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add max_length to Python streaming decompression
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TODO: tests
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@robryk
robryk committed Sep 18, 2024
1 parent f1bdfaa commit 762ae62
Showing 1 changed file with 130 additions and 59 deletions.
189 changes: 130 additions & 59 deletions python/_brotli.c
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Original file line number Diff line number Diff line change
Expand Up @@ -606,57 +606,6 @@ static PyTypeObject brotli_CompressorType = {
brotli_Compressor_new, /* tp_new */
};

static PyObject* decompress_stream(BrotliDecoderState* dec,
uint8_t* input, size_t input_length) {
BrotliDecoderResult result;

size_t available_in = input_length;
const uint8_t* next_in = input;

size_t available_out;
uint8_t* next_out;
BlocksOutputBuffer buffer = {.list=NULL};
PyObject *ret;

if (BlocksOutputBuffer_InitAndGrow(&buffer, PY_SSIZE_T_MAX, &available_out, &next_out) < 0) {
goto error;
}

while (1) {
Py_BEGIN_ALLOW_THREADS
result = BrotliDecoderDecompressStream(dec,
&available_in, &next_in,
&available_out, &next_out, NULL);
Py_END_ALLOW_THREADS

if (result == BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT) {
if (available_out == 0) {
if (BlocksOutputBuffer_Grow(&buffer, &available_out, &next_out) < 0) {
goto error;
}
}
continue;
}

break;
}

if (result == BROTLI_DECODER_RESULT_ERROR || available_in != 0) {
goto error;
}

ret = BlocksOutputBuffer_Finish(&buffer, available_out);
if (ret != NULL) {
goto finally;
}

error:
BlocksOutputBuffer_OnError(&buffer);
ret = NULL;
finally:
return ret;
}

PyDoc_STRVAR(brotli_Decompressor_doc,
"An object to decompress a byte string.\n"
"\n"
Expand All @@ -669,10 +618,14 @@ PyDoc_STRVAR(brotli_Decompressor_doc,
typedef struct {
PyObject_HEAD
BrotliDecoderState* dec;
uint8_t* unconsumed_data;
size_t unconsumed_data_length;
} brotli_Decompressor;

static void brotli_Decompressor_dealloc(brotli_Decompressor* self) {
BrotliDecoderDestroyInstance(self->dec);
if (self->unconsumed_data)
free(self->unconsumed_data);
#if PY_MAJOR_VERSION >= 3
Py_TYPE(self)->tp_free((PyObject*)self);
#else
Expand All @@ -688,6 +641,9 @@ static PyObject* brotli_Decompressor_new(PyTypeObject *type, PyObject *args, PyO
self->dec = BrotliDecoderCreateInstance(0, 0, 0);
}

self->unconsumed_data = NULL;
self->unconsumed_data_length = 0;

return (PyObject *)self;
}

Expand All @@ -706,35 +662,115 @@ static int brotli_Decompressor_init(brotli_Decompressor *self, PyObject *args, P
return 0;
}

static PyObject* decompress_stream(brotli_Decompressor* self,
uint8_t* input, size_t input_length, Py_ssize_t max_output_length) {
BrotliDecoderResult result;

size_t available_in = input_length;
const uint8_t* next_in = input;

size_t available_out;
uint8_t* next_out;
BlocksOutputBuffer buffer = {.list=NULL};
PyObject *ret;

if (BlocksOutputBuffer_InitAndGrow(&buffer, max_output_length, &available_out, &next_out) < 0) {
goto error;
}

while (1) {
Py_BEGIN_ALLOW_THREADS
result = BrotliDecoderDecompressStream(self->dec,
&available_in, &next_in,
&available_out, &next_out, NULL);
Py_END_ALLOW_THREADS

if (result == BROTLI_DECODER_RESULT_NEEDS_MORE_OUTPUT) {
if (available_out == 0) {
if (buffer.allocated == PY_SSIZE_T_MAX) {
PyErr_SetString(PyExc_MemoryError, unable_allocate_msg);
goto error;
}
if (buffer.allocated == max_output_length) {
// We've reached the output length limit.

