144 lines
4.0 KiB
C
144 lines
4.0 KiB
C
/*
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Copyright (C) 1998 by Tor Andersson and Jorrit Tyberghein
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free
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Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/* !!! not standard... written by Tor Andersson !!!
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* get data from memory buffer instead of from file
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* assumes that the entire file is in one large block of memory
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*
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*/
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/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
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#include "Jpeg6/jinclude.h"
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#include "Jpeg6/jpeglib.h"
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#include "Jpeg6/jerror.h"
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/* Expanded data source object for stdio input */
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typedef struct {
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struct jpeg_source_mgr pub; /* public fields */
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FILE * infile; /* source stream */
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JOCTET * buffer; /* start of buffer */
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boolean start_of_file; /* have we gotten any data yet? */
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} my_source_mgr;
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typedef my_source_mgr * my_src_ptr;
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/*
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* Initialize source --- called by jpeg_read_header
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* before any data is actually read.
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*/
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static void
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init_source (j_decompress_ptr cinfo)
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{
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my_src_ptr src = (my_src_ptr) cinfo->src;
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/* We reset the empty-input-file flag for each image,
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* but we don't clear the input buffer.
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* This is correct behavior for reading a series of images from one source.
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*/
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src->start_of_file = TRUE;
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}
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/*
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* Fill the input buffer --- called whenever buffer is emptied.
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* should never happen :)
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*/
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static boolean
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fill_input_buffer (j_decompress_ptr cinfo)
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{
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/* no-op */
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return TRUE;
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}
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/*
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* Skip data --- used to skip over a potentially large amount of
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* uninteresting data (such as an APPn marker).
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*/
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static void
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skip_input_data (j_decompress_ptr cinfo, long num_bytes)
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{
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my_src_ptr src = (my_src_ptr) cinfo->src;
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if (num_bytes > 0) {
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src->pub.next_input_byte += (size_t) num_bytes;
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src->pub.bytes_in_buffer -= (size_t) num_bytes;
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}
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}
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/*
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* Terminate source --- called by jpeg_finish_decompress
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* after all data has been read. Often a no-op.
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*
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* NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
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* application must deal with any cleanup that should happen even
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* for error exit.
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*/
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static void
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term_source (j_decompress_ptr cinfo)
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{
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/* no work necessary here */
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}
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/*
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* Prepare for input from mem buffer.
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* Leaves buffer untouched.
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*/
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void
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my_jpeg_memory_src (j_decompress_ptr cinfo, char * inbfr, int len)
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{
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my_src_ptr src;
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/* The source object and input buffer are made permanent so that a series
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* of JPEG images can be read from the same file by calling jpeg_stdio_src
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* only before the first one. (If we discarded the buffer at the end of
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* one image, we'd likely lose the start of the next one.)
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* This makes it unsafe to use this manager and a different source
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* manager serially with the same JPEG object. Caveat programmer.
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*/
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if (cinfo->src == NULL) { /* first time for this JPEG object? */
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cinfo->src = (struct jpeg_source_mgr *)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
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SIZEOF(my_source_mgr));
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src = (my_src_ptr) cinfo->src;
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src->buffer = (JOCTET *) inbfr;
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}
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src = (my_src_ptr) cinfo->src;
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src->pub.init_source = init_source;
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src->pub.fill_input_buffer = fill_input_buffer;
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src->pub.skip_input_data = skip_input_data;
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src->pub.resync_to_restart = my_jpeg_resync_to_restart; /* use default method */
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src->pub.term_source = term_source;
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src->infile = 0L;
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src->pub.bytes_in_buffer = len; /*!!! sets to entire file len */
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src->pub.next_input_byte = (JOCTET *)inbfr; /*!!! at start of buffer */
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}
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