[libpng16] refactor: Deduplicate the interlace arrays png_pass_*

Move the definitions of interlace arrays to the top of their respective translation units, to reduce their repeated copying in various places of the codebase. TODO: As they still exist in three copies, in pngpread.c, in pngrutil.c, and in pngwutil.c, they should all be further moved to a common place. This is a cherry-pick of commit 620a2b7 from branch 'libpng18'.
pnggroup · Oct 17, 2024 · d9d70e6 · d9d70e6
1 parent 76e5ec2
commit d9d70e6
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Showing 3 changed files with 48 additions and 93 deletions.
diff --git a/pngpread.c b/pngpread.c
@@ -31,6 +31,21 @@ if (png_ptr->push_length + 4 > png_ptr->buffer_size) \
 if (png_ptr->buffer_size < N) \
    { png_push_save_buffer(png_ptr); return; }
 
+#ifdef PNG_READ_INTERLACING_SUPPORTED
+/* Arrays to facilitate interlacing - use pass (0 - 6) as index. */
+
+/* Start of interlace block */
+static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+/* Offset to next interlace block */
+static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+/* Start of interlace block in the y direction */
+static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+/* Offset to next interlace block in the y direction */
+static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+
+/* TODO: Move these arrays to a common utility module to avoid duplication. */
+#endif
+
 void PNGAPI
 png_process_data(png_structrp png_ptr, png_inforp info_ptr,
     png_bytep buffer, size_t buffer_size)
@@ -975,27 +990,6 @@ png_push_process_row(png_structrp png_ptr)
 void /* PRIVATE */
 png_read_push_finish_row(png_structrp png_ptr)
 {
-#ifdef PNG_READ_INTERLACING_SUPPORTED
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static const png_byte png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static const png_byte png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static const png_byte png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static const png_byte png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};
-
-   /* Height of interlace block.  This is not currently used - if you need
-    * it, uncomment it here and in png.h
-   static const png_byte png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
-   */
-#endif
-
    png_ptr->row_number++;
    if (png_ptr->row_number < png_ptr->num_rows)
       return;

diff --git a/pngrutil.c b/pngrutil.c
@@ -17,6 +17,21 @@
 
 #ifdef PNG_READ_SUPPORTED
 
+#ifdef PNG_READ_INTERLACING_SUPPORTED
+/* Arrays to facilitate interlacing - use pass (0 - 6) as index. */
+
+/* Start of interlace block */
+static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+/* Offset to next interlace block */
+static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+/* Start of interlace block in the y direction */
+static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+/* Offset to next interlace block in the y direction */
+static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+
+/* TODO: Move these arrays to a common utility module to avoid duplication. */
+#endif
+
 png_uint_32 PNGAPI
 png_get_uint_31(png_const_structrp png_ptr, png_const_bytep buf)
 {
@@ -3683,10 +3698,6 @@ void /* PRIVATE */
 png_do_read_interlace(png_row_infop row_info, png_bytep row, int pass,
     png_uint_32 transformations /* Because these may affect the byte layout */)
 {
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-   /* Offset to next interlace block */
-   static const unsigned int png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
    png_debug(1, "in png_do_read_interlace");
    if (row != NULL && row_info != NULL)
    {
@@ -4324,20 +4335,6 @@ png_read_finish_IDAT(png_structrp png_ptr)
 void /* PRIVATE */
 png_read_finish_row(png_structrp png_ptr)
 {
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-
    png_debug(1, "in png_read_finish_row");
    png_ptr->row_number++;
    if (png_ptr->row_number < png_ptr->num_rows)
@@ -4389,20 +4386,6 @@ png_read_finish_row(png_structrp png_ptr)
 void /* PRIVATE */
 png_read_start_row(png_structrp png_ptr)
 {
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-
    unsigned int max_pixel_depth;
    size_t row_bytes;
 

diff --git a/pngwutil.c b/pngwutil.c
@@ -8,12 +8,30 @@
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
  * and license in png.h
+ *
+ * This file contains routines that are only called from within
+ * libpng itself during the course of writing an image.
  */
 
 #include "pngpriv.h"
 
 #ifdef PNG_WRITE_SUPPORTED
 
+#ifdef PNG_WRITE_INTERLACING_SUPPORTED
+/* Arrays to facilitate interlacing - use pass (0 - 6) as index. */
+
+/* Start of interlace block */
+static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
+/* Offset to next interlace block */
+static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
+/* Start of interlace block in the y direction */
+static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
+/* Offset to next interlace block in the y direction */
+static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
+
+/* TODO: Move these arrays to a common utility module to avoid duplication. */
+#endif
+
 #ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
 /* Place a 32-bit number into a buffer in PNG byte order.  We work
  * with unsigned numbers for convenience, although one supported
@@ -1888,22 +1906,6 @@ png_write_tIME(png_structrp png_ptr, png_const_timep mod_time)
 void /* PRIVATE */
 png_write_start_row(png_structrp png_ptr)
 {
-#ifdef PNG_WRITE_INTERLACING_SUPPORTED
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-#endif
-
    png_alloc_size_t buf_size;
    int usr_pixel_depth;
 
@@ -2003,22 +2005,6 @@ png_write_start_row(png_structrp png_ptr)
 void /* PRIVATE */
 png_write_finish_row(png_structrp png_ptr)
 {
-#ifdef PNG_WRITE_INTERLACING_SUPPORTED
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
-   /* Start of interlace block in the y direction */
-   static const png_byte png_pass_ystart[7] = {0, 0, 4, 0, 2, 0, 1};
-
-   /* Offset to next interlace block in the y direction */
-   static const png_byte png_pass_yinc[7] = {8, 8, 8, 4, 4, 2, 2};
-#endif
-
    png_debug(1, "in png_write_finish_row");
 
    /* Next row */
@@ -2094,14 +2080,6 @@ png_write_finish_row(png_structrp png_ptr)
 void /* PRIVATE */
 png_do_write_interlace(png_row_infop row_info, png_bytep row, int pass)
 {
-   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */
-
-   /* Start of interlace block */
-   static const png_byte png_pass_start[7] = {0, 4, 0, 2, 0, 1, 0};
-
-   /* Offset to next interlace block */
-   static const png_byte png_pass_inc[7] = {8, 8, 4, 4, 2, 2, 1};
-
    png_debug(1, "in png_do_write_interlace");
 
    /* We don't have to do anything on the last pass (6) */