jdatadst.c

00001 /*
00002  * jdatadst.c
00003  *
00004  * Copyright (C) 1994-1996, Thomas G. Lane.
00005  * Modified 2009-2012 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 
00029 /* Expanded data destination object for stdio output */
00030 
00031 typedef struct {
00032   struct jpeg_destination_mgr pub; /* public fields */
00033 
00034   FILE * outfile;       /* target stream */
00035   JOCTET * buffer;      /* start of buffer */
00036 } my_destination_mgr;
00037 
00038 typedef my_destination_mgr * my_dest_ptr;
00039 
00040 #define OUTPUT_BUF_SIZE  4096   /* choose an efficiently fwrite'able size */
00041 
00042 
00043 /* Expanded data destination object for memory output */
00044 
00045 typedef struct {
00046   struct jpeg_destination_mgr pub; /* public fields */
00047 
00048   unsigned char ** outbuffer;   /* target buffer */
00049   unsigned long * outsize;
00050   unsigned char * newbuffer;    /* newly allocated buffer */
00051   JOCTET * buffer;      /* start of buffer */
00052   size_t bufsize;
00053 } my_mem_destination_mgr;
00054 
00055 typedef my_mem_destination_mgr * my_mem_dest_ptr;
00056 
00057 
00058 /*
00059  * Initialize destination --- called by jpeg_start_compress
00060  * before any data is actually written.
00061  */
00062 
00063 METHODDEF(void)
00064 init_destination (j_compress_ptr cinfo)
00065 {
00066   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
00067 
00068   /* Allocate the output buffer --- it will be released when done with image */
00069   dest->buffer = (JOCTET *)
00070       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
00071                   OUTPUT_BUF_SIZE * SIZEOF(JOCTET));
00072 
00073   dest->pub.next_output_byte = dest->buffer;
00074   dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
00075 }
00076 
00077 METHODDEF(void)
00078 init_mem_destination (j_compress_ptr cinfo)
00079 {
00080   /* no work necessary here */
00081 }
00082 
00083 
00084 /*
00085  * Empty the output buffer --- called whenever buffer fills up.
00086  *
00087  * In typical applications, this should write the entire output buffer
00088  * (ignoring the current state of next_output_byte & free_in_buffer),
00089  * reset the pointer & count to the start of the buffer, and return TRUE
00090  * indicating that the buffer has been dumped.
00091  *
00092  * In applications that need to be able to suspend compression due to output
00093  * overrun, a FALSE return indicates that the buffer cannot be emptied now.
00094  * In this situation, the compressor will return to its caller (possibly with
00095  * an indication that it has not accepted all the supplied scanlines).  The
00096  * application should resume compression after it has made more room in the
00097  * output buffer.  Note that there are substantial restrictions on the use of
00098  * suspension --- see the documentation.
00099  *
00100  * When suspending, the compressor will back up to a convenient restart point
00101  * (typically the start of the current MCU). next_output_byte & free_in_buffer
00102  * indicate where the restart point will be if the current call returns FALSE.
00103  * Data beyond this point will be regenerated after resumption, so do not
00104  * write it out when emptying the buffer externally.
00105  */
00106 
00107 METHODDEF(boolean)
00108 empty_output_buffer (j_compress_ptr cinfo)
00109 {
00110   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
00111 
00112   if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) !=
00113       (size_t) OUTPUT_BUF_SIZE)
00114     ERREXIT(cinfo, JERR_FILE_WRITE);
00115 
00116   dest->pub.next_output_byte = dest->buffer;
00117   dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
00118 
00119   return TRUE;
00120 }
00121 
00122 METHODDEF(boolean)
00123 empty_mem_output_buffer (j_compress_ptr cinfo)
00124 {
00125   size_t nextsize;
00126   JOCTET * nextbuffer;
00127   my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
00128 
00129   /* Try to allocate new buffer with double size */
00130   nextsize = dest->bufsize * 2;
00131   nextbuffer = (JOCTET *) malloc(nextsize);
00132 
00133   if (nextbuffer == NULL)
00134     ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
00135 
00136   MEMCOPY(nextbuffer, dest->buffer, dest->bufsize);
00137 
00138   if (dest->newbuffer != NULL)
00139     free(dest->newbuffer);
00140 
00141   dest->newbuffer = nextbuffer;
00142 
00143   dest->pub.next_output_byte = nextbuffer + dest->bufsize;
00144   dest->pub.free_in_buffer = dest->bufsize;
00145 
00146   dest->buffer = nextbuffer;
00147   dest->bufsize = nextsize;
00148 
00149   return TRUE;
00150 }
00151 
00152 
00153 /*
00154  * Terminate destination --- called by jpeg_finish_compress
00155  * after all data has been written.  Usually needs to flush buffer.
