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jdatadst.c
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C/C++ Source or Header
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2000-11-29
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4KB
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133 lines
#include <stdio.h>
#include <stdlib.h>
#include "jpeg.h"
#include "jpeglib.h"
#include "jerror.h"
/* Expanded data destination object for stdio output */
typedef struct {
struct jpeg_destination_mgr pub; /* public fields */
JOCTET *buffer; /* Pointer to buffer */
mjpa_compress_engine *engine;
} my_destination_mgr;
typedef my_destination_mgr *my_dest_ptr;
/*
* 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;
/* Set the pointer to the preallocated buffer */
dest->buffer = dest->engine->output_buffer;
dest->pub.next_output_byte = dest->buffer;
dest->pub.free_in_buffer = dest->engine->output_allocated;
}
/*
* 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)
{
/* Allocate a bigger buffer. */
my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
char *new_buffer;
int new_size, i;
int offset = dest->engine->output_allocated;
new_size = dest->engine->output_allocated * 2;
new_buffer = malloc(new_size);
for(i = 0; i < offset; i++)
new_buffer[i] = dest->engine->output_buffer[i];
free(dest->engine->output_buffer);
dest->engine->output_buffer = new_buffer;
dest->engine->output_allocated = new_size;
dest->buffer = dest->engine->output_buffer;
dest->pub.next_output_byte = dest->buffer + offset;
dest->pub.free_in_buffer = dest->engine->output_allocated - offset;
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)
{
/* Just get the length */
my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
dest->engine->output_size = dest->engine->output_allocated - dest->pub.free_in_buffer;
}
/*
* 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_buffer_dest (j_compress_ptr cinfo, mjpa_compress_engine *engine)
{
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->engine = engine;
}