cpython/Modules/zlibmodule.c

/* zlibmodule.c -- gzip-compatible data compression */
/* See http://zlib.net/ */

/* Windows users:  read Python's PCbuild\readme.txt */

#define PY_SSIZE_T_CLEAN

#include "Python.h"
#include "zlib.h"

#ifdef WITH_THREAD
#include "pythread.h"

/* #defs ripped off from _tkinter.c, even though the situation here is much
   simpler, because we don't have to worry about waiting for Tcl
   events!  And, since zlib itself is threadsafe, we don't need to worry
   about re-entering zlib functions.

   N.B.

   Since ENTER_ZLIB and LEAVE_ZLIB only need to be called on functions
   that modify the components of preexisting de/compress objects, it
   could prove to be a performance gain on multiprocessor machines if
   there was an de/compress object-specific lock.  However, for the
   moment the ENTER_ZLIB and LEAVE_ZLIB calls are global for ALL
   de/compress objects.
 */

static PyThread_type_lock zlib_lock = NULL; /* initialized on module load */

#define ENTER_ZLIB \
        Py_BEGIN_ALLOW_THREADS \
        PyThread_acquire_lock(zlib_lock, 1); \
        Py_END_ALLOW_THREADS

#define LEAVE_ZLIB \
        PyThread_release_lock(zlib_lock);

#else

#define ENTER_ZLIB
#define LEAVE_ZLIB

#endif

/* The following parameters are copied from zutil.h, version 0.95 */
#define DEFLATED   8
#if MAX_MEM_LEVEL >= 8
#  define DEF_MEM_LEVEL 8
#else
#  define DEF_MEM_LEVEL  MAX_MEM_LEVEL
#endif
#define DEF_WBITS MAX_WBITS

/* The output buffer will be increased in chunks of DEFAULTALLOC bytes. */
#define DEFAULTALLOC (16*1024)
#define PyInit_zlib initzlib

static PyTypeObject Comptype;
static PyTypeObject Decomptype;

static PyObject *ZlibError;

typedef struct
{
    PyObject_HEAD
    z_stream zst;
    PyObject *unused_data;
    PyObject *unconsumed_tail;
    int is_initialised;
} compobject;

static void
zlib_error(z_stream zst, int err, char *msg)
{
    const char *zmsg = Z_NULL;
    /* In case of a version mismatch, zst.msg won't be initialized.
       Check for this case first, before looking at zst.msg. */
    if (err == Z_VERSION_ERROR)
        zmsg = "library version mismatch";
    if (zmsg == Z_NULL)
        zmsg = zst.msg;
    if (zmsg == Z_NULL) {
        switch (err) {
        case Z_BUF_ERROR:
            zmsg = "incomplete or truncated stream";
            break;
        case Z_STREAM_ERROR:
            zmsg = "inconsistent stream state";
            break;
        case Z_DATA_ERROR:
            zmsg = "invalid input data";
            break;
        }
    }
    if (zmsg == Z_NULL)
        PyErr_Format(ZlibError, "Error %d %s", err, msg);
    else
        PyErr_Format(ZlibError, "Error %d %s: %.200s", err, msg, zmsg);
}

PyDoc_STRVAR(compressobj__doc__,
"compressobj([level]) -- Return a compressor object.\n"
"\n"
"Optional arg level is the compression level, in 0-9 or -1.");

PyDoc_STRVAR(decompressobj__doc__,
"decompressobj([wbits]) -- Return a decompressor object.\n"
"\n"
"Optional arg wbits indicates the window buffer size and container format.");

static compobject *
newcompobject(PyTypeObject *type)
{
    compobject *self;
    self = PyObject_New(compobject, type);
    if (self == NULL)
        return NULL;
    self->is_initialised = 0;
    self->unused_data = PyString_FromString("");
    if (self->unused_data == NULL) {
        Py_DECREF(self);
        return NULL;
    }
    self->unconsumed_tail = PyString_FromString("");
    if (self->unconsumed_tail == NULL) {
        Py_DECREF(self);
        return NULL;
    }
    return self;
}

static void
arrange_input_buffer(z_stream *zst, Py_ssize_t *remains)
{
    if ((size_t)*remains > UINT_MAX) {
        zst->avail_in = UINT_MAX;
    } else {
        zst->avail_in = *remains;
    }
    *remains -= zst->avail_in;
}

static Py_ssize_t
arrange_output_buffer_with_maximum(z_stream *zst, PyObject **buffer,
                                   Py_ssize_t length,
                                   Py_ssize_t max_length)
{
    Py_ssize_t occupied;

    if (*buffer == NULL) {
        if (!(*buffer = PyBytes_FromStringAndSize(NULL, length)))
            return -1;
        occupied = 0;
    }
    else {
        occupied = zst->next_out - (Byte *)PyBytes_AS_STRING(*buffer);

