jdatadst-tj.c revision b5f2e450acbbae79c792f0ea5b47644fd2290a31 
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 * Modifications:
8 * Copyright (C) 2011, D. R. Commander.
9 * For conditions of distribution and use, see the accompanying README file.
10 *
11 * This file contains compression data destination routines for the case of
12 * emitting JPEG data to memory or to a file (or any stdio stream).
13 * While these routines are sufficient for most applications,
14 * some will want to use a different destination manager.
15 * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
16 * JOCTETs into 8-bit-wide elements on external storage.  If char is wider
17 * than 8 bits on your machine, you may need to do some tweaking.
18 */
19
20/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
21#include "jinclude.h"
22#include "jpeglib.h"
23#include "jerror.h"
24
25#ifndef HAVE_STDLIB_H		/* <stdlib.h> should declare malloc(),free() */
26extern void * malloc JPP((size_t size));
27extern void free JPP((void *ptr));
28#endif
29
30
31#define OUTPUT_BUF_SIZE  4096	/* choose an efficiently fwrite'able size */
32
33
34/* Expanded data destination object for memory output */
35
36typedef struct {
37  struct jpeg_destination_mgr pub; /* public fields */
38
39  unsigned char ** outbuffer;	/* target buffer */
40  unsigned long * outsize;
41  unsigned char * newbuffer;	/* newly allocated buffer */
42  JOCTET * buffer;		/* start of buffer */
43  size_t bufsize;
44  boolean alloc;
45} my_mem_destination_mgr;
46
47typedef my_mem_destination_mgr * my_mem_dest_ptr;
48
49
50/*
51 * Initialize destination --- called by jpeg_start_compress
52 * before any data is actually written.
53 */
54
55METHODDEF(void)
56init_mem_destination (j_compress_ptr cinfo)
57{
58  /* no work necessary here */
59}
60
61
62/*
63 * Empty the output buffer --- called whenever buffer fills up.
64 *
65 * In typical applications, this should write the entire output buffer
66 * (ignoring the current state of next_output_byte & free_in_buffer),
67 * reset the pointer & count to the start of the buffer, and return TRUE
68 * indicating that the buffer has been dumped.
69 *
70 * In applications that need to be able to suspend compression due to output
71 * overrun, a FALSE return indicates that the buffer cannot be emptied now.
72 * In this situation, the compressor will return to its caller (possibly with
73 * an indication that it has not accepted all the supplied scanlines).  The
74 * application should resume compression after it has made more room in the
75 * output buffer.  Note that there are substantial restrictions on the use of
76 * suspension --- see the documentation.
77 *
78 * When suspending, the compressor will back up to a convenient restart point
79 * (typically the start of the current MCU). next_output_byte & free_in_buffer
80 * indicate where the restart point will be if the current call returns FALSE.
81 * Data beyond this point will be regenerated after resumption, so do not
82 * write it out when emptying the buffer externally.
83 */
84
85METHODDEF(boolean)
86empty_mem_output_buffer (j_compress_ptr cinfo)
87{
88  size_t nextsize;
89  JOCTET * nextbuffer;
90  my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
91
92  if (!dest->alloc) ERREXIT(cinfo, JERR_BUFFER_SIZE);
93
94  /* Try to allocate new buffer with double size */
95  nextsize = dest->bufsize * 2;
96  nextbuffer = (JOCTET *) malloc(nextsize);
97
98  if (nextbuffer == NULL)
99    ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
100
101  MEMCOPY(nextbuffer, dest->buffer, dest->bufsize);
102
103  if (dest->newbuffer != NULL)
104    free(dest->newbuffer);
105
106  dest->newbuffer = nextbuffer;
107
108  dest->pub.next_output_byte = nextbuffer + dest->bufsize;
109  dest->pub.free_in_buffer = dest->bufsize;
110
111  dest->buffer = nextbuffer;
112  dest->bufsize = nextsize;
113
114  return TRUE;
115}
116
117
118/*
119 * Terminate destination --- called by jpeg_finish_compress
120 * after all data has been written.  Usually needs to flush buffer.
121 *
122 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
123 * application must deal with any cleanup that should happen even
124 * for error exit.
125 */
126
127METHODDEF(void)
128term_mem_destination (j_compress_ptr cinfo)
129{
130  my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
131
132  if(dest->alloc) *dest->outbuffer = dest->buffer;
133  *dest->outsize = (unsigned long)(dest->bufsize - dest->pub.free_in_buffer);
134}
135
136
137/*
138 * Prepare for output to a memory buffer.
139 * The caller may supply an own initial buffer with appropriate size.
140 * Otherwise, or when the actual data output exceeds the given size,
141 * the library adapts the buffer size as necessary.
142 * The standard library functions malloc/free are used for allocating
143 * larger memory, so the buffer is available to the application after
144 * finishing compression, and then the application is responsible for
145 * freeing the requested memory.
146 */
147
148GLOBAL(void)
149jpeg_mem_dest_tj (j_compress_ptr cinfo,
150	       unsigned char ** outbuffer, unsigned long * outsize,
151	       boolean alloc)
152{
153  my_mem_dest_ptr dest;
154
155  if (outbuffer == NULL || outsize == NULL)	/* sanity check */
156    ERREXIT(cinfo, JERR_BUFFER_SIZE);
157
158  /* The destination object is made permanent so that multiple JPEG images
159   * can be written to the same buffer without re-executing jpeg_mem_dest.
160   */
161  if (cinfo->dest == NULL) {	/* first time for this JPEG object? */
162    cinfo->dest = (struct jpeg_destination_mgr *)
163      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
164				  SIZEOF(my_mem_destination_mgr));
165    dest = (my_mem_dest_ptr) cinfo->dest;
166    dest->newbuffer = NULL;
167  }
168
169  dest = (my_mem_dest_ptr) cinfo->dest;
170  dest->pub.init_destination = init_mem_destination;
171  dest->pub.empty_output_buffer = empty_mem_output_buffer;
172  dest->pub.term_destination = term_mem_destination;
173  dest->outbuffer = outbuffer;
174  dest->outsize = outsize;
175  dest->alloc = alloc;
176
177  if (*outbuffer == NULL || *outsize == 0) {
178    if (alloc) {
179      /* Allocate initial buffer */
180      dest->newbuffer = *outbuffer = (unsigned char *) malloc(OUTPUT_BUF_SIZE);
181      if (dest->newbuffer == NULL)
182        ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
183      *outsize = OUTPUT_BUF_SIZE;
184    }
185    else ERREXIT(cinfo, JERR_BUFFER_SIZE);
186  }
187
188  dest->pub.next_output_byte = dest->buffer = *outbuffer;
189  dest->pub.free_in_buffer = dest->bufsize = *outsize;
190}
191