/** * @file bufferarray.cpp * @brief Implements the BufferArray scatter/gather buffer * * $LicenseInfo:firstyear=2012&license=viewerlgpl$ * Second Life Viewer Source Code * Copyright (C) 2012, Linden Research, Inc. * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; * version 2.1 of the License only. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA * * Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA * $/LicenseInfo$ */ #include "bufferarray.h" #include "llexception.h" #include "llmemory.h" // BufferArray is a list of chunks, each a BufferArray::Block, of contiguous // data presented as a single array. Chunks are at least BufferArray::BLOCK_ALLOC_SIZE // in length and can be larger. Any chunk may be partially filled or even // empty. // // The BufferArray itself is sharable as a RefCounted entity. As shared // reads don't work with the concept of a current position/seek value, // none is kept with the object. Instead, the read and write operations // all take position arguments. Single write/shared read isn't supported // directly and any such attempts have to be serialized outside of this // implementation. namespace LLCore { // ================================== // BufferArray::Block Declaration // ================================== class BufferArray::Block { public: ~Block(); void operator delete(void *); void operator delete(void *, size_t len); protected: Block(size_t len); Block(const Block &); // Not defined void operator=(const Block &); // Not defined // Allocate the block with the additional space for the // buffered data at the end of the object. void * operator new(size_t len, size_t addl_len); public: // Only public entry to get a block. static Block * alloc(size_t len); public: size_t mUsed; size_t mAlloced; // *NOTE: Must be last member of the object. We'll // overallocate as requested via operator new and index // into the array at will. char mData[1]; }; // ================================== // BufferArray Definitions // ================================== #if ! LL_WINDOWS const size_t BufferArray::BLOCK_ALLOC_SIZE; #endif // ! LL_WINDOWS BufferArray::BufferArray() : LLCoreInt::RefCounted(true), mLen(0) {} BufferArray::~BufferArray() { for (container_t::iterator it(mBlocks.begin()); it != mBlocks.end(); ++it) { delete *it; *it = NULL; } mBlocks.clear(); } size_t BufferArray::append(const void * src, size_t len) { const size_t ret(len); const char * c_src(static_cast<const char *>(src)); // First, try to copy into the last block if (len && ! mBlocks.empty()) { Block & last(*mBlocks.back()); if (last.mUsed < last.mAlloced) { // Some will fit... const size_t copy_len((std::min)(len, (last.mAlloced - last.mUsed))); memcpy(&last.mData[last.mUsed], c_src, copy_len); last.mUsed += copy_len; llassert_always(last.mUsed <= last.mAlloced); mLen += copy_len; c_src += copy_len; len -= copy_len; } } // Then get new blocks as needed while (len) { const size_t copy_len((std::min)(len, BLOCK_ALLOC_SIZE)); if (mBlocks.size() >= mBlocks.capacity()) { mBlocks.reserve(mBlocks.size() + 5); } Block * block; try { block = Block::alloc(BLOCK_ALLOC_SIZE); } catch (std::bad_alloc&) { LLMemory::logMemoryInfo(true); //output possible call stacks to log file. LLError::LLCallStacks::print(); LL_WARNS() << "Bad memory allocation in thrown by Block::alloc in read!" << LL_ENDL; break; } memcpy(block->mData, c_src, copy_len); block->mUsed = copy_len; llassert_always(block->mUsed <= block->mAlloced); mBlocks.push_back(block); mLen += copy_len; c_src += copy_len; len -= copy_len; } return ret - len; } void * BufferArray::appendBufferAlloc(size_t len) { // If someone asks for zero-length, we give them a valid pointer. if (mBlocks.size() >= mBlocks.capacity()) { mBlocks.reserve(mBlocks.size() + 5); } Block * block = Block::alloc((std::max)(BLOCK_ALLOC_SIZE, len)); block->mUsed = len; mBlocks.push_back(block); mLen += len; return block->mData; } size_t BufferArray::read(size_t pos, void * dst, size_t len) { char * c_dst(static_cast<char *>(dst)); if (pos >= mLen) return 0; size_t len_limit(mLen - pos); len = (std::min)(len, len_limit); if (0 == len) return 0; size_t result(0), offset(0); const auto block_limit(mBlocks.size()); int block_start(findBlock(pos, &offset)); if (block_start < 0) return 0; do { Block & block(*mBlocks[block_start]); size_t block_limit(block.mUsed - offset); size_t block_len((std::min)(block_limit, len)); memcpy(c_dst, &block.mData[offset], block_len); result += block_len; len -= block_len; c_dst += block_len; offset = 0; ++block_start; } while (len && block_start < block_limit); return result; } size_t BufferArray::write(size_t pos, const void * src, size_t len) { const char * c_src(static_cast<const char *>(src)); if (pos > mLen || 0 == len) return 0; size_t result(0), offset(0); const auto block_limit(mBlocks.size()); int block_start(findBlock(pos, &offset)); if (block_start >= 0) { // Some or all of the write will be on top of // existing data. do { Block & block(*mBlocks[block_start]); size_t block_limit(block.mUsed - offset); size_t block_len((std::min)(block_limit, len)); memcpy(&block.mData[offset], c_src, block_len); result += block_len; c_src += block_len; len -= block_len; offset = 0; ++block_start; } while (len && block_start < block_limit); } // Something left, see if it will fit in the free // space of the last block. if (len && ! mBlocks.empty()) { Block & last(*mBlocks.back()); if (last.mUsed < last.mAlloced) { // Some will fit... const size_t copy_len((std::min)(len, (last.mAlloced - last.mUsed))); memcpy(&last.mData[last.mUsed], c_src, copy_len); last.mUsed += copy_len; result += copy_len; llassert_always(last.mUsed <= last.mAlloced); mLen += copy_len; c_src += copy_len; len -= copy_len; } } if (len) { // Some or all of the remaining write data will // be an append. result += append(c_src, len); } return result; } int BufferArray::findBlock(size_t pos, size_t * ret_offset) { *ret_offset = 0; if (pos >= mLen) return -1; // Doesn't exist const int block_limit(narrow<size_t>(mBlocks.size())); for (int i(0); i < block_limit; ++i) { if (pos < mBlocks[i]->mUsed) { *ret_offset = pos; return i; } pos -= mBlocks[i]->mUsed; } // Shouldn't get here but... return -1; } bool BufferArray::getBlockStartEnd(int block, const char ** start, const char ** end) { if (block < 0 || block >= mBlocks.size()) { return false; } const Block & b(*mBlocks[block]); *start = &b.mData[0]; *end = &b.mData[b.mUsed]; return true; } // ================================== // BufferArray::Block Definitions // ================================== BufferArray::Block::Block(size_t len) : mUsed(0), mAlloced(len) { memset(mData, 0, len); } BufferArray::Block::~Block() { mUsed = 0; mAlloced = 0; } void * BufferArray::Block::operator new(size_t len, size_t addl_len) { void * mem = new char[len + addl_len + sizeof(void *)]; return mem; } void BufferArray::Block::operator delete(void * mem) { char * cmem = static_cast<char *>(mem); delete [] cmem; } void BufferArray::Block::operator delete(void * mem, size_t) { operator delete(mem); } BufferArray::Block * BufferArray::Block::alloc(size_t len) { Block * block = new (len) Block(len); return block; } } // end namespace LLCore