        if (length == occupied) {
            Py_ssize_t new_length;
            assert(length <= max_length);
            /* can not scale the buffer over max_length */
            if (length == max_length)
                return -2;
            if (length <= (max_length >> 1))
                new_length = length << 1;
            else
                new_length = max_length;
            if (_PyBytes_Resize(buffer, new_length) < 0)
                return -1;
            length = new_length;
        }
    }

    if ((size_t)(length - occupied) > UINT_MAX) {
        zst->avail_out = UINT_MAX;
    } else {
        zst->avail_out = length - occupied;
    }
    zst->next_out = (Byte *)PyBytes_AS_STRING(*buffer) + occupied;

    return length;
}

static Py_ssize_t
arrange_output_buffer(z_stream *zst, PyObject **buffer, Py_ssize_t length)
{
    Py_ssize_t ret;

    ret = arrange_output_buffer_with_maximum(zst, buffer, length,
                                             PY_SSIZE_T_MAX);
    if (ret == -2)
        PyErr_NoMemory();

    return ret;
}

PyDoc_STRVAR(compress__doc__,
"compress(string[, level]) -- Returned compressed string.\n"
"\n"
"Optional arg level is the compression level, in 0-9.");

static PyObject *
PyZlib_compress(PyObject *self, PyObject *args)
{
    PyObject *RetVal = NULL;
    Byte *ibuf;
    Py_ssize_t ibuflen, obuflen = DEFAULTALLOC;
    int level=Z_DEFAULT_COMPRESSION;
    int err, flush;
    z_stream zst;

    /* require Python string object, optional 'level' arg */
    if (!PyArg_ParseTuple(args, "s#|i:compress", &ibuf, &ibuflen, &level))
        return NULL;

    zst.zalloc = (alloc_func)NULL;
    zst.zfree = (free_func)Z_NULL;
    zst.next_in = ibuf;
    err = deflateInit(&zst, level);

    switch (err) {
    case Z_OK:
        break;
    case Z_MEM_ERROR:
        PyErr_SetString(PyExc_MemoryError,
                        "Out of memory while compressing data");
        goto error;
    case Z_STREAM_ERROR:
        PyErr_SetString(ZlibError, "Bad compression level");
        goto error;
    default:
        deflateEnd(&zst);
        zlib_error(zst, err, "while compressing data");
        goto error;
    }

    do {
        arrange_input_buffer(&zst, &ibuflen);
        flush = ibuflen == 0 ? Z_FINISH : Z_NO_FLUSH;

        do {
            obuflen = arrange_output_buffer(&zst, &RetVal, obuflen);
            if (obuflen < 0) {
                deflateEnd(&zst);
                goto error;
            }

            Py_BEGIN_ALLOW_THREADS
            err = deflate(&zst, flush);
            Py_END_ALLOW_THREADS

            if (err == Z_STREAM_ERROR) {
                deflateEnd(&zst);
                zlib_error(zst, err, "while compressing data");
                goto error;
            }

        } while (zst.avail_out == 0);
        assert(zst.avail_in == 0);

    } while (flush != Z_FINISH);
    assert(err == Z_STREAM_END);

    err = deflateEnd(&zst);
    if (err == Z_OK) {
        if (_PyBytes_Resize(&RetVal, zst.next_out -
                            (Byte *)PyBytes_AS_STRING(RetVal)) < 0)
            goto error;
        return RetVal;
    }
    else
        zlib_error(zst, err, "while finishing compression");
 error:
    Py_XDECREF(RetVal);
    return NULL;
}

PyDoc_STRVAR(decompress__doc__,
"decompress(string[, wbits[, bufsize]]) -- Return decompressed string.\n"
"\n"
"Optional arg wbits indicates the window buffer size and container format.\n"
"Optional arg bufsize is the initial output buffer size.");

static PyObject *
PyZlib_decompress(PyObject *self, PyObject *args)
{
    PyObject *RetVal = NULL;
    Byte *ibuf;
    Py_ssize_t ibuflen;
    int err, flush;
    int wsize=DEF_WBITS;
    Py_ssize_t r_strlen=DEFAULTALLOC;
    z_stream zst;

    if (!PyArg_ParseTuple(args, "s#|in:decompress",
                          &ibuf, &ibuflen, &wsize, &r_strlen))
        return NULL;

    if (r_strlen <= 0) {
        r_strlen = 1;
    }

    zst.zalloc = (alloc_func)NULL;
    zst.zfree = (free_func)Z_NULL;
    zst.avail_in = 0;
    zst.next_in = ibuf;
    err = inflateInit2(&zst, wsize);

    switch (err) {
    case Z_OK:
        break;
    case Z_MEM_ERROR:
        PyErr_SetString(PyExc_MemoryError,
                        "Out of memory while decompressing data");
        goto error;
    default:
        inflateEnd(&zst);
        zlib_error(zst, err, "while preparing to decompress data");
        goto error;
    }

    do {
        arrange_input_buffer(&zst, &ibuflen);
        flush = ibuflen == 0 ? Z_FINISH : Z_NO_FLUSH;

        do {
            r_strlen = arrange_output_buffer(&zst, &RetVal, r_strlen);
            if (r_strlen < 0) {
                inflateEnd(&zst);
                goto error;
            }

