lang/c++/impl/DataFile.cc

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "DataFile.hh"
#include "Compiler.hh"
#include "Exception.hh"

#include <sstream>

#include <boost/random/mersenne_twister.hpp>

namespace avro {
using std::auto_ptr;
using std::ostringstream;
using std::istringstream;
using std::vector;
using std::copy;
using std::string;

using boost::array;

const string AVRO_SCHEMA_KEY("avro.schema");
const string AVRO_CODEC_KEY("avro.codec");
const string AVRO_NULL_CODEC("null");

const size_t minSyncInterval = 32;
const size_t maxSyncInterval = 1u << 30;
const size_t defaultSyncInterval = 16 * 1024;

static string toString(const ValidSchema& schema)
{
    ostringstream oss;
    schema.toJson(oss);
    return oss.str();
}

DataFileWriterBase::DataFileWriterBase(const char* filename,
    const ValidSchema& schema, size_t syncInterval) :
    filename_(filename), schema_(schema), encoderPtr_(binaryEncoder()),
    syncInterval_(syncInterval),
    stream_(fileOutputStream(filename)),
    buffer_(memoryOutputStream()),
    sync_(makeSync()), objectCount_(0)
{
    if (syncInterval < minSyncInterval || syncInterval > maxSyncInterval) {
        throw Exception(boost::format("Invalid sync interval: %1%. "
            "Should be between %2% and %3%") % syncInterval %
            minSyncInterval % maxSyncInterval);
    }
    setMetadata(AVRO_CODEC_KEY, AVRO_NULL_CODEC);

    setMetadata(AVRO_SCHEMA_KEY, toString(schema));

    writeHeader();
    encoderPtr_->init(*buffer_);
}

DataFileWriterBase::~DataFileWriterBase()
{
    if (stream_.get()) {
        close();
    }
}

void DataFileWriterBase::close()
{
    flush();
    stream_.reset();
}

void DataFileWriterBase::sync()
{
    encoderPtr_->flush();

    encoderPtr_->init(*stream_);
    avro::encode(*encoderPtr_, objectCount_);
    int64_t byteCount = buffer_->byteCount();
    avro::encode(*encoderPtr_, byteCount);
    encoderPtr_->flush();

    auto_ptr<InputStream> in = memoryInputStream(*buffer_);
    copy(*in, *stream_);

    encoderPtr_->init(*stream_);
    avro::encode(*encoderPtr_, sync_);
    encoderPtr_->flush();


    buffer_ = memoryOutputStream();
    encoderPtr_->init(*buffer_);
    objectCount_ = 0;
}

void DataFileWriterBase::syncIfNeeded()
{
    encoderPtr_->flush();
    if (buffer_->byteCount() >= syncInterval_) {
        sync();
    }
}

void DataFileWriterBase::flush()
{
    sync();
}

boost::mt19937 random(time(0));

DataFileSync DataFileWriterBase::makeSync()
{
    DataFileSync sync;
    for (size_t i = 0; i < sync.size(); ++i) {
        sync[i] = random();
    }
    return sync;
}

typedef array<uint8_t, 4> Magic;
static Magic magic = { 'O', 'b', 'j', '\x01' };

void DataFileWriterBase::writeHeader()
{
    encoderPtr_->init(*stream_);
    avro::encode(*encoderPtr_, magic);
    avro::encode(*encoderPtr_, metadata_);
    avro::encode(*encoderPtr_, sync_);
    encoderPtr_->flush();
}

void DataFileWriterBase::setMetadata(const string& key, const string& value)
{
    vector<uint8_t> v(value.size());
    copy(value.begin(), value.end(), v.begin());
    metadata_[key] = v;
}

