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      1 /*
      2  * jdatadst-tj.c
      3  *
      4  * This file was part of the Independent JPEG Group's software:
      5  * Copyright (C) 1994-1996, Thomas G. Lane.
      6  * Modified 2009-2012 by Guido Vollbeding.
      7  * libjpeg-turbo Modifications:
      8  * Copyright (C) 2011, 2014, 2016, D. R. Commander.
      9  * For conditions of distribution and use, see the accompanying README.ijg
     10  * file.
     11  *
     12  * This file contains compression data destination routines for the case of
     13  * emitting JPEG data to memory or to a file (or any stdio stream).
     14  * While these routines are sufficient for most applications,
     15  * some will want to use a different destination manager.
     16  * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
     17  * JOCTETs into 8-bit-wide elements on external storage.  If char is wider
     18  * than 8 bits on your machine, you may need to do some tweaking.
     19  */
     20 
     21 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
     22 #include "jinclude.h"
     23 #include "jpeglib.h"
     24 #include "jerror.h"
     25 
     26 #ifndef HAVE_STDLIB_H           /* <stdlib.h> should declare malloc(),free() */
     27 extern void *malloc (size_t size);
     28 extern void free (void *ptr);
     29 #endif
     30 
     31 
     32 #define OUTPUT_BUF_SIZE  4096   /* choose an efficiently fwrite'able size */
     33 
     34 
     35 /* Expanded data destination object for memory output */
     36 
     37 typedef struct {
     38   struct jpeg_destination_mgr pub; /* public fields */
     39 
     40   unsigned char **outbuffer;    /* target buffer */
     41   unsigned long *outsize;
     42   unsigned char *newbuffer;     /* newly allocated buffer */
     43   JOCTET *buffer;               /* start of buffer */
     44   size_t bufsize;
     45   boolean alloc;
     46 } my_mem_destination_mgr;
     47 
     48 typedef my_mem_destination_mgr *my_mem_dest_ptr;
     49 
     50 
     51 /*
     52  * Initialize destination --- called by jpeg_start_compress
     53  * before any data is actually written.
     54  */
     55 
     56 METHODDEF(void)
     57 init_mem_destination (j_compress_ptr cinfo)
     58 {
     59   /* no work necessary here */
     60 }
     61 
     62 
     63 /*
     64  * Empty the output buffer --- called whenever buffer fills up.
     65  *
     66  * In typical applications, this should write the entire output buffer
     67  * (ignoring the current state of next_output_byte & free_in_buffer),
     68  * reset the pointer & count to the start of the buffer, and return TRUE
     69  * indicating that the buffer has been dumped.
     70  *
     71  * In applications that need to be able to suspend compression due to output
     72  * overrun, a FALSE return indicates that the buffer cannot be emptied now.
     73  * In this situation, the compressor will return to its caller (possibly with
     74  * an indication that it has not accepted all the supplied scanlines).  The
     75  * application should resume compression after it has made more room in the
     76  * output buffer.  Note that there are substantial restrictions on the use of
     77  * suspension --- see the documentation.
     78  *
     79  * When suspending, the compressor will back up to a convenient restart point
     80  * (typically the start of the current MCU). next_output_byte & free_in_buffer
     81  * indicate where the restart point will be if the current call returns FALSE.
     82  * Data beyond this point will be regenerated after resumption, so do not
     83  * write it out when emptying the buffer externally.
     84  */
     85 
     86 METHODDEF(boolean)
     87 empty_mem_output_buffer (j_compress_ptr cinfo)
     88 {
     89   size_t nextsize;
     90   JOCTET *nextbuffer;
     91   my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
     92 
     93   if (!dest->alloc) ERREXIT(cinfo, JERR_BUFFER_SIZE);
     94 
     95   /* Try to allocate new buffer with double size */
     96   nextsize = dest->bufsize * 2;
     97   nextbuffer = (JOCTET *) malloc(nextsize);
     98 
     99   if (nextbuffer == NULL)
    100     ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
    101 
    102   MEMCOPY(nextbuffer, dest->buffer, dest->bufsize);
    103 
    104   if (dest->newbuffer != NULL)
    105     free(dest->newbuffer);
    106 
    107   dest->newbuffer = nextbuffer;
    108 
    109   dest->pub.next_output_byte = nextbuffer + dest->bufsize;
    110   dest->pub.free_in_buffer = dest->bufsize;
    111 
    112   dest->buffer = nextbuffer;
    113   dest->bufsize = nextsize;
    114 
    115   return TRUE;
    116 }
    117 
    118 
    119 /*
    120  * Terminate destination --- called by jpeg_finish_compress
    121  * after all data has been written.  Usually needs to flush buffer.
