2 /* pngwio.c - functions for data output
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.)
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
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(...).
22 #define PNG_NO_PEDANTIC_WARNINGS
24 #ifdef PNG_WRITE_SUPPORTED
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.
34 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
36 if (png_ptr->write_data_fn != NULL )
37 (*(png_ptr->write_data_fn))(png_ptr, data, length);
39 png_error(png_ptr, "Call to NULL write function");
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.
48 #ifndef USE_FAR_KEYWORD
50 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
57 if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
60 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
63 png_error(png_ptr, "Write Error");
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
71 #define NEAR_BUF_SIZE 1024
72 #define MIN(a,b) (a <= b ? a : b)
75 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
78 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */
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)
89 if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
92 check = fwrite(near_data, 1, length, io_ptr);
97 png_byte buf[NEAR_BUF_SIZE];
98 png_size_t written, remaining, err;
103 written = MIN(NEAR_BUF_SIZE, remaining);
104 png_memcpy(buf, data, written); /* Copy far buffer to near buffer */
106 if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
109 err = fwrite(buf, 1, written, io_ptr);
118 remaining -= written;
120 while (remaining != 0);
123 png_error(png_ptr, "Write Error");
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.
133 #ifdef PNG_WRITE_FLUSH_SUPPORTED
135 png_flush(png_structp png_ptr)
137 if (png_ptr->output_flush_fn != NULL)
138 (*(png_ptr->output_flush_fn))(png_ptr);
141 #ifdef PNG_STDIO_SUPPORTED
143 png_default_flush(png_structp png_ptr)
151 io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
158 /* This function allows the application to supply new output functions for
159 * libpng if standard C streams aren't being used.
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
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
188 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
189 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
194 png_ptr->io_ptr = io_ptr;
196 #ifdef PNG_STDIO_SUPPORTED
197 if (write_data_fn != NULL)
198 png_ptr->write_data_fn = write_data_fn;
201 png_ptr->write_data_fn = png_default_write_data;
203 png_ptr->write_data_fn = write_data_fn;
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;
212 png_ptr->output_flush_fn = png_default_flush;
214 png_ptr->output_flush_fn = output_flush_fn;
216 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
218 /* It is an error to read while writing a png file */
219 if (png_ptr->read_data_fn != NULL)
221 png_ptr->read_data_fn = NULL;
223 "Attempted to set both read_data_fn and write_data_fn in");
225 "the same structure. Resetting read_data_fn to NULL.");
229 #ifdef USE_FAR_KEYWORD
231 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
235 FP_OFF(near_ptr) = FP_OFF(ptr);
236 far_ptr = (void FAR *)near_ptr;
239 if (FP_SEG(ptr) != FP_SEG(far_ptr))
240 png_error(png_ptr, "segment lost in conversion");
245 void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check)
249 near_ptr = (void FAR *)ptr;
250 far_ptr = (void FAR *)near_ptr;
254 png_error(png_ptr, "segment lost in conversion");
260 #endif /* PNG_WRITE_SUPPORTED */