JUCE/modules/juce_core/streams/juce_BufferedInputStream.cpp

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

   This file is part of the JUCE library.
   Copyright (c) 2017 - ROLI Ltd.

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

        requestedSize = jmax (256, requestedSize);

        const int64 sourceSize = source->getTotalLength();
        if (sourceSize >= 0 && sourceSize < requestedSize)
            requestedSize = jmax (32, (int) sourceSize);

        return requestedSize;
    }
}

//==============================================================================
BufferedInputStream::BufferedInputStream (InputStream* const sourceStream, const int bufferSize_,
                                          const bool deleteSourceWhenDestroyed)
   : source (sourceStream, deleteSourceWhenDestroyed),
     bufferSize (calcBufferStreamBufferSize (bufferSize_, sourceStream)),
     position (sourceStream->getPosition()),
     lastReadPos (0),
     bufferStart (position),
     bufferOverlap (128)
{
    buffer.malloc ((size_t) bufferSize);
}

BufferedInputStream::BufferedInputStream (InputStream& sourceStream, const int bufferSize_)
   : source (&sourceStream, false),
     bufferSize (calcBufferStreamBufferSize (bufferSize_, &sourceStream)),
     position (sourceStream.getPosition()),
     lastReadPos (0),
     bufferStart (position),
     bufferOverlap (128)
{
    buffer.malloc ((size_t) bufferSize);
}

BufferedInputStream::~BufferedInputStream()
{
}

//==============================================================================
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();
}

void BufferedInputStream::ensureBuffered()
{
    const int64 bufferEndOverlap = lastReadPos - bufferOverlap;

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

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

            bufferStart = position;

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

            lastReadPos += bytesRead;
            bytesRead += bytesToKeep;
        }
        else
        {
            bufferStart = position;
            source->setPosition (bufferStart);
            bytesRead = source->read (buffer, bufferSize);
            lastReadPos = bufferStart + bytesRead;
        }

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

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;
    }
    else
    {
        if (position < bufferStart || position >= lastReadPos)
            ensureBuffered();

        int bytesRead = 0;

        while (maxBytesToRead > 0)
        {
            const int bytesAvailable = jmin (maxBytesToRead, (int) (lastReadPos - position));

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

            const int64 oldLastReadPos = lastReadPos;
            ensureBuffered();

            if (oldLastReadPos == lastReadPos)
                break; // if ensureBuffered() failed to read any more data, bail out

            if (isExhausted())
                break;
        }

        return bytesRead;
    }
}

String BufferedInputStream::readString()
{
    if (position >= bufferStart
         && position < lastReadPos)
    {
        const int maxChars = (int) (lastReadPos - position);

        const char* const 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();
}