00156  *
00157  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
00158  * application must deal with any cleanup that should happen even
00159  * for error exit.
00160  */
00161 
00162 METHODDEF(void)
00163 term_destination (j_compress_ptr cinfo)
00164 {
00165   my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
00166   size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
00167 
00168   /* Write any data remaining in the buffer */
00169   if (datacount > 0) {
00170     if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount)
00171       ERREXIT(cinfo, JERR_FILE_WRITE);
00172   }
00173   fflush(dest->outfile);
00174   /* Make sure we wrote the output file OK */
00175   if (ferror(dest->outfile))
00176     ERREXIT(cinfo, JERR_FILE_WRITE);
00177 }
00178 
00179 METHODDEF(void)
00180 term_mem_destination (j_compress_ptr cinfo)
00181 {
00182   my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
00183 
00184   *dest->outbuffer = dest->buffer;
00185   *dest->outsize = dest->bufsize - dest->pub.free_in_buffer;
00186 }
00187 
00188 
00189 /*
00190  * Prepare for output to a stdio stream.
00191  * The caller must have already opened the stream, and is responsible
00192  * for closing it after finishing compression.
00193  */
00194 
00195 GLOBAL(void)
00196 jpeg_stdio_dest (j_compress_ptr cinfo, FILE * outfile)
00197 {
00198   my_dest_ptr dest;
00199 
00200   /* The destination object is made permanent so that multiple JPEG images
00201    * can be written to the same file without re-executing jpeg_stdio_dest.
00202    * This makes it dangerous to use this manager and a different destination
00203    * manager serially with the same JPEG object, because their private object
00204    * sizes may be different.  Caveat programmer.
00205    */
00206   if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
00207     cinfo->dest = (struct jpeg_destination_mgr *)
00208       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
00209                   SIZEOF(my_destination_mgr));
00210   }
00211 
00212   dest = (my_dest_ptr) cinfo->dest;
00213   dest->pub.init_destination = init_destination;
00214   dest->pub.empty_output_buffer = empty_output_buffer;
00215   dest->pub.term_destination = term_destination;
00216   dest->outfile = outfile;
00217 }
00218 
00219 
00220 /*
00221  * Prepare for output to a memory buffer.
00222  * The caller may supply an own initial buffer with appropriate size.
00223  * Otherwise, or when the actual data output exceeds the given size,
00224  * the library adapts the buffer size as necessary.
00225  * The standard library functions malloc/free are used for allocating
00226  * larger memory, so the buffer is available to the application after
00227  * finishing compression, and then the application is responsible for
00228  * freeing the requested memory.
00229  * Note:  An initial buffer supplied by the caller is expected to be
00230  * managed by the application.  The library does not free such buffer
00231  * when allocating a larger buffer.
00232  */
00233 
00234 GLOBAL(void)
00235 jpeg_mem_dest (j_compress_ptr cinfo,
00236            unsigned char ** outbuffer, unsigned long * outsize)
00237 {
00238   my_mem_dest_ptr dest;
00239 
00240   if (outbuffer == NULL || outsize == NULL) /* sanity check */
00241     ERREXIT(cinfo, JERR_BUFFER_SIZE);
00242 
00243   /* The destination object is made permanent so that multiple JPEG images
00244    * can be written to the same buffer without re-executing jpeg_mem_dest.
00245    */
00246   if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
00247     cinfo->dest = (struct jpeg_destination_mgr *)
00248       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
00249                   SIZEOF(my_mem_destination_mgr));
00250   }
00251 
00252   dest = (my_mem_dest_ptr) cinfo->dest;
00253   dest->pub.init_destination = init_mem_destination;
00254   dest->pub.empty_output_buffer = empty_mem_output_buffer;
00255   dest->pub.term_destination = term_mem_destination;
00256   dest->outbuffer = outbuffer;
00257   dest->outsize = outsize;
00258   dest->newbuffer = NULL;
00259 
00260   if (*outbuffer == NULL || *outsize == 0) {
00261     /* Allocate initial buffer */
00262     dest->newbuffer = *outbuffer = (unsigned char *) malloc(OUTPUT_BUF_SIZE);
00263     if (dest->newbuffer == NULL)
00264       ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
00265     *outsize = OUTPUT_BUF_SIZE;
00266   }
00267 
00268   dest->pub.next_output_byte = dest->buffer = *outbuffer;
00269   dest->pub.free_in_buffer = dest->bufsize = *outsize;
00270 }