bpo-31979: Simplify transforming decimals to ASCII (#4336)

in int(), float() and complex() parsers.

This also speeds up parsing non-ASCII numbers by around 20%.

Author: serhiy-storchaka

Include/unicodeobject.h

@@ -1723,6 +1723,7 @@ PyAPI_FUNC(PyObject*) PyUnicode_EncodeCodePage(
 
 #endif /* MS_WINDOWS */
 
+#ifndef Py_LIMITED_API
 /* --- Decimal Encoder ---------------------------------------------------- */
 
 /* Takes a Unicode string holding a decimal value and writes it into
@@ -1747,34 +1748,31 @@ PyAPI_FUNC(PyObject*) PyUnicode_EncodeCodePage(
 
 */
 
-#ifndef Py_LIMITED_API
 PyAPI_FUNC(int) PyUnicode_EncodeDecimal(
     Py_UNICODE *s,              /* Unicode buffer */
     Py_ssize_t length,          /* Number of Py_UNICODE chars to encode */
     char *output,               /* Output buffer; must have size >= length */
     const char *errors          /* error handling */
     ) /* Py_DEPRECATED(3.3) */;
-#endif
 
 /* Transforms code points that have decimal digit property to the
    corresponding ASCII digit code points.
 
    Returns a new Unicode string on success, NULL on failure.
 */
 
-#ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject*) PyUnicode_TransformDecimalToASCII(
     Py_UNICODE *s,              /* Unicode buffer */
     Py_ssize_t length           /* Number of Py_UNICODE chars to transform */
     ) /* Py_DEPRECATED(3.3) */;
-#endif
 
-/* Similar to PyUnicode_TransformDecimalToASCII(), but takes a PyObject
-   as argument instead of a raw buffer and length.  This function additionally
-   transforms spaces to ASCII because this is what the callers in longobject,
-   floatobject, and complexobject did anyways. */
+/* Coverts a Unicode object holding a decimal value to an ASCII string
+   for using in int, float and complex parsers.
+   Transforms code points that have decimal digit property to the
+   corresponding ASCII digit code points.  Transforms spaces to ASCII.
+   Transforms code points starting from the first non-ASCII code point that
+   is neither a decimal digit nor a space to the end into '?'. */
 
-#ifndef Py_LIMITED_API
 PyAPI_FUNC(PyObject*) _PyUnicode_TransformDecimalAndSpaceToASCII(
     PyObject *unicode           /* Unicode object */
     );

Lib/test/test_float.py

@@ -51,7 +51,7 @@ def test_float(self):
         self.assertRaises(TypeError, float, {})
         self.assertRaisesRegex(TypeError, "not 'dict'", float, {})
         # Lone surrogate
-        self.assertRaises(UnicodeEncodeError, float, '\uD8F0')
+        self.assertRaises(ValueError, float, '\uD8F0')
         # check that we don't accept alternate exponent markers
         self.assertRaises(ValueError, float, "-1.7d29")
         self.assertRaises(ValueError, float, "3D-14")

Lib/test/test_unicode.py

@@ -2068,11 +2068,14 @@ def test_codecs_errors(self):
         # Error handling (wrong arguments)
         self.assertRaises(TypeError, "hello".encode, 42, 42, 42)
 
-        # Error handling (lone surrogate in PyUnicode_TransformDecimalToASCII())
-        self.assertRaises(UnicodeError, float, "\ud800")
-        self.assertRaises(UnicodeError, float, "\udf00")
-        self.assertRaises(UnicodeError, complex, "\ud800")
-        self.assertRaises(UnicodeError, complex, "\udf00")
+        # Error handling (lone surrogate in
+        # _PyUnicode_TransformDecimalAndSpaceToASCII())
+        self.assertRaises(ValueError, int, "\ud800")
+        self.assertRaises(ValueError, int, "\udf00")
+        self.assertRaises(ValueError, float, "\ud800")
+        self.assertRaises(ValueError, float, "\udf00")
+        self.assertRaises(ValueError, complex, "\ud800")
+        self.assertRaises(ValueError, complex, "\udf00")
 
     def test_codecs(self):
         # Encoding

Objects/complexobject.c

@@ -914,10 +914,10 @@ complex_subtype_from_string(PyTypeObject *type, PyObject *v)
         if (s_buffer == NULL) {
             return NULL;
         }
+        assert(PyUnicode_IS_ASCII(s_buffer));
+        /* Simply get a pointer to existing ASCII characters. */
         s = PyUnicode_AsUTF8AndSize(s_buffer, &len);
-        if (s == NULL) {
-            goto exit;
-        }
+        assert(s != NULL);
     }
     else {
         PyErr_Format(PyExc_TypeError,
@@ -928,7 +928,6 @@ complex_subtype_from_string(PyTypeObject *type, PyObject *v)
 
     result = _Py_string_to_number_with_underscores(s, len, "complex", v, type,
                                                    complex_from_string_inner);
-  exit:
     Py_DECREF(s_buffer);
     return result;
 }

