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145 lines
3.1 KiB
C++
145 lines
3.1 KiB
C++
/**
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* =========================================================================
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* File : block_cache.cpp
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* Project : 0 A.D.
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* Description : cache for aligned I/O m_blocks.
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* =========================================================================
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*/
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// license: GPL; see lib/license.txt
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#include "precompiled.h"
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#include "block_cache.h"
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#include "lib/config2.h" // CONFIG2_CACHE_READ_ONLY
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#include "lib/file/common/file_stats.h"
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#include "lib/lockfree.h"
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#include "lib/allocators/pool.h"
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#include "lib/fnv_hash.h"
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#include "io_align.h"
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//-----------------------------------------------------------------------------
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BlockId::BlockId()
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: m_id(0)
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{
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}
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BlockId::BlockId(const Path& pathname, off_t ofs)
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{
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m_id = fnv_hash64(pathname.string().c_str(), pathname.string().length());
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const size_t indexBits = 16;
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m_id <<= indexBits;
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const off_t blockIndex = ofs / BLOCK_SIZE;
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debug_assert(blockIndex < (1ul << indexBits));
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m_id |= blockIndex;
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}
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bool BlockId::operator==(const BlockId& rhs) const
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{
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return m_id == rhs.m_id;
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}
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bool BlockId::operator!=(const BlockId& rhs) const
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{
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return !operator==(rhs);
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}
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//-----------------------------------------------------------------------------
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struct Block
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{
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Block(BlockId id, const shared_ptr<u8>& buf)
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{
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this->id = id;
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this->buf = buf;
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}
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// block is "valid" and can satisfy Retrieve() requests if a
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// (non-default-constructed) ID has been assigned.
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BlockId id;
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// this block is "in use" if use_count != 1.
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shared_ptr<u8> buf;
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};
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//-----------------------------------------------------------------------------
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class BlockCache::Impl
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{
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public:
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Impl(size_t numBlocks)
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: m_maxBlocks(numBlocks)
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{
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}
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void Add(BlockId id, const shared_ptr<u8>& buf)
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{
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if(m_blocks.size() > m_maxBlocks)
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{
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#if CONFIG2_CACHE_READ_ONLY
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mprotect((void*)m_blocks.front().buf.get(), BLOCK_SIZE, PROT_READ);
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#endif
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m_blocks.pop_front(); // evict oldest block
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}
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#if CONFIG2_CACHE_READ_ONLY
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mprotect((void*)buf.get(), BLOCK_SIZE, PROT_WRITE|PROT_READ);
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#endif
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m_blocks.push_back(Block(id, buf));
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}
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bool Retrieve(BlockId id, shared_ptr<u8>& buf)
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{
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// (linear search is ok since we only expect to manage a few blocks)
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for(size_t i = 0; i < m_blocks.size(); i++)
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{
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Block& block = m_blocks[i];
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if(block.id == id)
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{
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buf = block.buf;
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return true;
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}
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}
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return false;
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}
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void InvalidateAll()
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{
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// note: don't check whether any references are held etc. because
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// this should only be called at the end of the (test) program.
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m_blocks.clear();
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}
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private:
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size_t m_maxBlocks;
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typedef std::deque<Block> Blocks;
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Blocks m_blocks;
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};
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//-----------------------------------------------------------------------------
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BlockCache::BlockCache(size_t numBlocks)
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: impl(new Impl(numBlocks))
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{
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}
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void BlockCache::Add(BlockId id, const shared_ptr<u8>& buf)
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{
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impl->Add(id, buf);
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}
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bool BlockCache::Retrieve(BlockId id, shared_ptr<u8>& buf)
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{
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return impl->Retrieve(id, buf);
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}
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void BlockCache::InvalidateAll()
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{
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return impl->InvalidateAll();
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}
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