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pngwio.c
Go to the documentation of this file.
1
2 /* pngwio.c - functions for data output
3 *
4 * Last changed in libpng 1.5.0 [January 6, 2011]
5 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
8 *
9 * This code is released under the libpng license.
10 * For conditions of distribution and use, see the disclaimer
11 * and license in png.h
12 *
13 * This file provides a location for all output. Users who need
14 * special handling are expected to write functions that have the same
15 * arguments as these and perform similar functions, but that possibly
16 * use different output methods. Note that you shouldn't change these
17 * functions, but rather write replacement functions and then change
18 * them at run time with png_set_write_fn(...).
19 */
20
21 #include "pngpriv.h"
22
23 #ifdef PNG_WRITE_SUPPORTED
24
25 /* Write the data to whatever output you are using. The default routine
26 * writes to a file pointer. Note that this routine sometimes gets called
27 * with very small lengths, so you should implement some kind of simple
28 * buffering if you are using unbuffered writes. This should never be asked
29 * to write more than 64K on a 16 bit machine.
30 */
31
32 void /* PRIVATE */
33 png_write_data(png_structp png_ptr, png_const_bytep data, png_size_t length)
34 {
35 /* NOTE: write_data_fn must not change the buffer! */
36 if (png_ptr->write_data_fn != NULL )
37 (*(png_ptr->write_data_fn))(png_ptr, (png_bytep)data, length);
38
39 else
40 png_error(png_ptr, "Call to NULL write function");
41 }
42
43 #ifdef PNG_STDIO_SUPPORTED
44 /* This is the function that does the actual writing of data. If you are
45 * not writing to a standard C stream, you should create a replacement
46 * write_data function and use it at run time with png_set_write_fn(), rather
47 * than changing the library.
48 */
49 #ifndef USE_FAR_KEYWORD
50 void PNGCBAPI
51 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
52 {
53 png_size_t check;
54
55 if (png_ptr == NULL)
56 return;
57
58 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
59
60 if (check != length)
61 png_error(png_ptr, "Write Error");
62 }
63 #else
64 /* This is the model-independent version. Since the standard I/O library
65 * can't handle far buffers in the medium and small models, we have to copy
66 * the data.
67 */
68
69 #define NEAR_BUF_SIZE 1024
70 #define MIN(a,b) (a <= b ? a : b)
71
72 void PNGCBAPI
73 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
74 {
75 png_uint_32 check;
76 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */
77 png_FILE_p io_ptr;
78
79 if (png_ptr == NULL)
80 return;
81
82 /* Check if data really is near. If so, use usual code. */
83 near_data = (png_byte *)CVT_PTR_NOCHECK(data);
84 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
85
86 if ((png_bytep)near_data == data)
87 {
88 check = fwrite(near_data, 1, length, io_ptr);
89 }
90
91 else
92 {
93 png_byte buf[NEAR_BUF_SIZE];
94 png_size_t written, remaining, err;
95 check = 0;
96 remaining = length;
97
98 do
99 {
100 written = MIN(NEAR_BUF_SIZE, remaining);
101 png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
102 err = fwrite(buf, 1, written, io_ptr);
103
104 if (err != written)
105 break;
106
107 else
108 check += err;
109
110 data += written;
111 remaining -= written;
112 }
113 while (remaining != 0);
114 }
115
116 if (check != length)
117 png_error(png_ptr, "Write Error");
118 }
119
120 #endif
121 #endif
122
123 /* This function is called to output any data pending writing (normally
124 * to disk). After png_flush is called, there should be no data pending
125 * writing in any buffers.
126 */
127 #ifdef PNG_WRITE_FLUSH_SUPPORTED
128 void /* PRIVATE */
129 png_flush(png_structp png_ptr)
130 {
131 if (png_ptr->output_flush_fn != NULL)
132 (*(png_ptr->output_flush_fn))(png_ptr);
133 }
134
135 # ifdef PNG_STDIO_SUPPORTED
136 void PNGCBAPI
137 png_default_flush(png_structp png_ptr)
138 {
139 png_FILE_p io_ptr;
140
141 if (png_ptr == NULL)
142 return;
143
144 io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
145 fflush(io_ptr);
146 }
147 # endif
148 #endif
149
150 /* This function allows the application to supply new output functions for
151 * libpng if standard C streams aren't being used.
152 *
153 * This function takes as its arguments:
154 * png_ptr - pointer to a png output data structure
155 * io_ptr - pointer to user supplied structure containing info about
156 * the output functions. May be NULL.
157 * write_data_fn - pointer to a new output function that takes as its
158 * arguments a pointer to a png_struct, a pointer to
159 * data to be written, and a 32-bit unsigned int that is
160 * the number of bytes to be written. The new write
161 * function should call png_error(png_ptr, "Error msg")
162 * to exit and output any fatal error messages. May be
163 * NULL, in which case libpng's default function will
164 * be used.
