src/qpid/framing/FieldTable.cpp

/*
 *
 * 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 "qpid/framing/FieldTable.h"
#include "qpid/framing/Array.h"
#include "qpid/framing/Buffer.h"
#include "qpid/framing/FieldValue.h"
#include "qpid/Exception.h"
#include "qpid/framing/reply_exceptions.h"
#include "qpid/Msg.h"
#include <assert.h>

// The locking rationale in the FieldTable seems a little odd, but it
// maintains the concurrent guarantees and requirements that were in
// place before the cachedBytes/cachedSize were added:
//
// The FieldTable client code needs to make sure that they call no write
// operation in parallel with any other operation on the FieldTable.
// However multiple parallel read operations are safe.
//
// To this end the only code that is locked is code that can transparently
// change the state of the FieldTable during a read only operation.
// (In other words the code that required the mutable members in the class
// definition!)
//
namespace qpid {

using sys::Mutex;
using sys::ScopedLock;

namespace framing {

FieldTable::FieldTable() :
    cachedSize(0),
    newBytes(false)
{
}

FieldTable::FieldTable(const FieldTable& ft)
{
    ScopedLock<Mutex> l(ft.lock);   // lock _source_ FieldTable

    cachedBytes = ft.cachedBytes;
    cachedSize = ft.cachedSize;
    newBytes = ft.newBytes;

    // Only copy the values if we have no raw data
    // - copying the map is expensive and we can
    //   reconstruct it if necessary from the raw data
    if (cachedBytes) {
        newBytes = true;
        return;
    }
    // In practice Encoding the source field table and only copying
    // the encoded bytes is faster than copying the whole value map.
    // (Because we nearly always copy a field table internally before
    // encoding it to send, but don't change it after the copy)
    if (!ft.values.empty()) {
        // Side effect of getting encoded size will cache it in ft.cachedSize
        ft.cachedBytes = boost::shared_array<uint8_t>(new uint8_t[ft.encodedSize()]);

        Buffer buffer((char*)&ft.cachedBytes[0], ft.cachedSize);

        // Cut and paste ahead...
        buffer.putLong(ft.encodedSize() - 4);
        buffer.putLong(ft.values.size());
        for (ValueMap::const_iterator i = ft.values.begin(); i!=ft.values.end(); ++i) {
            buffer.putShortString(i->first);
            i->second->encode(buffer);
        }

        cachedBytes = ft.cachedBytes;
        cachedSize = ft.cachedSize;
        newBytes = true;
    }
}

FieldTable& FieldTable::operator=(const FieldTable& ft)
{
    FieldTable nft(ft);
    values.swap(nft.values);
    cachedBytes.swap(nft.cachedBytes);
    cachedSize = nft.cachedSize;
    newBytes = nft.newBytes;
    return (*this);
}

uint32_t FieldTable::encodedSize() const {
    ScopedLock<Mutex> l(lock);

    if (cachedSize != 0) {
        return cachedSize;
    }
    uint32_t len(4/*size field*/ + 4/*count field*/);
    for(ValueMap::const_iterator i = values.begin(); i != values.end(); ++i) {
        // shortstr_len_byte + key size + value size
        len += 1 + (i->first).size() + (i->second)->encodedSize();
    }
    cachedSize = len;
    return len;
}

int FieldTable::count() const {
    return values.size();
}

namespace 
{
std::ostream& operator<<(std::ostream& out, const FieldTable::ValueMap::value_type& i) {
    return out << i.first << ":" << *i.second;
}
}

std::ostream& operator<<(std::ostream& out, const FieldTable& t) {
    t.realDecode();
    out << "{";
    FieldTable::ValueMap::const_iterator i = t.begin();
    if (i != t.end()) out << *i++;
    while (i != t.end()) 
    {
        out << "," << *i++;
    }
    return out << "}";
}

void FieldTable::set(const std::string& name, const ValuePtr& value){
    realDecode();
    values[name] = value;
    flushRawCache();
}

