/*
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 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
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 * this software without specific prior written permission.
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/** @file
 * Implementation of a perfect compressor, which compresses data to its
 * maximum allowed compression ratio.
 */

#include "mem/cache/compressors/perfect.hh"

#include <algorithm>

#include "debug/CacheComp.hh"
#include "params/PerfectCompressor.hh"

PerfectCompressor::CompData::CompData(const uint64_t* data,
    std::size_t num_entries)
    : CompressionData(), entries(data, data + num_entries)
{
}

PerfectCompressor::PerfectCompressor(const Params *p)
    : BaseCacheCompressor(p),
      compressedSize(8 * blkSize / p->max_compression_ratio),
      compressionLatency(p->compression_latency),
      decompressionLatency(p->decompression_latency)
{
}

std::unique_ptr<BaseCacheCompressor::CompressionData>
PerfectCompressor::compress(const uint64_t* cache_line, Cycles& comp_lat,
    Cycles& decomp_lat)
{
    // Compress every word sequentially
    std::unique_ptr<BaseCacheCompressor::CompressionData> comp_data(
        new CompData(cache_line, blkSize/8));

    // Set relevant metadata
    comp_data->setSizeBits(compressedSize);
    comp_lat = compressionLatency;
    decomp_lat = decompressionLatency;

    return comp_data;
}

void
PerfectCompressor::decompress(const CompressionData* comp_data,
    uint64_t* data)
{
    // Decompress every entry sequentially
    const std::vector<uint64_t>& entries =
        static_cast<const CompData*>(comp_data)->entries;
    assert(entries.size() == (blkSize/8));
    std::copy(entries.begin(), entries.end(), data);
}

PerfectCompressor*
PerfectCompressorParams::create()
{
    return new PerfectCompressor(this);
}