JUCE/modules/juce_core/streams/juce_BufferedInputStream.cpp

/*
  ==============================================================================

   This file is part of the JUCE library.
   Copyright (c) 2020 - Raw Material Software Limited

   JUCE is an open source library subject to commercial or open-source
   licensing.

   The code included in this file is provided under the terms of the ISC license
   http://www.isc.org/downloads/software-support-policy/isc-license. Permission
   To use, copy, modify, and/or distribute this software for any purpose with or
   without fee is hereby granted provided that the above copyright notice and
   this permission notice appear in all copies.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

static int calcBufferStreamBufferSize (int requestedSize, InputStream* source) noexcept
{
    // You need to supply a real stream when creating a BufferedInputStream
    jassert (source != nullptr);

    requestedSize = jmax (256, requestedSize);
    auto sourceSize = source->getTotalLength();

    if (sourceSize >= 0 && sourceSize < requestedSize)
        return jmax (32, (int) sourceSize);

    return requestedSize;
}

//==============================================================================
BufferedInputStream::BufferedInputStream (InputStream* sourceStream, int size, bool takeOwnership)
   : source (sourceStream, takeOwnership),
     bufferSize (calcBufferStreamBufferSize (size, sourceStream)),
     position (sourceStream->getPosition()),
     bufferStart (position)
{
    buffer.malloc (bufferSize);
}

BufferedInputStream::BufferedInputStream (InputStream& sourceStream, int size)
   : BufferedInputStream (&sourceStream, size, false)
{
}

BufferedInputStream::~BufferedInputStream()
{
}

//==============================================================================
char BufferedInputStream::peekByte()
{
    if (! ensureBuffered())
        return 0;

    return position < lastReadPos ? buffer[(int) (position - bufferStart)] : 0;
}

int64 BufferedInputStream::getTotalLength()
{
    return source->getTotalLength();
}

int64 BufferedInputStream::getPosition()
{
    return position;
}

bool BufferedInputStream::setPosition (int64 newPosition)
{
    position = jmax ((int64) 0, newPosition);
    return true;
}

bool BufferedInputStream::isExhausted()
{
    return position >= lastReadPos && source->isExhausted();
}

bool BufferedInputStream::ensureBuffered()
{
    auto bufferEndOverlap = lastReadPos - bufferOverlap;

    if (position < bufferStart || position >= bufferEndOverlap)
    {
        int bytesRead;

        if (position < lastReadPos
             && position >= bufferEndOverlap
             && position >= bufferStart)
        {
            auto bytesToKeep = (int) (lastReadPos - position);
            memmove (buffer, buffer + (int) (position - bufferStart), (size_t) bytesToKeep);

            bufferStart = position;
            bytesRead = source->read (buffer + bytesToKeep,
                                      (int) (bufferSize - bytesToKeep));

            if (bytesRead < 0)
                return false;

            lastReadPos += bytesRead;
            bytesRead += bytesToKeep;
        }
        else
        {
            bufferStart = position;

            if (! source->setPosition (bufferStart))
                return false;

            bytesRead = source->read (buffer, bufferSize);

            if (bytesRead < 0)
                return false;

            lastReadPos = bufferStart + bytesRead;
        }

        while (bytesRead < bufferSize)
            buffer[bytesRead++] = 0;
    }

    return true;
}

int BufferedInputStream::read (void* destBuffer, int maxBytesToRead)
{
    jassert (destBuffer != nullptr && maxBytesToRead >= 0);

    if (position >= bufferStart
         && position + maxBytesToRead <= lastReadPos)
    {
        memcpy (destBuffer, buffer + (int) (position - bufferStart), (size_t) maxBytesToRead);
        position += maxBytesToRead;
        return maxBytesToRead;
    }

    if (position < bufferStart || position >= lastReadPos)
        if (! ensureBuffered())
            return 0;

    int bytesRead = 0;

