| |
| /* pngio.c - stub functions for i/o and memory allocation |
| |
| libpng 1.0 beta 2 - version 0.88 |
| For conditions of distribution and use, see copyright notice in png.h |
| Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. |
| January 25, 1996 |
| |
| This file provides a location for all input/output. Users which need |
| special handling are expected to write functions which have the same |
| arguments as these, and perform similar functions, but possibly have |
| different I/O methods. Note that you shouldn't change these functions, |
| but rather write replacement functions and then change them at run |
| time with png_set_write_fn(...) or png_set_read_fn(...), etc */ |
| |
| #define PNG_INTERNAL |
| #include "png.h" |
| |
| /* Write the data to whatever output you are using. The default routine |
| writes to a file pointer. Note that this routine sometimes gets called |
| with very small lengths, so you should implement some kind of simple |
| buffering if you are using unbuffered writes. This should never be asked |
| to write more then 64K on a 16 bit machine. The cast to png_size_t is |
| there to quiet warnings of certain compilers. */ |
| |
| void |
| png_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length) |
| { |
| if (png_ptr->write_data_fn) |
| (*(png_ptr->write_data_fn))(png_ptr, data, length); |
| else |
| png_error(png_ptr, "Call to NULL write function"); |
| } |
| |
| /* This is the function which does the actual writing of data. If you are |
| not writing to a standard C stream, you should create a replacement |
| write_data function and use it at run time with png_set_write_fn(), rather |
| than changing the library. */ |
| #ifndef USE_FAR_KEYWORD |
| void |
| png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length) |
| { |
| png_uint_32 check; |
| |
| check = fwrite(data, 1, (png_size_t)length, png_ptr->fp); |
| if (check != length) |
| { |
| png_error(png_ptr, "Write Error"); |
| } |
| } |
| #else |
| /* this is the model-independent version. Since the standard I/O library |
| can't handle far buffers in the medium and small models, we have to copy |
| the data. |
| */ |
| |
| #define NEAR_BUF_SIZE 1024 |
| #define MIN(a,b) (a <= b ? a : b) |
| |
| #ifdef _MSC_VER |
| /* for FP_OFF */ |
| #include <dos.h> |
| #endif |
| |
| void |
| png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length) |
| { |
| png_uint_32 check; |
| png_byte *n_data; |
| |
| /* Check if data really is near. If so, use usual code. */ |
| #ifdef _MSC_VER |
| /* do it this way just to quiet warning */ |
| FP_OFF(n_data) = FP_OFF(data); |
| if (FP_SEG(n_data) == FP_SEG(data)) |
| #else |
| /* this works in MSC also but with lost segment warning */ |
| n_data = (png_byte *)data; |
| if ((png_bytep)n_data == data) |
| #endif |
| { |
| check = fwrite(n_data, 1, (png_size_t)length, png_ptr->fp); |
| } |
| else |
| { |
| png_byte buf[NEAR_BUF_SIZE]; |
| png_size_t written, remaining, err; |
| check = 0; |
| remaining = (png_size_t)length; |
| do |
| { |
| written = MIN(NEAR_BUF_SIZE, remaining); |
| png_memcpy(buf, data, written); /* copy far buffer to near buffer */ |
| err = fwrite(buf, 1, written, png_ptr->fp); |
| if (err != written) |
| break; |
| else |
| check += err; |
| data += written; |
| remaining -= written; |
| } |
| while (remaining != 0); |
| } |
| if (check != length) |
| { |
| png_error(png_ptr, "Write Error"); |
| } |
| } |
| |
| #endif |
| |
| /* Read the data from whatever input you are using. The default routine |
| reads from a file pointer. Note that this routine sometimes gets called |
| with very small lengths, so you should implement some kind of simple |
| buffering if you are using unbuffered reads. This should never be asked |
| to read more then 64K on a 16 bit machine. The cast to png_size_t is |
| there to quiet some compilers */ |
| void |
| png_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length) |
| { |
| #ifdef PNG_PROGRESSIVE_READ_SUPPORTED |
| if (png_ptr->read_mode == PNG_READ_PUSH_MODE) |
| { |
| png_push_fill_buffer(png_ptr, data, length); |
| } |
| else |
| #endif |
| { |
| if (png_ptr->read_data_fn) |
| (*(png_ptr->read_data_fn))(png_ptr, data, length); |
| else |
| png_error(png_ptr, "Call to NULL read function"); |
| } |
| } |
| |
| /* This is the function which does the actual reading of data. If you are |
| not reading from a standard C stream, you should create a replacement |
| read_data function and use it at run time with png_set_read_fn(), rather |
| than changing the library. */ |
| #ifndef USE_FAR_KEYWORD |
| void |
| png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length) |
| { |
| png_uint_32 check; |
| |
| check = fread(data, 1, (size_t)length, png_ptr->fp); |
| if (check != length) |
| { |
| png_error(png_ptr, "Read Error"); |
| } |
| } |
| #else |
| void |
| png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length) |
| { |
| png_uint_32 check; |
| png_byte *n_data; |
| |
| /* Check if data really is near. If so, use usual code. */ |
| #ifdef _MSC_VER |
| /* do it this way just to quiet warning */ |
| FP_OFF(n_data) = FP_OFF(data); |
