65 lines
2.7 KiB
C
65 lines
2.7 KiB
C
/* inffast_chunk.h -- header to use inffast_chunk.c
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*
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* (C) 1995-2013 Jean-loup Gailly and Mark Adler
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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*
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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*
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*
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* Jean-loup Gailly Mark Adler
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* jloup@gzip.org madler@alumni.caltech.edu
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*
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* Copyright (C) 1995-2003, 2010 Mark Adler
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* Copyright (C) 2017 ARM, Inc.
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* Copyright 2023 The Chromium Authors
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* WARNING: this file should *not* be used by applications. It is
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part of the implementation of the compression library and is
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subject to change. Applications should only use zlib.h.
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*/
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#include "inffast.h"
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/* INFLATE_FAST_MIN_INPUT:
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The minimum number of input bytes needed so that we can safely call
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inflate_fast() with only one up-front bounds check. One
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length/distance code pair (15 bits for the length code, 5 bits for length
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extra, 15 bits for the distance code, 13 bits for distance extra) requires
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reading up to 48 input bits. Additionally, in the same iteraction, we may
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decode two literals from the root-table (requiring MIN_OUTPUT = 258 + 2).
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Each root-table entry is up to 10 bits, for a total of 68 input bits each
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iteraction.
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The refill variant reads 8 bytes from the buffer at a time, and advances
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the input pointer by up to 7 bytes, ensuring there are at least 56-bits
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available in the bit-buffer. The technique was documented by Fabian Giesen
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on his blog as variant 4 in the article 'Reading bits in far too many ways':
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https://fgiesen.wordpress.com/2018/02/20/
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In the worst case, we may refill twice in the same iteraction, requiring
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MIN_INPUT = 8 + 7.
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*/
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#ifdef INFLATE_CHUNK_READ_64LE
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#undef INFLATE_FAST_MIN_INPUT
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#define INFLATE_FAST_MIN_INPUT 15
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#undef INFLATE_FAST_MIN_OUTPUT
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#define INFLATE_FAST_MIN_OUTPUT 260
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#endif
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void ZLIB_INTERNAL inflate_fast_chunk_(z_streamp strm, unsigned start);
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