            Py_BEGIN_ALLOW_THREADS
            err = inflate(&zst, flush);
            Py_END_ALLOW_THREADS

            switch (err) {
            case Z_OK:            /* fall through */
            case Z_BUF_ERROR:     /* fall through */
            case Z_STREAM_END:
                break;
            case Z_MEM_ERROR:
                inflateEnd(&zst);
                PyErr_SetString(PyExc_MemoryError,
                                "Out of memory while decompressing data");
                goto error;
            default:
                inflateEnd(&zst);
                zlib_error(zst, err, "while decompressing data");
                goto error;
            }

        } while (zst.avail_out == 0);

    } while (err != Z_STREAM_END && ibuflen != 0);


    if (err != Z_STREAM_END) {
        inflateEnd(&zst);
        zlib_error(zst, err, "while decompressing data");
        goto error;
    }

    err = inflateEnd(&zst);
    if (err != Z_OK) {
        zlib_error(zst, err, "while finishing data decompression");
        goto error;
    }

    _PyString_Resize(&RetVal, zst.next_out -
                        (Byte *)PyBytes_AS_STRING(RetVal));
    return RetVal;

 error:
    Py_XDECREF(RetVal);
    return NULL;
}

static PyObject *
PyZlib_compressobj(PyObject *selfptr, PyObject *args)
{
    compobject *self;
    int level=Z_DEFAULT_COMPRESSION, method=DEFLATED;
    int wbits=MAX_WBITS, memLevel=DEF_MEM_LEVEL, strategy=0, err;

    if (!PyArg_ParseTuple(args, "|iiiii:compressobj", &level, &method, &wbits,
                          &memLevel, &strategy))
        return NULL;

    self = newcompobject(&Comptype);
    if (self == NULL)
        return(NULL);
    self->zst.zalloc = (alloc_func)NULL;
    self->zst.zfree = (free_func)Z_NULL;
    self->zst.next_in = NULL;
    self->zst.avail_in = 0;
    err = deflateInit2(&self->zst, level, method, wbits, memLevel, strategy);
    switch (err) {
    case Z_OK:
        self->is_initialised = 1;
        return (PyObject *)self;
    case Z_MEM_ERROR:
        Py_DECREF(self);
        PyErr_SetString(PyExc_MemoryError,
                        "Can't allocate memory for compression object");
        return NULL;
    case Z_STREAM_ERROR:
        Py_DECREF(self);
        PyErr_SetString(PyExc_ValueError, "Invalid initialization option");
        return NULL;
    default:
        zlib_error(self->zst, err, "while creating compression object");
        Py_DECREF(self);
        return NULL;
    }
}

static PyObject *
PyZlib_decompressobj(PyObject *selfptr, PyObject *args)
{
    int wbits=DEF_WBITS, err;
    compobject *self;
    if (!PyArg_ParseTuple(args, "|i:decompressobj", &wbits))
        return NULL;

    self = newcompobject(&Decomptype);
    if (self == NULL)
        return NULL;
    self->zst.zalloc = (alloc_func)NULL;
    self->zst.zfree = (free_func)Z_NULL;
    self->zst.next_in = NULL;
    self->zst.avail_in = 0;
    err = inflateInit2(&self->zst, wbits);
    switch (err) {
    case Z_OK:
        self->is_initialised = 1;
        return (PyObject *)self;
    case Z_STREAM_ERROR:
        Py_DECREF(self);
        PyErr_SetString(PyExc_ValueError, "Invalid initialization option");
        return NULL;
    case Z_MEM_ERROR:
        Py_DECREF(self);
        PyErr_SetString(PyExc_MemoryError,
                        "Can't allocate memory for decompression object");
        return NULL;
    default:
        zlib_error(self->zst, err, "while creating decompression object");
        Py_DECREF(self);
        return NULL;
    }
}

static void
Comp_dealloc(compobject *self)
{
    if (self->is_initialised)
        deflateEnd(&self->zst);
    Py_XDECREF(self->unused_data);
    Py_XDECREF(self->unconsumed_tail);
    PyObject_Del(self);
}

static void
Decomp_dealloc(compobject *self)
{
    if (self->is_initialised)
        inflateEnd(&self->zst);
    Py_XDECREF(self->unused_data);
    Py_XDECREF(self->unconsumed_tail);
    PyObject_Del(self);
}

