[libpng15] Removed non-working progressive reader 'skip' function.

ANNOUNCE

@@ -1,5 +1,5 @@
 
-Libpng 1.5.23beta02 - June 2, 2015
+Libpng 1.5.23beta02 - June 3, 2015
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -38,13 +38,14 @@ Version 1.5.23beta01 [May 21, 2015]
   Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
     report from Christopher Ferris).
 
-Version 1.5.23beta02 [June 2, 2015]
+Version 1.5.23beta02 [June 3, 2015]
   Removed WRITE_WEIGHTED_FILTERED code, to save a few kbytes of the
     compiled library size. It never worked properly and as far as we can
     tell, no one uses it. The png_set_filter_heuristics() and
     png_set_filter_heuristics_fixed() APIs are retained but deprecated
     and do nothing.
   Quieted Coverity issues in pngvalid.c.
+  Removed non-working progressive reader 'skip' function.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

CHANGES

@@ -4350,13 +4350,14 @@ Version 1.5.23beta01 [May 21, 2015]
   Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
     report from Christopher Ferris).
 
-Version 1.5.23beta02 [June 2, 2015]
+Version 1.5.23beta02 [June 3, 2015]
   Removed WRITE_WEIGHTED_FILTERED code, to save a few kbytes of the
     compiled library size. It never worked properly and as far as we can
     tell, no one uses it. The png_set_filter_heuristics() and
     png_set_filter_heuristics_fixed() APIs are retained but deprecated
     and do nothing.
   Quieted Coverity issues in pngvalid.c.
+  Removed non-working progressive reader 'skip' function.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit

pngpread.c

@@ -19,7 +19,6 @@
 #define PNG_READ_SIG_MODE   0
 #define PNG_READ_CHUNK_MODE 1
 #define PNG_READ_IDAT_MODE  2
-#define PNG_SKIP_MODE       3
 #define PNG_READ_tEXt_MODE  4
 #define PNG_READ_zTXt_MODE  5
 #define PNG_READ_DONE_MODE  6
@@ -71,32 +70,15 @@ png_process_data_pause(png_structp png_ptr, int save)
 png_uint_32 PNGAPI
 png_process_data_skip(png_structp png_ptr)
 {
-   png_uint_32 remaining = 0;
+    /* TODO: somewhere the implementation of this seems to have been lost,
-
+     * or abandoned.  It was only to support some internal snooping done by
-   if (png_ptr != NULL && png_ptr->process_mode == PNG_SKIP_MODE &&
+     * Mozilla (i.e. back-door access to png_struct) in 1.4; apparently they
-      png_ptr->skip_length > 0)
+     * must have stopped doing it.
-   {
-      /* At the end of png_process_data the buffer size must be 0 (see the loop
-       * above) so we can detect a broken call here:
      */
-      if (png_ptr->buffer_size != 0)
+   png_warning(png_ptr,
-         png_error(png_ptr,
+       "png_process_data_skip is not implemented in any current version"
-            "png_process_data_skip called inside png_process_data");
+       " of libpng");
-
+   return 0;
-      /* If is impossible for there to be a saved buffer at this point -
-       * otherwise we could not be in SKIP mode.  This will also happen if
-       * png_process_skip is called inside png_process_data (but only very
-       * rarely.)
-       */
-      if (png_ptr->save_buffer_size != 0)
-         png_error(png_ptr, "png_process_data_skip called with saved data");
-
-      remaining = png_ptr->skip_length;
-      png_ptr->skip_length = 0;
-      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
-   }
-
-   return remaining;
 }
 
 /* What we do with the incoming data depends on what we were previously
@@ -128,12 +110,6 @@ png_process_some_data(png_structp png_ptr, png_infop info_ptr)
          break;
       }
 
-      case PNG_SKIP_MODE:
-      {
-         png_push_crc_finish(png_ptr);
-         break;
-      }
-
       default:
       {
          png_ptr->buffer_size = 0;
@@ -564,76 +540,6 @@ png_push_read_chunk(png_structp png_ptr, png_infop info_ptr)
    png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
 }
 
-void /* PRIVATE */
-png_push_crc_skip(png_structp png_ptr, png_uint_32 skip)
-{
-   png_ptr->process_mode = PNG_SKIP_MODE;
-   png_ptr->skip_length = skip;
-}
-
-void /* PRIVATE */
-png_push_crc_finish(png_structp png_ptr)
-{
-   if (png_ptr->skip_length && png_ptr->save_buffer_size)
-   {
-      png_size_t save_size = png_ptr->save_buffer_size;
-      png_uint_32 skip_length = png_ptr->skip_length;
-
-      /* We want the smaller of 'skip_length' and 'save_buffer_size', but
-       * they are of different types and we don't know which variable has the
-       * fewest bits.  Carefully select the smaller and cast it to the type of
-       * the larger - this cannot overflow.  Do not cast in the following test
-       * - it will break on either 16 or 64 bit platforms.
-       */
-      if (skip_length < save_size)
-         save_size = (png_size_t)skip_length;
-
-      else
-         skip_length = (png_uint_32)save_size;
-
-      png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);
-
-      png_ptr->skip_length -= skip_length;
-      png_ptr->buffer_size -= save_size;
-      png_ptr->save_buffer_size -= save_size;
-      png_ptr->save_buffer_ptr += save_size;
-   }
-
-   if (png_ptr->skip_length && png_ptr->current_buffer_size)
-   {
-      png_size_t save_size = png_ptr->current_buffer_size;
-      png_uint_32 skip_length = png_ptr->skip_length;
-
-      /* We want the smaller of 'skip_length' and 'current_buffer_size', here,
-       * the same problem exists as above and the same solution.
-       */
-      if (skip_length < save_size)
-         save_size = (png_size_t)skip_length;
-
-      else
-         skip_length = (png_uint_32)save_size;
-
-      png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);
-
-      png_ptr->skip_length -= skip_length;
-      png_ptr->buffer_size -= save_size;
-      png_ptr->current_buffer_size -= save_size;
-      png_ptr->current_buffer_ptr += save_size;
-   }
-
-   if (!png_ptr->skip_length)
-   {
-      if (png_ptr->buffer_size < 4)
-      {
-         png_push_save_buffer(png_ptr);
-         return;
-      }
-
-      png_crc_finish(png_ptr, 0);
-      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
-   }
-}
-
 void PNGCBAPI
 png_push_fill_buffer(png_structp png_ptr, png_bytep buffer, png_size_t length)
 {

pngpriv.h

@@ -1317,9 +1317,6 @@ PNG_EXTERN void png_push_read_chunk PNGARG((png_structp png_ptr,
 PNG_EXTERN void png_push_read_sig PNGARG((png_structp png_ptr,
     png_infop info_ptr));
 PNG_EXTERN void png_push_check_crc PNGARG((png_structp png_ptr));
-PNG_EXTERN void png_push_crc_skip PNGARG((png_structp png_ptr,
-    png_uint_32 length));
-PNG_EXTERN void png_push_crc_finish PNGARG((png_structp png_ptr));
 PNG_EXTERN void png_push_save_buffer PNGARG((png_structp png_ptr));
 PNG_EXTERN void png_push_restore_buffer PNGARG((png_structp png_ptr,
     png_bytep buffer, png_size_t buffer_length));