/*
 * (C) Copyright 1996-2017 ECMWF.
 * 
 * This software is licensed under the terms of the Apache Licence Version 2.0
 * which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. 
 * In applying this licence, ECMWF does not waive the privileges and immunities 
 * granted to it by virtue of its status as an intergovernmental organisation nor
 * does it submit to any jurisdiction.
 */

#include <unistd.h>
#include <sys/mman.h>

#include "eckit/eckit.h"
#include "eckit/memory/MapAllocator.h"
#include "eckit/exception/Exceptions.h"

//-----------------------------------------------------------------------------

namespace eckit {

//-----------------------------------------------------------------------------

static size_t whole_page(size_t size)
{
        static size_t page = sysconf(_SC_PAGE_SIZE);
        return ((size + page - 1) / page) * page;
}

MapAllocatorTooSmall::MapAllocatorTooSmall(size_t,size_t):
        Exception("MapAllocator too small")
{
}

MapAllocator::MapAllocator(size_t length):
        fd_(-1),    
        length_(whole_page(length)),
        count_(0),
        more_(0)
{
        addr_ = ::mmap(0,length_,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANONYMOUS,fd_,0);

        if(addr_ == MAP_FAILED)
            throw FailedSystemCall("mmap",Here());

        next_ = (char*)addr_;
        left_ = length_;
//	Log::warning() << "MapAllocator created " << length_ << std::endl;
}

MapAllocator::~MapAllocator()
{
//	Log::warning() << "MapAllocator deleted " << length_ << std::endl;
        munmap(addr_,length_);
        if(fd_>=0) close(fd_);
        delete more_;
}

union Align {
        char      char_;
        double    double_;
        long long longlong_;
        void*     voidstar_;
        float     float_;
};

const int WORD = sizeof(Align);

void *MapAllocator::allocate(size_t size)
{
        //return ::operator new(size);

        size = ((size + WORD - 1) / WORD) * WORD;

        if(size > left_)
        {
                if(!more_)
                {
//			Log::warning() << "MapAllocator too small: length=" << length_ << " left=" << left_ << " request=" << size << std::endl;
                        more_ = new MapAllocator(std::max(length_,size));
                        ASSERT(more_);
                }
                return more_->allocate(size);
        }

        char *addr = next_;
        next_ += size;
        left_ -= size;
        count_++;

        return addr;
}

void MapAllocator::deallocate(void* addr)
{
        //::operator delete(addr); return;

        char* p = (char*)addr;
        char* q = (char*)addr_;

        if(p >= q && p < q + length_)
        {
                count_--;
                if(count_ == 0)
                {
//			Log::warning() << "MapAllocator empty" << std::endl;
                        next_ = (char*)addr_;
                        left_ = length_;
                }
        }
        else
        {
                ASSERT(more_);
                more_->deallocate(addr);
                if(more_->count_ == 0 && more_->more_ == 0)
                {
                        delete more_;
                        more_ = 0;
                }
        }
}

//-----------------------------------------------------------------------------

} // namespace eckit