PyDoc_STRVAR(comp_compress__doc__,
"compress(data) -- Return a string containing data compressed.\n"
"\n"
"After calling this function, some of the input data may still\n"
"be stored in internal buffers for later processing.\n"
"Call the flush() method to clear these buffers.");


static PyObject *
PyZlib_objcompress(compobject *self, PyObject *args)
{
    PyObject *RetVal = NULL;
    Py_ssize_t ibuflen, obuflen = DEFAULTALLOC;
    int err;

    if (!PyArg_ParseTuple(args, "s#:compress", &self->zst.next_in, &ibuflen))
        return NULL;

    ENTER_ZLIB

    do {
        arrange_input_buffer(&self->zst, &ibuflen);

        do {
            obuflen = arrange_output_buffer(&self->zst, &RetVal, obuflen);
            if (obuflen < 0)
                goto error;

            Py_BEGIN_ALLOW_THREADS
            err = deflate(&self->zst, Z_NO_FLUSH);
            Py_END_ALLOW_THREADS

            if (err == Z_STREAM_ERROR) {
                zlib_error(self->zst, err, "while compressing data");
                goto error;
            }

        } while (self->zst.avail_out == 0);
        assert(self->zst.avail_in == 0);

    } while (ibuflen != 0);

    _PyString_Resize(&RetVal, self->zst.next_out -
                        (Byte *)PyBytes_AS_STRING(RetVal));
    goto success;

 error:
    Py_CLEAR(RetVal);
 success:
    LEAVE_ZLIB
    return RetVal;
}

/* Helper for objdecompress() and unflush(). Saves any unconsumed input data in
   self->unused_data or self->unconsumed_tail, as appropriate. */
static int
save_unconsumed_input(compobject *self, Byte *input, Py_ssize_t inplen,
    int err)
{
    if (err == Z_STREAM_END) {
        /* The end of the compressed data has been reached. Store the leftover
           input data in self->unused_data. */
        if (self->zst.avail_in > 0) {
            Py_ssize_t old_size = PyString_GET_SIZE(self->unused_data);
            Py_ssize_t new_size, left_size;
            PyObject *new_data;
            left_size = input + inplen - self->zst.next_in;
            if (left_size > (PY_SSIZE_T_MAX - old_size)) {
                PyErr_NoMemory();
                return -1;
            }
            new_size = old_size + left_size;
            new_data = PyString_FromStringAndSize(NULL, new_size);
            if (new_data == NULL)
                return -1;
            Py_MEMCPY(PyString_AS_STRING(new_data),
                      PyString_AS_STRING(self->unused_data), old_size);
            Py_MEMCPY(PyString_AS_STRING(new_data) + old_size,
                      self->zst.next_in, left_size);
            Py_SETREF(self->unused_data, new_data);
            self->zst.avail_in = 0;
        }
    }

    if (self->zst.avail_in > 0 || PyString_GET_SIZE(self->unconsumed_tail)) {
        /* This code handles two distinct cases:
           1. Output limit was reached. Save leftover input in unconsumed_tail.
           2. All input data was consumed. Clear unconsumed_tail. */
        Py_ssize_t left_size = input + inplen - self->zst.next_in;
        PyObject *new_data = PyString_FromStringAndSize(
                (char *)self->zst.next_in, left_size);
        if (new_data == NULL)
            return -1;
        Py_SETREF(self->unconsumed_tail, new_data);
    }

    return 0;
}

PyDoc_STRVAR(decomp_decompress__doc__,
"decompress(data, max_length) -- Return a string containing the decompressed\n"
"version of the data.\n"
"\n"
"After calling this function, some of the input data may still be stored in\n"
"internal buffers for later processing.\n"
"Call the flush() method to clear these buffers.\n"
"If the max_length parameter is specified then the return value will be\n"
"no longer than max_length.  Unconsumed input data will be stored in\n"
"the unconsumed_tail attribute.");

static PyObject *
PyZlib_objdecompress(compobject *self, PyObject *args)
{
    int err = Z_OK;
    Py_ssize_t inplen, max_length = 0;
    Py_ssize_t ibuflen, obuflen = DEFAULTALLOC, hard_limit;
    PyObject *RetVal = NULL;
    Byte *input;

    if (!PyArg_ParseTuple(args, "s#|n:decompress", &input,
                          &inplen, &max_length))
        return NULL;
    if (max_length < 0) {
        PyErr_SetString(PyExc_ValueError,
                        "max_length must be greater than zero");
        return NULL;
    } else if (max_length == 0)
        hard_limit = PY_SSIZE_T_MAX;
    else
        hard_limit = max_length;

    self->zst.next_in = input;
    ibuflen = inplen;

    /* limit amount of data allocated to max_length */
    if (max_length && obuflen > max_length)
        obuflen = max_length;

