+++ /dev/null
-/*---------------------------------------------------------------------------
-
- rpng2 - progressive-model PNG display program readpng2.c
-
- ---------------------------------------------------------------------------
-
- Changelog:
- - 1.01: initial public release
- - 1.02: added code to skip unused chunks (GR-P)
-
- ---------------------------------------------------------------------------
-
- Copyright (c) 1998-2002 Greg Roelofs. All rights reserved.
-
- This software is provided "as is," without warranty of any kind,
- express or implied. In no event shall the author or contributors
- be held liable for any damages arising in any way from the use of
- this software.
-
- Permission is granted to anyone to use this software for any purpose,
- including commercial applications, and to alter it and redistribute
- it freely, subject to the following restrictions:
-
- 1. Redistributions of source code must retain the above copyright
- notice, disclaimer, and this list of conditions.
- 2. Redistributions in binary form must reproduce the above copyright
- notice, disclaimer, and this list of conditions in the documenta-
- tion and/or other materials provided with the distribution.
- 3. All advertising materials mentioning features or use of this
- software must display the following acknowledgment:
-
- This product includes software developed by Greg Roelofs
- and contributors for the book, "PNG: The Definitive Guide,"
- published by O'Reilly and Associates.
-
- ---------------------------------------------------------------------------*/
-
-
-#include <stdlib.h> /* for exit() prototype */
-
-#include "png.h" /* libpng header; includes zlib.h and setjmp.h */
-#include "readpng2.h" /* typedefs, common macros, public prototypes */
-
-
-/* local prototypes */
-
-static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr);
-static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
- png_uint_32 row_num, int pass);
-static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr);
-static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg);
-
-
-
-
-void readpng2_version_info(void)
-{
-#if defined(PNG_ASSEMBLER_CODE_SUPPORTED) && \
- (defined(__i386__) || defined(_M_IX86)) && \
- defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
- /*
- * WARNING: This preprocessor approach means that the following code
- * cannot be used with a libpng DLL older than 1.2.0--the
- * compiled-in symbols for the new functions will not exist.
- * (Could use dlopen() and dlsym() on Unix and corresponding
- * calls for Windows, but not portable...)
- */
- {
- int mmxsupport = png_mmx_support();
- if (mmxsupport < 0)
- fprintf(stderr, " Compiled with libpng %s; using libpng %s "
- "without MMX support.\n", PNG_LIBPNG_VER_STRING, png_libpng_ver);
- else {
- int compilerID;
- png_uint_32 mmx_mask = png_get_mmx_flagmask(
- PNG_SELECT_READ | PNG_SELECT_WRITE, &compilerID);
-
- fprintf(stderr, " Compiled with libpng %s; using libpng %s "
- "with MMX support\n (%s version).", PNG_LIBPNG_VER_STRING,
- png_libpng_ver, compilerID == 1? "MSVC++" :
- (compilerID == 2? "GNU C" : "unknown"));
- fprintf(stderr, " Processor %s MMX instructions.\n",
- mmxsupport? "supports" : "does not support");
- if (mmxsupport > 0) {
