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Diffstat (limited to 'gs/libpng/pngrio.c')
| -rw-r--r-- | gs/libpng/pngrio.c | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/gs/libpng/pngrio.c b/gs/libpng/pngrio.c new file mode 100644 index 000000000..1a7f0388c --- /dev/null +++ b/gs/libpng/pngrio.c @@ -0,0 +1,137 @@ + +/* pngrio.c - functions for data input + + libpng 1.0 beta 6 - version 0.96 + 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 + May 12, 1997 + + 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"); +} + +/* 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 (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 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 != NULL) + 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 */ +} + |