SAMV71 Xplained Ultra Software Package 1.5

jdatadst_stdio.c

00001 /*
00002  * jdatadst_stdio.c
00003  *
00004  * Copyright (C) 1994-1996, Thomas G. Lane.
00005  * Modified 2009 by Guido Vollbeding.
00006  * This file is part of the Independent JPEG Group's software.
00007  * For conditions of distribution and use, see the accompanying README file.
00008  *
00009  * This file contains compression data destination routines for the case of
00010  * emitting JPEG data to memory or to a file (or any stdio stream).
00011  * While these routines are sufficient for most applications,
00012  * some will want to use a different destination manager.
00013  * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
00014  * JOCTETs into 8-bit-wide elements on external storage.  If char is wider
00015  * than 8 bits on your machine, you may need to do some tweaking.
00016  */
00017 
00018 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
00019 #include "jinclude.h"
00020 #include "jpeglib.h"
00021 #include "jerror.h"
00022 
00023 #ifndef HAVE_STDLIB_H       /* <stdlib.h> should declare malloc(),free() */
00024 extern void * malloc JPP((size_t size));
00025 extern void free JPP((void *ptr));
00026 #endif
00027 
00028 /* Expanded data destination object for stdio output */
00029 
00030 typedef struct {
00031   struct jpeg_destination_mgr pub; /* public fields */
00032 
00033   FILE * outfile;       /* target stream */
00034   JOCTET * buffer;      /* start of buffer */
00035 } my_destination_mgr;
00036 
00037 typedef my_destination_mgr * my_dest_ptr;
00038 
00039 #define OUTPUT_BUF_SIZE  4096   /* choose an efficiently fwrite'able size */
00040 
00041 /*
00042  * Initialize destination --- called by jpeg_start_compress
00043  * before any data is actually written.
00044  */
00045 
00046 METHODDEF(void)
00047 init_destination (j_compress_ptr cinfo)
00048 {
00049   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
00050 
00051   /* Allocate the output buffer --- it will be released when done with image */
00052   dest->buffer = (JOCTET *)
00053       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00054                   OUTPUT_BUF_SIZE * SIZEOF(JOCTET));
00055 
00056   dest->pub.next_output_byte = dest->buffer;
00057   dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
00058 }
00059 
00060 /*
00061  * Empty the output buffer --- called whenever buffer fills up.
00062  *
00063  * In typical applications, this should write the entire output buffer
00064  * (ignoring the current state of next_output_byte & free_in_buffer),
00065  * reset the pointer & count to the start of the buffer, and return TRUE
00066  * indicating that the buffer has been dumped.
00067  *
00068  * In applications that need to be able to suspend compression due to output
00069  * overrun, a FALSE return indicates that the buffer cannot be emptied now.
00070  * In this situation, the compressor will return to its caller (possibly with
00071  * an indication that it has not accepted all the supplied scanlines).  The
00072  * application should resume compression after it has made more room in the
00073  * output buffer.  Note that there are substantial restrictions on the use of
00074  * suspension --- see the documentation.
00075  *
00076  * When suspending, the compressor will back up to a convenient restart point
00077  * (typically the start of the current MCU). next_output_byte & free_in_buffer
00078  * indicate where the restart point will be if the current call returns FALSE.
00079  * Data beyond this point will be regenerated after resumption, so do not
00080  * write it out when emptying the buffer externally.
00081  */
00082 
00083 METHODDEF(boolean)
00084 empty_output_buffer (j_compress_ptr cinfo)
00085 {
00086   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
00087 
00088   if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) !=
00089       (size_t) OUTPUT_BUF_SIZE)
00090     ERREXIT(cinfo, JERR_FILE_WRITE);
00091 
00092   dest->pub.next_output_byte = dest->buffer;
00093   dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
00094 
00095   return TRUE;
00096 }
00097 
00098 /*
00099  * Terminate destination --- called by jpeg_finish_compress
00100  * after all data has been written.  Usually needs to flush buffer.
00101  *
00102  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
00103  * application must deal with any cleanup that should happen even
00104  * for error exit.
00105  */
00106 
00107 METHODDEF(void)
00108 term_destination (j_compress_ptr cinfo)
00109 {
00110   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
00111   size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
00112 
00113   /* Write any data remaining in the buffer */
00114   if (datacount > 0) {
00115     if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount)
00116       ERREXIT(cinfo, JERR_FILE_WRITE);
00117   }
00118   fflush(dest->outfile);
00119   /* Make sure we wrote the output file OK */
00120   if (ferror(dest->outfile))
00121     ERREXIT(cinfo, JERR_FILE_WRITE);
00122 }
00123 
00124 /*
00125  * Prepare for output to a stdio stream.
00126  * The caller must have already opened the stream, and is responsible
00127  * for closing it after finishing compression.
00128  */
00129 
00130 GLOBAL(void)
00131 jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile)
00132 {
00133   my_dest_ptr dest;
00134 
00135   /* The destination object is made permanent so that multiple JPEG images
00136    * can be written to the same file without re-executing jpeg_stdio_dest.
00137    * This makes it dangerous to use this manager and a different destination
00138    * manager serially with the same JPEG object, because their private object
00139    * sizes may be different.  Caveat programmer.
00140    */
00141   if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
00142     cinfo->dest = (struct jpeg_destination_mgr *)
00143       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
00144                   SIZEOF(my_destination_mgr));
00145   }
00146 
00147   dest = (my_dest_ptr) cinfo->dest;
00148   dest->pub.init_destination = init_destination;
00149   dest->pub.empty_output_buffer = empty_output_buffer;
00150   dest->pub.term_destination = term_destination;
00151   dest->outfile = outfile;
00152 }
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