Remove compress/decompress and mark module as not reliant on the GIL

The `compress`/`decompress` functions will be moved to Python code for simplicity.
C implementations can always be re-added in the future.

Also, mark _zstd as not requiring the GIL.

Author: emmatyping

Modules/_zstd/_zstdmodule.c

@@ -588,198 +588,13 @@ _zstd__set_parameter_types_impl(PyObject *module, PyObject *c_parameter_type,
     Py_RETURN_NONE;
 }
 
-/*[clinic input]
-_zstd.compress
-
-    data: Py_buffer
-        A bytes-like object, data to be compressed.
-    level: object  = None
-        The compression level to use, defaults to ZSTD_CLEVEL_DEFAULT.
-    options: object  = None
-        A dict object that contains advanced compression parameters.
-    zstd_dict: object  = None
-        A ZstdDict object, a pre-trained zstd dictionary.
-
-Compress a block of data, return a bytes object of zstd compressed data.
-
-Refer to ZstdCompressor's docstring for a description of the
-optional arguments *level*, *options*, and *zstd_dict*.
-
-For incremental compression, use an ZstdCompressor instead.
-[clinic start generated code]*/
-
-static PyObject *
-_zstd_compress_impl(PyObject *module, Py_buffer *data, PyObject *level,
-                    PyObject *options, PyObject *zstd_dict)
-/*[clinic end generated code: output=0cca9399ca5c95cc input=e8a7c59073af923c]*/
-{
-    _zstd_state* const _module_state = PyModule_GetState(module);
-    if (_module_state == NULL) {
-        return NULL;
-    }
-    PyObject *ret = NULL;
-    ZstdCompressor self = {0};
-
-    /* Initialize & set ZstdCompressor */
-    self.cctx = ZSTD_createCCtx();
-    if (self.cctx == NULL) {
-        PyErr_SetString(_module_state->ZstdError,
-                        "Unable to create ZSTD_CCtx instance.");
-        goto error;
-    }
-
-    if (level != Py_None && options != Py_None) {
-        PyErr_SetString(PyExc_RuntimeError, "Only one of level or options should be used.");
-        return NULL;
-    }
-
-    /* Set compressLevel/options to compression context */
-    if (level != Py_None) {
-        if (_PyZstd_set_c_parameters(&self, level, "level", "int") < 0) {
-            goto error;
-        }
-    }
-
-    if (options != Py_None) {
-        if (_PyZstd_set_c_parameters(&self, options, "options", "dict") < 0) {
-            goto error;
-        }
-    }
-
-    /* Load dictionary to compression context */
-    if (zstd_dict != Py_None) {
-        if (_PyZstd_load_c_dict(&self, zstd_dict) < 0) {
-            goto error;
-        }
-        self.dict = zstd_dict;
-    }
-
-    ret = compress_impl(&self, data, ZSTD_e_end);
-    if (ret == NULL) {
-        goto error;
-    } else {
-        goto success;
-    }
-error:
-    Py_CLEAR(ret);
-success:
-    /* Free decompression context */
-    ZSTD_freeCCtx(self.cctx);
-    return ret;
-}
-
-/*[clinic input]
-_zstd.decompress
-
-    data: Py_buffer
-        A bytes-like object, zstd data to be decompressed.
-    zstd_dict: object  = None
-        A ZstdDict object, a pre-trained zstd dictionary.
-    options: object  = None
-        A dict object that contains advanced decompression parameters.
-
-Decompress one or more frames of data.
-
-Refer to ZstdDecompressor's docstring for a description of the
-optional arguments *zstd_dict*, *options*.
-
-For incremental decompression, use an ZstdDecompressor instead.
-[clinic start generated code]*/
-
-static PyObject *
-_zstd_decompress_impl(PyObject *module, Py_buffer *data, PyObject *zstd_dict,
-                      PyObject *options)
-/*[clinic end generated code: output=2e8423588fb3b178 input=c18346e620e59039]*/
-{
-    uint64_t decompressed_size;
-    Py_ssize_t initial_size;
-    ZstdDecompressor self = {0};
-    ZSTD_inBuffer in;
-    _zstd_state* const _module_state = PyModule_GetState(module);
-    if (_module_state == NULL) {
-        return NULL;
-    }
-    PyObject *ret = NULL;
-
-    /* Initialize & set ZstdDecompressor */
-    self.dctx = ZSTD_createDCtx();
-    if (self.dctx == NULL) {
-        PyErr_SetString(_module_state->ZstdError,
-                        "Unable to create ZSTD_DCtx instance.");
-        goto error;
-    }
-    self.at_frame_edge = 1;
-
-    /* Load dictionary to decompression context */
-    if (zstd_dict != Py_None) {
-        if (_PyZstd_load_d_dict(&self, zstd_dict) < 0) {
-            goto error;
-        }
-    }
-
-    /* Set option to decompression context */
-    if (options != Py_None) {
-        if (_PyZstd_set_d_parameters(&self, options) < 0) {
-            goto error;
-        }
-    }
-
-    /* Prepare input data */
-    in.src = data->buf;
-    in.size = data->len;
-    in.pos = 0;
-
-    /* Get decompressed size */
-    decompressed_size = ZSTD_getFrameContentSize(data->buf, data->len);
-    /* These two zstd constants always > PY_SSIZE_T_MAX:
-            ZSTD_CONTENTSIZE_UNKNOWN is (0ULL - 1)
-            ZSTD_CONTENTSIZE_ERROR   is (0ULL - 2) */
-    if (decompressed_size <= (uint64_t) PY_SSIZE_T_MAX) {
-        initial_size = (Py_ssize_t) decompressed_size;
-    } else {
-        initial_size = -1;
-    }
-
-    /* Decompress */
-    ret = decompress_impl(&self, &in, -1, initial_size,
-                            TYPE_ENDLESS_DECOMPRESSOR);
-    if (ret == NULL) {
-        goto error;
-    }
-
-    /* Check data integrity. at_frame_edge flag is 1 when both the input and
-        output streams are at a frame edge. */
-    if (self.at_frame_edge == 0) {
-        char *extra_msg = (Py_SIZE(ret) == 0) ? "." :
-                            ", if want to output these decompressed data, use "
-                            "the ZstdDecompressor class to decompress.";
-        PyErr_Format(_module_state->ZstdError,
-                        "Decompression failed: zstd data ends in an incomplete "
-                        "frame, maybe the input data was truncated. Decompressed "
-                        "data is %zd bytes%s",
-                        Py_SIZE(ret), extra_msg);
-        goto error;
-    }
-
-    goto success;
-
-error:
-    Py_CLEAR(ret);
-success:
-    /* Free decompression context */
-    ZSTD_freeDCtx(self.dctx);
-    return ret;
-}
-
 static PyMethodDef _zstd_methods[] = {
     _ZSTD__TRAIN_DICT_METHODDEF
     _ZSTD__FINALIZE_DICT_METHODDEF
     _ZSTD__GET_PARAM_BOUNDS_METHODDEF
     _ZSTD_GET_FRAME_SIZE_METHODDEF
     _ZSTD__GET_FRAME_INFO_METHODDEF
     _ZSTD__SET_PARAMETER_TYPES_METHODDEF
-    _ZSTD_COMPRESS_METHODDEF
-    _ZSTD_DECOMPRESS_METHODDEF
 
     {0}
 };
@@ -1130,6 +945,8 @@ _zstd_free(void *module)
 
 static struct PyModuleDef_Slot _zstd_slots[] = {
     {Py_mod_exec, _zstd_exec},
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
+
     {0}
 };