pngwio.c revision 893912bfc2683463dc3e2c445336752d012563d3 
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