pythongh-91349: add support for libdeflate library.

for now, this only exposes the crc32 function.

Author: rmmancom

Modules/Setup

@@ -200,6 +200,7 @@ PYTHONPATH=$(COREPYTHONPATH)
 #_gdbm _gdbmmodule.c -lgdbm
 #_lzma _lzmamodule.c -llzma
 #_uuid _uuidmodule.c -luuid
+#deflate deflatemodule.c -ldeflate
 #zlib  zlibmodule.c -lz
 
 # The readline module also supports libeditline (-leditline).

Modules/Setup.stdlib.in

@@ -66,6 +66,7 @@
 @MODULE_BINASCII_TRUE@binascii binascii.c
 @MODULE__BZ2_TRUE@_bz2 _bz2module.c
 @MODULE__LZMA_TRUE@_lzma _lzmamodule.c
+@MODULE_DEFLATE_TRUE@deflate deflatemodule.c
 @MODULE_ZLIB_TRUE@zlib zlibmodule.c
 
 # dbm/gdbm

Modules/clinic/deflatemodule.c.h

@@ -0,0 +1,66 @@
+/* deflate module */
+
+/* This module provides an interface to deflate library. */
+
+/* deflate objects */
+
+#ifndef Py_BUILD_CORE_BUILTIN
+#  define Py_BUILD_CORE_MODULE 1
+#endif
+
+#include "Python.h"
+#include "clinic/deflatemodule.c.h"
+#include "libdeflate.h"
+
+/*[clinic input]
+module deflate
+[clinic start generated code]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=e8fe2232b5d8509a]*/
+
+/*[clinic input]
+deflate.crc32 -> unsigned_int
+
+    data: Py_buffer
+    value: unsigned_int(bitwise=True) = 0
+        Starting value of the checksum.
+    /
+
+Compute a CRC-32 checksum of data.
+
+The returned checksum is an integer.
+[clinic start generated code]*/
+
+static unsigned int
+deflate_crc32_impl(PyObject *module, Py_buffer *data, unsigned int value)
+/*[clinic end generated code: output=1509d54a8b6329c0 input=50ff444788572aa2]*/
+{
+    /* Releasing the GIL for very small buffers is inefficient
+       and may lower performance */
+    if (data->len > 1024*5) {
+        Py_BEGIN_ALLOW_THREADS
+        value = libdeflate_crc32((uint32_t)value, data->buf, (size_t)data->len);
+        Py_END_ALLOW_THREADS
+    } else {
+        value = libdeflate_crc32((uint32_t)value, data->buf, (size_t)data->len);
+    }
+    return value;
+}
+
+static PyMethodDef deflate_methods[] = {
+    DEFLATE_CRC32_METHODDEF
+    {NULL}
+};
+
+static struct PyModuleDef deflate_module = {
+    PyModuleDef_HEAD_INIT,
+    .m_name = "deflate",
+    .m_doc = "Module that provides a CRC32 function.",
+    .m_size = -1,
+    .m_methods = deflate_methods,
+};
+
+PyMODINIT_FUNC
+PyInit_deflate(void)
+{
+    return PyModule_Create(&deflate_module);
+}