @@ bitTransferCallback (pTW_IMAGEINFO     imageInfo,
                    theClientData->format, destBuf,
                    GEGL_AUTO_ROWSTRIDE);
 
+  /* Free the buffer */
+  gegl_scratch_free (destBuf);
+
   /* Update the user on our progress */
   theClientData->completedPixels += (cols * rows);
   gimp_progress_update ((double) theClientData->completedPixels /
@@ -703,14 +705,14 @@ oneBytePerSampleTransferCallback (pTW_IMAGEINFO     imageInfo,
 {
   int   row;
   char *srcBuf;
+  char *destBuf;
   int   bytesPerPixel = imageInfo->BitsPerPixel / 8;
   int   rows = imageMemXfer->Rows;
   int   cols = imageMemXfer->Columns;
   pClientDataStruct theClientData = (pClientDataStruct) clientData;
 
   /* Allocate a buffer as necessary */
-  if (! destBuf)
-    destBuf = g_new (char, rows * cols * bytesPerPixel);
+  destBuf = gegl_scratch_new (char, rows * cols * bytesPerPixel);
 
   /* The bytes coming from the source may not be padded in
    * a way that GIMP is terribly happy with.  It is
@@ -736,6 +738,9 @@ oneBytePerSampleTransferCallback (pTW_IMAGEINFO     imageInfo,
                    theClientData->format, destBuf,
                    GEGL_AUTO_ROWSTRIDE);
 
+  /* Free the buffer */
+  gegl_scratch_free (destBuf);
+
   /* Update the user on our progress */
   theClientData->completedPixels += (cols * rows);
   gimp_progress_update ((double) theClientData->completedPixels /
@@ -758,6 +763,7 @@ twoBytesPerSampleTransferCallback (pTW_IMAGEINFO     imageInfo,
 {
   static float  ratio = 0.00390625;
   int           row, col, sample;
+  char         *destBuf;
   char         *destByte;
   int           rows = imageMemXfer->Rows;
   int           cols = imageMemXfer->Columns;
@@ -766,8 +772,7 @@ twoBytesPerSampleTransferCallback (pTW_IMAGEINFO     imageInfo,
   pClientDataStruct theClientData = (pClientDataStruct) clientData;
 
   /* Allocate a buffer as necessary */
-  if (! destBuf)
-    destBuf = g_new (char, rows * cols * imageInfo->SamplesPerPixel);
+  destBuf = gegl_scratch_new (char, rows * cols * imageInfo->SamplesPerPixel);
 
   /* The bytes coming from the source may not be padded in
    * a way that GIMP is terribly happy with.  It is
@@ -815,6 +820,9 @@ twoBytesPerSampleTransferCallback (pTW_IMAGEINFO     imageInfo,
                    theClientData->format, destBuf,
                    GEGL_AUTO_ROWSTRIDE);
 
+  /* Free the buffer */
+  gegl_scratch_free (destBuf);
+
   /* Update the user on our progress */
   theClientData->completedPixels += (cols * rows);
   gimp_progress_update ((double) theClientData->completedPixels /
@@ -844,6 +852,7 @@ palettedTransferCallback (pTW_IMAGEINFO     imageInfo,
   int   row, col;
   int   rows = imageMemXfer->Rows;
   int   cols = imageMemXfer->Columns;
+  char *destBuf;
   char *destPtr = NULL;
   char *srcPtr = NULL;
 
@@ -855,8 +864,7 @@ palettedTransferCallback (pTW_IMAGEINFO     imageInfo,
     (theClientData->paletteData->PaletteType == TWPA_RGB) ? 3 : 1;
 
   /* Allocate a buffer as necessary */
-  if (! destBuf)
-    destBuf = g_new (char, rows * cols * channelsPerEntry);
+  destBuf = gegl_scratch_new (char, rows * cols * channelsPerEntry);
 
   /* Work through the rows */
   destPtr = destBuf;
@@ -898,6 +906,9 @@ palettedTransferCallback (pTW_IMAGEINFO     imageInfo,
                    theClientData->format, destBuf,
                    GEGL_AUTO_ROWSTRIDE);
 
+  /* Free the buffer */
+  gegl_scratch_free (destBuf);
+
   /* Update the user on our progress */
   theClientData->completedPixels += (cols * rows);
   gimp_progress_update ((double) theClientData->completedPixels /