    ENTER_ZLIB

    do {
        arrange_input_buffer(&self->zst, &ibuflen);

        do {
            obuflen = arrange_output_buffer_with_maximum(&self->zst, &RetVal,
                                                         obuflen, hard_limit);
            if (obuflen == -2) {
                if (max_length > 0) {
                    goto save;
                }
                PyErr_NoMemory();
            }
            if (obuflen < 0) {
                goto abort;
            }

            Py_BEGIN_ALLOW_THREADS
            err = inflate(&self->zst, Z_SYNC_FLUSH);
            Py_END_ALLOW_THREADS

            switch (err) {
            case Z_OK:            /* fall through */
            case Z_BUF_ERROR:     /* fall through */
            case Z_STREAM_END:
                break;
            default:
                goto save;
            }

        } while (self->zst.avail_out == 0);

    } while (err != Z_STREAM_END && ibuflen != 0);

 save:
    if (save_unconsumed_input(self, input, inplen, err) < 0)
        goto abort;

    /* This is the logical place to call inflateEnd, but the old behaviour of
       only calling it on flush() is preserved. */

    if (err != Z_STREAM_END && err != Z_OK && err != Z_BUF_ERROR) {
        /* We will only get Z_BUF_ERROR if the output buffer was full
           but there wasn't more output when we tried again, so it is
           not an error condition.
        */
        zlib_error(self->zst, err, "while decompressing");
        goto abort;
    }

    _PyString_Resize(&RetVal, self->zst.next_out -
                        (Byte *)PyBytes_AS_STRING(RetVal));
    goto success;

 abort:
    Py_CLEAR(RetVal);
 success:
    LEAVE_ZLIB

    return RetVal;
}

PyDoc_STRVAR(comp_flush__doc__,
"flush( [mode] ) -- Return a string containing any remaining compressed data.\n"
"\n"
"mode can be one of the constants Z_SYNC_FLUSH, Z_FULL_FLUSH, Z_FINISH; the\n"
"default value used when mode is not specified is Z_FINISH.\n"
"If mode == Z_FINISH, the compressor object can no longer be used after\n"
"calling the flush() method.  Otherwise, more data can still be compressed.");

static PyObject *
PyZlib_flush(compobject *self, PyObject *args)
{
    int err;
    Py_ssize_t length = DEFAULTALLOC;
    PyObject *RetVal = NULL;
    int flushmode = Z_FINISH;

    if (!PyArg_ParseTuple(args, "|i:flush", &flushmode))
        return NULL;

    /* Flushing with Z_NO_FLUSH is a no-op, so there's no point in
       doing any work at all; just return an empty string. */
    if (flushmode == Z_NO_FLUSH) {
        return PyString_FromStringAndSize(NULL, 0);
    }

    ENTER_ZLIB

    self->zst.avail_in = 0;

    do {
        length = arrange_output_buffer(&self->zst, &RetVal, length);
        if (length < 0) {
            Py_CLEAR(RetVal);
            goto error;
        }

        Py_BEGIN_ALLOW_THREADS
        err = deflate(&self->zst, flushmode);
        Py_END_ALLOW_THREADS

        if (err == Z_STREAM_ERROR) {
            zlib_error(self->zst, err, "while flushing");
            Py_CLEAR(RetVal);
            goto error;
        }
    } while (self->zst.avail_out == 0);
    assert(self->zst.avail_in == 0);

    /* If flushmode is Z_FINISH, we also have to call deflateEnd() to free
       various data structures. Note we should only get Z_STREAM_END when
       flushmode is Z_FINISH, but checking both for safety*/
    if (err == Z_STREAM_END && flushmode == Z_FINISH) {
        err = deflateEnd(&self->zst);
        if (err != Z_OK) {
            zlib_error(self->zst, err, "from deflateEnd()");
            Py_CLEAR(RetVal);
            goto error;
        }
        else
            self->is_initialised = 0;

        /* We will only get Z_BUF_ERROR if the output buffer was full
           but there wasn't more output when we tried again, so it is
           not an error condition.
        */
    } else if (err != Z_OK && err != Z_BUF_ERROR) {
        zlib_error(self->zst, err, "while flushing");
        Py_CLEAR(RetVal);
        goto error;
    }

    _PyString_Resize(&RetVal, self->zst.next_out -
                        (Byte *)PyBytes_AS_STRING(RetVal));

 error:
    LEAVE_ZLIB
    return RetVal;
}

#ifdef HAVE_ZLIB_COPY
PyDoc_STRVAR(comp_copy__doc__,
"copy() -- Return a copy of the compression object.");

static PyObject *
PyZlib_copy(compobject *self)
{
    compobject *retval = NULL;
    int err;

    retval = newcompobject(&Comptype);
    if (!retval) return NULL;

