4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * Modified 2009 by Guido Vollbeding.
6 * This file is part of the Independent JPEG Group's software.
7 * For conditions of distribution and use, see the accompanying README file.
9 * This file contains compression data destination routines for the case of
10 * emitting JPEG data to memory or to a file (or any stdio stream).
11 * While these routines are sufficient for most applications,
12 * some will want to use a different destination manager.
13 * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
14 * JOCTETs into 8-bit-wide elements on external storage. If char is wider
15 * than 8 bits on your machine, you may need to do some tweaking.
18 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
23 #ifndef HAVE_STDLIB_H /* <stdlib.h> should declare malloc(),free() */
24 extern void * malloc JPP((size_t size));
25 extern void free JPP((void *ptr));
29 #define OUTPUT_BUF_SIZE 4096 /* choose an efficiently fwrite'able size */
32 /* Expanded data destination object for memory output */
35 struct jpeg_destination_mgr pub; /* public fields */
37 unsigned char ** outbuffer; /* target buffer */
38 unsigned long * outsize;
39 unsigned char * newbuffer; /* newly allocated buffer */
40 JOCTET * buffer; /* start of buffer */
43 } my_mem_destination_mgr;
45 typedef my_mem_destination_mgr * my_mem_dest_ptr;
49 * Initialize destination --- called by jpeg_start_compress
50 * before any data is actually written.
54 init_mem_destination (j_compress_ptr cinfo)
56 /* no work necessary here */
61 * Empty the output buffer --- called whenever buffer fills up.
63 * In typical applications, this should write the entire output buffer
64 * (ignoring the current state of next_output_byte & free_in_buffer),
65 * reset the pointer & count to the start of the buffer, and return TRUE
66 * indicating that the buffer has been dumped.
68 * In applications that need to be able to suspend compression due to output
69 * overrun, a FALSE return indicates that the buffer cannot be emptied now.
70 * In this situation, the compressor will return to its caller (possibly with
71 * an indication that it has not accepted all the supplied scanlines). The
72 * application should resume compression after it has made more room in the
73 * output buffer. Note that there are substantial restrictions on the use of
74 * suspension --- see the documentation.
76 * When suspending, the compressor will back up to a convenient restart point
77 * (typically the start of the current MCU). next_output_byte & free_in_buffer
78 * indicate where the restart point will be if the current call returns FALSE.
79 * Data beyond this point will be regenerated after resumption, so do not
80 * write it out when emptying the buffer externally.
84 empty_mem_output_buffer (j_compress_ptr cinfo)
88 my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
90 if (!dest->alloc) ERREXIT(cinfo, JERR_BUFFER_SIZE);
92 /* Try to allocate new buffer with double size */
93 nextsize = dest->bufsize * 2;
94 nextbuffer = malloc(nextsize);
96 if (nextbuffer == NULL)
97 ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
99 MEMCOPY(nextbuffer, dest->buffer, dest->bufsize);
101 if (dest->newbuffer != NULL)
102 free(dest->newbuffer);
104 dest->newbuffer = nextbuffer;
106 dest->pub.next_output_byte = nextbuffer + dest->bufsize;
107 dest->pub.free_in_buffer = dest->bufsize;
109 dest->buffer = nextbuffer;
110 dest->bufsize = nextsize;
117 * Terminate destination --- called by jpeg_finish_compress
118 * after all data has been written. Usually needs to flush buffer.
120 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
121 * application must deal with any cleanup that should happen even
126 term_mem_destination (j_compress_ptr cinfo)
128 my_mem_dest_ptr dest = (my_mem_dest_ptr) cinfo->dest;
130 if(dest->alloc) *dest->outbuffer = dest->buffer;
131 *dest->outsize = (unsigned long)(dest->bufsize - dest->pub.free_in_buffer);
136 * Prepare for output to a memory buffer.
137 * The caller may supply an own initial buffer with appropriate size.
138 * Otherwise, or when the actual data output exceeds the given size,
139 * the library adapts the buffer size as necessary.
140 * The standard library functions malloc/free are used for allocating
141 * larger memory, so the buffer is available to the application after
142 * finishing compression, and then the application is responsible for
143 * freeing the requested memory.
147 jpeg_mem_dest_tj (j_compress_ptr cinfo,
148 unsigned char ** outbuffer, unsigned long * outsize,
151 my_mem_dest_ptr dest;
153 if (outbuffer == NULL || outsize == NULL) /* sanity check */
154 ERREXIT(cinfo, JERR_BUFFER_SIZE);
156 /* The destination object is made permanent so that multiple JPEG images
157 * can be written to the same buffer without re-executing jpeg_mem_dest.
159 if (cinfo->dest == NULL) { /* first time for this JPEG object? */
160 cinfo->dest = (struct jpeg_destination_mgr *)
161 (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
162 SIZEOF(my_mem_destination_mgr));
163 dest = (my_mem_dest_ptr) cinfo->dest;
164 dest->newbuffer = NULL;
167 dest = (my_mem_dest_ptr) cinfo->dest;
168 dest->pub.init_destination = init_mem_destination;
169 dest->pub.empty_output_buffer = empty_mem_output_buffer;
170 dest->pub.term_destination = term_mem_destination;
171 dest->outbuffer = outbuffer;
172 dest->outsize = outsize;
175 if (*outbuffer == NULL || *outsize == 0) {
177 /* Allocate initial buffer */
178 dest->newbuffer = *outbuffer = malloc(OUTPUT_BUF_SIZE);
179 if (dest->newbuffer == NULL)
180 ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
181 *outsize = OUTPUT_BUF_SIZE;
183 else ERREXIT(cinfo, JERR_BUFFER_SIZE);
186 dest->pub.next_output_byte = dest->buffer = *outbuffer;
187 dest->pub.free_in_buffer = dest->bufsize = *outsize;