pngwio.c revision a0bb96c34e65378853ee518bac502842d26c2d1a 
1
2/* pngwio.c - functions for data output
3 *
4 * Last changed in libpng 1.2.37 [June 4, 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#include "png.h"
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
32void /* PRIVATE */
33png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
34{
35   if (png_ptr->write_data_fn != NULL )
36      (*(png_ptr->write_data_fn))(png_ptr, data, length);
37   else
38      png_error(png_ptr, "Call to NULL write function");
39}
40
41#if !defined(PNG_NO_STDIO)
42/* This is the function that does the actual writing of data.  If you are
43 * not writing to a standard C stream, you should create a replacement
44 * write_data function and use it at run time with png_set_write_fn(), rather
45 * than changing the library.
46 */
47#ifndef USE_FAR_KEYWORD
48void PNGAPI
49png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
50{
51   png_uint_32 check;
52
53   if (png_ptr == NULL)
54      return;
55#if defined(_WIN32_WCE)
56   if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
57      check = 0;
58#else
59   check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
60#endif
61   if (check != length)
62      png_error(png_ptr, "Write Error");
63}
64#else
65/* This is the model-independent version. Since the standard I/O library
66 * can't handle far buffers in the medium and small models, we have to copy
67 * the data.
68 */
69
70#define NEAR_BUF_SIZE 1024
71#define MIN(a,b) (a <= b ? a : b)
72
73void PNGAPI
74png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
75{
76   png_uint_32 check;
77   png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
78   png_FILE_p io_ptr;
79
80   if (png_ptr == NULL)
81      return;
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   if ((png_bytep)near_data == data)
86   {
87#if defined(_WIN32_WCE)
88      if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
89         check = 0;
90#else
91      check = fwrite(near_data, 1, length, io_ptr);
92#endif
93   }
94   else
95   {
96      png_byte buf[NEAR_BUF_SIZE];
97      png_size_t written, remaining, err;
98      check = 0;
99      remaining = length;
100      do
101      {
102         written = MIN(NEAR_BUF_SIZE, remaining);
103         png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
104#if defined(_WIN32_WCE)
105         if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
106            err = 0;
107#else
108         err = fwrite(buf, 1, written, io_ptr);
109#endif
110         if (err != written)
111            break;
112
113         else
114            check += err;
115
116         data += written;
117         remaining -= written;
118      }
119      while (remaining != 0);
120   }
121   if (check != length)
122      png_error(png_ptr, "Write Error");
123}
124
125#endif
126#endif
127
128/* This function is called to output any data pending writing (normally
129 * to disk).  After png_flush is called, there should be no data pending
130 * writing in any buffers.
131 */
132#if defined(PNG_WRITE_FLUSH_SUPPORTED)
133void /* PRIVATE */
134png_flush(png_structp png_ptr)
135{
136   if (png_ptr->output_flush_fn != NULL)
137      (*(png_ptr->output_flush_fn))(png_ptr);
138}
139
140#if !defined(PNG_NO_STDIO)
141void PNGAPI
142png_default_flush(png_structp png_ptr)
143{
144#if !defined(_WIN32_WCE)
145   png_FILE_p io_ptr;
146#endif
147   if (png_ptr == NULL)
148      return;
149#if !defined(_WIN32_WCE)
150   io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
151   fflush(io_ptr);
152#endif
153}
154#endif
155#endif
156
157/* This function allows the application to supply new output functions for
158 * libpng if standard C streams aren't being used.
159 *
160 * This function takes as its arguments:
161 * png_ptr       - pointer to a png output data structure
162 * io_ptr        - pointer to user supplied structure containing info about
163 *                 the output functions.  May be NULL.
164 * write_data_fn - pointer to a new output function that takes as its
165 *                 arguments a pointer to a png_struct, a pointer to
166 *                 data to be written, and a 32-bit unsigned int that is
167 *                 the number of bytes to be written.  The new write
168 *                 function should call png_error(png_ptr, "Error msg")
169 *                 to exit and output any fatal error messages.  May be
170 *                 NULL, in which case libpng's default function will
171 *                 be used.
172 * flush_data_fn - pointer to a new flush function that takes as its
173 *                 arguments a pointer to a png_struct.  After a call to
174 *                 the flush function, there should be no data in any buffers
175 *                 or pending transmission.  If the output method doesn't do
176 *                 any buffering of ouput, a function prototype must still be
177 *                 supplied although it doesn't have to do anything.  If
178 *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
179 *                 time, output_flush_fn will be ignored, although it must be
180 *                 supplied for compatibility.  May be NULL, in which case
181 *                 libpng's default function will be used, if
182 *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
183 *                 a good idea if io_ptr does not point to a standard
184 *                 *FILE structure.
185 */
186void PNGAPI
187png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
188   png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
189{
190   if (png_ptr == NULL)
191      return;
192
193   png_ptr->io_ptr = io_ptr;
194
195#if !defined(PNG_NO_STDIO)
196   if (write_data_fn != NULL)
197      png_ptr->write_data_fn = write_data_fn;
198
199   else
200      png_ptr->write_data_fn = png_default_write_data;
201#else
202   png_ptr->write_data_fn = write_data_fn;
203#endif
204
205#if defined(PNG_WRITE_FLUSH_SUPPORTED)
206#if !defined(PNG_NO_STDIO)
207   if (output_flush_fn != NULL)
208      png_ptr->output_flush_fn = output_flush_fn;
209
210   else
211      png_ptr->output_flush_fn = png_default_flush;
212#else
213   png_ptr->output_flush_fn = output_flush_fn;
214#endif
215#endif /* PNG_WRITE_FLUSH_SUPPORTED */
216
217   /* It is an error to read while writing a png file */
218   if (png_ptr->read_data_fn != NULL)
219   {
220      png_ptr->read_data_fn = NULL;
221      png_warning(png_ptr,
222         "Attempted to set both read_data_fn and write_data_fn in");
223      png_warning(png_ptr,
224         "the same structure.  Resetting read_data_fn to NULL.");
225   }
226}
227
228#if defined(USE_FAR_KEYWORD)
229#if defined(_MSC_VER)
230void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
231{
232   void *near_ptr;
233   void FAR *far_ptr;
234   FP_OFF(near_ptr) = FP_OFF(ptr);
235   far_ptr = (void FAR *)near_ptr;
236
237   if (check != 0)
238      if (FP_SEG(ptr) != FP_SEG(far_ptr))
239         png_error(png_ptr, "segment lost in conversion");
240
241   return(near_ptr);
242}
243#  else
244void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
245{
246   void *near_ptr;
247   void FAR *far_ptr;
248   near_ptr = (void FAR *)ptr;
249   far_ptr = (void FAR *)near_ptr;
250
251   if (check != 0)
252      if (far_ptr != ptr)
253         png_error(png_ptr, "segment lost in conversion");
254
255   return(near_ptr);
256}
257#   endif
258#   endif
259#endif /* PNG_WRITE_SUPPORTED */
260