FlateEncoder.cc

//========================================================================
//
// FlateEncoder.cc
//
// Copyright (C) 2016, William Bader <williambader@hotmail.com>
// Copyright (C) 2017 Adrian Johnson <ajohnson@redneon.com>
// Copyright (C) 2021 Even Rouault <even.rouault@spatialys.com>
// Copyright (C) 2022 Albert Astals Cid <aacid@kde.org>
// Copyright (C) 2025 Nelson Benítez León <nbenitezl@gmail.com>
//
// This file is under the GPLv2 or later license
//
//========================================================================

#include <config.h>

#include "FlateEncoder.h"

//------------------------------------------------------------------------
// FlateEncoder
//------------------------------------------------------------------------

FlateEncoder::FlateEncoder(Stream *strA) : FilterStream(strA)
{
    int zlib_status;

    outBufPtr = outBufEnd = outBuf;
    inBufEof = outBufEof = false;

    // We used to assign Z_NULL to the 3 following members of zlib_stream,
    // but as Z_NULL is a #define to 0, using it triggers the
    // -Wzero-as-null-pointer-constant warning.
    // For safety, check that the Z_NULL definition is equivalent to
    // 0 / null pointer.
    static_assert(static_cast<int>(Z_NULL) == 0);
    zlib_stream.zalloc = nullptr;
    zlib_stream.zfree = nullptr;
    zlib_stream.opaque = nullptr;

    zlib_status = deflateInit(&zlib_stream, Z_DEFAULT_COMPRESSION);

    if (zlib_status != Z_OK) {
        inBufEof = outBufEof = true;
        error(errInternal, -1, "Internal: deflateInit() failed in FlateEncoder::FlateEncoder()");
    }

    zlib_stream.next_out = outBufEnd;
    zlib_stream.avail_out = 1; /* anything but 0 to trigger a read */
}

FlateEncoder::~FlateEncoder()
{
    deflateEnd(&zlib_stream);
    if (str->isEncoder()) {
        delete str;
    }
}

bool FlateEncoder::reset()
{
    int zlib_status;

    str->reset();

    outBufPtr = outBufEnd = outBuf;
    inBufEof = outBufEof = false;

    deflateEnd(&zlib_stream);

    zlib_status = deflateInit(&zlib_stream, Z_DEFAULT_COMPRESSION);

    if (zlib_status != Z_OK) {
        inBufEof = outBufEof = true;
        error(errInternal, -1, "Internal: deflateInit() failed in FlateEncoder::reset()");
        return false;
    }

    zlib_stream.next_out = outBufEnd;
    zlib_stream.avail_out = 1; /* anything but 0 to trigger a read */

    return true;
}

bool FlateEncoder::fillBuf()
{
    unsigned int starting_avail_out;
    int zlib_status;

    /* If the output is done, don't try to read more. */

    if (outBufEof) {
        return false;
    }

    /* The output buffer should be empty. */
    /* If it is not empty, push any processed data to the start. */

    if (outBufPtr > outBuf && outBufPtr < outBufEnd) {
        const ptrdiff_t n = outBufEnd - outBufPtr;
        memmove(outBuf, outBufPtr, n);
        outBufEnd = &outBuf[n];
    } else {
        outBufEnd = outBuf;
    }
    outBufPtr = outBuf;

    /* Keep feeding zlib until we get output. */
    /* zlib might consume a few input buffers */
    /* before it starts producing output. */

    do {

        /* avail_out > 0 means that zlib has depleted its input */
        /* and needs a new chunk of input in order to generate */
        /* more output. */

        if (zlib_stream.avail_out != 0) {

            /* Fill the input buffer */

            const int n = (inBufEof ? 0 : str->doGetChars(inBufSize, inBuf));

            if (n == 0) {
                inBufEof = true;
            }

            zlib_stream.next_in = inBuf;
            zlib_stream.avail_in = n;
        }

        /* Ask zlib for output. */

        zlib_stream.next_out = outBufEnd;
        starting_avail_out = static_cast<unsigned int>(&outBuf[outBufSize] - outBufEnd);
        zlib_stream.avail_out = starting_avail_out;

        zlib_status = deflate(&zlib_stream, (inBufEof ? Z_FINISH : Z_NO_FLUSH));

        if (zlib_status == Z_STREAM_ERROR || zlib_stream.avail_out > starting_avail_out) {
            /* Unrecoverable error */
            inBufEof = outBufEof = true;
            error(errInternal, -1, "Internal: deflate() failed in FlateEncoder::fillBuf()");
            return false;
        }

    } while (zlib_stream.avail_out == outBufSize && !inBufEof);

    outBufEnd = &outBuf[outBufSize] - zlib_stream.avail_out;

    if (inBufEof && zlib_stream.avail_out != 0) {
        outBufEof = true;
    }

    return outBufPtr < outBufEnd;
}