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https://gitea.wildfiregames.com/0ad/0ad
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71 lines
2.4 KiB
C++
71 lines
2.4 KiB
C++
/* Copyright (c) 2010 Wildfire Games
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#ifndef INCLUDED_IO_ALIGN
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#define INCLUDED_IO_ALIGN
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#include "lib/bits.h" // IsAligned, round_up
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/**
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* block := power-of-two sized chunk of a file.
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* all transfers are expanded to naturally aligned, whole blocks.
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* (this makes caching parts of files feasible; it is also much faster
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* for some aio implementations, e.g. wposix.)
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* (blocks are also thereby page-aligned, which allows write-protecting
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* file buffers without worrying about their boundaries.)
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**/
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static const size_t BLOCK_SIZE = 1024*KiB;
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// note: *sizes* and *offsets* are aligned to blocks to allow zero-copy block cache.
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// that the *buffer* need only be sector-aligned (we assume 4kb for simplicity)
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// (this is a requirement of the underlying Windows OS)
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static const size_t SECTOR_SIZE = 4*KiB;
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template<class T>
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inline bool IsAligned_Data(T* address)
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{
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return IsAligned((uintptr_t)address, SECTOR_SIZE);
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}
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inline bool IsAligned_Offset(off_t ofs)
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{
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return IsAligned(ofs, BLOCK_SIZE);
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}
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inline off_t AlignedOffset(off_t ofs)
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{
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return (off_t)round_down<size_t>(size_t(ofs), BLOCK_SIZE);
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}
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inline off_t AlignedSize(off_t size)
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{
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return (off_t)round_up<size_t>(size_t(size), BLOCK_SIZE);
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}
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inline off_t PaddedSize(off_t size, off_t ofs)
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{
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return (off_t)round_up<size_t>(size_t(size + ofs - AlignedOffset(ofs)), BLOCK_SIZE);
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}
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#endif // #ifndef INCLUDED_IO_ALIGN
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