    while (maxBytesToRead > 0)
    {
        auto numToRead = jmin (maxBytesToRead, (int) (lastReadPos - position));

        if (numToRead > 0)
        {
            memcpy (destBuffer, buffer + (int) (position - bufferStart), (size_t) numToRead);
            maxBytesToRead -= numToRead;
            bytesRead += numToRead;
            position += numToRead;
            destBuffer = static_cast<char*> (destBuffer) + numToRead;
        }

        auto oldLastReadPos = lastReadPos;

        if (! ensureBuffered()
             || oldLastReadPos == lastReadPos
             || isExhausted())
            break;
    }

    return bytesRead;
}

String BufferedInputStream::readString()
{
    if (position >= bufferStart
         && position < lastReadPos)
    {
        auto maxChars = (int) (lastReadPos - position);
        auto* src = buffer + (int) (position - bufferStart);

        for (int i = 0; i < maxChars; ++i)
        {
            if (src[i] == 0)
            {
                position += i + 1;
                return String::fromUTF8 (src, i);
            }
        }
    }

    return InputStream::readString();
}


//==============================================================================
//==============================================================================
#if JUCE_UNIT_TESTS

struct BufferedInputStreamTests   : public UnitTest
{
    BufferedInputStreamTests()
        : UnitTest ("BufferedInputStream", UnitTestCategories::streams)
    {}

    void runTest() override
    {
        const MemoryBlock data ("abcdefghijklmnopqrstuvwxyz", 26);
        MemoryInputStream mi (data, true);

        BufferedInputStream stream (mi, (int) data.getSize());

        beginTest ("Read");

        expectEquals (stream.getPosition(), (int64) 0);
        expectEquals (stream.getTotalLength(), (int64) data.getSize());
        expectEquals (stream.getNumBytesRemaining(), stream.getTotalLength());
        expect (! stream.isExhausted());

        size_t numBytesRead = 0;
        MemoryBlock readBuffer (data.getSize());

        while (numBytesRead < data.getSize())
        {
            expectEquals (stream.peekByte(), *(char*) (data.begin() + numBytesRead));

            numBytesRead += (size_t) stream.read (&readBuffer[numBytesRead], 3);

            expectEquals (stream.getPosition(), (int64) numBytesRead);
            expectEquals (stream.getNumBytesRemaining(), (int64) (data.getSize() - numBytesRead));
            expect (stream.isExhausted() == (numBytesRead == data.getSize()));
        }

        expectEquals (stream.getPosition(), (int64) data.getSize());
        expectEquals (stream.getNumBytesRemaining(), (int64) 0);
        expect (stream.isExhausted());

        expect (readBuffer == data);

        beginTest ("Skip");

        stream.setPosition (0);
        expectEquals (stream.getPosition(), (int64) 0);
        expectEquals (stream.getTotalLength(), (int64) data.getSize());
        expectEquals (stream.getNumBytesRemaining(), stream.getTotalLength());
        expect (! stream.isExhausted());

        numBytesRead = 0;
        const int numBytesToSkip = 5;

        while (numBytesRead < data.getSize())
        {
            expectEquals (stream.peekByte(), *(char*) (data.begin() + numBytesRead));

            stream.skipNextBytes (numBytesToSkip);
            numBytesRead += numBytesToSkip;
            numBytesRead = std::min (numBytesRead, data.getSize());

            expectEquals (stream.getPosition(), (int64) numBytesRead);
            expectEquals (stream.getNumBytesRemaining(), (int64) (data.getSize() - numBytesRead));
            expect (stream.isExhausted() == (numBytesRead == data.getSize()));
        }

        expectEquals (stream.getPosition(), (int64) data.getSize());
        expectEquals (stream.getNumBytesRemaining(), (int64) 0);
        expect (stream.isExhausted());
    }
};

static BufferedInputStreamTests bufferedInputStreamTests;

#endif

} // namespace juce