    /* Copy the zstream state
     * We use ENTER_ZLIB / LEAVE_ZLIB to make this thread-safe
     */
    ENTER_ZLIB
    err = deflateCopy(&retval->zst, &self->zst);
    switch (err) {
    case Z_OK:
        break;
    case Z_STREAM_ERROR:
        PyErr_SetString(PyExc_ValueError, "Inconsistent stream state");
        goto error;
    case Z_MEM_ERROR:
        PyErr_SetString(PyExc_MemoryError,
                        "Can't allocate memory for compression object");
        goto error;
    default:
        zlib_error(self->zst, err, "while copying compression object");
        goto error;
    }

    Py_INCREF(self->unused_data);
    Py_XSETREF(retval->unused_data, self->unused_data);
    Py_INCREF(self->unconsumed_tail);
    Py_XSETREF(retval->unconsumed_tail, self->unconsumed_tail);

    /* Mark it as being initialized */
    retval->is_initialised = 1;

    LEAVE_ZLIB
    return (PyObject *)retval;

error:
    LEAVE_ZLIB
    Py_XDECREF(retval);
    return NULL;
}

PyDoc_STRVAR(decomp_copy__doc__,
"copy() -- Return a copy of the decompression object.");

static PyObject *
PyZlib_uncopy(compobject *self)
{
    compobject *retval = NULL;
    int err;

    retval = newcompobject(&Decomptype);
    if (!retval) return NULL;

    /* Copy the zstream state
     * We use ENTER_ZLIB / LEAVE_ZLIB to make this thread-safe
     */
    ENTER_ZLIB
    err = inflateCopy(&retval->zst, &self->zst);
    switch (err) {
    case Z_OK:
        break;
    case Z_STREAM_ERROR:
        PyErr_SetString(PyExc_ValueError, "Inconsistent stream state");
        goto error;
    case Z_MEM_ERROR:
        PyErr_SetString(PyExc_MemoryError,
                        "Can't allocate memory for decompression object");
        goto error;
    default:
        zlib_error(self->zst, err, "while copying decompression object");
        goto error;
    }

    Py_INCREF(self->unused_data);
    Py_XSETREF(retval->unused_data, self->unused_data);
    Py_INCREF(self->unconsumed_tail);
    Py_XSETREF(retval->unconsumed_tail, self->unconsumed_tail);

    /* Mark it as being initialized */
    retval->is_initialised = 1;

    LEAVE_ZLIB
    return (PyObject *)retval;

error:
    LEAVE_ZLIB
    Py_XDECREF(retval);
    return NULL;
}
#endif

PyDoc_STRVAR(decomp_flush__doc__,
"flush( [length] ) -- Return a string containing any remaining\n"
"decompressed data. length, if given, is the initial size of the\n"
"output buffer.\n"
"\n"
"The decompressor object can no longer be used after this call.");

static PyObject *
PyZlib_unflush(compobject *self, PyObject *args)
{
    Py_ssize_t length = DEFAULTALLOC;
    int err, flush;
    PyObject *RetVal = NULL;
    Py_ssize_t ibuflen;

    if (!PyArg_ParseTuple(args, "|n:flush", &length))
        return NULL;
    if (length <= 0) {
        PyErr_SetString(PyExc_ValueError, "length must be greater than zero");
        return NULL;
    }

    ENTER_ZLIB

    self->zst.next_in = (Byte *)PyString_AS_STRING(self->unconsumed_tail);
    ibuflen = PyString_GET_SIZE(self->unconsumed_tail);

    do {
        arrange_input_buffer(&self->zst, &ibuflen);
        flush = ibuflen == 0 ? Z_FINISH : Z_NO_FLUSH;

        do {
            length = arrange_output_buffer(&self->zst, &RetVal, length);
            if (length < 0)
                goto abort;

            Py_BEGIN_ALLOW_THREADS
            err = inflate(&self->zst, flush);
            Py_END_ALLOW_THREADS

            switch (err) {
            case Z_OK:            /* fall through */
            case Z_BUF_ERROR:     /* fall through */
            case Z_STREAM_END:
                break;
            default:
                goto save;
            }

        } while (self->zst.avail_out == 0);

    } while (err != Z_STREAM_END && ibuflen != 0);

 save:
    if (save_unconsumed_input(self,
            (Byte *)PyString_AS_STRING(self->unconsumed_tail),
            PyString_GET_SIZE(self->unconsumed_tail), err) < 0)
        goto abort;

    /* If flushmode is Z_FINISH, we also have to call deflateEnd() to free
       various data structures. Note we should only get Z_STREAM_END when
       flushmode is Z_FINISH */
    if (err == Z_STREAM_END) {
        err = inflateEnd(&self->zst);
        self->is_initialised = 0;
        if (err != Z_OK) {
            zlib_error(self->zst, err, "from inflateEnd()");
            goto abort;
        }
    }