uint8_t* new_tail = available_in > 0 ? malloc(available_in) : NULL;
if (available_in > 0) {
memcpy(new_tail, next_in, available_in);
}
if (self->unconsumed_data) {
free(self->unconsumed_data);
}
self->unconsumed_data = new_tail;
break;
}
if (BlocksOutputBuffer_Grow(&buffer, &available_out, &next_out) < 0) {
goto error;
}
}
continue;
}

if (result == BROTLI_DECODER_RESULT_ERROR || available_in != 0) {
goto error;
}

break;
}

ret = BlocksOutputBuffer_Finish(&buffer, available_out);
if (ret != NULL) {
goto finally;
}

error:
BlocksOutputBuffer_OnError(&buffer);
ret = NULL;
finally:
return ret;
}


PyDoc_STRVAR(brotli_Decompressor_process_doc,
"Process \"string\" for decompression, returning a string that contains \n"
"decompressed output data. This data should be concatenated to the output \n"
"produced by any preceding calls to the \"process()\" method. \n"
"Some or all of the input may be kept in internal buffers for later \n"
"processing, and the decompressed output data may be empty until enough input \n"
"has been accumulated.\n"
"If max_output_length is set, no more than max_output_length bytes will be\n"
"returned. If the limit is reached (or an implicit limit of the largest\n"
"constructible string is reached), further calls to process (potentially with\n"
"empty input) will continue to yield more data. If, after returning a string of\n"
"the length equal to limit, can_accept_more_data() returns False, process()\n"
"must only be called with empty input until can_accept_more_data() once again\n"
"returns True.\n"
"\n"
"Signature:\n"
" decompress(string)\n"
" decompress(string, max_output_length=int)\n"
"\n"
"Args:\n"
" string (bytes): The input data\n"
"\n"
"Returns:\n"
"\n""Returns:\n"
" The decompressed output data (bytes)\n"
"\n"
"Raises:\n"
" brotli.error: If decompression fails\n");

static PyObject* brotli_Decompressor_process(brotli_Decompressor *self, PyObject *args) {
static PyObject* brotli_Decompressor_process(brotli_Decompressor *self, PyObject *args, PyObject* keywds) {
PyObject* ret;
Py_buffer input;
int ok;
Py_ssize_t max_output_length = PY_SSIZE_T_MAX;
uint8_t* data;
size_t data_length;

static char* kwlist[] = { "", "max_output_length", NULL };

#if PY_MAJOR_VERSION >= 3
ok = PyArg_ParseTuple(args, "y*:process", &input);
ok = PyArg_ParseTupleAndKeywords(args, keywds, "y*|n:process", kwlist, &input, &max_output_length);
#else
ok = PyArg_ParseTuple(args, "s*:process", &input);
ok = PyArg_ParseTupleAndKeywords(args, keywds, "s*|n:process", kwlist, &input, &max_output_length);
#endif

if (!ok) {
Expand All @@ -745,7 +781,20 @@ static PyObject* brotli_Decompressor_process(brotli_Decompressor *self, PyObject
goto error;
}

ret = decompress_stream(self->dec, (uint8_t*) input.buf, input.len);
if (self->unconsumed_data_length > 0) {
if (input.len > 0) {
PyErr_SetString(BrotliError, "process called with data when accept_more_data is False");
ret = NULL;
goto finally;
}
data = self->unconsumed_data;
data_length = self->unconsumed_data_length;
} else {
data = (uint8_t*)input.buf;
data_length = input.len;
}

ret = decompress_stream(self, data, data_length, max_output_length);
if (ret != NULL) {
goto finally;
}
Expand Down Expand Up @@ -787,13 +836,35 @@ static PyObject* brotli_Decompressor_is_finished(brotli_Decompressor *self) {
}
}

PyDoc_STRVAR(brotli_Decompressor_can_accept_more_data_doc,
"Checks if the decoder instance can accept more compressed data. If the decompress()\n"
"method on this instance of decompressor was never called with max_length,\n"
"this method will always return True.\n"
"\n"
"Signature:"
" can_accept_more_data()\n"
"\n"
"Returns:\n"
" True if the decoder is ready to accept more compressed data via decompress()\n"
" False if the decoder needs to output some data via decompress(b'') before\n"
" being provided any more compressed data\n");

static PyObject* brotli_Decompressor_can_accept_more_data(brotli_Decompressor* self) {
if (self->unconsumed_data_length > 0) {
Py_RETURN_FALSE;
} else {
Py_RETURN_TRUE;
}
}

static PyMemberDef brotli_Decompressor_members[] = {
{NULL} /* Sentinel */
};

static PyMethodDef brotli_Decompressor_methods[] = {
{"process", (PyCFunction)brotli_Decompressor_process, METH_VARARGS, brotli_Decompressor_process_doc},
{"process", (PyCFunction)brotli_Decompressor_process, METH_VARARGS | METH_KEYWORDS, brotli_Decompressor_process_doc},
{"is_finished", (PyCFunction)brotli_Decompressor_is_finished, METH_NOARGS, brotli_Decompressor_is_finished_doc},
{"can_accept_more_data", (PyCFunction)brotli_Decompressor_can_accept_more_data, METH_NOARGS, brotli_Decompressor_can_accept_more_data_doc},
{NULL} /* Sentinel */
};

Expand Down

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