Support building against the Limited API by providing fallback implementations.

Author: scoder

Makefile

@@ -41,6 +41,9 @@ clean:
 realclean: clean
 	rm -fr src/*.c src/*.html
 
+src/todecimal.h: gen_todecimal.py
+	$(PYTHON) $< > $@
+
 qemu-user-static:
 	docker run --rm --privileged hypriot/qemu-register
 

gen_todecimal.py

@@ -0,0 +1,53 @@
+
+import sys
+import unicodedata
+from collections import defaultdict
+
+
+def list_digits():
+    category_of = unicodedata.category
+    return [
+        ch for ch in range(128, 1114111+1)
+        if category_of(chr(ch)) == 'Nd'
+    ]
+
+
+def map_to_ascii_digit(digits):
+    adigit_to_udigit = defaultdict(list)
+    for ch in digits:
+        adigit = int(chr(ch))
+        if ch & 15 == adigit:
+            adigit_to_udigit['{digit} & 15'].append(ch)
+        elif (ch - 6) & 15 == adigit:
+            adigit_to_udigit['({digit} - 6) & 15'].append(ch)
+        elif (ch - 0x116da) & 15 == adigit:
+            adigit_to_udigit['({digit} - 0x116da) & 15'].append(ch)
+        elif (ch - 0x1e5f1) & 15 == adigit:
+            adigit_to_udigit['({digit} - 0x1e5f1) & 15'].append(ch)
+        elif ch >= 0x1d7ce and (ch - 0x1d7ce) % 10 == adigit:
+            adigit_to_udigit['({digit} - 0x1d7ce) % 10'].append(ch)
+        else:
+            adigit_to_udigit[str(adigit)].append(ch)
+    return adigit_to_udigit
+
+
+def gen_switch_cases(digits_by_adigit):
+    pyver = sys.version_info
+    print(f"/* Switch cases generated from Python {pyver[0]}.{pyver[1]}.{pyver[2]} {pyver[3]} {pyver[4]} */")
+    print("/* Deliberately excluding ASCII digit characters. */")
+    print()
+    print(f"/* Lowest digit: {min(ch for characters in digits_by_adigit.values() for ch in characters)} */")
+    print("switch (digit) {")
+
+    for adigit_format, udigits in digits_by_adigit.items():
+        for ch in udigits:
+            print(f'    case 0x{ch:x}:')
+
+        print(f"        return {adigit_format.format(digit='digit')};")
+
+    print("    default:")
+    print("        return -1;")
+    print("}")
+
+if __name__ == '__main__':
+    gen_switch_cases(map_to_ascii_digit(list_digits()))

setup.py

@@ -6,10 +6,6 @@
 from setuptools import setup, Extension
 
 
-ext_modules = [
-    Extension("quicktions", ["src/quicktions.pyx"]),
-]
-
 try:
     sys.argv.remove("--with-profile")
 except ValueError:
@@ -20,6 +16,44 @@
 enable_coverage = os.environ.get("WITH_COVERAGE") == "1"
 force_rebuild = os.environ.get("FORCE_REBUILD") == "1"
 
+def check_limited_api_option(value):
+    if not value:
+        return None
+    value = value.lower()
+    if value == "true":
+        # The default Limited API version is 3.9, unless we're on a lower Python version
+        # (which is mainly for the sake of testing 3.8 on the CI)
+        if sys.version_info >= (3, 9):
+            return (3, 9)
+        else:
+            return sys.version_info[:2]
+    if value == 'false':
+        return None
+    major, minor = value.split('.', 1)
+    return (int(major), int(minor))
+
+extra_setup_args = {}
+c_defines = []
+
+option_limited_api = check_limited_api_option(os.environ.get("QUICKTIONS_LIMITED_API"))
+if option_limited_api:
+    c_defines.append(('Py_LIMITED_API', f'0x{option_limited_api[0]:02x}{option_limited_api[1]:02x}0000'))
+
+    setup_options = extra_setup_args.setdefault('options', {})
+    bdist_wheel_options = setup_options.setdefault('bdist_wheel', {})
+    bdist_wheel_options['py_limited_api'] = f'cp{option_limited_api[0]}{option_limited_api[1]}'
+
+
+ext_modules = [
+    Extension(
+        "quicktions",
+        ["src/quicktions.pyx"],
+        py_limited_api=True if option_limited_api else False,
+        define_macros=c_defines,
+    ),
+]
+
+
 try:
     sys.argv.remove("--with-cython")
 except ValueError:
@@ -101,4 +135,5 @@
         "Topic :: Scientific/Engineering :: Mathematics",
         "Topic :: Office/Business :: Financial",
     ],
+    **extra_setup_args,
 )