- int num_optims = 0;
-
- fprintf(stderr,
- " Potential MMX optimizations supported by libpng:\n");
- if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_SUB)
- ++num_optims;
- if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_UP)
- ++num_optims;
- if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_AVG)
- ++num_optims;
- if (mmx_mask & PNG_ASM_FLAG_MMX_READ_FILTER_PAETH)
- ++num_optims;
- if (num_optims)
- fprintf(stderr,
- " decoding %s row filters (reading)\n",
- (num_optims == 4)? "all non-trivial" : "some");
- if (mmx_mask & PNG_ASM_FLAG_MMX_READ_COMBINE_ROW) {
- fprintf(stderr, " combining rows (reading)\n");
- ++num_optims;
- }
- if (mmx_mask & PNG_ASM_FLAG_MMX_READ_INTERLACE) {
- fprintf(stderr,
- " expanding interlacing (reading)\n");
- ++num_optims;
- }
- mmx_mask &= ~( PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \
- | PNG_ASM_FLAG_MMX_READ_INTERLACE \
- | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \
- | PNG_ASM_FLAG_MMX_READ_FILTER_UP \
- | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \
- | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH );
- if (mmx_mask) {
- fprintf(stderr, " other (unknown)\n");
- ++num_optims;
- }
- if (num_optims == 0)
- fprintf(stderr, " (none)\n");
- }
- }
- }
-#else
- fprintf(stderr, " Compiled with libpng %s; using libpng %s "
- "without MMX support.\n", PNG_LIBPNG_VER_STRING, png_libpng_ver);
-#endif
-
- fprintf(stderr, " Compiled with zlib %s; using zlib %s.\n",
- ZLIB_VERSION, zlib_version);
-}
-
-
-
-
-int readpng2_check_sig(uch *sig, int num)
-{
- return png_check_sig(sig, num);
-}
-
-
-
-
-/* returns 0 for success, 2 for libpng problem, 4 for out of memory */
-
-int readpng2_init(mainprog_info *mainprog_ptr)
-{
- png_structp png_ptr; /* note: temporary variables! */
- png_infop info_ptr;
-
-
- /* could also replace libpng warning-handler (final NULL), but no need: */
-
- png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr,
- readpng2_error_handler, NULL);
- if (!png_ptr)
- return 4; /* out of memory */
-
- info_ptr = png_create_info_struct(png_ptr);
- if (!info_ptr) {
- png_destroy_read_struct(&png_ptr, NULL, NULL);
- return 4; /* out of memory */
- }
-
-
- /* we could create a second info struct here (end_info), but it's only
- * useful if we want to keep pre- and post-IDAT chunk info separated
- * (mainly for PNG-aware image editors and converters) */
-
-
- /* setjmp() must be called in every function that calls a PNG-reading
- * libpng function, unless an alternate error handler was installed--
- * but compatible error handlers must either use longjmp() themselves
- * (as in this program) or exit immediately, so here we are: */
-
- if (setjmp(mainprog_ptr->jmpbuf)) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- return 2;
- }
-
- /* prepare the reader to ignore all recognized chunks whose data isn't
- * going to be used, i.e., all chunks recognized by libpng except for
- * IHDR, PLTE, IDAT, IEND, tRNS, bKGD, gAMA, and sRGB : */
-
-#if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
- {
-#ifndef HANDLE_CHUNK_NEVER
-/* prior to libpng-1.2.5, this macro was internal, so we define it here. */
-# define HANDLE_CHUNK_NEVER 1
-#endif
- /* these byte strings were copied from png.h.
