1
2/* pngwio.c - functions for data output
3 *
4 * Last changed in libpng 1.2.13 November 13, 2006
5 * For conditions of distribution and use, see copyright notice in png.h
6 * Copyright (c) 1998-2006 Glenn Randers-Pehrson
7 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
8 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
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#ifdef PNG_WRITE_SUPPORTED
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 than 64K on a 16 bit machine. */
27
28void /* PRIVATE */
29png_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 that 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
43void PNGAPI
44png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
45{
46 png_uint_32 check;
47
48 if(png_ptr == NULL) return;
49#if defined(_WIN32_WCE)
50 if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
51 check = 0;
52#else
53 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
54#endif
55 if (check != length)
56 png_error(png_ptr, "Write Error");
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
67void PNGAPI
68png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
69{
70 png_uint_32 check;
71 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */
72 png_FILE_p io_ptr;
73
74 if(png_ptr == NULL) return;
75 /* Check if data really is near. If so, use usual code. */
76 near_data = (png_byte *)CVT_PTR_NOCHECK(data);
77 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
78 if ((png_bytep)near_data == data)
79 {
80#if defined(_WIN32_WCE)
81 if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
82 check = 0;
83#else
84 check = fwrite(near_data, 1, length, io_ptr);
85#endif
86 }
87 else
88 {
89 png_byte buf[NEAR_BUF_SIZE];
90 png_size_t written, remaining, err;
91 check = 0;
92 remaining = length;
93 do
94 {
95 written = MIN(NEAR_BUF_SIZE, remaining);
96 png_memcpy(buf, data, written); /* copy far buffer to near buffer */
97#if defined(_WIN32_WCE)
98 if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
99 err = 0;
100#else
101 err = fwrite(buf, 1, written, io_ptr);
102#endif
103 if (err != written)
104 break;
105 else
106 check += err;
107 data += written;
108 remaining -= written;
109 }
110 while (remaining != 0);
111 }
112 if (check != length)
113 png_error(png_ptr, "Write Error");
114}
115
116#endif
117#endif
118
119/* This function is called to output any data pending writing (normally
120 to disk). After png_flush is called, there should be no data pending
121 writing in any buffers. */
122#if defined(PNG_WRITE_FLUSH_SUPPORTED)
123void /* PRIVATE */
124png_flush(png_structp png_ptr)
125{
126 if (png_ptr->output_flush_fn != NULL)
127 (*(png_ptr->output_flush_fn))(png_ptr);
128}
129
130#if !defined(PNG_NO_STDIO)
131void PNGAPI
132png_default_flush(png_structp png_ptr)
133{
134#if !defined(_WIN32_WCE)
135 png_FILE_p io_ptr;
136#endif
137 if(png_ptr == NULL) return;
138#if !defined(_WIN32_WCE)
139 io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
140 if (io_ptr != NULL)
141 fflush(io_ptr);
142#endif
143}
144#endif
145#endif
146
147/* This function allows the application to supply new output functions for
148 libpng if standard C streams aren't being used.
149
150 This function takes as its arguments:
151 png_ptr - pointer to a png output data structure
152 io_ptr - pointer to user supplied structure containing info about
153 the output functions. May be NULL.
154 write_data_fn - pointer to a new output function that takes as its
155 arguments a pointer to a png_struct, a pointer to
156 data to be written, and a 32-bit unsigned int that is
157 the number of bytes to be written. The new write
158 function should call png_error(png_ptr, "Error msg")
159 to exit and output any fatal error messages.
160 flush_data_fn - pointer to a new flush function that takes as its
161 arguments a pointer to a png_struct. After a call to
162 the flush function, there should be no data in any buffers
163 or pending transmission. If the output method doesn't do
164 any buffering of ouput, a function prototype must still be
165 supplied although it doesn't have to do anything. If
166 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
167 time, output_flush_fn will be ignored, although it must be
168 supplied for compatibility. */
169void PNGAPI
170png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
171 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
172{
173 if(png_ptr == NULL) return;
174 png_ptr->io_ptr = io_ptr;
175
176#if !defined(PNG_NO_STDIO)
177 if (write_data_fn != NULL)
178 png_ptr->write_data_fn = write_data_fn;
179 else
180 png_ptr->write_data_fn = png_default_write_data;
181#else
182 png_ptr->write_data_fn = write_data_fn;
183#endif
184
185#if defined(PNG_WRITE_FLUSH_SUPPORTED)
186#if !defined(PNG_NO_STDIO)
187 if (output_flush_fn != NULL)
188 png_ptr->output_flush_fn = output_flush_fn;
189 else
190 png_ptr->output_flush_fn = png_default_flush;
191#else
192 png_ptr->output_flush_fn = output_flush_fn;
193#endif
194#endif /* PNG_WRITE_FLUSH_SUPPORTED */
195
196 /* It is an error to read while writing a png file */
197 if (png_ptr->read_data_fn != NULL)
198 {
199 png_ptr->read_data_fn = NULL;
200 png_warning(png_ptr,
201 "Attempted to set both read_data_fn and write_data_fn in");
202 png_warning(png_ptr,
203 "the same structure. Resetting read_data_fn to NULL.");
204 }
205}
206
207#if defined(USE_FAR_KEYWORD)
208#if defined(_MSC_VER)
209void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
210{
211 void *near_ptr;
212 void FAR *far_ptr;
213 FP_OFF(near_ptr) = FP_OFF(ptr);
214 far_ptr = (void FAR *)near_ptr;
215 if(check != 0)
216 if(FP_SEG(ptr) != FP_SEG(far_ptr))
217 png_error(png_ptr,"segment lost in conversion");
218 return(near_ptr);
219}
220# else
221void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
222{
223 void *near_ptr;
224 void FAR *far_ptr;
225 near_ptr = (void FAR *)ptr;
226 far_ptr = (void FAR *)near_ptr;
227 if(check != 0)
228 if(far_ptr != ptr)
229 png_error(png_ptr,"segment lost in conversion");
230 return(near_ptr);
231}
232# endif
233# endif
234#endif /* PNG_WRITE_SUPPORTED */
235