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/**
* @file bufferarray.h
* @brief Public-facing declaration for the BufferArray scatter/gather class
*
* $LicenseInfo:firstyear=2012&license=viewerlgpl$
* 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
* $/LicenseInfo$
*/
#ifndef _LLCORE_BUFFER_ARRAY_H_
#define _LLCORE_BUFFER_ARRAY_H_
#include <cstdlib>
#include <vector>
#include "_refcounted.h"
namespace LLCore
{
class BufferArrayStreamBuf;
/// A very simple scatter/gather type map for bulk data. The motivation
/// for this class is the writedata callback used by libcurl. Response
/// bodies are delivered to the caller in a sequence of sequential write
/// operations and this class captures them without having to reallocate
/// and move data.
///
/// The interface looks a little like a unix file descriptor but only
/// just. There is a notion of a current position, starting from 0,
/// which is used as the position in the data when performing read and
/// write operations. The position also moves after various operations:
/// - seek(...)
/// - read(...)
/// - write(...)
/// - append(...)
/// - appendBufferAlloc(...)
/// The object also keeps a total length value which is updated after
/// write and append operations and beyond which the current position
/// cannot be set.
///
/// Threading: not thread-safe
///
/// Allocation: Refcounted, heap only. Caller of the constructor
/// is given a single refcount.
///
class BufferArray : public LLCoreInt::RefCounted
{
public:
// BufferArrayStreamBuf has intimate knowledge of this
// implementation to implement a buffer-free adapter.
// Changes here will likely need to be reflected there.
friend class BufferArrayStreamBuf;
BufferArray();
protected:
virtual ~BufferArray(); // Use release()
private:
BufferArray(const BufferArray &); // Not defined
void operator=(const BufferArray &); // Not defined
public:
// Internal magic number, may be used by unit tests.
static const size_t BLOCK_ALLOC_SIZE = 65540;
/// Appends the indicated data to the BufferArray
/// modifying current position and total size. New
/// position is one beyond the final byte of the buffer.
///
/// @return Count of bytes copied to BufferArray
size_t append(const void * src, size_t len);
/// Similar to @see append(), this call guarantees a
/// contiguous block of memory of requested size placed
/// at the current end of the BufferArray. On return,
/// the data in the memory is considered valid whether
/// the caller writes to it or not.
///
/// @return Pointer to contiguous region at end
/// of BufferArray of 'len' size.
void * appendBufferAlloc(size_t len);
/// Current count of bytes in BufferArray instance.
size_t size() const
{
return mLen;
}
/// Copies data from the given position in the instance
/// to the caller's buffer. Will return a short count of
/// bytes copied if the 'len' extends beyond the data.
size_t read(size_t pos, void * dst, size_t len);
/// Copies data from the caller's buffer to the instance
/// at the current position. May overwrite existing data,
/// append data when current position is equal to the
/// size of the instance or do a mix of both.
size_t write(size_t pos, const void * src, size_t len);
protected:
int findBlock(size_t pos, size_t * ret_offset);
bool getBlockStartEnd(int block, const char ** start, const char ** end);
protected:
class Block;
typedef std::vector<Block *> container_t;
container_t mBlocks;
size_t mLen;
}; // end class BufferArray
} // end namespace LLCore
#endif // _LLCORE_BUFFER_ARRAY_H_
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