- * If a future libpng version recognizes more chunks, add them
- * to this list. If a future version of readpng2.c recognizes
- * more chunks, delete them from this list. */
- png_byte png_chunk_types_to_ignore[]=
- { 99, 72, 82, 77, '\0', /* cHRM */
- 104, 73, 83, 84, '\0', /* hIST */
- 105, 67, 67, 80, '\0', /* iCCP */
- 105, 84, 88, 116, '\0', /* iTXt */
- 111, 70, 70, 115, '\0', /* oFFs */
- 112, 67, 65, 76, '\0', /* pCAL */
- 115, 67, 65, 76, '\0', /* sCAL */
- 112, 72, 89, 115, '\0', /* pHYs */
- 115, 66, 73, 84, '\0', /* sBIT */
- 115, 80, 76, 84, '\0', /* sPLT */
- 116, 69, 88, 116, '\0', /* tEXt */
- 116, 73, 77, 69, '\0', /* tIME */
- 122, 84, 88, 116, '\0'}; /* zTXt */
-#define NUM_PNG_CHUNK_TYPES_TO_IGNORE 13
-
- png_set_keep_unknown_chunks(png_ptr, HANDLE_CHUNK_NEVER,
- png_chunk_types_to_ignore, NUM_PNG_CHUNK_TYPES_TO_IGNORE);
- }
-#endif
-
- /* instead of doing png_init_io() here, now we set up our callback
- * functions for progressive decoding */
-
- png_set_progressive_read_fn(png_ptr, mainprog_ptr,
- readpng2_info_callback, readpng2_row_callback, readpng2_end_callback);
-
-
- /*
- * may as well enable or disable MMX routines here, if supported;
- *
- * to enable all: mask = png_get_mmx_flagmask (
- * PNG_SELECT_READ | PNG_SELECT_WRITE, &compilerID);
- * flags = png_get_asm_flags (png_ptr);
- * flags |= mask;
- * png_set_asm_flags (png_ptr, flags);
- *
- * to disable all: mask = png_get_mmx_flagmask (
- * PNG_SELECT_READ | PNG_SELECT_WRITE, &compilerID);
- * flags = png_get_asm_flags (png_ptr);
- * flags &= ~mask;
- * png_set_asm_flags (png_ptr, flags);
- */
-
-#if (defined(__i386__) || defined(_M_IX86)) && \
- defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
- /*
- * WARNING: This preprocessor approach means that the following code
- * cannot be used with a libpng DLL older than 1.2.0--the
- * compiled-in symbols for the new functions will not exist.
- * (Could use dlopen() and dlsym() on Unix and corresponding
- * calls for Windows, but not portable...)
- */
- {
-#ifdef PNG_ASSEMBLER_CODE_SUPPORTED
- png_uint_32 mmx_disable_mask = 0;
- png_uint_32 asm_flags, mmx_mask;
- int compilerID;
-
- if (mainprog_ptr->nommxfilters)
- mmx_disable_mask |= ( PNG_ASM_FLAG_MMX_READ_FILTER_SUB \
- | PNG_ASM_FLAG_MMX_READ_FILTER_UP \
- | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \
- | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH );
- if (mainprog_ptr->nommxcombine)
- mmx_disable_mask |= PNG_ASM_FLAG_MMX_READ_COMBINE_ROW;
- if (mainprog_ptr->nommxinterlace)
- mmx_disable_mask |= PNG_ASM_FLAG_MMX_READ_INTERLACE;
- asm_flags = png_get_asm_flags(png_ptr);
- png_set_asm_flags(png_ptr, asm_flags & ~mmx_disable_mask);
-
-
- /* Now query libpng's asm settings, just for yuks. Note that this
- * differs from the querying of its *potential* MMX capabilities
- * in readpng2_version_info(); this is true runtime verification. */
-
- asm_flags = png_get_asm_flags(png_ptr);
- mmx_mask = png_get_mmx_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE,
- &compilerID);
- if (asm_flags & PNG_ASM_FLAG_MMX_SUPPORT_COMPILED)
- fprintf(stderr,
- " MMX support (%s version) is compiled into libpng\n",
- compilerID == 1? "MSVC++" :
- (compilerID == 2? "GNU C" : "unknown"));
- else
- fprintf(stderr, " MMX support is not compiled into libpng\n");
- fprintf(stderr, " MMX instructions are %ssupported by CPU\n",
- (asm_flags & PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU)? "" : "not ");
- fprintf(stderr, " MMX read support for combining rows is %sabled\n",
- (asm_flags & PNG_ASM_FLAG_MMX_READ_COMBINE_ROW)? "en" : "dis");
- fprintf(stderr,