    _PyString_Resize(&RetVal, self->zst.next_out -
                        (Byte *)PyBytes_AS_STRING(RetVal));
    goto success;

 abort:
    Py_CLEAR(RetVal);
 success:
    LEAVE_ZLIB
    return RetVal;
}

static PyMethodDef comp_methods[] =
{
    {"compress", (binaryfunc)PyZlib_objcompress, METH_VARARGS,
                 comp_compress__doc__},
    {"flush", (binaryfunc)PyZlib_flush, METH_VARARGS,
              comp_flush__doc__},
#ifdef HAVE_ZLIB_COPY
    {"copy",  (PyCFunction)PyZlib_copy, METH_NOARGS,
              comp_copy__doc__},
#endif
    {NULL, NULL}
};

static PyMethodDef Decomp_methods[] =
{
    {"decompress", (binaryfunc)PyZlib_objdecompress, METH_VARARGS,
                   decomp_decompress__doc__},
    {"flush", (binaryfunc)PyZlib_unflush, METH_VARARGS,
              decomp_flush__doc__},
#ifdef HAVE_ZLIB_COPY
    {"copy",  (PyCFunction)PyZlib_uncopy, METH_NOARGS,
              decomp_copy__doc__},
#endif
    {NULL, NULL}
};

static PyObject *
Comp_getattr(compobject *self, char *name)
{
  /* No ENTER/LEAVE_ZLIB is necessary because this fn doesn't touch
     internal data. */

  return Py_FindMethod(comp_methods, (PyObject *)self, name);
}

static PyObject *
Decomp_getattr(compobject *self, char *name)
{
    PyObject * retval;

    ENTER_ZLIB

    if (strcmp(name, "unused_data") == 0) {
        Py_INCREF(self->unused_data);
        retval = self->unused_data;
    } else if (strcmp(name, "unconsumed_tail") == 0) {
        Py_INCREF(self->unconsumed_tail);
        retval = self->unconsumed_tail;
    } else
        retval = Py_FindMethod(Decomp_methods, (PyObject *)self, name);

    LEAVE_ZLIB

    return retval;
}

PyDoc_STRVAR(adler32__doc__,
"adler32(string[, start]) -- Compute an Adler-32 checksum of string.\n"
"\n"
"An optional starting value can be specified.  The returned checksum is\n"
"a signed integer.");

static PyObject *
PyZlib_adler32(PyObject *self, PyObject *args)
{
    unsigned int adler32val = 1;  /* adler32(0L, Z_NULL, 0) */
    Byte *buf;
    Py_ssize_t len;
    int signed_val;

    if (!PyArg_ParseTuple(args, "s#|I:adler32", &buf, &len, &adler32val))
        return NULL;

    /* Avoid truncation of length for very large buffers. adler32() takes
       length as an unsigned int, which may be narrower than Py_ssize_t. */
    while ((size_t)len > UINT_MAX) {
        adler32val = adler32(adler32val, buf, UINT_MAX);
        buf += (size_t) UINT_MAX;
        len -= (size_t) UINT_MAX;
    }
    /* In Python 2.x we return a signed integer regardless of native platform
     * long size (the 32bit unsigned long is treated as 32-bit signed and sign
     * extended into a 64-bit long inside the integer object).  3.0 does the
     * right thing and returns unsigned. http://bugs.python.org/issue1202 */
    signed_val = adler32(adler32val, buf, (unsigned int)len);
    return PyInt_FromLong(signed_val);
}

PyDoc_STRVAR(crc32__doc__,
"crc32(string[, start]) -- Compute a CRC-32 checksum of string.\n"
"\n"
"An optional starting value can be specified.  The returned checksum is\n"
"a signed integer.");

static PyObject *
PyZlib_crc32(PyObject *self, PyObject *args)
{
    unsigned int crc32val = 0;  /* crc32(0L, Z_NULL, 0) */
    Byte *buf;
    Py_ssize_t len;
    int signed_val;

    if (!PyArg_ParseTuple(args, "s#|I:crc32", &buf, &len, &crc32val))
        return NULL;

    /* Avoid truncation of length for very large buffers. crc32() takes
       length as an unsigned int, which may be narrower than Py_ssize_t. */
    while ((size_t)len > UINT_MAX) {
        crc32val = crc32(crc32val, buf, UINT_MAX);
        buf += (size_t) UINT_MAX;
        len -= (size_t) UINT_MAX;
    }
    /* In Python 2.x we return a signed integer regardless of native platform
     * long size (the 32bit unsigned long is treated as 32-bit signed and sign
     * extended into a 64-bit long inside the integer object).  3.0 does the
     * right thing and returns unsigned. http://bugs.python.org/issue1202 */
    signed_val = crc32(crc32val, buf, (unsigned int)len);
    return PyInt_FromLong(signed_val);
}


