/*

 * Copyright 2013-2022 Step Function I/O, LLC

 *

 * Licensed to Green Energy Corp (www.greenenergycorp.com) and Step Function I/O

 * LLC (https://stepfunc.io) under one or more contributor license agreements.

 * See the NOTICE file distributed with this work for additional information

 * regarding copyright ownership. Green Energy Corp and Step Function I/O LLC license

 * 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 "ShiftableBuffer.h"

#include <cassert>

#include <cstring>

#include <iostream>

namespace opendnp3

{

ShiftableBuffer::ShiftableBuffer(uint8_t* pBuffer_, size_t size)

    : pBuffer(pBuffer_), M_SIZE(size), writePos(0), readPos(0)

{

}

void ShiftableBuffer::Shift()

{

    auto numRead = this->NumBytesRead();

    // copy all unread data to the front of the buffer

    memmove(pBuffer, pBuffer + readPos, numRead);

    readPos = 0;

    writePos = numRead;

}

void ShiftableBuffer::Reset()

{

    writePos = 0;

    readPos = 0;

}

void ShiftableBuffer::AdvanceRead(size_t numBytes)

{

    assert(numBytes <= this->NumBytesRead());

    readPos += numBytes;

}

void ShiftableBuffer::AdvanceWrite(size_t aNumBytes)

{

    assert(aNumBytes <= this->NumWriteBytes());

    writePos += aNumBytes;

}

bool ShiftableBuffer::Sync(size_t& skipCount)

{

    while (this->NumBytesRead() > 1) // at least 2 bytes

    {

        if (this->ReadBuffer()[0] == 0x05 && this->ReadBuffer()[1] == 0x64)

        {

            return true;

        }

        this->AdvanceRead(1); // skip the first byte

        ++skipCount;

    }

    return false;

}

} // namespace opendnp3