void FieldTable::setString(const std::string& name, const std::string& value){
    realDecode();
    values[name] = ValuePtr(new Str16Value(value));
    flushRawCache();
}

void FieldTable::setInt(const std::string& name, const int value){
    realDecode();
    values[name] = ValuePtr(new IntegerValue(value));
    flushRawCache();
}

void FieldTable::setInt64(const std::string& name, const int64_t value){
    realDecode();
    values[name] = ValuePtr(new Integer64Value(value));
    flushRawCache();
}

void FieldTable::setTimestamp(const std::string& name, const uint64_t value){
    realDecode();
    values[name] = ValuePtr(new TimeValue(value));
    flushRawCache();
}

void FieldTable::setUInt64(const std::string& name, const uint64_t value){
    realDecode();
    values[name] = ValuePtr(new Unsigned64Value(value));
    flushRawCache();
}

void FieldTable::setTable(const std::string& name, const FieldTable& value)
{
    realDecode();
    values[name] = ValuePtr(new FieldTableValue(value));
    flushRawCache();
}
void FieldTable::setArray(const std::string& name, const Array& value)
{
    realDecode();
    values[name] = ValuePtr(new ArrayValue(value));
    flushRawCache();
}

void FieldTable::setFloat(const std::string& name, const float value){
    realDecode();
    values[name] = ValuePtr(new FloatValue(value));
    flushRawCache();
}

void FieldTable::setDouble(const std::string& name, const double value){
    realDecode();
    values[name] = ValuePtr(new DoubleValue(value));
    flushRawCache();
}

FieldTable::ValuePtr FieldTable::get(const std::string& name) const
{
    // Ensure we have any values we're trying to read
    realDecode();
    ValuePtr value;
    ValueMap::const_iterator i = values.find(name);
    if ( i!=values.end() )
        value = i->second;
    return value;
}

namespace {
    template <class T> T default_value() { return T(); }
    template <> int default_value<int>() { return 0; }
  //template <> uint64_t default_value<uint64_t>() { return 0; }
}

template <class T>
T getValue(const FieldTable::ValuePtr value)
{
    if (!value || !value->convertsTo<T>())
        return default_value<T>();

    return value->get<T>();
}

std::string FieldTable::getAsString(const std::string& name) const {
    return getValue<std::string>(get(name));
}

int FieldTable::getAsInt(const std::string& name) const {
    return getValue<int>(get(name));
}

uint64_t FieldTable::getAsUInt64(const std::string& name) const {
    return static_cast<uint64_t>( getValue<int64_t>(get(name)));
}

int64_t FieldTable::getAsInt64(const std::string& name) const {
    return getValue<int64_t>(get(name));
}

bool FieldTable::getTable(const std::string& name, FieldTable& value) const {
    return getEncodedValue<FieldTable>(get(name), value);
}

bool FieldTable::getArray(const std::string& name, Array& value) const {
    return getEncodedValue<Array>(get(name), value);
}

template <class T, int width, uint8_t typecode>
bool getRawFixedWidthValue(FieldTable::ValuePtr vptr, T& value) 
{
    if (vptr && vptr->getType() == typecode) {
        value = vptr->get<T>();
        return true;
    }
    return false;
}

bool FieldTable::getFloat(const std::string& name, float& value) const {    
    return getRawFixedWidthValue<float, 4, 0x23>(get(name), value);
}

bool FieldTable::getDouble(const std::string& name, double& value) const {    
    return getRawFixedWidthValue<double, 8, 0x33>(get(name), value);
}

//uint64_t FieldTable::getTimestamp(const std::string& name) const {
//    return getValue<uint64_t>(name);
//}

void FieldTable::encode(Buffer& buffer) const {
    // If we've still got the input field table
    // we can just copy it directly to the output
    if (cachedBytes) {
        ScopedLock<Mutex> l(lock);
        buffer.putRawData(&cachedBytes[0], cachedSize);
    } else {
        buffer.putLong(encodedSize() - 4);
        buffer.putLong(values.size());
        for (ValueMap::const_iterator i = values.begin(); i!=values.end(); ++i) {
            buffer.putShortString(i->first);
            i->second->encode(buffer);
        }
    }
}

