nuclear@26: /*
nuclear@26:  * jdatadst.c
nuclear@26:  *
nuclear@26:  * Copyright (C) 1994-1996, Thomas G. Lane.
nuclear@26:  * This file is part of the Independent JPEG Group's software.
nuclear@26:  * For conditions of distribution and use, see the accompanying README file.
nuclear@26:  *
nuclear@26:  * This file contains compression data destination routines for the case of
nuclear@26:  * emitting JPEG data to a file (or any stdio stream).  While these routines
nuclear@26:  * are sufficient for most applications, some will want to use a different
nuclear@26:  * destination manager.
nuclear@26:  * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
nuclear@26:  * JOCTETs into 8-bit-wide elements on external storage.  If char is wider
nuclear@26:  * than 8 bits on your machine, you may need to do some tweaking.
nuclear@26:  */
nuclear@26: 
nuclear@26: /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
nuclear@26: #include "jinclude.h"
nuclear@26: #include "jpeglib.h"
nuclear@26: #include "jerror.h"
nuclear@26: 
nuclear@26: 
nuclear@26: /* Expanded data destination object for stdio output */
nuclear@26: 
nuclear@26: typedef struct {
nuclear@26:   struct jpeg_destination_mgr pub; /* public fields */
nuclear@26: 
nuclear@26:   FILE * outfile;		/* target stream */
nuclear@26:   JOCTET * buffer;		/* start of buffer */
nuclear@26: } my_destination_mgr;
nuclear@26: 
nuclear@26: typedef my_destination_mgr * my_dest_ptr;
nuclear@26: 
nuclear@26: #define OUTPUT_BUF_SIZE  4096	/* choose an efficiently fwrite'able size */
nuclear@26: 
nuclear@26: 
nuclear@26: /*
nuclear@26:  * Initialize destination --- called by jpeg_start_compress
nuclear@26:  * before any data is actually written.
nuclear@26:  */
nuclear@26: 
nuclear@26: METHODDEF(void)
nuclear@26: init_destination (j_compress_ptr cinfo)
nuclear@26: {
nuclear@26:   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
nuclear@26: 
nuclear@26:   /* Allocate the output buffer --- it will be released when done with image */
nuclear@26:   dest->buffer = (JOCTET *)
nuclear@26:       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
nuclear@26: 				  OUTPUT_BUF_SIZE * SIZEOF(JOCTET));
nuclear@26: 
nuclear@26:   dest->pub.next_output_byte = dest->buffer;
nuclear@26:   dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
nuclear@26: }
nuclear@26: 
nuclear@26: 
nuclear@26: /*
nuclear@26:  * Empty the output buffer --- called whenever buffer fills up.
nuclear@26:  *
nuclear@26:  * In typical applications, this should write the entire output buffer
nuclear@26:  * (ignoring the current state of next_output_byte & free_in_buffer),
nuclear@26:  * reset the pointer & count to the start of the buffer, and return TRUE
nuclear@26:  * indicating that the buffer has been dumped.
nuclear@26:  *
nuclear@26:  * In applications that need to be able to suspend compression due to output
nuclear@26:  * overrun, a FALSE return indicates that the buffer cannot be emptied now.
nuclear@26:  * In this situation, the compressor will return to its caller (possibly with
nuclear@26:  * an indication that it has not accepted all the supplied scanlines).  The
nuclear@26:  * application should resume compression after it has made more room in the
nuclear@26:  * output buffer.  Note that there are substantial restrictions on the use of
nuclear@26:  * suspension --- see the documentation.
nuclear@26:  *
nuclear@26:  * When suspending, the compressor will back up to a convenient restart point
nuclear@26:  * (typically the start of the current MCU). next_output_byte & free_in_buffer
nuclear@26:  * indicate where the restart point will be if the current call returns FALSE.
nuclear@26:  * Data beyond this point will be regenerated after resumption, so do not
nuclear@26:  * write it out when emptying the buffer externally.
nuclear@26:  */
nuclear@26: 
nuclear@26: METHODDEF(boolean)
nuclear@26: empty_output_buffer (j_compress_ptr cinfo)
nuclear@26: {
nuclear@26:   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
nuclear@26: 
nuclear@26:   if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) !=
nuclear@26:       (size_t) OUTPUT_BUF_SIZE)
nuclear@26:     ERREXIT(cinfo, JERR_FILE_WRITE);
nuclear@26: 
nuclear@26:   dest->pub.next_output_byte = dest->buffer;
nuclear@26:   dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
nuclear@26: 
nuclear@26:   return TRUE;
nuclear@26: }
nuclear@26: 
nuclear@26: 
nuclear@26: /*
nuclear@26:  * Terminate destination --- called by jpeg_finish_compress
nuclear@26:  * after all data has been written.  Usually needs to flush buffer.
nuclear@26:  *
nuclear@26:  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
nuclear@26:  * application must deal with any cleanup that should happen even
nuclear@26:  * for error exit.
nuclear@26:  */
nuclear@26: 
nuclear@26: METHODDEF(void)
nuclear@26: term_destination (j_compress_ptr cinfo)
nuclear@26: {
nuclear@26:   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
nuclear@26:   size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
nuclear@26: 
nuclear@26:   /* Write any data remaining in the buffer */
nuclear@26:   if (datacount > 0) {
nuclear@26:     if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount)
nuclear@26:       ERREXIT(cinfo, JERR_FILE_WRITE);
nuclear@26:   }
nuclear@26:   fflush(dest->outfile);
nuclear@26:   /* Make sure we wrote the output file OK */
nuclear@26:   if (ferror(dest->outfile))
nuclear@26:     ERREXIT(cinfo, JERR_FILE_WRITE);
nuclear@26: }
nuclear@26: 
nuclear@26: 
nuclear@26: /*
nuclear@26:  * Prepare for output to a stdio stream.
nuclear@26:  * The caller must have already opened the stream, and is responsible
nuclear@26:  * for closing it after finishing compression.
nuclear@26:  */
nuclear@26: 
nuclear@26: GLOBAL(void)
nuclear@26: jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile)
nuclear@26: {
nuclear@26:   my_dest_ptr dest;
nuclear@26: 
nuclear@26:   /* The destination object is made permanent so that multiple JPEG images
nuclear@26:    * can be written to the same file without re-executing jpeg_stdio_dest.
nuclear@26:    * This makes it dangerous to use this manager and a different destination
nuclear@26:    * manager serially with the same JPEG object, because their private object
nuclear@26:    * sizes may be different.  Caveat programmer.
nuclear@26:    */
nuclear@26:   if (cinfo->dest == NULL) {	/* first time for this JPEG object? */
nuclear@26:     cinfo->dest = (struct jpeg_destination_mgr *)
nuclear@26:       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
nuclear@26: 				  SIZEOF(my_destination_mgr));
nuclear@26:   }
nuclear@26: 
nuclear@26:   dest = (my_dest_ptr) cinfo->dest;
nuclear@26:   dest->pub.init_destination = init_destination;
nuclear@26:   dest->pub.empty_output_buffer = empty_output_buffer;
nuclear@26:   dest->pub.term_destination = term_destination;
nuclear@26:   dest->outfile = outfile;
nuclear@26: }