DataFileReaderBase::DataFileReaderBase(const char* filename) :
    filename_(filename), stream_(fileInputStream(filename)),
    decoder_(binaryDecoder()), objectCount_(0)
{
    readHeader();
}

void DataFileReaderBase::init()
{
    readerSchema_ = dataSchema_;
    dataDecoder_  = binaryDecoder();
    readDataBlock();
}

void DataFileReaderBase::init(const ValidSchema& readerSchema)
{
    readerSchema_ = readerSchema;
    dataDecoder_  = (toString(readerSchema_) != toString(dataSchema_)) ?
        resolvingDecoder(dataSchema_, readerSchema_, binaryDecoder()) :
        binaryDecoder();
    readDataBlock();
}

static void drain(InputStream& in)
{
    const uint8_t *p = 0;
    size_t n = 0;
    while (in.next(&p, &n));
}

char hex(unsigned int x)
{
    return x + (x < 10 ? '0' :  ('a' - 10));
}

std::ostream& operator << (std::ostream& os, const DataFileSync& s)
{
    for (size_t i = 0; i < s.size(); ++i) {
        os << hex(s[i] / 16)  << hex(s[i] % 16) << ' ';
    }
    os << std::endl;
    return os;
}


bool DataFileReaderBase::hasMore()
{
    if (objectCount_ != 0) {
        return true;
    }
    dataDecoder_->init(*dataStream_);
    drain(*dataStream_);
    DataFileSync s;
    decoder_->init(*stream_);
    avro::decode(*decoder_, s);
    if (s != sync_) {
        throw Exception("Sync mismatch");
    }
    return readDataBlock();
}

class BoundedInputStream : public InputStream {
    InputStream& in_;
    size_t limit_;

    bool next(const uint8_t** data, size_t* len) {
        if (limit_ != 0 && in_.next(data, len)) {
            if (*len > limit_) {
                in_.backup(*len - limit_);
                *len = limit_;
            }
            limit_ -= *len;
            return true;
        }
        return false;
    }

    void backup(size_t len) {
        in_.backup(len);
        limit_ += len;
    }

    void skip(size_t len) {
        if (len > limit_) {
            len = limit_;
        }
        in_.skip(len);
        limit_ -= len;
    }

    size_t byteCount() const {
        return in_.byteCount();
    }

public:
    BoundedInputStream(InputStream& in, size_t limit) :
        in_(in), limit_(limit) { }
};

auto_ptr<InputStream> boundedInputStream(InputStream& in, size_t limit)
{
    return auto_ptr<InputStream>(new BoundedInputStream(in, limit));
}

bool DataFileReaderBase::readDataBlock()
{
    decoder_->init(*stream_);
    const uint8_t* p = 0;
    size_t n = 0;
    if (! stream_->next(&p, &n)) {
        return false;
    }
    stream_->backup(n);
    avro::decode(*decoder_, objectCount_);
    int64_t byteCount;
    avro::decode(*decoder_, byteCount);
    decoder_->init(*stream_);

    auto_ptr<InputStream> st = boundedInputStream(*stream_, byteCount);
    dataDecoder_->init(*st);
    dataStream_ = st;
    return true;
}

void DataFileReaderBase::close()
{
}

static string toString(const vector<uint8_t>& v)
{
    string result;
    result.resize(v.size());
    copy(v.begin(), v.end(), result.begin());
    return result;
}

static ValidSchema makeSchema(const vector<uint8_t>& v)
{
    istringstream iss(toString(v));
    ValidSchema vs;
    compileJsonSchema(iss, vs);
    return ValidSchema(vs);
}

void DataFileReaderBase::readHeader()
{
    decoder_->init(*stream_);
    Magic m;
    avro::decode(*decoder_, m);
    if (magic != m) {
        throw Exception("Invalid data file. Magic does not match: "
            + filename_);
    }
    avro::decode(*decoder_, metadata_);
    Metadata::const_iterator it = metadata_.find(AVRO_SCHEMA_KEY);
    if (it == metadata_.end()) {
        throw Exception("No schema in metadata");
    }

    dataSchema_ = makeSchema(it->second);
    if (! readerSchema_.root()) {
        readerSchema_ = dataSchema();
    }

    it = metadata_.find(AVRO_CODEC_KEY);
    if (it != metadata_.end() && toString(it->second) != AVRO_NULL_CODEC) {
        throw Exception("Unknown codec in data file: " + toString(it->second));
    }

    avro::decode(*decoder_, sync_);
}

}   // namespace avro