StreamBuffer.h

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/****
 * Sming Framework Project - Open Source framework for high efficiency native ESP8266 development.
 * Created 2015 by Skurydin Alexey
 * http://github.com/SmingHub/Sming
 * All files of the Sming Core are provided under the LGPL v3 license.
 *
 * StreamBuffer.h - Buffering for more efficient reading of byte streams
 *
 * @author Sept 2019 mikee47 <mike@sillyhouse.net>
 *
 ****/

#pragma once

#include <Data/Stream/DataSourceStream.h>
#include <memory>

template <unsigned bufSize> class StreamBuffer
{
public:
    void setStream(IDataSourceStream* stream)
    {
        this->stream.reset(stream);
        if(stream == nullptr) {
            streamPos = 0;
            pos = len = 0;
        } else {
            streamPos = stream->seekFrom(0, SeekOrigin::Current);
            fill();
        }
    }

    bool setPos(unsigned pos)
    {
        if(!stream) {
            return false;
        }

        if(stream->seekFrom(pos, SeekOrigin::Start) < 0) {
            return false;
        }

        streamPos = pos;
        fill();
        return !eof();
    }

    char peekChar()
    {
        return (pos < len) ? data[pos] : '\0';
    };

    char readChar()
    {
        char c = data[pos++];
        if(pos >= len) {
            fill();
        }
        return c;
    };

    unsigned getPos()
    {
        return streamPos - len + pos;
    }

    bool eof()
    {
        return len == 0;
    }

private:
    void fill()
    {
        len = stream->readMemoryBlock(data, sizeof(data));
        stream->seek(len);
        streamPos += len;
        pos = 0;
    };

private:
    std::unique_ptr<IDataSourceStream> stream;
    unsigned streamPos = 0;
    char data[bufSize];
    uint8_t pos = 0;
    uint8_t len = 0;
};