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Issue #15955: Add an option to limit output size when decompressing LZMA data.

Browse source 
Patch by Nikolaus Rath and Martin Panter.
This commit is contained in:
Antoine Pitrou 2015-01-17 16:22:18 +01:00
parent e262074ede
commit 26795baaa8
5 changed files with 327 additions and 59 deletions
Download patch file Download diff file Expand all files Collapse all files

37
Doc/library/lzma.rst
View file

@ -221,13 +221,32 @@ Compressing and decompressing data in memory
decompress a multi-stream input with :class:`LZMADecompressor`, you must
create a new decompressor for each stream.
.. method:: decompress(data)
.. method:: decompress(data, max_length=-1)
Decompress *data* (a :class:`bytes` object), returning a :class:`bytes`
object containing the decompressed data for at least part of the input.
Some of *data* may be buffered internally, for use in later calls to
:meth:`decompress`. The returned data should be concatenated with the
output of any previous calls to :meth:`decompress`.
Decompress *data* (a :term:`bytes-like object`), returning
uncompressed data as bytes. Some of *data* may be buffered
internally, for use in later calls to :meth:`decompress`. The
returned data should be concatenated with the output of any
previous calls to :meth:`decompress`.
If *max_length* is nonnegative, returns at most *max_length*
bytes of decompressed data. If this limit is reached and further
output can be produced, the :attr:`~.needs_input` attribute will
be set to ``False``. In this case, the next call to
:meth:`~.decompress` may provide *data* as ``b''`` to obtain
more of the output.
If all of the input data was decompressed and returned (either
because this was less than *max_length* bytes, or because
*max_length* was negative), the :attr:`~.needs_input` attribute
will be set to ``True``.
Attempting to decompress data after the end of stream is reached
raises an `EOFError`. Any data found after the end of the
stream is ignored and saved in the :attr:`~.unused_data` attribute.
.. versionchanged:: 3.5
Added the *max_length* parameter.
.. attribute:: check
@ -245,6 +264,12 @@ Compressing and decompressing data in memory
Before the end of the stream is reached, this will be ``b""``.
.. attribute:: needs_input
``False`` if the :meth:`.decompress` method can provide more
decompressed data before requiring new uncompressed input.
.. versionadded:: 3.5
.. function:: compress(data, format=FORMAT_XZ, check=-1, preset=None, filters=None)

91
Lib/test/test_lzma.py
View file

@ -135,6 +135,97 @@ class CompressorDecompressorTestCase(unittest.TestCase):
self.assertTrue(lzd.eof)
self.assertEqual(lzd.unused_data, b"")
def test_decompressor_chunks_maxsize(self):
lzd = LZMADecompressor()
max_length = 100
out = []
# Feed first half the input
len_ = len(COMPRESSED_XZ) // 2
out.append(lzd.decompress(COMPRESSED_XZ[:len_],
max_length=max_length))
self.assertFalse(lzd.needs_input)
self.assertEqual(len(out[-1]), max_length)
# Retrieve more data without providing more input
out.append(lzd.decompress(b'', max_length=max_length))
self.assertFalse(lzd.needs_input)
self.assertEqual(len(out[-1]), max_length)
# Retrieve more data while providing more input
out.append(lzd.decompress(COMPRESSED_XZ[len_:],
max_length=max_length))
self.assertLessEqual(len(out[-1]), max_length)
# Retrieve remaining uncompressed data
while not lzd.eof:
out.append(lzd.decompress(b'', max_length=max_length))
self.assertLessEqual(len(out[-1]), max_length)
out = b"".join(out)
self.assertEqual(out, INPUT)
self.assertEqual(lzd.check, lzma.CHECK_CRC64)
self.assertEqual(lzd.unused_data, b"")
def test_decompressor_inputbuf_1(self):
# Test reusing input buffer after moving existing
# contents to beginning
lzd = LZMADecompressor()
out = []
# Create input buffer and fill it
self.assertEqual(lzd.decompress(COMPRESSED_XZ[:100],
max_length=0), b'')
# Retrieve some results, freeing capacity at beginning
# of input buffer
out.append(lzd.decompress(b'', 2))
# Add more data that fits into input buffer after
# moving existing data to beginning
out.append(lzd.decompress(COMPRESSED_XZ[100:105], 15))
# Decompress rest of data
out.append(lzd.decompress(COMPRESSED_XZ[105:]))
self.assertEqual(b''.join(out), INPUT)
def test_decompressor_inputbuf_2(self):
# Test reusing input buffer by appending data at the
# end right away
lzd = LZMADecompressor()
out = []
# Create input buffer and empty it
self.assertEqual(lzd.decompress(COMPRESSED_XZ[:200],
max_length=0), b'')
out.append(lzd.decompress(b''))
# Fill buffer with new data
out.append(lzd.decompress(COMPRESSED_XZ[200:280], 2))
# Append some more data, not enough to require resize
out.append(lzd.decompress(COMPRESSED_XZ[280:300], 2))
# Decompress rest of data
out.append(lzd.decompress(COMPRESSED_XZ[300:]))
self.assertEqual(b''.join(out), INPUT)
def test_decompressor_inputbuf_3(self):
# Test reusing input buffer after extending it
lzd = LZMADecompressor()
out = []
# Create almost full input buffer
out.append(lzd.decompress(COMPRESSED_XZ[:200], 5))
# Add even more data to it, requiring resize
out.append(lzd.decompress(COMPRESSED_XZ[200:300], 5))
# Decompress rest of data
out.append(lzd.decompress(COMPRESSED_XZ[300:]))
self.assertEqual(b''.join(out), INPUT)
def test_decompressor_unused_data(self):
lzd = LZMADecompressor()
extra = b"fooblibar"

