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Diffstat (limited to 'src/jpeg-6b/jdatadst.c')
-rw-r--r-- | src/jpeg-6b/jdatadst.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/src/jpeg-6b/jdatadst.c b/src/jpeg-6b/jdatadst.c new file mode 100644 index 00000000..a8f6fb0e --- /dev/null +++ b/src/jpeg-6b/jdatadst.c @@ -0,0 +1,151 @@ +/* + * jdatadst.c + * + * Copyright (C) 1994-1996, Thomas G. Lane. + * This file is part of the Independent JPEG Group's software. + * For conditions of distribution and use, see the accompanying README file. + * + * This file contains compression data destination routines for the case of + * emitting JPEG data to a file (or any stdio stream). While these routines + * are sufficient for most applications, some will want to use a different + * destination manager. + * IMPORTANT: we assume that fwrite() will correctly transcribe an array of + * JOCTETs into 8-bit-wide elements on external storage. If char is wider + * than 8 bits on your machine, you may need to do some tweaking. + */ + +/* this is not a core library module, so it doesn't define JPEG_INTERNALS */ +#include "jinclude.h" +#include "jpeglib.h" +#include "jerror.h" + + +/* Expanded data destination object for stdio output */ + +typedef struct { + struct jpeg_destination_mgr pub; /* public fields */ + + FILE * outfile; /* target stream */ + JOCTET * buffer; /* start of buffer */ +} my_destination_mgr; + +typedef my_destination_mgr * my_dest_ptr; + +#define OUTPUT_BUF_SIZE 4096 /* choose an efficiently fwrite'able size */ + + +/* + * Initialize destination --- called by jpeg_start_compress + * before any data is actually written. + */ + +METHODDEF(void) +init_destination (j_compress_ptr cinfo) +{ + my_dest_ptr dest = (my_dest_ptr) cinfo->dest; + + /* Allocate the output buffer --- it will be released when done with image */ + dest->buffer = (JOCTET *) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, + OUTPUT_BUF_SIZE * SIZEOF(JOCTET)); + + dest->pub.next_output_byte = dest->buffer; + dest->pub.free_in_buffer = OUTPUT_BUF_SIZE; +} + + +/* + * Empty the output buffer --- called whenever buffer fills up. + * + * In typical applications, this should write the entire output buffer + * (ignoring the current state of next_output_byte & free_in_buffer), + * reset the pointer & count to the start of the buffer, and return TRUE + * indicating that the buffer has been dumped. + * + * In applications that need to be able to suspend compression due to output + * overrun, a FALSE return indicates that the buffer cannot be emptied now. + * In this situation, the compressor will return to its caller (possibly with + * an indication that it has not accepted all the supplied scanlines). The + * application should resume compression after it has made more room in the + * output buffer. Note that there are substantial restrictions on the use of + * suspension --- see the documentation. + * + * When suspending, the compressor will back up to a convenient restart point + * (typically the start of the current MCU). next_output_byte & free_in_buffer + * indicate where the restart point will be if the current call returns FALSE. + * Data beyond this point will be regenerated after resumption, so do not + * write it out when emptying the buffer externally. + */ + +METHODDEF(boolean) +empty_output_buffer (j_compress_ptr cinfo) +{ + my_dest_ptr dest = (my_dest_ptr) cinfo->dest; + + if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) != + (size_t) OUTPUT_BUF_SIZE) + ERREXIT(cinfo, JERR_FILE_WRITE); + + dest->pub.next_output_byte = dest->buffer; + dest->pub.free_in_buffer = OUTPUT_BUF_SIZE; + + return TRUE; +} + + +/* + * Terminate destination --- called by jpeg_finish_compress + * after all data has been written. Usually needs to flush buffer. + * + * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding + * application must deal with any cleanup that should happen even + * for error exit. + */ + +METHODDEF(void) +term_destination (j_compress_ptr cinfo) +{ + my_dest_ptr dest = (my_dest_ptr) cinfo->dest; + size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer; + + /* Write any data remaining in the buffer */ + if (datacount > 0) { + if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount) + ERREXIT(cinfo, JERR_FILE_WRITE); + } + fflush(dest->outfile); + /* Make sure we wrote the output file OK */ + if (ferror(dest->outfile)) + ERREXIT(cinfo, JERR_FILE_WRITE); +} + + +/* + * Prepare for output to a stdio stream. + * The caller must have already opened the stream, and is responsible + * for closing it after finishing compression. + */ + +GLOBAL(void) +jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile) +{ + my_dest_ptr dest; + + /* The destination object is made permanent so that multiple JPEG images + * can be written to the same file without re-executing jpeg_stdio_dest. + * This makes it dangerous to use this manager and a different destination + * manager serially with the same JPEG object, because their private object + * sizes may be different. Caveat programmer. + */ + if (cinfo->dest == NULL) { /* first time for this JPEG object? */ + cinfo->dest = (struct jpeg_destination_mgr *) + (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, + SIZEOF(my_destination_mgr)); + } + + dest = (my_dest_ptr) cinfo->dest; + dest->pub.init_destination = init_destination; + dest->pub.empty_output_buffer = empty_output_buffer; + dest->pub.term_destination = term_destination; + dest->outfile = outfile; +} |