Encoder.cpp

// Copyright 2021 Rainer Schoenberger
// 
// Licensed 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 "Encoder.hpp"
#include <string.h>

namespace ZCMessagePack
{
Encoder::Encoder(uint8_t * f_out_borrow_messageBuffer, uint8_t f_bufferSize) :
    m_messageBuffer(f_out_borrow_messageBuffer),
    m_bufferSize(f_bufferSize)
{
}

// FIXME: experimental, untested and inefficient:
//        currently all values stored as 32bit signed int
bool Encoder::addInt(int32_t f_number)
{
    if(sizeLeft() < 5)
    {
        return false;
    }
    m_messageBuffer[m_position] = 0xd2;
    m_messageBuffer[m_position+1] = f_number>>24;
    m_messageBuffer[m_position+2] = f_number>>16;
    m_messageBuffer[m_position+3] = f_number>>8;
    m_messageBuffer[m_position+4] = f_number;
    m_position += 5;
    return true;
}

bool Encoder::addUint(uint32_t f_number)
{
    if(f_number <= 0x7f)
    {
        if(sizeLeft() < 1)
        {
            return false;
        }
        m_messageBuffer[m_position] = f_number;
        m_position += 1;
    }
    else if(f_number <= 0xff)
    {
        if(sizeLeft() < 2)
        {
            return false;
        }
        m_messageBuffer[m_position] = 0xcc;
        m_messageBuffer[m_position+1] = f_number;
        m_position += 2;
    }
    else if(f_number <= 0xffff)
    {
        if(sizeLeft() < 3)
        {
            return false;
        }
        m_messageBuffer[m_position] = 0xcd;
        m_messageBuffer[m_position+1] = f_number>>8;
        m_messageBuffer[m_position+2] = f_number;
        m_position += 3;
    }
    else
    {
        if(sizeLeft() < 5)
        {
            return false;
        }
        m_messageBuffer[m_position] = 0xce;
        m_messageBuffer[m_position+1] = f_number>>24;
        m_messageBuffer[m_position+2] = f_number>>16;
        m_messageBuffer[m_position+3] = f_number>>8;
        m_messageBuffer[m_position+4] = f_number;
        m_position += 5;
    }
    return true;
}

bool Encoder::addString(const char * f_string)
{
    size_t len = strlen(f_string);
    if(len <= 0x1f)
    {
        if(sizeLeft() < len+1)
        {
            return false;
        }
        m_messageBuffer[m_position] = 0xa0 | len;
        m_position += 1;
        memcpy(&m_messageBuffer[m_position], f_string, len);
        m_position += len;
    }
    else if(len <= 0xff)
    {
        if(sizeLeft() < len+2)
        {
            return false;
        }
        m_messageBuffer[m_position] = 0xd9;
        m_messageBuffer[m_position+1] = len;
        m_position += 2;
        memcpy(&m_messageBuffer[m_position], f_string, len);
        m_position += len;
    }
    else
    {
        return false;
    }
    return true;
}

bool Encoder::addBinary(const uint8_t * f_data, uint8_t f_size)
{
    if(f_size <= 0xff)
    {
        if(sizeLeft() < f_size+2)
        {
            return false;
        }
        m_messageBuffer[m_position] = 0xc4;
        m_messageBuffer[m_position+1] = f_size;
        m_position += 2;
        memcpy(&m_messageBuffer[m_position], f_data, f_size);
        m_position += f_size;
    }
    else
    {
        return false;
    }
    return true;
}

bool Encoder::addBool(bool f_value)
{
    if(sizeLeft() < 1)
    {
        return false;
    }
    m_messageBuffer[m_position] = f_value ? 0xc3 : 0xc2;
    m_position += 1;
    return true;
}

bool Encoder::addNil()
{
    if(sizeLeft() < 1)
    {
        return false;
    }
    m_messageBuffer[m_position] = 0xc0;
    m_position += 1;
    return true;
}

bool Encoder::addMap(uint8_t f_numElements)
{
    return addNestedStructure(f_numElements, 0x80, 0xde);
}

bool Encoder::addArray(uint8_t f_numElements)
{
    return addNestedStructure(f_numElements, 0x90, 0xdc);
}

uint8_t Encoder::getMessageSize() const
{
    return m_position;
}
uint8_t Encoder::sizeLeft()
{
    return m_bufferSize - m_position;
}
bool Encoder::addNestedStructure(uint8_t f_numElements, uint8_t f_smallPrefix, uint8_t f_bigPrefix)
{
    if(f_numElements <= 0x0f)
    {
        if(sizeLeft() < 1)
        {
            return false;
        }
        m_messageBuffer[m_position] = f_smallPrefix | f_numElements;
        m_position += 1;
    }
    else
    {
        if(sizeLeft() < 3)
        {
            return false;
        }
        m_messageBuffer[m_position] = f_bigPrefix;
        //Note: only support size < 256
        m_messageBuffer[m_position+1] = 0;
        m_messageBuffer[m_position+2] = f_numElements;
        m_position += 3;
    }
    return true;
}
}