src/quicktions.pyx

@@ -26,7 +26,6 @@ __all__ = ['Fraction']
 __version__ = '1.23'
 
 cimport cython
-from cpython.unicode cimport Py_UNICODE_TODECIMAL
 from cpython.object cimport Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, Py_GE
 from cpython.long cimport PyLong_FromString
 
@@ -1830,31 +1829,50 @@ cdef _raise_parse_overflow(s):
 
 cdef extern from *:
     """
+    static CYTHON_INLINE int __QUICKTIONS_to_decimal(Py_UCS4 digit) {
+        #if CYTHON_COMPILING_IN_LIMITED_API
+        #include "todigit.h"
+        #else
+        return Py_UNICODE_TODECIMAL(digit);
+        #endif
+    }
+
     static CYTHON_INLINE int __QUICKTIONS_unpack_ustring(
             PyObject* string, Py_ssize_t *length, void** data, int *kind) {
-        if (PyUnicode_READY(string) < 0) return -1;
-        *kind   = PyUnicode_KIND(string);
-        *length = PyUnicode_GET_LENGTH(string);
-        *data   = PyUnicode_DATA(string);
+        if (__Pyx_PyUnicode_READY(string) < 0) return -1;
+        *kind   = __Pyx_PyUnicode_KIND(string);
+        *length = __Pyx_PyUnicode_GET_LENGTH(string);
+
+        #if CYTHON_COMPILING_IN_LIMITED_API
+        *data   = (void*) string;
+        #else
+        *data   = __Pyx_PyUnicode_DATA(string);
+        #endif
+
         return 0;
     }
+
+    #if CYTHON_COMPILING_IN_LIMITED_API
+    #define __QUICKTIONS_char_at(data, kind, index) (Py_UCS4) (((void)kind), PyUnicode_ReadChar(data, index))
+    #else
     #define __QUICKTIONS_char_at(data, kind, index) \
         (((kind == 1) ? (Py_UCS4) ((char*) data)[index] : (Py_UCS4) PyUnicode_READ(kind, data, index)))
+    #endif
     """
     int _unpack_ustring "__QUICKTIONS_unpack_ustring" (
         object string, Py_ssize_t *length, void **data, int *kind) except -1
     Py_UCS4 _char_at "__QUICKTIONS_char_at" (void *data, int kind, Py_ssize_t index)
-    Py_UCS4 PyUnicode_READ(int kind, void *data, Py_ssize_t index)
+    int _to_decimal "__QUICKTIONS_to_decimal" (Py_UCS4 c)
 
 
-cdef inline int _parse_digit(char** c_digits, Py_UCS4 c, int allow_unicode):
+cdef inline int _parse_digit(char** c_digits, Py_UCS4 c, int allow_unicode) noexcept:
     cdef unsigned int unum
     cdef int num
     unum = (<unsigned int> c) - <unsigned int> '0'  # Relies on integer underflow for dots etc.
     if unum > 9:
         if not allow_unicode:
             return -1
-        num = Py_UNICODE_TODECIMAL(c)
+        num = _to_decimal(c)
         if num == -1:
             return -1
         unum = <unsigned int> num