static PyMethodDef zlib_methods[] =
{
    {"adler32", (PyCFunction)PyZlib_adler32, METH_VARARGS,
                adler32__doc__},
    {"compress", (PyCFunction)PyZlib_compress,  METH_VARARGS,
                 compress__doc__},
    {"compressobj", (PyCFunction)PyZlib_compressobj, METH_VARARGS,
                    compressobj__doc__},
    {"crc32", (PyCFunction)PyZlib_crc32, METH_VARARGS,
              crc32__doc__},
    {"decompress", (PyCFunction)PyZlib_decompress, METH_VARARGS,
                   decompress__doc__},
    {"decompressobj", (PyCFunction)PyZlib_decompressobj, METH_VARARGS,
                   decompressobj__doc__},
    {NULL, NULL}
};

static PyTypeObject Comptype = {
    PyVarObject_HEAD_INIT(0, 0)
    "zlib.Compress",
    sizeof(compobject),
    0,
    (destructor)Comp_dealloc,       /*tp_dealloc*/
    0,                              /*tp_print*/
    (getattrfunc)Comp_getattr,      /*tp_getattr*/
    0,                              /*tp_setattr*/
    0,                              /*tp_compare*/
    0,                              /*tp_repr*/
    0,                              /*tp_as_number*/
    0,                              /*tp_as_sequence*/
    0,                              /*tp_as_mapping*/
};

static PyTypeObject Decomptype = {
    PyVarObject_HEAD_INIT(0, 0)
    "zlib.Decompress",
    sizeof(compobject),
    0,
    (destructor)Decomp_dealloc,     /*tp_dealloc*/
    0,                              /*tp_print*/
    (getattrfunc)Decomp_getattr,    /*tp_getattr*/
    0,                              /*tp_setattr*/
    0,                              /*tp_compare*/
    0,                              /*tp_repr*/
    0,                              /*tp_as_number*/
    0,                              /*tp_as_sequence*/
    0,                              /*tp_as_mapping*/
};

PyDoc_STRVAR(zlib_module_documentation,
"The functions in this module allow compression and decompression using the\n"
"zlib library, which is based on GNU zip.\n"
"\n"
"adler32(string[, start]) -- Compute an Adler-32 checksum.\n"
"compress(string[, level]) -- Compress string, with compression level in 0-9.\n"
"compressobj([level]) -- Return a compressor object.\n"
"crc32(string[, start]) -- Compute a CRC-32 checksum.\n"
"decompress(string,[wbits],[bufsize]) -- Decompresses a compressed string.\n"
"decompressobj([wbits]) -- Return a decompressor object.\n"
"\n"
"'wbits' is window buffer size and container format.\n"
"Compressor objects support compress() and flush() methods; decompressor\n"
"objects support decompress() and flush().");

PyMODINIT_FUNC
PyInit_zlib(void)
{
    PyObject *m, *ver;
    Py_TYPE(&Comptype) = &PyType_Type;
    Py_TYPE(&Decomptype) = &PyType_Type;
    m = Py_InitModule4("zlib", zlib_methods,
                       zlib_module_documentation,
                       (PyObject*)NULL,PYTHON_API_VERSION);
    if (m == NULL)
        return;

    ZlibError = PyErr_NewException("zlib.error", NULL, NULL);
    if (ZlibError != NULL) {
        Py_INCREF(ZlibError);
        PyModule_AddObject(m, "error", ZlibError);
    }
    PyModule_AddIntConstant(m, "MAX_WBITS", MAX_WBITS);
    PyModule_AddIntConstant(m, "DEFLATED", DEFLATED);
    PyModule_AddIntConstant(m, "DEF_MEM_LEVEL", DEF_MEM_LEVEL);
    PyModule_AddIntConstant(m, "Z_BEST_SPEED", Z_BEST_SPEED);
    PyModule_AddIntConstant(m, "Z_BEST_COMPRESSION", Z_BEST_COMPRESSION);
    PyModule_AddIntConstant(m, "Z_DEFAULT_COMPRESSION", Z_DEFAULT_COMPRESSION);
    PyModule_AddIntConstant(m, "Z_FILTERED", Z_FILTERED);
    PyModule_AddIntConstant(m, "Z_HUFFMAN_ONLY", Z_HUFFMAN_ONLY);
    PyModule_AddIntConstant(m, "Z_DEFAULT_STRATEGY", Z_DEFAULT_STRATEGY);

    PyModule_AddIntConstant(m, "Z_FINISH", Z_FINISH);
    PyModule_AddIntConstant(m, "Z_NO_FLUSH", Z_NO_FLUSH);
    PyModule_AddIntConstant(m, "Z_SYNC_FLUSH", Z_SYNC_FLUSH);
    PyModule_AddIntConstant(m, "Z_FULL_FLUSH", Z_FULL_FLUSH);

    ver = PyString_FromString(ZLIB_VERSION);
    if (ver != NULL)
        PyModule_AddObject(m, "ZLIB_VERSION", ver);

    PyModule_AddStringConstant(m, "__version__", "1.0");

#ifdef WITH_THREAD
    zlib_lock = PyThread_allocate_lock();
#endif /* WITH_THREAD */
}