/src/FreeImage/Source/LibPNG/pngwio.c

  1
  2/* pngwio.c - functions for data output
  3 *
  4 * Last changed in libpng 1.5.0 [January 6, 2011]
  5 * Copyright (c) 1998-2011 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#include "pngpriv.h"
 22
 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_const_bytep data, png_size_t length)
 34{
 35   /* NOTE: write_data_fn must not change the buffer! */
 36   if (png_ptr->write_data_fn != NULL )
 37      (*(png_ptr->write_data_fn))(png_ptr, (png_bytep)data, length);
 38
 39   else
 40      png_error(png_ptr, "Call to NULL write function");
 41}
 42
 43#ifdef PNG_STDIO_SUPPORTED
 44/* This is the function that does the actual writing of data.  If you are
 45 * not writing to a standard C stream, you should create a replacement
 46 * write_data function and use it at run time with png_set_write_fn(), rather
 47 * than changing the library.
 48 */
 49#ifndef USE_FAR_KEYWORD
 50void PNGCBAPI
 51png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
 52{
 53   png_size_t check;
 54
 55   if (png_ptr == NULL)
 56      return;
 57
 58   check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
 59
 60   if (check != length)
 61      png_error(png_ptr, "Write Error");
 62}
 63#else
 64/* This is the model-independent version. Since the standard I/O library
 65 * can't handle far buffers in the medium and small models, we have to copy
 66 * the data.
 67 */
 68
 69#define NEAR_BUF_SIZE 1024
 70#define MIN(a,b) (a <= b ? a : b)
 71
 72void PNGCBAPI
 73png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
 74{
 75   png_uint_32 check;
 76   png_byte *near_data;  /* Needs to be "png_byte *" instead of "png_bytep" */
 77   png_FILE_p io_ptr;
 78
 79   if (png_ptr == NULL)
 80      return;
 81
 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
 86   if ((png_bytep)near_data == data)
 87   {
 88      check = fwrite(near_data, 1, length, io_ptr);
 89   }
 90
 91   else
 92   {
 93      png_byte buf[NEAR_BUF_SIZE];
 94      png_size_t written, remaining, err;
 95      check = 0;
 96      remaining = length;
 97
 98      do
 99      {
100         written = MIN(NEAR_BUF_SIZE, remaining);
101         png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
102         err = fwrite(buf, 1, written, io_ptr);
103
104         if (err != written)
105            break;
106
107         else
108            check += err;
109
110         data += written;
111         remaining -= written;
112      }
113      while (remaining != 0);
114   }
115
116   if (check != length)
117      png_error(png_ptr, "Write Error");
118}
119
120#endif
121#endif
122
123/* This function is called to output any data pending writing (normally
124 * to disk).  After png_flush is called, there should be no data pending
125 * writing in any buffers.
126 */
127#ifdef PNG_WRITE_FLUSH_SUPPORTED
128void /* PRIVATE */
129png_flush(png_structp png_ptr)
130{
131   if (png_ptr->output_flush_fn != NULL)
132      (*(png_ptr->output_flush_fn))(png_ptr);
133}
134
135#  ifdef PNG_STDIO_SUPPORTED
136void PNGCBAPI
137png_default_flush(png_structp png_ptr)
138{
139   png_FILE_p io_ptr;
140
141   if (png_ptr == NULL)
142      return;
143
144   io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
145   fflush(io_ptr);
146}
147#  endif
148#endif
149
150/* This function allows the application to supply new output functions for
151 * libpng if standard C streams aren't being used.
152 *
153 * This function takes as its arguments:
154 * png_ptr       - pointer to a png output data structure
155 * io_ptr        - pointer to user supplied structure containing info about
156 *                 the output functions.  May be NULL.
157 * write_data_fn - pointer to a new output function that takes as its
158 *                 arguments a pointer to a png_struct, a pointer to
159 *                 data to be written, and a 32-bit unsigned int that is
160 *                 the number of bytes to be written.  The new write
161 *                 function should call png_error(png_ptr, "Error msg")
162 *                 to exit and output any fatal error messages.  May be
163 *                 NULL, in which case libpng's default function will
164 *                 be used.
165 * flush_data_fn - pointer to a new flush function that takes as its
166 *                 arguments a pointer to a png_struct.  After a call to
167 *                 the flush function, there should be no data in any buffers
168 *                 or pending transmission.  If the output method doesn't do
169 *                 any buffering of output, a function prototype must still be
170 *                 supplied although it doesn't have to do anything.  If
171 *                 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
172 *                 time, output_flush_fn will be ignored, although it must be
173 *                 supplied for compatibility.  May be NULL, in which case
174 *                 libpng's default function will be used, if
175 *                 PNG_WRITE_FLUSH_SUPPORTED is defined.  This is not
176 *                 a good idea if io_ptr does not point to a standard
177 *                 *FILE structure.
178 */
179void PNGAPI
180png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
181    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
182{
183   if (png_ptr == NULL)
184      return;
185
186   png_ptr->io_ptr = io_ptr;
187
188#ifdef PNG_STDIO_SUPPORTED
189   if (write_data_fn != NULL)
190      png_ptr->write_data_fn = write_data_fn;
191
192   else
193      png_ptr->write_data_fn = png_default_write_data;
194#else
195   png_ptr->write_data_fn = write_data_fn;
196#endif
197
198#ifdef PNG_WRITE_FLUSH_SUPPORTED
199#  ifdef PNG_STDIO_SUPPORTED
200
201   if (output_flush_fn != NULL)
202      png_ptr->output_flush_fn = output_flush_fn;
203
204   else
205      png_ptr->output_flush_fn = png_default_flush;
206
207#  else
208   png_ptr->output_flush_fn = output_flush_fn;
209#  endif
210#endif /* PNG_WRITE_FLUSH_SUPPORTED */
211
212   /* It is an error to read while writing a png file */
213   if (png_ptr->read_data_fn != NULL)
214   {
215      png_ptr->read_data_fn = NULL;
216
217      png_warning(png_ptr,
218          "Can't set both read_data_fn and write_data_fn in the"
219          " same structure");
220   }
221}
222
223#ifdef USE_FAR_KEYWORD
224#  ifdef _MSC_VER
225void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
226{
227   void *near_ptr;
228   void FAR *far_ptr;
229   FP_OFF(near_ptr) = FP_OFF(ptr);
230   far_ptr = (void FAR *)near_ptr;
231
232   if (check != 0)
233      if (FP_SEG(ptr) != FP_SEG(far_ptr))
234         png_error(png_ptr, "segment lost in conversion");
235
236   return(near_ptr);
237}
238#  else
239void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
240{
241   void *near_ptr;
242   void FAR *far_ptr;
243   near_ptr = (void FAR *)ptr;
244   far_ptr = (void FAR *)near_ptr;
245
246   if (check != 0)
247      if (far_ptr != ptr)
248         png_error(png_ptr, "segment lost in conversion");
249
250   return(near_ptr);
251}
252#  endif
253#endif
254#endif /* PNG_WRITE_SUPPORTED */