1
2/* pngwio.c - functions for data output
3 *
4 * Last changed in libpng 1.2.41 [December 3, 2009]
5 * Copyright (c) 1998-2009 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#define PNG_INTERNAL
22#define PNG_NO_PEDANTIC_WARNINGS
23#include "png.h"
24#ifdef PNG_WRITE_SUPPORTED
25
26/* Write the data to whatever output you are using.  The default routine
27 * writes to a file pointer.  Note that this routine sometimes gets called
28 * with very small lengths, so you should implement some kind of simple
29 * buffering if you are using unbuffered writes.  This should never be asked
30 * to write more than 64K on a 16 bit machine.
31 */
32
33void /* PRIVATE */
34png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
35{
36   if (png_ptr->write_data_fn != NULL )
37      (*(png_ptr->write_data_fn))(png_ptr, data, length);
38   else
39      png_error(png_ptr, "Call to NULL write function");
40}
41
42#ifdef PNG_STDIO_SUPPORTED
43/* This is the function that does the actual writing of data.  If you are
44 * not writing to a standard C stream, you should create a replacement
45 * write_data function and use it at run time with png_set_write_fn(), rather
46 * than changing the library.
47 */
48#ifndef USE_FAR_KEYWORD
49void PNGAPI
50png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
51{
52   png_uint_32 check;
53
54   if (png_ptr == NULL)
55      return;
56#ifdef _WIN32_WCE
57   if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
58      check = 0;
59#else
60   check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
61#endif
62   if (check != length)
63      png_error(png_ptr, "Write Error");
64}
65#else
66/* This is the model-independent version. Since the standard I/O library
67 * can't handle far buffers in the medium and small models, we have to copy
68 * the data.
69 */
70
71#define NEAR_BUF_SIZE 1024
72#define MIN(a,b) (a <= b ? a : b)
73
74void PNGAPI
75png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
76{
77   png_uint_32 check;
78   png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
79   png_FILE_p io_ptr;
80
81   if (png_ptr == NULL)
82      return;
83   /* Check if data really is near. If so, use usual code. */
84   near_data = (png_byte *)CVT_PTR_NOCHECK(data);
85   io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
86   if ((png_bytep)near_data == data)
87   {
88#ifdef _WIN32_WCE
89      if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
90         check = 0;
91#else
92      check = fwrite(near_data, 1, length, io_ptr);
93#endif
94   }
95   else
96   {
97      png_byte buf[NEAR_BUF_SIZE];
98      png_size_t written, remaining, err;
99      check = 0;
100      remaining = length;
101      do
102      {
103         written = MIN(NEAR_BUF_SIZE, remaining);
104         png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
105#ifdef _WIN32_WCE
106         if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
107            err = 0;
108#else
109         err = fwrite(buf, 1, written, io_ptr);
110#endif
111         if (err != written)
112            break;
113
114         else
115            check += err;
116
117         data += written;
118         remaining -= written;
119      }
120      while (remaining != 0);
121   }
122   if (check != length)
123      png_error(png_ptr, "Write Error");
124}
125
126#endif
127#endif
128
129/* This function is called to output any data pending writing (normally
130 * to disk).  After png_flush is called, there should be no data pending
131 * writing in any buffers.
132 */
133#ifdef PNG_WRITE_FLUSH_SUPPORTED
134void /* PRIVATE */
135png_flush(png_structp png_ptr)
136{
137   if (png_ptr->output_flush_fn != NULL)
138      (*(png_ptr->output_flush_fn))(png_ptr);
139}
140
141#ifdef PNG_STDIO_SUPPORTED
142void PNGAPI
143png_default_flush(png_structp png_ptr)
144{
145#ifndef _WIN32_WCE
146   png_FILE_p io_ptr;
147#endif
148   if (png_ptr == NULL)
149      return;
150#ifndef _WIN32_WCE
151   io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
152   fflush(io_ptr);
153#endif
154}
155#endif
156#endif
157
158/* This function allows the application to supply new output functions for
159 * libpng if standard C streams aren't being used.
160 *
161 * This function takes as its arguments:
162 * png_ptr       - pointer to a png output data structure
163 * io_ptr        - pointer to user supplied structure containing info about
164 *                 the output functions.  May be NULL.
165 * write_data_fn - pointer to a new output function that takes as its
166 *                 arguments a pointer to a png_struct, a pointer to
167 *                 data to be written, and a 32-bit unsigned int that is
168 *                 the number of bytes to be written.  The new write
169 *                 function should call png_error(png_ptr, "Error msg")
170 *                 to exit and output any fatal error messages.  May be
171 *                 NULL, in which case libpng's default function will
172 *                 be used.
173 * flush_data_fn - pointer to a new flush function that takes as its
174 *                 arguments a pointer to a png_struct.  After a call to
175 *                 the flush function, there should be no data in any buffers
176 *                 or pending transmission.  If the output method doesn't do
177 *                 any buffering of output, a function prototype must still be
178 *                 supplied although it doesn't have to do anything.  If
179 *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
180 *                 time, output_flush_fn will be ignored, although it must be
181 *                 supplied for compatibility.  May be NULL, in which case
182 *                 libpng's default function will be used, if
183 *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
184 *                 a good idea if io_ptr does not point to a standard
185 *                 *FILE structure.
186 */
187void PNGAPI
188png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
189   png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
190{
191   if (png_ptr == NULL)
192      return;
193
194   png_ptr->io_ptr = io_ptr;
195
196#ifdef PNG_STDIO_SUPPORTED
197   if (write_data_fn != NULL)
198      png_ptr->write_data_fn = write_data_fn;
199
200   else
201      png_ptr->write_data_fn = png_default_write_data;
202#else
203   png_ptr->write_data_fn = write_data_fn;
204#endif
205
206#ifdef PNG_WRITE_FLUSH_SUPPORTED
207#ifdef PNG_STDIO_SUPPORTED
208   if (output_flush_fn != NULL)
209      png_ptr->output_flush_fn = output_flush_fn;
210
211   else
212      png_ptr->output_flush_fn = png_default_flush;
213#else
214   png_ptr->output_flush_fn = output_flush_fn;
215#endif
216#endif /* PNG_WRITE_FLUSH_SUPPORTED */
217
218   /* It is an error to read while writing a png file */
219   if (png_ptr->read_data_fn != NULL)
220   {
221      png_ptr->read_data_fn = NULL;
222      png_warning(png_ptr,
223         "Attempted to set both read_data_fn and write_data_fn in");
224      png_warning(png_ptr,
225         "the same structure.  Resetting read_data_fn to NULL.");
226   }
227}
228
229#ifdef USE_FAR_KEYWORD
230#ifdef _MSC_VER
231void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
232{
233   void *near_ptr;
234   void FAR *far_ptr;
235   FP_OFF(near_ptr) = FP_OFF(ptr);
236   far_ptr = (void FAR *)near_ptr;
237
238   if (check != 0)
239      if (FP_SEG(ptr) != FP_SEG(far_ptr))
240         png_error(png_ptr, "segment lost in conversion");
241
242   return(near_ptr);
243}
244#  else
245void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
246{
247   void *near_ptr;
248   void FAR *far_ptr;
249   near_ptr = (void FAR *)ptr;
250   far_ptr = (void FAR *)near_ptr;
251
252   if (check != 0)
253      if (far_ptr != ptr)
254         png_error(png_ptr, "segment lost in conversion");
255
256   return(near_ptr);
257}
258#   endif
259#   endif
260#endif /* PNG_WRITE_SUPPORTED */
261