| /* pngrio.c - functions for data input | |
| * | |
| * Last changed in libpng 1.6.0 [February 14, 2013] | |
| * Copyright (c) 1998-2013 Glenn Randers-Pehrson | |
| * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) | |
| * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) | |
| * | |
| * This code is released under the libpng license. | |
| * For conditions of distribution and use, see the disclaimer | |
| * and license in png.h | |
| * | |
| * This file provides a location for all input. Users who need | |
| * special handling are expected to write a function that has the same | |
| * arguments as this and performs a similar function, but that 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(...). | |
| */ | |
| /* 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 /* PRIVATE */ | |
| png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length) | |
| { | |
| png_debug1(4, "reading %d bytes", (int)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"); | |
| } | |
| /* This is the function that 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. | |
| */ | |
| void PNGCBAPI | |
| png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) | |
| { | |
| png_size_t check; | |
| if (png_ptr == NULL) | |
| return; | |
| /* 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 = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr)); | |
| if (check != length) | |
| png_error(png_ptr, "Read Error"); | |
| } | |
| /* 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 that takes as its | |
| * arguments a pointer to a png_struct, a pointer to | |
| * a location where input data can be stored, and a 32-bit | |
| * unsigned int that 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"). | |
| * May be NULL, in which case libpng's default function will | |
| * be used. | |
| */ | |
| void PNGAPI | |
| png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr, | |
| png_rw_ptr read_data_fn) | |
| { | |
| if (png_ptr == NULL) | |
| return; | |
| png_ptr->io_ptr = io_ptr; | |
| if (read_data_fn != NULL) | |
| png_ptr->read_data_fn = read_data_fn; | |
| else | |
| png_ptr->read_data_fn = png_default_read_data; | |
| png_ptr->read_data_fn = read_data_fn; | |
| /* It is an error to write to a read device */ | |
| if (png_ptr->write_data_fn != NULL) | |
| { | |
| png_ptr->write_data_fn = NULL; | |
| png_warning(png_ptr, | |
| "Can't set both read_data_fn and write_data_fn in the" | |
| " same structure"); | |
| } | |
| png_ptr->output_flush_fn = NULL; | |
| } | |