jdatadst.c
Go to the documentation of this file.
1 /*
2  * jdatadst.c
3  *
4  * Copyright (C) 1994-1996, Thomas G. Lane.
5  * This file is part of the Independent JPEG Group's software.
6  * For conditions of distribution and use, see the accompanying README file.
7  *
8  * This file contains compression data destination routines for the case of
9  * emitting JPEG data to a file (or any stdio stream). While these routines
10  * are sufficient for most applications, some will want to use a different
11  * destination manager.
12  * IMPORTANT: we assume that fwrite() will correctly transcribe an array of
13  * JOCTETs into 8-bit-wide elements on external storage. If char is wider
14  * than 8 bits on your machine, you may need to do some tweaking.
15  */
16 
17 /* this is not a core library module, so it doesn't define JPEG_INTERNALS */
18 #include "jinclude.h"
19 #include "jpeglib.h"
20 #include "jerror.h"
21 
22 
23 /* Expanded data destination object for stdio output */
24 
25 typedef struct {
26  struct jpeg_destination_mgr pub; /* public fields */
27 
28  FILE * outfile; /* target stream */
29  JOCTET * buffer; /* start of buffer */
31 
33 
34 #define OUTPUT_BUF_SIZE 4096 /* choose an efficiently fwrite'able size */
35 
36 
37 /*
38  * Initialize destination --- called by jpeg_start_compress
39  * before any data is actually written.
40  */
41 
42 METHODDEF(void)
44 {
45  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
46 
47  /* Allocate the output buffer --- it will be released when done with image */
48  dest->buffer = (JOCTET *)
49  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
51 
52  dest->pub.next_output_byte = dest->buffer;
54 }
55 
56 
57 /*
58  * Empty the output buffer --- called whenever buffer fills up.
59  *
60  * In typical applications, this should write the entire output buffer
61  * (ignoring the current state of next_output_byte & free_in_buffer),
62  * reset the pointer & count to the start of the buffer, and return TRUE
63  * indicating that the buffer has been dumped.
64  *
65  * In applications that need to be able to suspend compression due to output
66  * overrun, a FALSE return indicates that the buffer cannot be emptied now.
67  * In this situation, the compressor will return to its caller (possibly with
68  * an indication that it has not accepted all the supplied scanlines). The
69  * application should resume compression after it has made more room in the
70  * output buffer. Note that there are substantial restrictions on the use of
71  * suspension --- see the documentation.
72  *
73  * When suspending, the compressor will back up to a convenient restart point
74  * (typically the start of the current MCU). next_output_byte & free_in_buffer
75  * indicate where the restart point will be if the current call returns FALSE.
76  * Data beyond this point will be regenerated after resumption, so do not
77  * write it out when emptying the buffer externally.
78  */
79 
80 METHODDEF(boolean)
82 {
83  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
84 
85  if (JFWRITE(dest->outfile, dest->buffer, OUTPUT_BUF_SIZE) !=
86  (size_t) OUTPUT_BUF_SIZE)
87  ERREXIT(cinfo, JERR_FILE_WRITE);
88 
89  dest->pub.next_output_byte = dest->buffer;
91 
92  return TRUE;
93 }
94 
95 
96 /*
97  * Terminate destination --- called by jpeg_finish_compress
98  * after all data has been written. Usually needs to flush buffer.
99  *
100  * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
101  * application must deal with any cleanup that should happen even
102  * for error exit.
103  */
104 
105 METHODDEF(void)
107 {
108  my_dest_ptr dest = (my_dest_ptr) cinfo->dest;
109  size_t datacount = OUTPUT_BUF_SIZE - dest->pub.free_in_buffer;
110 
111  /* Write any data remaining in the buffer */
112  if (datacount > 0) {
113  if (JFWRITE(dest->outfile, dest->buffer, datacount) != datacount)
114  ERREXIT(cinfo, JERR_FILE_WRITE);
115  }
116  fflush(dest->outfile);
117  /* Make sure we wrote the output file OK */
118  if (ferror(dest->outfile))
119  ERREXIT(cinfo, JERR_FILE_WRITE);
120 }
121 
122 
123 /*
124  * Prepare for output to a stdio stream.
125  * The caller must have already opened the stream, and is responsible
126  * for closing it after finishing compression.
127  */
128 
129 GLOBAL(void)
131 {
132  my_dest_ptr dest;
133 
134  /* The destination object is made permanent so that multiple JPEG images
135  * can be written to the same file without re-executing jpeg_stdio_dest.
136  * This makes it dangerous to use this manager and a different destination
137  * manager serially with the same JPEG object, because their private object
138  * sizes may be different. Caveat programmer.
139  */
140  if (cinfo->dest == NULL) { /* first time for this JPEG object? */
141  cinfo->dest = (struct jpeg_destination_mgr *)
142  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
144  }
145 
146  dest = (my_dest_ptr) cinfo->dest;
147  dest->pub.init_destination = init_destination;
148  dest->pub.empty_output_buffer = empty_output_buffer;
149  dest->pub.term_destination = term_destination;
150  dest->outfile = outfile;
151 }
my_destination_mgr * my_dest_ptr
Definition: jdatadst.c:32
struct jpeg_common_struct * j_common_ptr
Definition: jpeglib.h:261
size_t free_in_buffer
Definition: jpeglib.h:715
#define ERREXIT(cinfo, code)
Definition: jerror.h:205
#define TRUE
Definition: OPC_IceHook.h:13
#define SIZEOF(object)
Definition: jinclude.h:80
jpeg_stdio_dest(j_compress_ptr cinfo, FILE *outfile)
Definition: jdatadst.c:130
#define JFWRITE(file, buf, sizeofbuf)
Definition: jinclude.h:90
#define JPOOL_IMAGE
Definition: jpeglib.h:749
struct jpeg_destination_mgr pub
Definition: jdatadst.c:26
term_destination(j_compress_ptr cinfo)
Definition: jdatadst.c:106
FILE * outfile
Definition: jpeglib.h:910
init_destination(j_compress_ptr cinfo)
Definition: jdatadst.c:43
#define GLOBAL(type)
Definition: jmorecfg.h:188
#define METHODDEF(type)
Definition: jmorecfg.h:184
empty_output_buffer(j_compress_ptr cinfo)
Definition: jdatadst.c:81
JOCTET * buffer
Definition: jdatadst.c:29
#define JPOOL_PERMANENT
Definition: jpeglib.h:748
char JOCTET
Definition: jmorecfg.h:115
JOCTET * next_output_byte
Definition: jpeglib.h:714
#define OUTPUT_BUF_SIZE
Definition: jdatadst.c:34


openhrp3
Author(s): AIST, General Robotix Inc., Nakamura Lab of Dept. of Mechano Informatics at University of Tokyo
autogenerated on Sat May 8 2021 02:42:39