| |
| /* pngrio.c - functions for data input |
| * |
| * libpng 1.00 |
| * For conditions of distribution and use, see copyright notice in png.h |
| * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. |
| * Copyright (c) 1996, 1997 Andreas Dilger |
| * Copyright (c) 1998, Glenn Randers-Pehrson |
| * March 7, 1998 |
| * |
| * This file provides a location for all input. Users which need |
| * special handling are expected to write a function which has the same |
| * arguments as this, and perform a similar function, but possibly has |
| * a different input method. Note that you shouldn't change this |
| * function, but rather write a replacement function and then make |
| * libpng use it at run time with png_set_read_fn(...). |
| */ |
| |
| #define PNG_INTERNAL |
| #include "png.h" |
| |
| /* 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. */ |
| void |
| png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| { |
| png_debug1(4,"reading %d bytes\n", length); |
| if (png_ptr->read_data_fn != NULL) |
| (*(png_ptr->read_data_fn))(png_ptr, data, length); |
| else |
| png_error(png_ptr, "Call to NULL read function"); |
| } |
| |
| #if !defined(PNG_NO_STDIO) |
| /* 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 |
| static void |
| png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| { |
| png_size_t check; |
| |
| /* fread() returns 0 on error, so it is OK to store this in a png_size_t |
| * instead of an int, which is what fread() actually returns. |
| */ |
| check = (png_size_t)fread(data, (png_size_t)1, length, |
| (FILE *)png_ptr->io_ptr); |
| |
| if (check != length) |
| { |
| png_error(png_ptr, "Read 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) |
| |
| static void |
| png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| { |
| int check; |
| png_byte *n_data; |
| FILE *io_ptr; |
| |
| /* Check if data really is near. If so, use usual code. */ |
| n_data = (png_byte *)CVT_PTR_NOCHECK(data); |
| io_ptr = (FILE *)CVT_PTR(png_ptr->io_ptr); |
| if ((png_bytep)n_data == data) |
| { |
| check = fread(n_data, 1, length, io_ptr); |
| } |
| else |
| { |
| png_byte buf[NEAR_BUF_SIZE]; |
| png_size_t read, remaining, err; |
| check = 0; |
| remaining = length; |
| do |
| { |
| read = MIN(NEAR_BUF_SIZE, remaining); |
| err = fread(buf, (png_size_t)1, read, io_ptr); |
| 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 ((png_uint_32)check != (png_uint_32)length) |
| { |
| png_error(png_ptr, "read Error"); |
| } |
| } |
| #endif |
| #endif |
| |
| /* 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 !defined(PNG_NO_STDIO) |
| if (read_data_fn != NULL) |
| png_ptr->read_data_fn = read_data_fn; |
| else |
| png_ptr->read_data_fn = png_default_read_data; |
| #else |
| png_ptr->read_data_fn = read_data_fn; |
| #endif |
| |
| /* 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 */ |
| } |
| |