| if (FP_SEG(n_data) == FP_SEG(data)) |
| #else |
| /* this works in MSC also but with lost segment warning */ |
| n_data = (png_byte *)data; |
| if ((png_bytep)n_data == data) |
| #endif |
| { |
| check = fread(n_data, 1, (size_t)length, png_ptr->fp); |
| } |
| else |
| { |
| png_byte buf[NEAR_BUF_SIZE]; |
| png_size_t read, remaining, err; |
| check = 0; |
| remaining = (png_size_t)length; |
| do |
| { |
| read = MIN(NEAR_BUF_SIZE, remaining); |
| err = fread(buf, 1, read, png_ptr->fp); |
| png_memcpy(data, buf, read); /* copy far buffer to near buffer */ |
| if(err != read) |
| break; |
| else |
| check += err; |
| data += read; |
| remaining -= read; |
| } |
| while (remaining != 0); |
| } |
| if (check != length) |
| { |
| png_error(png_ptr, "read Error"); |
| } |
| } |
| #endif |
| |
| /* This function is called to output any data pending writing (normally |
| to disk. After png_flush is called, there should be no data pending |
| writing in any buffers. */ |
| #if defined(PNG_WRITE_FLUSH_SUPPORTED) |
| void |
| png_flush(png_structp png_ptr) |
| { |
| if (png_ptr->output_flush_fn) |
| (*(png_ptr->output_flush_fn))(png_ptr); |
| } |
| |
| void |
| png_default_flush(png_structp png_ptr) |
| { |
| if (png_ptr->fp) |
| fflush(png_ptr->fp); |
| } |
| #endif |
| |
| /* This function allows the application to supply new output functions for |
| libpng if standard C streams aren't being used. |
| |
| This function takes as its arguments: |
| png_ptr - pointer to a png output data structure |
| io_ptr - pointer to user supplied structure containing info about |
| the output functions. May be NULL. |
| write_data_fn - pointer to a new output function which takes as its |
| arguments a pointer to a png_struct, a pointer to |
| data to be written, and a 32-bit unsigned int which is |
| the number of bytes to be written. The new write |
| function should call png_error(png_ptr, "Error msg") |
| to exit and output any fatal error messages. |
| flush_data_fn - pointer to a new flush function which takes as its |
| arguments a pointer to a png_struct. After a call to |
| the flush function, there should be no data in any buffers |
| or pending transmission. If the output method doesn't do |
| any buffering of ouput, a function prototype must still be |
| supplied although it doesn't have to do anything. If |
| PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile |
| time, output_flush_fn will be ignored, although it must be |
| supplied for compatibility. */ |
| void |
| png_set_write_fn(png_structp png_ptr, png_voidp io_ptr, |
| png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn) |
| { |
| png_ptr->io_ptr = io_ptr; |
| |
| if (write_data_fn) |
| png_ptr->write_data_fn = write_data_fn; |
| else |
| png_ptr->write_data_fn = png_default_write_data; |
| |
| #if defined(PNG_WRITE_FLUSH_SUPPORTED) |
| if (output_flush_fn) |
| png_ptr->output_flush_fn = output_flush_fn; |
| else |
| png_ptr->output_flush_fn = png_default_flush; |
| #endif /* PNG_WRITE_FLUSH_SUPPORTED */ |
| |
| /* It is an error to read while writing a png file */ |
| png_ptr->read_data_fn = NULL; |
| } |
| |
| |
| /* This function allows the application to supply a new input function |
| for libpng if standard C streams aren't being used. |
| |
| This function takes as its arguments: |
| png_ptr - pointer to a png input data structure |
| io_ptr - pointer to user supplied structure containing info about |
| the input functions. May be NULL. |
| read_data_fn - pointer to a new input function which takes as it's |
| arguments a pointer to a png_struct, a pointer to |
| a location where input data can be stored, and a 32-bit |
| unsigned int which is the number of bytes to be read. |
| To exit and output any fatal error messages the new write |
| function should call png_error(png_ptr, "Error msg"). */ |
| void |
| png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, |
| png_rw_ptr read_data_fn) |
| { |
| png_ptr->io_ptr = io_ptr; |
| |
| if (read_data_fn) |
| png_ptr->read_data_fn = read_data_fn; |
| else |
| png_ptr->read_data_fn = png_default_read_data; |
| |
| /* It is an error to write to a read device */ |
| png_ptr->write_data_fn = NULL; |
| |
| #if defined(PNG_WRITE_FLUSH_SUPPORTED) |
| png_ptr->output_flush_fn = NULL; |
| #endif /* PNG_WRITE_FLUSH_SUPPORTED */ |
| } |
| |
| |
| /* This function returns a pointer to the io_ptr associated with the user |
| functions. The application should free any memory associated with this |
| pointer before png_write_destroy and png_read_destroy are called. */ |
| png_voidp |
| png_get_io_ptr(png_structp png_ptr) |
| { |
| return png_ptr->io_ptr; |
| } |
| |
| /* Initialize the default input/output functions for the png file. If you |
| change the read, or write routines, you can call either png_set_read_fn() |
| or png_set_write_fn() instead of png_init_io(). */ |
| void |
| png_init_io(png_structp png_ptr, FILE *fp) |
| { |
| png_ptr->fp = fp; |
| png_ptr->read_data_fn = png_default_read_data; |
| png_ptr->write_data_fn = png_default_write_data; |
| #ifdef PNG_WRITE_FLUSH_SUPPORTED |
| png_ptr->output_flush_fn = png_default_flush; |
| #endif |
| } |
| |