/* pngrio.c - functions for data input * * Last changed in libpng 1.2.43 [February 25, 2010] * Copyright (c) 1998-2010 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(...). */ #define PNG_INTERNAL #define PNG_NO_PEDANTIC_WARNINGS #include "png.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_structp 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_INDEX_SUPPORTED png_ptr->total_data_read += length; #endif } #ifdef PNG_INDEX_SUPPORTED void /* PRIVATE */ png_seek_data(png_structp png_ptr, png_uint_32 offset) { if (png_ptr->seek_data_fn != NULL) (*(png_ptr->seek_data_fn))(png_ptr, offset); else png_error(png_ptr, "Call to NULL seek function"); } #endif #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. */ #ifndef USE_FAR_KEYWORD void PNGAPI 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. */ #ifdef _WIN32_WCE if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) check = 0; #else check = (png_size_t)fread(data, (png_size_t)1, length, (png_FILE_p)png_ptr->io_ptr); #endif 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 PNGAPI png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) { int check; png_byte *n_data; png_FILE_p io_ptr; if (png_ptr == NULL) return; /* Check if data really is near. If so, use usual code. */ n_data = (png_byte *)CVT_PTR_NOCHECK(data); io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); if ((png_bytep)n_data == data) { #ifdef _WIN32_WCE if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) check = 0; #else check = fread(n_data, 1, length, io_ptr); #endif } else { png_byte buf[NEAR_BUF_SIZE]; png_size_t read, remaining, err; check = 0; remaining = length; do { read = MIN(NEAR_BUF_SIZE, remaining); #ifdef _WIN32_WCE if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) ) err = 0; #else err = fread(buf, (png_size_t)1, read, io_ptr); #endif 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 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_structp 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 /* 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, "It's an error to set both read_data_fn and write_data_fn in the "); png_warning(png_ptr, "same structure. Resetting write_data_fn to NULL."); } #ifdef PNG_WRITE_FLUSH_SUPPORTED png_ptr->output_flush_fn = NULL; #endif } #ifdef PNG_INDEX_SUPPORTED void PNGAPI png_set_seek_fn(png_structp png_ptr, png_seek_ptr seek_data_fn) { if (png_ptr == NULL) return; png_ptr->seek_data_fn = seek_data_fn; } #endif #endif /* PNG_READ_SUPPORTED */