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87 lines
2.4 KiB
C++
87 lines
2.4 KiB
C++
// SPDX-License-Identifier: MIT OR MPL-2.0 OR LGPL-2.1-or-later OR GPL-2.0-or-later
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// Copyright 2011, SIL International, All rights reserved.
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/*
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Description:
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A set of fast template based decoders for decoding values of any C integer
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type up to long int size laid out with most significant byte first or least
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significant byte first (aka big endian or little endian). These are CPU
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byte order agnostic and will function the same regardless of the CPUs native
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byte order.
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Being template based means if the either le or be class is not used then
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template code of unused functions will not be instantiated by the compiler
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and thus shouldn't cause any overhead.
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*/
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#include <cstddef>
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#pragma once
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class be
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{
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template<int S>
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inline static unsigned long int _peek(const unsigned char * p) {
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return _peek<S/2>(p) << (S/2)*8 | _peek<S/2>(p+S/2);
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}
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public:
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template<typename T>
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inline static T peek(const void * p) {
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return T(_peek<sizeof(T)>(static_cast<const unsigned char *>(p)));
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}
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template<typename T>
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inline static T read(const unsigned char * &p) {
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const T r = T(_peek<sizeof(T)>(p));
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p += sizeof r;
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return r;
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}
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template<typename T>
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inline static T swap(const T x) {
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return T(_peek<sizeof(T)>(reinterpret_cast<const unsigned char *>(&x)));
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}
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template<typename T>
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inline static void skip(const unsigned char * &p, size_t n=1) {
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p += sizeof(T)*n;
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}
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};
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template<>
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inline unsigned long int be::_peek<1>(const unsigned char * p) { return *p; }
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class le
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{
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template<int S>
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inline static unsigned long int _peek(const unsigned char * p) {
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return _peek<S/2>(p) | _peek<S/2>(p+S/2) << (S/2)*8;
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}
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public:
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template<typename T>
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inline static T peek(const void * p) {
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return T(_peek<sizeof(T)>(static_cast<const unsigned char *>(p)));
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}
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template<typename T>
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inline static T read(const unsigned char * &p) {
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const T r = T(_peek<sizeof(T)>(p));
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p += sizeof r;
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return r;
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}
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template<typename T>
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inline static T swap(const T x) {
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return T(_peek<sizeof(T)>(reinterpret_cast<const unsigned char *>(&x)));
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}
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template<typename T>
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inline static void skip(const unsigned char * &p, size_t n=1) {
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p += sizeof(T)*n;
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}
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};
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template<>
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inline unsigned long int le::_peek<1>(const unsigned char * p) { return *p; }
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