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1
2 /* pngwio.c - functions for data output
3 *
4 * libpng 1.0.3 - January 14, 1999
5 * For conditions of distribution and use, see copyright notice in png.h
6 * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
7 * Copyright (c) 1996, 1997 Andreas Dilger
8 * Copyright (c) 1998, 1999 Glenn Randers-Pehrson
9 *
10 * This file provides a location for all output. Users who need
11 * special handling are expected to write functions that have the same
12 * arguments as these and perform similar functions, but that possibly
13 * use different output methods. Note that you shouldn't change these
14 * functions, but rather write replacement functions and then change
15 * them at run time with png_set_write_fn(...).
16 */
17
18 #define PNG_INTERNAL
19 #include "png.h"
20
21 /* Write the data to whatever output you are using. The default routine
22 writes to a file pointer. Note that this routine sometimes gets called
23 with very small lengths, so you should implement some kind of simple
24 buffering if you are using unbuffered writes. This should never be asked
25 to write more than 64K on a 16 bit machine. */
26
27 void
28 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
29 {
30 if (png_ptr->write_data_fn != NULL )
31 (*(png_ptr->write_data_fn))(png_ptr, data, length);
32 else
33 png_error(png_ptr, "Call to NULL write function");
34 }
35
36 #if !defined(PNG_NO_STDIO)
37 /* This is the function that does the actual writing of data. If you are
38 not writing to a standard C stream, you should create a replacement
39 write_data function and use it at run time with png_set_write_fn(), rather
40 than changing the library. */
41 #ifndef USE_FAR_KEYWORD
42 #ifdef __VISAGECPP__
43 static void _Optlink
44 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
45 #else
46 static void
47 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
48 #endif
49 {
50 png_uint_32 check;
51
52 check = fwrite(data, 1, length, (FILE *)(png_ptr->io_ptr));
53 if (check != length)
54 {
55 png_error(png_ptr, "Write Error");
56 }
57 }
58 #else
59 /* this is the model-independent version. Since the standard I/O library
60 can't handle far buffers in the medium and small models, we have to copy
61 the data.
62 */
63
64 #define NEAR_BUF_SIZE 1024
65 #define MIN(a,b) (a <= b ? a : b)
66
67 #ifdef __VISAGECPP__
68 static void _Optlink
69 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
70 #else
71 static void
72 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
73 #endif
74 {
75 png_uint_32 check;
76 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */
77 FILE *io_ptr;
78
79 /* Check if data really is near. If so, use usual code. */
80 near_data = (png_byte *)CVT_PTR_NOCHECK(data);
81 io_ptr = (FILE *)CVT_PTR(png_ptr->io_ptr);
82 if ((png_bytep)near_data == data)
83 {
84 check = fwrite(near_data, 1, length, io_ptr);
85 }
86 else
87 {
88 png_byte buf[NEAR_BUF_SIZE];
89 png_size_t written, remaining, err;
90 check = 0;
91 remaining = length;
92 do
93 {
94 written = MIN(NEAR_BUF_SIZE, remaining);
95 png_memcpy(buf, data, written); /* copy far buffer to near buffer */
96 err = fwrite(buf, 1, written, io_ptr);
97 if (err != written)
98 break;
99 else
100 check += err;
101 data += written;
102 remaining -= written;
103 }
104 while (remaining != 0);
105 }
106 if (check != length)
107 {
108 png_error(png_ptr, "Write Error");
109 }
110 }
111
112 #endif
113 #endif
114
115 /* This function is called to output any data pending writing (normally
116 to disk). After png_flush is called, there should be no data pending
117 writing in any buffers. */
118 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
119 void
120 png_flush(png_structp png_ptr)
121 {
122 if (png_ptr->output_flush_fn != NULL)
123 (*(png_ptr->output_flush_fn))(png_ptr);
124 }
125
126 #if !defined(PNG_NO_STDIO)
127 #ifdef __VISAGECPP__
128 static void _Optlink
129 png_default_flush(png_structp png_ptr)
130 #else
131 static void
132 png_default_flush(png_structp png_ptr)
133 #endif
134 {
135 FILE *io_ptr;
136 io_ptr = (FILE *)CVT_PTR((png_ptr->io_ptr));
137 if (io_ptr != NULL)
138 fflush(io_ptr);
139 }
140 #endif
141 #endif
142
143 /* This function allows the application to supply new output functions for
144 libpng if standard C streams aren't being used.
145
146 This function takes as its arguments:
147 png_ptr - pointer to a png output data structure
148 io_ptr - pointer to user supplied structure containing info about
149 the output functions. May be NULL.
150 write_data_fn - pointer to a new output function that takes as its
151 arguments a pointer to a png_struct, a pointer to
152 data to be written, and a 32-bit unsigned int that is
153 the number of bytes to be written. The new write
154 function should call png_error(png_ptr, "Error msg")
155 to exit and output any fatal error messages.
156 flush_data_fn - pointer to a new flush function that takes as its
157 arguments a pointer to a png_struct. After a call to
158 the flush function, there should be no data in any buffers
159 or pending transmission. If the output method doesn't do
160 any buffering of ouput, a function prototype must still be
161 supplied although it doesn't have to do anything. If
162 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
163 time, output_flush_fn will be ignored, although it must be
164 supplied for compatibility. */
165 void
166 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
167 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
168 {
169 png_ptr->io_ptr = io_ptr;
170
171 #if !defined(PNG_NO_STDIO)
172 if (write_data_fn != NULL)
173 png_ptr->write_data_fn = write_data_fn;
174 else
175 png_ptr->write_data_fn = png_default_write_data;
176 #else
177 png_ptr->write_data_fn = write_data_fn;
178 #endif
179
180 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
181 #if !defined(PNG_NO_STDIO)
182 if (output_flush_fn != NULL)
183 png_ptr->output_flush_fn = output_flush_fn;
184 else
185 png_ptr->output_flush_fn = png_default_flush;
186 #else
187 png_ptr->output_flush_fn = output_flush_fn;
188 #endif
189 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
190
191 /* It is an error to read while writing a png file */
192 if (png_ptr->read_data_fn != NULL)
193 {
194 png_ptr->read_data_fn = NULL;
195 png_warning(png_ptr,
196 "Attempted to set both read_data_fn and write_data_fn in");
197 png_warning(png_ptr,
198 "the same structure. Resetting read_data_fn to NULL.");
199 }
200 }
201
202 #if defined(USE_FAR_KEYWORD)
203 #if defined(_MSC_VER)
204 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
205 {
206 void *near_ptr;
207 void FAR *far_ptr;
208 FP_OFF(near_ptr) = FP_OFF(ptr);
209 far_ptr = (void FAR *)near_ptr;
210 if(check != 0)
211 if(FP_SEG(ptr) != FP_SEG(far_ptr))
212 png_error(png_ptr,"segment lost in conversion");
213 return(near_ptr);
214 }
215 # else
216 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
217 {
218 void *near_ptr;
219 void FAR *far_ptr;
220 near_ptr = (void FAR *)ptr;
221 far_ptr = (void FAR *)near_ptr;
222 if(check != 0)
223 if(far_ptr != ptr)
224 png_error(png_ptr,"segment lost in conversion");
225 return(near_ptr);
226 }
227 # endif
228 # endif