JUCE/modules/juce_core/streams/juce_BufferedInputStream.cpp

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

   This file is part of the JUCE library.
   Copyright (c) 2016 - ROLI Ltd.

   Permission is granted to use this software 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.

   THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
   TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
   OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
   USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
   OF THIS SOFTWARE.

   -----------------------------------------------------------------------------

   To release a closed-source product which uses other parts of JUCE not
   licensed under the ISC terms, commercial licenses are available: visit
   www.juce.com for more information.

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

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();
}