Objects/floatobject.c

@@ -176,11 +176,10 @@ PyFloat_FromString(PyObject *v)
         s_buffer = _PyUnicode_TransformDecimalAndSpaceToASCII(v);
         if (s_buffer == NULL)
             return NULL;
+        assert(PyUnicode_IS_ASCII(s_buffer));
+        /* Simply get a pointer to existing ASCII characters. */
         s = PyUnicode_AsUTF8AndSize(s_buffer, &len);
-        if (s == NULL) {
-            Py_DECREF(s_buffer);
-            return NULL;
-        }
+        assert(s != NULL);
     }
     else if (PyBytes_Check(v)) {
         s = PyBytes_AS_STRING(v);

Objects/longobject.c

@@ -2509,21 +2509,18 @@ PyLong_FromUnicodeObject(PyObject *u, int base)
     asciidig = _PyUnicode_TransformDecimalAndSpaceToASCII(u);
     if (asciidig == NULL)
         return NULL;
+    assert(PyUnicode_IS_ASCII(asciidig));
+    /* Simply get a pointer to existing ASCII characters. */
     buffer = PyUnicode_AsUTF8AndSize(asciidig, &buflen);
-    if (buffer == NULL) {
-        Py_DECREF(asciidig);
-        if (!PyErr_ExceptionMatches(PyExc_UnicodeEncodeError))
-            return NULL;
-    }
-    else {
-        result = PyLong_FromString(buffer, &end, base);
-        if (end == NULL || (result != NULL && end == buffer + buflen)) {
-            Py_DECREF(asciidig);
-            return result;
-        }
+    assert(buffer != NULL);
+
+    result = PyLong_FromString(buffer, &end, base);
+    if (end == NULL || (result != NULL && end == buffer + buflen)) {
         Py_DECREF(asciidig);
-        Py_XDECREF(result);
+        return result;
     }
+    Py_DECREF(asciidig);
+    Py_XDECREF(result);
     PyErr_Format(PyExc_ValueError,
                  "invalid literal for int() with base %d: %.200R",
                  base, u);

Objects/unicodeobject.c

@@ -840,9 +840,6 @@ ensure_unicode(PyObject *obj)
 
 /* --- Unicode Object ----------------------------------------------------- */
 
-static PyObject *
-fixup(PyObject *self, Py_UCS4 (*fixfct)(PyObject *s));
-
 static inline Py_ssize_t
 findchar(const void *s, int kind,
          Py_ssize_t size, Py_UCS4 ch,
@@ -9062,42 +9059,6 @@ PyUnicode_Translate(PyObject *str,
     return _PyUnicode_TranslateCharmap(str, mapping, errors);
 }
 
