2 /* pngwio.c - functions for data output
4 * libpng 1.0.9 - January 31, 2001
5 * For conditions of distribution and use, see copyright notice in png.h
6 * Copyright (c) 1998-2001 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.)
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(...).
21 /* Write the data to whatever output you are using. The default routine
22 writes to a file pointer. Note that this routine sometimes gets called
23 with very small lengths, so you should implement some kind of simple
24 buffering if you are using unbuffered writes. This should never be asked
25 to write more than 64K on a 16 bit machine. */
28 png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
30 if (png_ptr->write_data_fn != NULL )
31 (*(png_ptr->write_data_fn))(png_ptr, data, length);
33 png_error(png_ptr, "Call to NULL write function");
36 #if !defined(PNG_NO_STDIO)
37 /* This is the function that does the actual writing of data. If you are
38 not writing to a standard C stream, you should create a replacement
39 write_data function and use it at run time with png_set_write_fn(), rather
40 than changing the library. */
41 #ifndef USE_FAR_KEYWORD
42 static void /* PRIVATE */
43 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
47 #if defined(_WIN32_WCE)
48 if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
51 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr));
54 png_error(png_ptr, "Write Error");
57 /* this is the model-independent version. Since the standard I/O library
58 can't handle far buffers in the medium and small models, we have to copy
62 #define NEAR_BUF_SIZE 1024
63 #define MIN(a,b) (a <= b ? a : b)
65 static void /* PRIVATE */
66 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
69 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */
72 /* Check if data really is near. If so, use usual code. */
73 near_data = (png_byte *)CVT_PTR_NOCHECK(data);
74 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
75 if ((png_bytep)near_data == data)
77 #if defined(_WIN32_WCE)
78 if ( !WriteFile(io_ptr, near_data, length, &check, NULL) )
81 check = fwrite(near_data, 1, length, io_ptr);
86 png_byte buf[NEAR_BUF_SIZE];
87 png_size_t written, remaining, err;
92 written = MIN(NEAR_BUF_SIZE, remaining);
93 png_memcpy(buf, data, written); /* copy far buffer to near buffer */
94 #if defined(_WIN32_WCE)
95 if ( !WriteFile(io_ptr, buf, written, &err, NULL) )
98 err = fwrite(buf, 1, written, io_ptr);
105 remaining -= written;
107 while (remaining != 0);
110 png_error(png_ptr, "Write Error");
116 /* This function is called to output any data pending writing (normally
117 to disk). After png_flush is called, there should be no data pending
118 writing in any buffers. */
119 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
121 png_flush(png_structp png_ptr)
123 if (png_ptr->output_flush_fn != NULL)
124 (*(png_ptr->output_flush_fn))(png_ptr);
127 #if !defined(PNG_NO_STDIO)
128 static void /* PRIVATE */
129 png_default_flush(png_structp png_ptr)
131 #if !defined(_WIN32_WCE)
133 io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr));
141 /* This function allows the application to supply new output functions for
142 libpng if standard C streams aren't being used.
144 This function takes as its arguments:
145 png_ptr - pointer to a png output data structure
146 io_ptr - pointer to user supplied structure containing info about
147 the output functions. May be NULL.
148 write_data_fn - pointer to a new output function that takes as its
149 arguments a pointer to a png_struct, a pointer to
150 data to be written, and a 32-bit unsigned int that is
151 the number of bytes to be written. The new write
152 function should call png_error(png_ptr, "Error msg")
153 to exit and output any fatal error messages.
154 flush_data_fn - pointer to a new flush function that takes as its
155 arguments a pointer to a png_struct. After a call to
156 the flush function, there should be no data in any buffers
157 or pending transmission. If the output method doesn't do
158 any buffering of ouput, a function prototype must still be
159 supplied although it doesn't have to do anything. If
160 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
161 time, output_flush_fn will be ignored, although it must be
162 supplied for compatibility. */
164 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
165 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
167 png_ptr->io_ptr = io_ptr;
169 #if !defined(PNG_NO_STDIO)
170 if (write_data_fn != NULL)
171 png_ptr->write_data_fn = write_data_fn;
173 png_ptr->write_data_fn = png_default_write_data;
175 png_ptr->write_data_fn = write_data_fn;
178 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
179 #if !defined(PNG_NO_STDIO)
180 if (output_flush_fn != NULL)
181 png_ptr->output_flush_fn = output_flush_fn;
183 png_ptr->output_flush_fn = png_default_flush;
185 png_ptr->output_flush_fn = output_flush_fn;
187 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
189 /* It is an error to read while writing a png file */
190 if (png_ptr->read_data_fn != NULL)
192 png_ptr->read_data_fn = NULL;
194 "Attempted to set both read_data_fn and write_data_fn in");
196 "the same structure. Resetting read_data_fn to NULL.");
200 #if defined(USE_FAR_KEYWORD)
201 #if defined(_MSC_VER)
202 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
206 FP_OFF(near_ptr) = FP_OFF(ptr);
207 far_ptr = (void FAR *)near_ptr;
209 if(FP_SEG(ptr) != FP_SEG(far_ptr))
210 png_error(png_ptr,"segment lost in conversion");
214 void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check)
218 near_ptr = (void FAR *)ptr;
219 far_ptr = (void FAR *)near_ptr;
222 png_error(png_ptr,"segment lost in conversion");