- " MMX read support for expanding interlacing is %sabled\n",
- (asm_flags & PNG_ASM_FLAG_MMX_READ_INTERLACE)? "en" : "dis");
- fprintf(stderr, " MMX read support for \"sub\" filter is %sabled\n",
- (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_SUB)? "en" : "dis");
- fprintf(stderr, " MMX read support for \"up\" filter is %sabled\n",
- (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_UP)? "en" : "dis");
- fprintf(stderr, " MMX read support for \"avg\" filter is %sabled\n",
- (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_AVG)? "en" : "dis");
- fprintf(stderr, " MMX read support for \"Paeth\" filter is %sabled\n",
- (asm_flags & PNG_ASM_FLAG_MMX_READ_FILTER_PAETH)? "en" : "dis");
- asm_flags &= (mmx_mask & ~( PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \
- | PNG_ASM_FLAG_MMX_READ_INTERLACE \
- | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \
- | PNG_ASM_FLAG_MMX_READ_FILTER_UP \
- | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \
- | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH ));
- if (asm_flags)
- fprintf(stderr,
- " additional MMX support is also enabled (0x%02lx)\n",
- asm_flags);
-#else /* !PNG_ASSEMBLER_CODE_SUPPORTED */
- fprintf(stderr, " MMX querying is disabled in libpng.\n");
-#endif /* ?PNG_ASSEMBLER_CODE_SUPPORTED */
- }
-#endif
-
-
- /* make sure we save our pointers for use in readpng2_decode_data() */
-
- mainprog_ptr->png_ptr = png_ptr;
- mainprog_ptr->info_ptr = info_ptr;
-
-
- /* and that's all there is to initialization */
-
- return 0;
-}
-
-
-
-
-/* returns 0 for success, 2 for libpng (longjmp) problem */
-
-int readpng2_decode_data(mainprog_info *mainprog_ptr, uch *rawbuf, ulg length)
-{
- png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
- png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
-
-
- /* setjmp() must be called in every function that calls a PNG-reading
- * libpng function */
-
- if (setjmp(mainprog_ptr->jmpbuf)) {
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- mainprog_ptr->png_ptr = NULL;
- mainprog_ptr->info_ptr = NULL;
- return 2;
- }
-
-
- /* hand off the next chunk of input data to libpng for decoding */
-
- png_process_data(png_ptr, info_ptr, rawbuf, length);
-
- return 0;
-}
-
-
-
-
-static void readpng2_info_callback(png_structp png_ptr, png_infop info_ptr)
-{
- mainprog_info *mainprog_ptr;
- int color_type, bit_depth;
- double gamma;
-
-
- /* setjmp() doesn't make sense here, because we'd either have to exit(),
- * longjmp() ourselves, or return control to libpng, which doesn't want
- * to see us again. By not doing anything here, libpng will instead jump
- * to readpng2_decode_data(), which can return an error value to the main
- * program. */
-
-
- /* retrieve the pointer to our special-purpose struct, using the png_ptr
- * that libpng passed back to us (i.e., not a global this time--there's
- * no real difference for a single image, but for a multithreaded browser
- * decoding several PNG images at the same time, one needs to avoid mixing
- * up different images' structs) */
-
- mainprog_ptr = png_get_progressive_ptr(png_ptr);
-
- if (mainprog_ptr == NULL) { /* we be hosed */
- fprintf(stderr,
- "readpng2 error: main struct not recoverable in info_callback.\n");
- fflush(stderr);
- return;
- /*
- * Alternatively, we could call our error-handler just like libpng
- * does, which would effectively terminate the program. Since this
- * can only happen if png_ptr gets redirected somewhere odd or the
- * main PNG struct gets wiped, we're probably toast anyway. (If
- * png_ptr itself is NULL, we would not have been called.)
