ref: 2c23de27d5006e969106fad672399fafe6464845
dir: /DoConfig/fltk/png/pngrio.c/
/* pngrio.c - functions for data input * * Last changed in libpng 1.6.15 [November 20, 2014] * Copyright (c) 1998-2014 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(...). */ #include "pngpriv.h" #ifdef PNG_READ_SUPPORTED /* 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"); } #ifdef PNG_STDIO_SUPPORTED /* 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"); } #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 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; #ifdef PNG_STDIO_SUPPORTED 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 #ifdef PNG_WRITE_SUPPORTED /* 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"); } #endif #ifdef PNG_WRITE_FLUSH_SUPPORTED png_ptr->output_flush_fn = NULL; #endif } #endif /* READ */