3
Misc/NEWS
View file

@ -203,6 +203,9 @@ Core and Builtins
Library
-------
- Issue #15955: Add an option to limit output size when decompressing LZMA
data. Patch by Nikolaus Rath and Martin Panter.
- Issue #23250: In the http.cookies module, capitalize "HttpOnly" and "Secure"
as they are written in the standard.

218
Modules/_lzmamodule.c
View file

@ -66,6 +66,9 @@ typedef struct {
int check;
char eof;
PyObject *unused_data;
char needs_input;
uint8_t *input_buffer;
size_t input_buffer_size;
#ifdef WITH_THREAD
PyThread_type_lock lock;
#endif
@ -142,10 +145,15 @@ PyLzma_Free(void *opaque, void *ptr)
#endif
static int
grow_buffer(PyObject **buf)
grow_buffer(PyObject **buf, Py_ssize_t max_length)
{
size_t size = PyBytes_GET_SIZE(*buf);
return _PyBytes_Resize(buf, size + (size >> 3) + 6);
Py_ssize_t size = PyBytes_GET_SIZE(*buf);
Py_ssize_t newsize = size + (size >> 3) + 6;
if (max_length > 0 && newsize > max_length)
newsize = max_length;
return _PyBytes_Resize(buf, newsize);
}
@ -504,7 +512,7 @@ class lzma_filter_converter(CConverter):
static PyObject *
compress(Compressor *c, uint8_t *data, size_t len, lzma_action action)
{
size_t data_size = 0;
Py_ssize_t data_size = 0;
PyObject *result;
result = PyBytes_FromStringAndSize(NULL, INITIAL_BUFFER_SIZE);
@ -527,13 +535,13 @@ compress(Compressor *c, uint8_t *data, size_t len, lzma_action action)
(action == LZMA_FINISH && lzret == LZMA_STREAM_END)) {
break;
} else if (c->lzs.avail_out == 0) {
if (grow_buffer(&result) == -1)
if (grow_buffer(&result, -1) == -1)
goto error;
c->lzs.next_out = (uint8_t *)PyBytes_AS_STRING(result) + data_size;
c->lzs.avail_out = PyBytes_GET_SIZE(result) - data_size;
}
}
if (data_size != (size_t)PyBytes_GET_SIZE(result))
if (data_size != PyBytes_GET_SIZE(result))
if (_PyBytes_Resize(&result, data_size) == -1)
goto error;
return result;
@ -888,25 +896,33 @@ static PyTypeObject Compressor_type = {
/* LZMADecompressor class. */
static PyObject *
decompress(Decompressor *d, uint8_t *data, size_t len)
/* Decompress data of length d->lzs.avail_in in d->lzs.next_in. The output
buffer is allocated dynamically and returned. At most max_length bytes are
returned, so some of the input may not be consumed. d->lzs.next_in and
d->lzs.avail_in are updated to reflect the consumed input. */
static PyObject*
decompress_buf(Decompressor *d, Py_ssize_t max_length)
{
size_t data_size = 0;
Py_ssize_t data_size = 0;
PyObject *result;
result = PyBytes_FromStringAndSize(NULL, INITIAL_BUFFER_SIZE);
lzma_stream *lzs = &d->lzs;
if (max_length < 0 || max_length >= INITIAL_BUFFER_SIZE)
result = PyBytes_FromStringAndSize(NULL, INITIAL_BUFFER_SIZE);
else
result = PyBytes_FromStringAndSize(NULL, max_length);
if (result == NULL)
return NULL;
d->lzs.next_in = data;
d->lzs.avail_in = len;
d->lzs.next_out = (uint8_t *)PyBytes_AS_STRING(result);
d->lzs.avail_out = PyBytes_GET_SIZE(result);
lzs->next_out = (uint8_t *)PyBytes_AS_STRING(result);
lzs->avail_out = PyBytes_GET_SIZE(result);
for (;;) {
lzma_ret lzret;
Py_BEGIN_ALLOW_THREADS
lzret = lzma_code(&d->lzs, LZMA_RUN);
data_size = (char *)d->lzs.next_out - PyBytes_AS_STRING(result);
lzret = lzma_code(lzs, LZMA_RUN);
data_size = (char *)lzs->next_out - PyBytes_AS_STRING(result);
Py_END_ALLOW_THREADS
if (catch_lzma_error(lzret))
goto error;
@ -914,26 +930,131 @@ decompress(Decompressor *d, uint8_t *data, size_t len)
d->check = lzma_get_check(&d->lzs);
if (lzret == LZMA_STREAM_END) {