165 * flush_data_fn - pointer to a new flush function that takes as its
166 * arguments a pointer to a png_struct. After a call to
167 * the flush function, there should be no data in any buffers
168 * or pending transmission. If the output method doesn't do
169 * any buffering of output, a function prototype must still be
170 * supplied although it doesn't have to do anything. If
171 * PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
172 * time, output_flush_fn will be ignored, although it must be
173 * supplied for compatibility. May be NULL, in which case
174 * libpng's default function will be used, if
175 * PNG_WRITE_FLUSH_SUPPORTED is defined. This is not
176 * a good idea if io_ptr does not point to a standard
177 * *FILE structure.
178 */
179 void PNGAPI
180 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
181 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
182 {
183 if (png_ptr == NULL)
184 return;
185
186 png_ptr->io_ptr = io_ptr;
187
188 #ifdef PNG_STDIO_SUPPORTED
189 if (write_data_fn != NULL)
190 png_ptr->write_data_fn = write_data_fn;
191
192 else
193 png_ptr->write_data_fn = png_default_write_data;
194 #else
195 png_ptr->write_data_fn = write_data_fn;
196 #endif
197
198 #ifdef PNG_WRITE_FLUSH_SUPPORTED
199 # ifdef PNG_STDIO_SUPPORTED
200
201 if (output_flush_fn != NULL)
202 png_ptr->output_flush_fn = output_flush_fn;
203
204 else
205 png_ptr->output_flush_fn = png_default_flush;
206
207 # else
208 png_ptr->output_flush_fn = output_flush_fn;
209 # endif
210 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
211
212 /* It is an error to read while writing a png file */
213 if (png_ptr->read_data_fn != NULL)
214 {
215 png_ptr->read_data_fn = NULL;
216
217 png_warning(png_ptr,
218 "Can't set both read_data_fn and write_data_fn in the"
219 " same structure");
220 }
221 }
222
223 #ifdef USE_FAR_KEYWORD
224 # ifdef _MSC_VER
225 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
226 {
227 void *near_ptr;
228 void FAR *far_ptr;
229 FP_OFF(near_ptr) = FP_OFF(ptr);
230 far_ptr = (void FAR *)near_ptr;
231
232 if (check != 0)
233 if (FP_SEG(ptr) != FP_SEG(far_ptr))
234 png_error(png_ptr, "segment lost in conversion");
235
236 return(near_ptr);
237 }
238 # else
239 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
240 {
241 void *near_ptr;
242 void FAR *far_ptr;
243 near_ptr = (void FAR *)ptr;
244 far_ptr = (void FAR *)near_ptr;
245
246 if (check != 0)
247 if (far_ptr != ptr)
248 png_error(png_ptr, "segment lost in conversion");
249
250 return(near_ptr);
251 }
252 # endif
253 #endif
254 #endif /* PNG_WRITE_SUPPORTED */
png_memcpy
#define png_memcpy
Definition: pngpriv.h:226
CVT_PTR_NOCHECK
#define CVT_PTR_NOCHECK(ptr)
Definition: pngpriv.h:221
PNGCBAPI
#define PNGCBAPI
Definition: pngconf.h:253
MIN
#define MIN(a, b)
Definition: jpegint.h:269
png_default_write_data
void PNGCBAPI png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
Definition: pngwio.c:51
png_set_write_fn
void PNGAPI png_set_write_fn(png_structp png_ptr, png_voidp io_ptr, png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
Definition: pngwio.c:180
png_flush
void png_flush(png_structp png_ptr)
Definition: pngwio.c:129
png_write_data
void png_write_data(png_structp png_ptr, png_const_bytep data, png_size_t length)
Definition: pngwio.c:33
png_uint_32
unsigned long png_uint_32
Definition: pngconf.h:480
PNGAPI
#define PNGAPI
Definition: pngconf.h:256
png_structp
png_struct FAR * png_structp
Definition: png.h:797
png_byte
unsigned char png_byte
Definition: pngconf.h:485
png_warning
void PNGAPI png_warning(png_structp png_ptr, png_const_charp warning_message)
Definition: pngerror.c:108
FAR
#define FAR
Definition: jmorecfg.h:215
png_default_flush
void PNGCBAPI png_default_flush(png_structp png_ptr)
Definition: pngwio.c:137
png_const_bytep
PNG_CONST png_byte FAR * png_const_bytep
Definition: pngconf.h:563
png_bytep
png_byte FAR * png_bytep
Definition: pngconf.h:562
pngpriv.h
CVT_PTR
#define CVT_PTR(ptr)
Definition: pngpriv.h:220
png_voidp
void FAR * png_voidp
Definition: pngconf.h:560
png_size_t
size_t png_size_t
Definition: pngconf.h:490
data
JSAMPIMAGE data
Definition: jpeglib.h:945