- */
- }
-
-
- /* this is just like in the non-progressive case */
-
- png_get_IHDR(png_ptr, info_ptr, &mainprog_ptr->width,
- &mainprog_ptr->height, &bit_depth, &color_type, NULL, NULL, NULL);
-
-
- /* since we know we've read all of the PNG file's "header" (i.e., up
- * to IDAT), we can check for a background color here */
-
- if (mainprog_ptr->need_bgcolor &&
- png_get_valid(png_ptr, info_ptr, PNG_INFO_bKGD))
- {
- png_color_16p pBackground;
-
- /* it is not obvious from the libpng documentation, but this function
- * takes a pointer to a pointer, and it always returns valid red,
- * green and blue values, regardless of color_type: */
- png_get_bKGD(png_ptr, info_ptr, &pBackground);
-
- /* however, it always returns the raw bKGD data, regardless of any
- * bit-depth transformations, so check depth and adjust if necessary */
- if (bit_depth == 16) {
- mainprog_ptr->bg_red = pBackground->red >> 8;
- mainprog_ptr->bg_green = pBackground->green >> 8;
- mainprog_ptr->bg_blue = pBackground->blue >> 8;
- } else if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) {
- if (bit_depth == 1)
- mainprog_ptr->bg_red = mainprog_ptr->bg_green =
- mainprog_ptr->bg_blue = pBackground->gray? 255 : 0;
- else if (bit_depth == 2)
- mainprog_ptr->bg_red = mainprog_ptr->bg_green =
- mainprog_ptr->bg_blue = (255/3) * pBackground->gray;
- else /* bit_depth == 4 */
- mainprog_ptr->bg_red = mainprog_ptr->bg_green =
- mainprog_ptr->bg_blue = (255/15) * pBackground->gray;
- } else {
- mainprog_ptr->bg_red = (uch)pBackground->red;
- mainprog_ptr->bg_green = (uch)pBackground->green;
- mainprog_ptr->bg_blue = (uch)pBackground->blue;
- }
- }
-
-
- /* as before, let libpng expand palette images to RGB, low-bit-depth
- * grayscale images to 8 bits, transparency chunks to full alpha channel;
- * strip 16-bit-per-sample images to 8 bits per sample; and convert
- * grayscale to RGB[A] */
-
- if (color_type == PNG_COLOR_TYPE_PALETTE)
- png_set_expand(png_ptr);
- if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
- png_set_expand(png_ptr);
- if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
- png_set_expand(png_ptr);
- if (bit_depth == 16)
- png_set_strip_16(png_ptr);
- if (color_type == PNG_COLOR_TYPE_GRAY ||
- color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
- png_set_gray_to_rgb(png_ptr);
-
-
- /* Unlike the basic viewer, which was designed to operate on local files,
- * this program is intended to simulate a web browser--even though we
- * actually read from a local file, too. But because we are pretending
- * that most of the images originate on the Internet, we follow the recom-
- * mendation of the sRGB proposal and treat unlabelled images (no gAMA
- * chunk) as existing in the sRGB color space. That is, we assume that
- * such images have a file gamma of 0.45455, which corresponds to a PC-like
- * display system. This change in assumptions will have no effect on a
- * PC-like system, but on a Mac, SGI, NeXT or other system with a non-
- * identity lookup table, it will darken unlabelled images, which effec-
- * tively favors images from PC-like systems over those originating on
- * the local platform. Note that mainprog_ptr->display_exponent is the
- * "gamma" value for the entire display system, i.e., the product of
- * LUT_exponent and CRT_exponent. */
-
- if (png_get_gAMA(png_ptr, info_ptr, &gamma))
- png_set_gamma(png_ptr, mainprog_ptr->display_exponent, gamma);
- else
- png_set_gamma(png_ptr, mainprog_ptr->display_exponent, 0.45455);
-
-
- /* we'll let libpng expand interlaced images, too */
-
- mainprog_ptr->passes = png_set_interlace_handling(png_ptr);
-
-
- /* all transformations have been registered; now update info_ptr data and
