128 lines
3.9 KiB
C++
128 lines
3.9 KiB
C++
/**
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* @file bufferarray.h
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* @brief Public-facing declaration for the BufferArray scatter/gather class
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*
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* $LicenseInfo:firstyear=2012&license=viewerlgpl$
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* Second Life Viewer Source Code
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* Copyright (C) 2012, Linden Research, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation;
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* version 2.1 of the License only.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
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* $/LicenseInfo$
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*/
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#ifndef _LLCORE_BUFFER_ARRAY_H_
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#define _LLCORE_BUFFER_ARRAY_H_
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#include <cstdlib>
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#include <vector>
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#include "_refcounted.h"
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namespace LLCore
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{
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/// A very simple scatter/gather type map for bulk data. The motivation
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/// for this class is the writedata callback used by libcurl. Response
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/// bodies are delivered to the caller in a sequence of sequential write
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/// operations and this class captures them without having to reallocate
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/// and move data.
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///
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/// The interface looks a little like a unix file descriptor but only
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/// just. There is a notion of a current position, starting from 0,
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/// which is used as the position in the data when performing read and
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/// write operations. The position also moves after various operations:
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/// - seek(...)
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/// - read(...)
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/// - write(...)
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/// - append(...)
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/// - appendBufferAlloc(...)
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/// The object also keeps a total length value which is updated after
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/// write and append operations and beyond which the current position
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/// cannot be set.
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///
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/// Threading: not thread-safe
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///
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/// Allocation: Refcounted, heap only. Caller of the constructor
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/// is given a single refcount.
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///
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class BufferArray : public LLCoreInt::RefCounted
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{
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public:
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BufferArray();
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virtual ~BufferArray();
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private:
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BufferArray(const BufferArray &); // Not defined
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void operator=(const BufferArray &); // Not defined
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public:
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// Internal magic number, may be used by unit tests.
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static const size_t BLOCK_ALLOC_SIZE = 1504;
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/// Appends the indicated data to the BufferArray
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/// modifying current position and total size. New
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/// position is one beyond the final byte of the buffer.
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///
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/// @return Count of bytes copied to BufferArray
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size_t append(const void * src, size_t len);
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/// Similar to @see append(), this call guarantees a
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/// contiguous block of memory of requested size placed
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/// at the current end of the BufferArray. On return,
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/// the data in the memory is considered valid whether
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/// the caller writes to it or not.
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///
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/// @return Pointer to contiguous region at end
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/// of BufferArray of 'len' size.
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void * appendBufferAlloc(size_t len);
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/// Current count of bytes in BufferArray instance.
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size_t size() const
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{
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return mLen;
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}
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/// Copies data from the given position in the instance
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/// to the caller's buffer. Will return a short count of
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/// bytes copied if the 'len' extends beyond the data.
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size_t read(size_t pos, void * dst, size_t len);
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/// Copies data from the caller's buffer to the instance
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/// at the current position. May overwrite existing data,
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/// append data when current position is equal to the
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/// size of the instance or do a mix of both.
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size_t write(size_t pos, const void * src, size_t len);
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protected:
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int findBlock(size_t pos, size_t * ret_offset);
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protected:
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class Block;
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typedef std::vector<Block *> container_t;
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container_t mBlocks;
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size_t mLen;
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}; // end class BufferArray
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} // end namespace LLCore
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#endif // _LLCORE_BUFFER_ARRAY_H_
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