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, 2019, 2022-2023, D. R. Commander.
9 * For conditions of distribution and use, see the accompanying README.ijg
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.
21 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
26 void jpeg_mem_dest_tj(j_compress_ptr cinfo, unsigned char **outbuffer,
27 size_t *outsize, boolean alloc);
30 #define OUTPUT_BUF_SIZE 4096 /* choose an efficiently fwrite'able size */
33 /* Expanded data destination object for memory output */
36 struct jpeg_destination_mgr pub; /* public fields */
38 unsigned char **outbuffer; /* target buffer */
40 unsigned char *newbuffer; /* newly allocated buffer */
41 JOCTET *buffer; /* start of buffer */
44 } my_mem_destination_mgr;
46 typedef my_mem_destination_mgr *my_mem_dest_ptr;
50 * Initialize destination --- called by jpeg_start_compress
51 * before any data is actually written.
55 init_mem_destination(j_compress_ptr cinfo)
57 /* no work necessary here */
62 * Empty the output buffer --- called whenever buffer fills up.
64 * In typical applications, this should write the entire output buffer
65 * (ignoring the current state of next_output_byte & free_in_buffer),
66 * reset the pointer & count to the start of the buffer, and return TRUE
67 * indicating that the buffer has been dumped.
69 * In applications that need to be able to suspend compression due to output
70 * overrun, a FALSE return indicates that the buffer cannot be emptied now.
71 * In this situation, the compressor will return to its caller (possibly with
72 * an indication that it has not accepted all the supplied scanlines). The
73 * application should resume compression after it has made more room in the
74 * output buffer. Note that there are substantial restrictions on the use of
75 * suspension --- see the documentation.
77 * When suspending, the compressor will back up to a convenient restart point
78 * (typically the start of the current MCU). next_output_byte & free_in_buffer
79 * indicate where the restart point will be if the current call returns FALSE.
80 * Data beyond this point will be regenerated after resumption, so do not
81 * write it out when emptying the buffer externally.
85 empty_mem_output_buffer(j_compress_ptr cinfo)
89 my_mem_dest_ptr dest = (my_mem_dest_ptr)cinfo->dest;
91 if (!dest->alloc) ERREXIT(cinfo, JERR_BUFFER_SIZE);
93 /* Try to allocate new buffer with double size */
94 nextsize = dest->bufsize * 2;
95 nextbuffer = (JOCTET *)malloc(nextsize);
97 if (nextbuffer == NULL)
98 ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
100 memcpy(nextbuffer, dest->buffer, dest->bufsize);
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 = 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, unsigned char **outbuffer,
148 size_t *outsize, boolean alloc)
150 boolean reused = FALSE;
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;
166 } else if (cinfo->dest->init_destination != init_mem_destination) {
167 /* It is unsafe to reuse the existing destination manager unless it was
168 * created by this function.
170 ERREXIT(cinfo, JERR_BUFFER_SIZE);
173 dest = (my_mem_dest_ptr)cinfo->dest;
174 dest->pub.init_destination = init_mem_destination;
175 dest->pub.empty_output_buffer = empty_mem_output_buffer;
176 dest->pub.term_destination = term_mem_destination;
177 if (dest->buffer == *outbuffer && *outbuffer != NULL && alloc)
179 dest->outbuffer = outbuffer;
180 dest->outsize = outsize;
183 if (*outbuffer == NULL || *outsize == 0) {
185 /* Allocate initial buffer */
186 dest->newbuffer = *outbuffer = (unsigned char *)malloc(OUTPUT_BUF_SIZE);
187 if (dest->newbuffer == NULL)
188 ERREXIT1(cinfo, JERR_OUT_OF_MEMORY, 10);
189 *outsize = OUTPUT_BUF_SIZE;
191 ERREXIT(cinfo, JERR_BUFFER_SIZE);
194 dest->pub.next_output_byte = dest->buffer = *outbuffer;
196 dest->bufsize = *outsize;
197 dest->pub.free_in_buffer = dest->bufsize;