- * then get rowbytes and channels */
-
- png_read_update_info(png_ptr, info_ptr);
-
- mainprog_ptr->rowbytes = (int)png_get_rowbytes(png_ptr, info_ptr);
- mainprog_ptr->channels = png_get_channels(png_ptr, info_ptr);
-
-
- /* Call the main program to allocate memory for the image buffer and
- * initialize windows and whatnot. (The old-style function-pointer
- * invocation is used for compatibility with a few supposedly ANSI
- * compilers that nevertheless barf on "fn_ptr()"-style syntax.) */
-
- (*mainprog_ptr->mainprog_init)();
-
-
- /* and that takes care of initialization */
-
- return;
-}
-
-
-
-
-
-static void readpng2_row_callback(png_structp png_ptr, png_bytep new_row,
- png_uint_32 row_num, int pass)
-{
- mainprog_info *mainprog_ptr;
-
-
- /* first check whether the row differs from the previous pass; if not,
- * nothing to combine or display */
-
- if (!new_row)
- return;
-
-
- /* retrieve the pointer to our special-purpose struct so we can access
- * the old rows and image-display callback function */
-
- mainprog_ptr = png_get_progressive_ptr(png_ptr);
-
-
- /* save the pass number for optional use by the front end */
-
- mainprog_ptr->pass = pass;
-
-
- /* have libpng either combine the new row data with the existing row data
- * from previous passes (if interlaced) or else just copy the new row
- * into the main program's image buffer */
-
- png_progressive_combine_row(png_ptr, mainprog_ptr->row_pointers[row_num],
- new_row);
-
-
- /* finally, call the display routine in the main program with the number
- * of the row we just updated */
-
- (*mainprog_ptr->mainprog_display_row)(row_num);
-
-
- /* and we're ready for more */
-
- return;
-}
-
-
-
-
-
-static void readpng2_end_callback(png_structp png_ptr, png_infop info_ptr)
-{
- mainprog_info *mainprog_ptr;
-
-
- /* retrieve the pointer to our special-purpose struct */
-
- mainprog_ptr = png_get_progressive_ptr(png_ptr);
-
-
- /* let the main program know that it should flush any buffered image
- * data to the display now and set a "done" flag or whatever, but note
- * that it SHOULD NOT DESTROY THE PNG STRUCTS YET--in other words, do
- * NOT call readpng2_cleanup() either here or in the finish_display()
- * routine; wait until control returns to the main program via
- * readpng2_decode_data() */
-
- (*mainprog_ptr->mainprog_finish_display)();
-
-
- /* all done */
-
- return;
-}
-
-
-
-
-
-void readpng2_cleanup(mainprog_info *mainprog_ptr)
-{
- png_structp png_ptr = (png_structp)mainprog_ptr->png_ptr;
- png_infop info_ptr = (png_infop)mainprog_ptr->info_ptr;
-
- if (png_ptr && info_ptr)
- png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
-
- mainprog_ptr->png_ptr = NULL;
- mainprog_ptr->info_ptr = NULL;
-}
-
-
-
-
-
-static void readpng2_error_handler(png_structp png_ptr, png_const_charp msg)
-{
- mainprog_info *mainprog_ptr;
-
- /* This function, aside from the extra step of retrieving the "error
- * pointer" (below) and the fact that it exists within the application
- * rather than within libpng, is essentially identical to libpng's
- * default error handler. The second point is critical: since both
- * setjmp() and longjmp() are called from the same code, they are
- * guaranteed to have compatible notions of how big a jmp_buf is,
- * regardless of whether _BSD_SOURCE or anything else has (or has not)
- * been defined. */
-
- fprintf(stderr, "readpng2 libpng error: %s\n", msg);
- fflush(stderr);
-
- mainprog_ptr = png_get_error_ptr(png_ptr);
- if (mainprog_ptr == NULL) { /* we are completely hosed now */
- fprintf(stderr,
- "readpng2 severe error: jmpbuf not recoverable; terminating.\n");
- fflush(stderr);
- exit(99);
- }
-
- longjmp(mainprog_ptr->jmpbuf, 1);
-}
projects / synfig.git / blobdiff