-static Py_UCS4
-fix_decimal_and_space_to_ascii(PyObject *self)
-{
-    /* No need to call PyUnicode_READY(self) because this function is only
-       called as a callback from fixup() which does it already. */
-    const Py_ssize_t len = PyUnicode_GET_LENGTH(self);
-    const int kind = PyUnicode_KIND(self);
-    void *data = PyUnicode_DATA(self);
-    Py_UCS4 maxchar = 127, ch, fixed;
-    int modified = 0;
-    Py_ssize_t i;
-
-    for (i = 0; i < len; ++i) {
-        ch = PyUnicode_READ(kind, data, i);
-        fixed = 0;
-        if (ch > 127) {
-            if (Py_UNICODE_ISSPACE(ch))
-                fixed = ' ';
-            else {
-                const int decimal = Py_UNICODE_TODECIMAL(ch);
-                if (decimal >= 0)
-                    fixed = '0' + decimal;
-            }
-            if (fixed != 0) {
-                modified = 1;
-                maxchar = Py_MAX(maxchar, fixed);
-                PyUnicode_WRITE(kind, data, i, fixed);
-            }
-            else
-                maxchar = Py_MAX(maxchar, ch);
-        }
-    }
-
-    return (modified) ? maxchar : 0;
-}
-
 PyObject *
 _PyUnicode_TransformDecimalAndSpaceToASCII(PyObject *unicode)
 {
@@ -9107,12 +9068,42 @@ _PyUnicode_TransformDecimalAndSpaceToASCII(PyObject *unicode)
     }
     if (PyUnicode_READY(unicode) == -1)
         return NULL;
-    if (PyUnicode_MAX_CHAR_VALUE(unicode) <= 127) {
+    if (PyUnicode_IS_ASCII(unicode)) {
         /* If the string is already ASCII, just return the same string */
         Py_INCREF(unicode);
         return unicode;
     }
-    return fixup(unicode, fix_decimal_and_space_to_ascii);
+
+    Py_ssize_t len = PyUnicode_GET_LENGTH(unicode);
+    PyObject *result = PyUnicode_New(len, 127);
+    if (result == NULL) {
+        return NULL;
+    }
+
+    Py_UCS1 *out = PyUnicode_1BYTE_DATA(result);
+    int kind = PyUnicode_KIND(unicode);
+    const void *data = PyUnicode_DATA(unicode);
+    Py_ssize_t i;
+    for (i = 0; i < len; ++i) {
+        Py_UCS4 ch = PyUnicode_READ(kind, data, i);
+        if (ch < 127) {
+            out[i] = ch;
+        }
+        else if (Py_UNICODE_ISSPACE(ch)) {
+            out[i] = ' ';
+        }
+        else {
+            int decimal = Py_UNICODE_TODECIMAL(ch);
+            if (decimal < 0) {
+                out[i] = '?';
+                _PyUnicode_LENGTH(result) = i + 1;
+                break;
+            }
+            out[i] = '0' + decimal;
+        }
+    }
+
+    return result;
 }
 
 PyObject *
@@ -9588,69 +9579,6 @@ PyUnicode_Tailmatch(PyObject *str,
     return tailmatch(str, substr, start, end, direction);
 }
 
-/* Apply fixfct filter to the Unicode object self and return a
-   reference to the modified object */
-
-static PyObject *
-fixup(PyObject *self,
-      Py_UCS4 (*fixfct)(PyObject *s))
-{
-    PyObject *u;
-    Py_UCS4 maxchar_old, maxchar_new = 0;
-    PyObject *v;
-
-    u = _PyUnicode_Copy(self);
-    if (u == NULL)
-        return NULL;
-    maxchar_old = PyUnicode_MAX_CHAR_VALUE(u);
-
-    /* fix functions return the new maximum character in a string,
-       if the kind of the resulting unicode object does not change,
-       everything is fine.  Otherwise we need to change the string kind
-       and re-run the fix function. */
-    maxchar_new = fixfct(u);
-
-    if (maxchar_new == 0) {
-        /* no changes */;
-        if (PyUnicode_CheckExact(self)) {
-            Py_DECREF(u);
-            Py_INCREF(self);
-            return self;
-        }
-        else
-            return u;
-    }
-
-    maxchar_new = align_maxchar(maxchar_new);
-
-    if (maxchar_new == maxchar_old)
-        return u;
-
-    /* In case the maximum character changed, we need to
-       convert the string to the new category. */
-    v = PyUnicode_New(PyUnicode_GET_LENGTH(self), maxchar_new);
-    if (v == NULL) {
-        Py_DECREF(u);
-        return NULL;
-    }
-    if (maxchar_new > maxchar_old) {
-        /* If the maxchar increased so that the kind changed, not all
-           characters are representable anymore and we need to fix the
-           string again. This only happens in very few cases. */
-        _PyUnicode_FastCopyCharacters(v, 0,
-                                      self, 0, PyUnicode_GET_LENGTH(self));
-        maxchar_old = fixfct(v);
-        assert(maxchar_old > 0 && maxchar_old <= maxchar_new);
-    }
-    else {
-        _PyUnicode_FastCopyCharacters(v, 0,
-                                      u, 0, PyUnicode_GET_LENGTH(self));
-    }
-    Py_DECREF(u);
-    assert(_PyUnicode_CheckConsistency(v, 1));
-    return v;
-}
-
 static PyObject *
 ascii_upper_or_lower(PyObject *self, int lower)
 {