    122  *
    123  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
    124  * application must deal with any cleanup that should happen even
    125  * for error exit.
    126  */
    127 
    128 METHODDEF(void)
    129 term_mem_destination (j_compress_ptr cinfo)
    130 {
    131   my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
    132 
    133   if (dest->alloc) *dest->outbuffer = dest->buffer;
    134   *dest->outsize = (unsigned long)(dest->bufsize - dest->pub.free_in_buffer);
    135 }
    136 
    137 
    138 /*
    139  * Prepare for output to a memory buffer.
    140  * The caller may supply an own initial buffer with appropriate size.
    141  * Otherwise, or when the actual data output exceeds the given size,
    142  * the library adapts the buffer size as necessary.
    143  * The standard library functions malloc/free are used for allocating
    144  * larger memory, so the buffer is available to the application after
    145  * finishing compression, and then the application is responsible for
    146  * freeing the requested memory.
    147  */
    148 
    149 GLOBAL(void)
    150 jpeg_mem_dest_tj (j_compress_ptr cinfo,
    151                unsigned char **outbuffer, unsigned long *outsize,
    152                boolean alloc)
    153 {
    154   boolean reused = FALSE;
    155   my_mem_dest_ptr dest;
    156 
    157   if (outbuffer == NULL || outsize == NULL)     /* sanity check */
    158     ERREXIT(cinfo, JERR_BUFFER_SIZE);
    159 
    160   /* The destination object is made permanent so that multiple JPEG images
    161    * can be written to the same buffer without re-executing jpeg_mem_dest.
    162    */
    163   if (cinfo->dest == NULL) {    /* first time for this JPEG object? */
    164     cinfo->dest = (struct jpeg_destination_mgr *)
    165       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
    166                                   sizeof(my_mem_destination_mgr));
    167     dest = (my_mem_dest_ptr) cinfo->dest;
    168     dest->newbuffer = NULL;
    169     dest->buffer = NULL;
    170   } else if (cinfo->dest->init_destination != init_mem_destination) {
    171     /* It is unsafe to reuse the existing destination manager unless it was
    172      * created by this function.
    173      */
    174     ERREXIT(cinfo, JERR_BUFFER_SIZE);
    175   }
    176 
    177   dest = (my_mem_dest_ptr) cinfo->dest;
    178   dest->pub.init_destination = init_mem_destination;
    179   dest->pub.empty_output_buffer = empty_mem_output_buffer;
    180   dest->pub.term_destination = term_mem_destination;
    181   if (dest->buffer == *outbuffer && *outbuffer != NULL && alloc)
    182     reused = TRUE;
    183   dest->outbuffer = outbuffer;
    184   dest->outsize = outsize;
    185   dest->alloc = alloc;
    186 
    187   if (*outbuffer == NULL || *outsize == 0) {
    188     if (alloc) {
    189       /* Allocate initial buffer */
    190       dest->newbuffer = *outbuffer = (unsigned char *) malloc(OUTPUT_BUF_SIZE);
    191       if (dest->newbuffer == NULL)
    192         ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
    193       *outsize = OUTPUT_BUF_SIZE;
    194     }
    195     else ERREXIT(cinfo, JERR_BUFFER_SIZE);
    196   }
    197 
    198   dest->pub.next_output_byte = dest->buffer = *outbuffer;
    199   if (!reused)
    200     dest->bufsize = *outsize;
    201   dest->pub.free_in_buffer = dest->bufsize;
    202 }
    203