d->eof = 1;
if (d->lzs.avail_in > 0) {
Py_CLEAR(d->unused_data);
d->unused_data = PyBytes_FromStringAndSize(
(char *)d->lzs.next_in, d->lzs.avail_in);
if (d->unused_data == NULL)
goto error;
}
break;
} else if (d->lzs.avail_in == 0) {
} else if (lzs->avail_in == 0) {
break;
} else if (d->lzs.avail_out == 0) {
if (grow_buffer(&result) == -1)
} else if (lzs->avail_out == 0) {
if (data_size == max_length)
break;
if (grow_buffer(&result, max_length) == -1)
goto error;
d->lzs.next_out = (uint8_t *)PyBytes_AS_STRING(result) + data_size;
d->lzs.avail_out = PyBytes_GET_SIZE(result) - data_size;
lzs->next_out = (uint8_t *)PyBytes_AS_STRING(result) + data_size;
lzs->avail_out = PyBytes_GET_SIZE(result) - data_size;
}
}
if (data_size != (size_t)PyBytes_GET_SIZE(result))
if (data_size != PyBytes_GET_SIZE(result))
if (_PyBytes_Resize(&result, data_size) == -1)
goto error;
return result;
error:
Py_XDECREF(result);
return NULL;
}
static PyObject *
decompress(Decompressor *d, uint8_t *data, size_t len, Py_ssize_t max_length)
{
char input_buffer_in_use;
PyObject *result;
lzma_stream *lzs = &d->lzs;
/* Prepend unconsumed input if necessary */
if (lzs->next_in != NULL) {
size_t avail_now, avail_total;
/* Number of bytes we can append to input buffer */
avail_now = (d->input_buffer + d->input_buffer_size)
- (lzs->next_in + lzs->avail_in);
/* Number of bytes we can append if we move existing
contents to beginning of buffer (overwriting
consumed input) */
avail_total = d->input_buffer_size - lzs->avail_in;
if (avail_total < len) {
size_t offset = lzs->next_in - d->input_buffer;
uint8_t *tmp;
size_t new_size = d->input_buffer_size + len - avail_now;
/* Assign to temporary variable first, so we don't
lose address of allocated buffer if realloc fails */
tmp = PyMem_Realloc(d->input_buffer, new_size);
if (tmp == NULL) {
PyErr_SetNone(PyExc_MemoryError);
return NULL;
}
d->input_buffer = tmp;
d->input_buffer_size = new_size;
lzs->next_in = d->input_buffer + offset;
}
else if (avail_now < len) {
memmove(d->input_buffer, lzs->next_in,
lzs->avail_in);
lzs->next_in = d->input_buffer;
}
memcpy((void*)(lzs->next_in + lzs->avail_in), data, len);
lzs->avail_in += len;
input_buffer_in_use = 1;
}
else {
lzs->next_in = data;
lzs->avail_in = len;
input_buffer_in_use = 0;
}
result = decompress_buf(d, max_length);
if(result == NULL)
return NULL;
if (d->eof) {
d->needs_input = 0;
if (lzs->avail_in > 0) {
Py_CLEAR(d->unused_data);
d->unused_data = PyBytes_FromStringAndSize(
(char *)lzs->next_in, lzs->avail_in);
if (d->unused_data == NULL)
goto error;
}
}
else if (lzs->avail_in == 0) {
lzs->next_in = NULL;
d->needs_input = 1;
}
else {
d->needs_input = 0;
/* If we did not use the input buffer, we now have
to copy the tail from the caller's buffer into the
input buffer */
if (!input_buffer_in_use) {
/* Discard buffer if it's too small
(resizing it may needlessly copy the current contents) */
if (d->input_buffer != NULL &&
d->input_buffer_size < lzs->avail_in) {
PyMem_Free(d->input_buffer);
d->input_buffer = NULL;
}
/* Allocate if necessary */
if (d->input_buffer == NULL) {
d->input_buffer = PyMem_Malloc(lzs->avail_in);
if (d->input_buffer == NULL) {
PyErr_SetNone(PyExc_MemoryError);
goto error;
}
d->input_buffer_size = lzs->avail_in;
}
/* Copy tail */
memcpy(d->input_buffer, lzs->next_in, lzs->avail_in);
lzs->next_in = d->input_buffer;
}
}
return result;
error:
@ -946,20 +1067,27 @@ _lzma.LZMADecompressor.decompress
