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4c099b8724
This time correctly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116247 91177308-0d34-0410-b5e6-96231b3b80d8
102 lines
3.2 KiB
C++
102 lines
3.2 KiB
C++
//===- SwapByteOrder.h - Generic and optimized byte swaps -------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file declares generic and optimized functions to swap the byte order of
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// an integral type.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SYSTEM_SWAP_BYTE_ORDER_H
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#define LLVM_SYSTEM_SWAP_BYTE_ORDER_H
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#include "llvm/Support/type_traits.h"
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#include "llvm/System/DataTypes.h"
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#include <cstddef>
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#include <limits>
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namespace llvm {
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namespace sys {
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template<typename value_type>
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inline
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typename enable_if_c<sizeof(value_type) == 1
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&& std::numeric_limits<value_type>::is_integer,
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value_type>::type
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SwapByteOrder(value_type Value) {
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// No swapping needed.
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return Value;
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}
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template<typename value_type>
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inline
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typename enable_if_c<sizeof(value_type) == 2
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&& std::numeric_limits<value_type>::is_integer,
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value_type>::type
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SwapByteOrder(value_type Value) {
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// Cast signed types to unsigned before swapping.
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uint16_t value = static_cast<uint16_t>(Value);
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#if defined(_MSC_VER) && !defined(_DEBUG)
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// The DLL version of the runtime lacks these functions (bug!?), but in a
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// release build they're replaced with BSWAP instructions anyway.
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return _byteswap_ushort(value);
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#else
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uint16_t Hi = value << 8;
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uint16_t Lo = value >> 8;
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return value_type(Hi | Lo);
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#endif
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}
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template<typename value_type>
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inline
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typename enable_if_c<sizeof(value_type) == 4
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&& std::numeric_limits<value_type>::is_integer,
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value_type>::type
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SwapByteOrder(value_type Value) {
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// Cast signed types to unsigned before swapping.
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uint32_t value = static_cast<uint32_t>(Value);
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#if defined(__llvm__) || \
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(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) && !defined(__ICC)
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return __builtin_bswap32(value);
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#elif defined(_MSC_VER) && !defined(_DEBUG)
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return _byteswap_ulong(value);
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#else
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uint32_t Byte0 = value & 0x000000FF;
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uint32_t Byte1 = value & 0x0000FF00;
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uint32_t Byte2 = value & 0x00FF0000;
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uint32_t Byte3 = value & 0xFF000000;
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return value_type(
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(Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24));
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#endif
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}
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template<typename value_type>
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inline
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typename enable_if_c<sizeof(value_type) == 8
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&& std::numeric_limits<value_type>::is_integer,
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value_type>::type
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SwapByteOrder(value_type Value) {
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// Cast signed types to unsigned before swapping.
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uint64_t value = static_cast<uint64_t>(Value);
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#if defined(__llvm__) || \
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(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) && !defined(__ICC)
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return __builtin_bswap64(value);
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#elif defined(_MSC_VER) && !defined(_DEBUG)
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return _byteswap_uint64(value);
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#else
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uint64_t Hi = SwapByteOrder<uint32_t>(uint32_t(value));
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uint32_t Lo = SwapByteOrder<uint32_t>(uint32_t(value >> 32));
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return value_type((Hi << 32) | Lo);
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#endif
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}
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} // end namespace sys
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} // end namespace llvm
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#endif
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