mem_file.cpp

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/***************************************************************************
 * lib/io/mem_file.cpp
 *
 * Part of the STXXL. See http://stxxl.sourceforge.net
 *
 * Copyright (C) 2008 Andreas Beckmann <[email protected]>
 * Copyright (C) 2013 Timo Bingmann <[email protected]>
 *
 * Distributed under the Boost Software License, Version 1.0.
 * (See accompanying file LICENSE_1_0.txt or copy at
 * http://www.boost.org/LICENSE_1_0.txt)
 **************************************************************************/

#include <cstring>
#include <limits>
#include <cassert>

#include <stxxl/bits/io/mem_file.h>
#include <stxxl/bits/io/iostats.h>


STXXL_BEGIN_NAMESPACE


void mem_file::serve(const request* req) throw (io_error)
{
 scoped_mutex_lock lock(m_mutex);

 assert(req->get_file() == this);
 offset_type offset = req->get_offset();
 void* buffer = req->get_buffer();
 size_type bytes = req->get_size();
 request::request_type type = req->get_type();

 if (type == request::READ)
 {
 stats::scoped_read_timer read_timer(bytes);
 memcpy(buffer, ptr + offset, bytes);
 }
 else
 {
 stats::scoped_write_timer write_timer(bytes);
 memcpy(ptr + offset, buffer, bytes);
 }
}

const char* mem_file::io_type() const
{
 return "memory";
}

mem_file::~mem_file()
{
 free(ptr);
 ptr = NULL;
}

void mem_file::lock()
{
 // nothing to do
}

file::offset_type mem_file::size()
{
 return sz;
}

void mem_file::set_size(offset_type newsize)
{
 scoped_mutex_lock lock(m_mutex);
 assert(newsize <= std::numeric_limits<offset_type>::max());

 ptr = (char*)realloc(ptr, (size_t)newsize);
 sz = newsize;
}

void mem_file::discard(offset_type offset, offset_type size)
{
 scoped_mutex_lock lock(m_mutex);
#ifndef STXXL_MEMFILE_DONT_CLEAR_FREED_MEMORY
 // overwrite the freed region with uninitialized memory
 STXXL_VERBOSE("discard at " << offset << " len " << size);
 void* uninitialized = malloc(BLOCK_ALIGN);
 while (size >= BLOCK_ALIGN) {
 memcpy(ptr + offset, uninitialized, BLOCK_ALIGN);
 offset += BLOCK_ALIGN;
 size -= BLOCK_ALIGN;
 }
 assert(size <= std::numeric_limits<offset_type>::max());
 if (size > 0)
 memcpy(ptr + offset, uninitialized, (size_t)size);
 free(uninitialized);
#else
 STXXL_UNUSED(offset);
 STXXL_UNUSED(size);
#endif
}

STXXL_END_NAMESPACE