[96425] | 1 |
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| 2 | /* pngrio.c - functions for data input
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| 3 | *
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| 4 | * Copyright (c) 2018 Cosmin Truta
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| 5 | * Copyright (c) 1998-2002,2004,2006-2016,2018 Glenn Randers-Pehrson
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| 6 | * Copyright (c) 1996-1997 Andreas Dilger
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| 7 | * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
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| 8 | *
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| 9 | * This code is released under the libpng license.
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| 10 | * For conditions of distribution and use, see the disclaimer
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| 11 | * and license in png.h
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| 12 | *
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| 13 | * This file provides a location for all input. Users who need
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| 14 | * special handling are expected to write a function that has the same
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| 15 | * arguments as this and performs a similar function, but that possibly
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| 16 | * has a different input method. Note that you shouldn't change this
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| 17 | * function, but rather write a replacement function and then make
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| 18 | * libpng use it at run time with png_set_read_fn(...).
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| 19 | */
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| 20 |
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| 21 | #include "pngpriv.h"
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| 22 |
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| 23 | #ifdef PNG_READ_SUPPORTED
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| 24 |
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| 25 | /* Read the data from whatever input you are using. The default routine
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| 26 | * reads from a file pointer. Note that this routine sometimes gets called
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| 27 | * with very small lengths, so you should implement some kind of simple
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| 28 | * buffering if you are using unbuffered reads. This should never be asked
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| 29 | * to read more than 64K on a 16-bit machine.
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| 30 | */
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| 31 | void /* PRIVATE */
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| 32 | png_read_data(png_structrp png_ptr, png_bytep data, size_t length)
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| 33 | {
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| 34 | png_debug1(4, "reading %d bytes", (int)length);
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| 35 |
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| 36 | if (png_ptr->read_data_fn != NULL)
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| 37 | (*(png_ptr->read_data_fn))(png_ptr, data, length);
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| 38 |
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| 39 | else
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| 40 | png_error(png_ptr, "Call to NULL read function");
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| 41 | }
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| 42 |
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| 43 | #ifdef PNG_STDIO_SUPPORTED
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| 44 | /* This is the function that does the actual reading of data. If you are
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| 45 | * not reading from a standard C stream, you should create a replacement
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| 46 | * read_data function and use it at run time with png_set_read_fn(), rather
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| 47 | * than changing the library.
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| 48 | */
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| 49 | void PNGCBAPI
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| 50 | png_default_read_data(png_structp png_ptr, png_bytep data, size_t length)
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| 51 | {
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| 52 | size_t check;
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| 53 |
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| 54 | if (png_ptr == NULL)
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| 55 | return;
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| 56 |
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| 57 | /* fread() returns 0 on error, so it is OK to store this in a size_t
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| 58 | * instead of an int, which is what fread() actually returns.
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| 59 | */
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| 60 | check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
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| 61 |
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| 62 | if (check != length)
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| 63 | png_error(png_ptr, "Read Error");
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| 64 | }
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| 65 | #endif
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| 66 |
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| 67 | /* This function allows the application to supply a new input function
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| 68 | * for libpng if standard C streams aren't being used.
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| 69 | *
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| 70 | * This function takes as its arguments:
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| 71 | *
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| 72 | * png_ptr - pointer to a png input data structure
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| 73 | *
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| 74 | * io_ptr - pointer to user supplied structure containing info about
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| 75 | * the input functions. May be NULL.
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| 76 | *
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| 77 | * read_data_fn - pointer to a new input function that takes as its
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| 78 | * arguments a pointer to a png_struct, a pointer to
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| 79 | * a location where input data can be stored, and a 32-bit
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| 80 | * unsigned int that is the number of bytes to be read.
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| 81 | * To exit and output any fatal error messages the new write
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| 82 | * function should call png_error(png_ptr, "Error msg").
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| 83 | * May be NULL, in which case libpng's default function will
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| 84 | * be used.
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| 85 | */
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| 86 | void PNGAPI
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| 87 | png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
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| 88 | png_rw_ptr read_data_fn)
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| 89 | {
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| 90 | if (png_ptr == NULL)
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| 91 | return;
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| 92 |
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| 93 | png_ptr->io_ptr = io_ptr;
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| 94 |
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| 95 | #ifdef PNG_STDIO_SUPPORTED
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| 96 | if (read_data_fn != NULL)
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| 97 | png_ptr->read_data_fn = read_data_fn;
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| 98 |
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| 99 | else
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| 100 | png_ptr->read_data_fn = png_default_read_data;
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| 101 | #else
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| 102 | png_ptr->read_data_fn = read_data_fn;
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| 103 | #endif
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| 104 |
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| 105 | #ifdef PNG_WRITE_SUPPORTED
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| 106 | /* It is an error to write to a read device */
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| 107 | if (png_ptr->write_data_fn != NULL)
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| 108 | {
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| 109 | png_ptr->write_data_fn = NULL;
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| 110 | png_warning(png_ptr,
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| 111 | "Can't set both read_data_fn and write_data_fn in the"
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| 112 | " same structure");
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| 113 | }
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| 114 | #endif
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| 115 |
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| 116 | #ifdef PNG_WRITE_FLUSH_SUPPORTED
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| 117 | png_ptr->output_flush_fn = NULL;
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| 118 | #endif
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| 119 | }
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| 120 | #endif /* READ */
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