self: self(type="Decompressor *")
data: Py_buffer
/
max_length: Py_ssize_t=-1
Provide data to the decompressor object.
Decompress *data*, returning uncompressed data as bytes.
Returns a chunk of decompressed data if possible, or b'' otherwise.
If *max_length* is nonnegative, returns at most *max_length* bytes of
decompressed data. If this limit is reached and further output can be
produced, *self.needs_input* will be set to ``False``. In this case, the next
call to *decompress()* may provide *data* as b'' to obtain more of the output.
Attempting to decompress data after the end of stream is reached
raises an EOFError. Any data found after the end of the stream
is ignored and saved in the unused_data attribute.
If all of the input data was decompressed and returned (either because this
was less than *max_length* bytes, or because *max_length* was negative),
*self.needs_input* will be set to True.
Attempting to decompress data after the end of stream is reached raises an
EOFError. Any data found after the end of the stream is ignored and saved in
the unused_data attribute.
[clinic start generated code]*/
static PyObject *
_lzma_LZMADecompressor_decompress_impl(Decompressor *self, Py_buffer *data)
/*[clinic end generated code: output=d86e78da7ff0ff21 input=50c4768b821bf0ef]*/
_lzma_LZMADecompressor_decompress_impl(Decompressor *self, Py_buffer *data, Py_ssize_t max_length)
/*[clinic end generated code: output=1532a5bb23629001 input=262e4e217f49039b]*/
{
PyObject *result = NULL;
@ -967,7 +1095,7 @@ _lzma_LZMADecompressor_decompress_impl(Decompressor *self, Py_buffer *data)
if (self->eof)
PyErr_SetString(PyExc_EOFError, "Already at end of stream");
else
result = decompress(self, data->buf, data->len);
result = decompress(self, data->buf, data->len, max_length);
RELEASE_LOCK(self);
return result;
}
@ -1055,6 +1183,7 @@ _lzma_LZMADecompressor___init___impl(Decompressor *self, int format, PyObject *m
self->alloc.alloc = PyLzma_Malloc;
self->alloc.free = PyLzma_Free;
self->lzs.allocator = &self->alloc;
self->lzs.next_in = NULL;
#ifdef WITH_THREAD
self->lock = PyThread_allocate_lock();
@ -1065,6 +1194,9 @@ _lzma_LZMADecompressor___init___impl(Decompressor *self, int format, PyObject *m
#endif
self->check = LZMA_CHECK_UNKNOWN;
self->needs_input = 1;
self->input_buffer = NULL;
self->input_buffer_size = 0;
self->unused_data = PyBytes_FromStringAndSize(NULL, 0);
if (self->unused_data == NULL)
goto error;
@ -1113,6 +1245,9 @@ error:
static void
Decompressor_dealloc(Decompressor *self)
{
if(self->input_buffer != NULL)
PyMem_Free(self->input_buffer);
lzma_end(&self->lzs);
Py_CLEAR(self->unused_data);
#ifdef WITH_THREAD
@ -1134,6 +1269,9 @@ PyDoc_STRVAR(Decompressor_check_doc,
PyDoc_STRVAR(Decompressor_eof_doc,
"True if the end-of-stream marker has been reached.");
PyDoc_STRVAR(Decompressor_needs_input_doc,
"True if more input is needed before more decompressed data can be produced.");
PyDoc_STRVAR(Decompressor_unused_data_doc,
"Data found after the end of the compressed stream.");
@ -1142,6 +1280,8 @@ static PyMemberDef Decompressor_members[] = {
Decompressor_check_doc},
{"eof", T_BOOL, offsetof(Decompressor, eof), READONLY,
Decompressor_eof_doc},
{"needs_input", T_BOOL, offsetof(Decompressor, needs_input), READONLY,
Decompressor_needs_input_doc},
{"unused_data", T_OBJECT_EX, offsetof(Decompressor, unused_data), READONLY,
Decompressor_unused_data_doc},
{NULL}