// Decode lazily - just record the raw bytes until we need them
void FieldTable::decode(Buffer& buffer){
    if (buffer.available() < 4)
        throw IllegalArgumentException(QPID_MSG("Not enough data for field table."));
    uint32_t p = buffer.getPosition();
    uint32_t len = buffer.getLong();
    if (len) {
        uint32_t available = buffer.available();
        if ((available < len) || (available < 4))
            throw IllegalArgumentException(QPID_MSG("Not enough data for field table."));
    }
    ScopedLock<Mutex> l(lock);
    // Throw away previous stored values
    values.clear();
    // Copy data into our buffer
    cachedBytes = boost::shared_array<uint8_t>(new uint8_t[len + 4]);
    cachedSize = len + 4;
    newBytes = true;
    buffer.setPosition(p);
    buffer.getRawData(&cachedBytes[0], cachedSize);
}

void FieldTable::realDecode() const
{
    ScopedLock<Mutex> l(lock);

    // If we've got no raw data stored up then nothing to do
    if (!newBytes)
        return;

    Buffer buffer((char*)&cachedBytes[0], cachedSize);
    uint32_t len = buffer.getLong();
    if (len) {
        uint32_t available = buffer.available();
        uint32_t count = buffer.getLong();
        uint32_t leftover = available - len;
        while(buffer.available() > leftover && count--){
            std::string name;
            ValuePtr value(new FieldValue);

            buffer.getShortString(name);
            value->decode(buffer);
            values[name] = ValuePtr(value);
        }
    }
    newBytes = false;
}

void FieldTable::flushRawCache()
{
    ScopedLock<Mutex> l(lock);
    // We can only flush the cache if there are no cached bytes to decode
    assert(newBytes==false);
    // Avoid recreating shared array unless we actually have one.
    if (cachedBytes) cachedBytes.reset();
    cachedSize = 0;
}

bool FieldTable::operator==(const FieldTable& x) const {
    realDecode();
    x.realDecode();
    if (values.size() != x.values.size()) return false;
    for (ValueMap::const_iterator i =  values.begin(); i != values.end(); ++i) {
        ValueMap::const_iterator j = x.values.find(i->first);
        if (j == x.values.end()) return false;
        if (*(i->second) != *(j->second)) return false;
    }
    return true;
}

void FieldTable::erase(const std::string& name) 
{
    realDecode();
    if (values.find(name) != values.end()) {
        values.erase(name);
        flushRawCache();
    }
}

void FieldTable::clear()
{
    values.clear();
    newBytes = false;
    flushRawCache();
}

// Map-like interface.
FieldTable::ValueMap::const_iterator FieldTable::begin() const
{
    realDecode();
    return values.begin();
}

FieldTable::ValueMap::const_iterator FieldTable::end() const
{
    realDecode();
    return values.end();
}

FieldTable::ValueMap::const_iterator FieldTable::find(const std::string& s) const
{
    realDecode();
    return values.find(s);
}

FieldTable::ValueMap::iterator FieldTable::begin()
{
    realDecode();
    flushRawCache();
    return values.begin();
}

FieldTable::ValueMap::iterator FieldTable::end()
{
    realDecode();
    flushRawCache();
    return values.end();
}

FieldTable::ValueMap::iterator FieldTable::find(const std::string& s)
{
    realDecode();
    flushRawCache();
    return values.find(s);
}

std::pair<FieldTable::ValueMap::iterator, bool> FieldTable::insert(const ValueMap::value_type& value)
{
    realDecode();
    flushRawCache();
    return values.insert(value);
}

FieldTable::ValueMap::iterator FieldTable::insert(ValueMap::iterator position, const ValueMap::value_type& value)
{
    realDecode();
    flushRawCache();
    return values.insert(position, value);
}

}
}