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1
2 /* pngwio.c - functions for data output
3 *
4 * libpng 1.0.1
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, Glenn Randers-Pehrson
9 * March 15, 1998
10 *
11 * This file provides a location for all output. Users which need
12 * special handling are expected to write functions which have the same
13 * arguments as these, and perform similar functions, but possibly use
14 * different output methods. Note that you shouldn't change these
15 * functions, but rather write replacement functions and then change
16 * them at run time with png_set_write_fn(...).
17 */
18
19 #define PNG_INTERNAL
20 #include "../png/png.h"
21
22 /* Write the data to whatever output you are using. The default routine
23 writes to a file pointer. Note that this routine sometimes gets called
24 with very small lengths, so you should implement some kind of simple
25 buffering if you are using unbuffered writes. This should never be asked
26 to write more then 64K on a 16 bit machine. */
27
28 void
29 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
30 {
31 if (png_ptr->write_data_fn != NULL )
32 (*(png_ptr->write_data_fn))(png_ptr, data, length);
33 else
34 png_error(png_ptr, "Call to NULL write function");
35 }
36
37 #if !defined(PNG_NO_STDIO)
38 /* This is the function which does the actual writing of data. If you are
39 not writing to a standard C stream, you should create a replacement
40 write_data function and use it at run time with png_set_write_fn(), rather
41 than changing the library. */
42 #ifndef USE_FAR_KEYWORD
43 static void
44 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
45 {
46 png_uint_32 check;
47
48 check = fwrite(data, 1, length, (FILE *)(png_ptr->io_ptr));
49 if (check != length)
50 {
51 png_error(png_ptr, "Write Error");
52 }
53 }
54 #else
55 /* this is the model-independent version. Since the standard I/O library
56 can't handle far buffers in the medium and small models, we have to copy
57 the data.
58 */
59
60 #define NEAR_BUF_SIZE 1024
61 #define MIN(a,b) (a <= b ? a : b)
62
63 static void
64 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
65 {
66 png_uint_32 check;
67 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */
68 FILE *io_ptr;
69
70 /* Check if data really is near. If so, use usual code. */
71 near_data = (png_byte *)CVT_PTR_NOCHECK(data);
72 io_ptr = (FILE *)CVT_PTR(png_ptr->io_ptr);
73 if ((png_bytep)near_data == data)
74 {
75 check = fwrite(near_data, 1, length, io_ptr);
76 }
77 else
78 {
79 png_byte buf[NEAR_BUF_SIZE];
80 png_size_t written, remaining, err;
81 check = 0;
82 remaining = length;
83 do
84 {
85 written = MIN(NEAR_BUF_SIZE, remaining);
86 png_memcpy(buf, data, written); /* copy far buffer to near buffer */
87 err = fwrite(buf, 1, written, io_ptr);
88 if (err != written)
89 break;
90 else
91 check += err;
92 data += written;
93 remaining -= written;
94 }
95 while (remaining != 0);
96 }
97 if (check != length)
98 {
99 png_error(png_ptr, "Write Error");
100 }
101 }
102
103 #endif
104 #endif
105
106 /* This function is called to output any data pending writing (normally
107 to disk). After png_flush is called, there should be no data pending
108 writing in any buffers. */
109 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
110 void
111 png_flush(png_structp png_ptr)
112 {
113 if (png_ptr->output_flush_fn != NULL)
114 (*(png_ptr->output_flush_fn))(png_ptr);
115 }
116
117 #if !defined(PNG_NO_STDIO)
118 static void
119 png_default_flush(png_structp png_ptr)
120 {
121 FILE *io_ptr;
122 io_ptr = (FILE *)CVT_PTR((png_ptr->io_ptr));
123 if (io_ptr != NULL)
124 fflush(io_ptr);
125 }
126 #endif
127 #endif
128
129 /* This function allows the application to supply new output functions for
130 libpng if standard C streams aren't being used.
131
132 This function takes as its arguments:
133 png_ptr - pointer to a png output data structure
134 io_ptr - pointer to user supplied structure containing info about
135 the output functions. May be NULL.
136 write_data_fn - pointer to a new output function which takes as its
137 arguments a pointer to a png_struct, a pointer to
138 data to be written, and a 32-bit unsigned int which is
139 the number of bytes to be written. The new write
140 function should call png_error(png_ptr, "Error msg")
141 to exit and output any fatal error messages.
142 flush_data_fn - pointer to a new flush function which takes as its
143 arguments a pointer to a png_struct. After a call to
144 the flush function, there should be no data in any buffers
145 or pending transmission. If the output method doesn't do
146 any buffering of ouput, a function prototype must still be
147 supplied although it doesn't have to do anything. If
148 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
149 time, output_flush_fn will be ignored, although it must be
150 supplied for compatibility. */
151 void
152 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
153 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
154 {
155 png_ptr->io_ptr = io_ptr;
156
157 #if !defined(PNG_NO_STDIO)
158 if (write_data_fn != NULL)
159 png_ptr->write_data_fn = write_data_fn;
160 else
161 png_ptr->write_data_fn = png_default_write_data;
162 #else
163 png_ptr->write_data_fn = write_data_fn;
164 #endif
165
166 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
167 #if !defined(PNG_NO_STDIO)
168 if (output_flush_fn != NULL)
169 png_ptr->output_flush_fn = output_flush_fn;
170 else
171 png_ptr->output_flush_fn = png_default_flush;
172 #else
173 png_ptr->output_flush_fn = output_flush_fn;
174 #endif
175 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
176
177 /* It is an error to read while writing a png file */
178 png_ptr->read_data_fn = NULL;
179 }
180
181 #if defined(USE_FAR_KEYWORD)
182 #if defined(_MSC_VER)
183 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
184 {
185 void *near_ptr;
186 void FAR *far_ptr;
187 FP_OFF(near_ptr) = FP_OFF(ptr);
188 far_ptr = (void FAR *)near_ptr;
189 if(check != 0)
190 if(FP_SEG(ptr) != FP_SEG(far_ptr))
191 png_error(png_ptr,"segment lost in conversion");
192 return(near_ptr);
193 }
194 # else
195 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
196 {
197 void *near_ptr;
198 void FAR *far_ptr;
199 near_ptr = (void FAR *)ptr;
200 far_ptr = (void FAR *)near_ptr;
201 if(check != 0)
202 if(far_ptr != ptr)
203 png_error(png_ptr,"segment lost in conversion");
204 return(near_ptr);
205 }
206 # endif
207 # endif