37
Modules/clinic/_lzmamodule.c.h
View file

@ -62,34 +62,43 @@ _lzma_LZMACompressor_flush(Compressor *self, PyObject *Py_UNUSED(ignored))
}
PyDoc_STRVAR(_lzma_LZMADecompressor_decompress__doc__,
"decompress($self, data, /)\n"
"decompress($self, /, data, max_length=-1)\n"
"--\n"
"\n"
"Provide data to the decompressor object.\n"
"Decompresses *data*, returning uncompressed data as bytes.\n"
"\n"
"Returns a chunk of decompressed data if possible, or b\'\' otherwise.\n"
"If *max_length* is nonnegative, returns at most *max_length* bytes of\n"
"decompressed data. If this limit is reached and further output can be\n"
"produced, *self.needs_input* will be set to ``False``. In this case, the next\n"
"call to *decompress()* may provide *data* as b\'\' to obtain more of the output.\n"
"\n"
"Attempting to decompress data after the end of stream is reached\n"
"raises an EOFError. Any data found after the end of the stream\n"
"is ignored and saved in the unused_data attribute.");
"If all of the input data was decompressed and returned (either because this\n"
"was less than *max_length* bytes, or because *max_length* was negative),\n"
"*self.needs_input* will be set to True.\n"
"\n"
"Attempting to decompress data after the end of stream is reached raises an\n"
"EOFError. Any data found after the end of the stream is ignored and saved in\n"
"the unused_data attribute.");
#define _LZMA_LZMADECOMPRESSOR_DECOMPRESS_METHODDEF \
{"decompress", (PyCFunction)_lzma_LZMADecompressor_decompress, METH_VARARGS, _lzma_LZMADecompressor_decompress__doc__},
{"decompress", (PyCFunction)_lzma_LZMADecompressor_decompress, METH_VARARGS|METH_KEYWORDS, _lzma_LZMADecompressor_decompress__doc__},
static PyObject *
_lzma_LZMADecompressor_decompress_impl(Decompressor *self, Py_buffer *data);
_lzma_LZMADecompressor_decompress_impl(Decompressor *self, Py_buffer *data, Py_ssize_t max_length);
static PyObject *
_lzma_LZMADecompressor_decompress(Decompressor *self, PyObject *args)
_lzma_LZMADecompressor_decompress(Decompressor *self, PyObject *args, PyObject *kwargs)
{
PyObject *return_value = NULL;
static char *_keywords[] = {"data", "max_length", NULL};
Py_buffer data = {NULL, NULL};
Py_ssize_t max_length = -1;
if (!PyArg_ParseTuple(args,
"y*:decompress",
&data))
if (!PyArg_ParseTupleAndKeywords(args, kwargs,
"y*|n:decompress", _keywords,
&data, &max_length))
goto exit;
return_value = _lzma_LZMADecompressor_decompress_impl(self, &data);
return_value = _lzma_LZMADecompressor_decompress_impl(self, &data, max_length);
exit:
/* Cleanup for data */
@ -242,4 +251,4 @@ exit:
return return_value;
}
/*[clinic end generated code: output=808fec8216ac712b input=a9049054013a1b77]*/
/*[clinic end generated code: output=d17fac38b09626d8 input=a9049054013a1b77]*/