optimise C integer formatting

Cython/Compiler/ExprNodes.py

@@ -3012,10 +3012,13 @@ class FormattedValueNode(ExprNode):
     # value           ExprNode                The expression itself
     # conversion_char str or None             Type conversion (!s, !r, !a, or none)
     # format_spec     JoinedStrNode or None   Format string passed to __format__
+    # c_format_spec   str or None             Formatting that can be done at the C level
+
     subexprs = ['value', 'format_spec']
 
     type = unicode_type
     is_temp = True
+    c_format_spec = None
 
     find_conversion_func = {
         's': 'PyObject_Str',
@@ -3029,14 +3032,31 @@ class FormattedValueNode(ExprNode):
 
     def analyse_types(self, env):
         self.value = self.value.analyse_types(env)
+        if not self.format_spec or self.format_spec.is_string_literal:
+            c_format_spec = self.format_spec.value if self.format_spec else None
+            if self.value.type.can_coerce_to_pystring(env, format_spec=c_format_spec):
+                if c_format_spec is None and self.value.type.is_int:
+                    c_format_spec = 'd'
+                self.c_format_spec = c_format_spec
+
         if self.format_spec:
             self.format_spec = self.format_spec.analyse_types(env).coerce_to_pyobject(env)
-        elif not self.conversion_char and self.value.type.can_coerce_to_pyunicode(env):
-            return FormattedCValueNode(self.pos, value=self.value)
-        self.value = self.value.coerce_to_pyobject(env)
+        if not self.c_format_spec:
+            self.value = self.value.coerce_to_pyobject(env)
         return self
 
     def generate_result_code(self, code):
+        if self.c_format_spec and not self.value.type.is_pyobject:
+            convert_func = self.value.type.to_pystring_function(code)
+            code.putln("%s = %s(%s, '%s'); %s" % (
+                self.result(),
+                convert_func,
+                self.value.result(),
+                self.c_format_spec,
+                code.error_goto_if_null(self.result(), self.pos)))
+            code.put_gotref(self.py_result())
+            return
+
         value_result = self.value.py_result()
         if self.format_spec:
             format_func = '__Pyx_PyObject_Format'
@@ -3067,20 +3087,6 @@ class FormattedValueNode(ExprNode):
         code.put_gotref(self.py_result())
 
 
-class FormattedCValueNode(FormattedValueNode):
-    conversion_char = None
-    format_spec = None
-
-    def generate_result_code(self, code):
-        convert_func = self.value.type.to_pyunicode_utility_code(code)
-        code.putln("%s = %s(%s); %s" % (
-            self.result(),
-            convert_func,
-            self.value.result(),
-            code.error_goto_if_null(self.result(), self.pos)))
-        code.put_gotref(self.py_result())
-
-
 #-------------------------------------------------------------------
 #
 #  Parallel nodes (cython.parallel.thread(savailable|id))

Cython/Compiler/PyrexTypes.py

@@ -30,7 +30,7 @@ class BaseType(object):
     def can_coerce_to_pyobject(self, env):
         return False
 
-    def can_coerce_to_pyunicode(self, env):
+    def can_coerce_to_pystring(self, env, format_spec=None):
         return False
 
     def cast_code(self, expr_code):
@@ -1629,10 +1629,12 @@ class CIntType(CNumericType):
     def can_coerce_to_pyobject(self, env):
         return True
 
-    def can_coerce_to_pyunicode(self, env):
+    def can_coerce_to_pystring(self, env, format_spec=None):
+        if format_spec and format_spec not in ('o', 'd', 'x', 'X'):
+            return False
         return True
 
-    def to_pyunicode_utility_code(self, code):
+    def to_pystring_function(self, code):
         if self.to_pyunicode_utility is None:
             utility_code_name = "__Pyx_PyUnicode_From_" + self.specialization_name()
             to_pyunicode_utility = TempitaUtilityCode.load_cached(
@@ -1752,7 +1754,7 @@ class CReturnCodeType(CIntType):
     is_returncode = True
     exception_check = False
 
-    def can_coerce_to_pyunicode(self, env):
+    def can_coerce_to_pystring(self, env, format_spec=None):
         return False
 
 
@@ -1762,7 +1764,7 @@ class CBIntType(CIntType):
     from_py_function = "__Pyx_PyObject_IsTrue"
     exception_check = 1 # for C++ bool
 
-    def can_coerce_to_pyunicode(self, env):
+    def can_coerce_to_pystring(self, env, format_spec=None):
         return False
 
     def declaration_code(self, entity_code,
@@ -1799,7 +1801,7 @@ class CPyUCS4IntType(CIntType):
     to_py_function = "PyUnicode_FromOrdinal"
     from_py_function = "__Pyx_PyObject_AsPy_UCS4"
 
-    def can_coerce_to_pyunicode(self, env):
+    def can_coerce_to_pystring(self, env, format_spec=None):
         return False
 
     def create_from_py_utility_code(self, env):
@@ -1823,7 +1825,7 @@ class CPyUnicodeIntType(CIntType):
     to_py_function = "PyUnicode_FromOrdinal"
     from_py_function = "__Pyx_PyObject_AsPy_UNICODE"
 
-    def can_coerce_to_pyunicode(self, env):
+    def can_coerce_to_pystring(self, env, format_spec=None):
         return False
 
     def create_from_py_utility_code(self, env):

Cython/Utility/TypeConversion.c

@@ -570,51 +570,87 @@ static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value) {
 
 /////////////// CIntToPyUnicode.proto ///////////////
 
-static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value);
+static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, char format_char);
 
 /////////////// CIntToPyUnicode ///////////////
 
-static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value) {
-    // simple and conservative string allocation on the stack
+// NOTE: inlining because "format_char" is always a constant, which collapses lots of code below
+
+static CYTHON_INLINE PyObject* {{TO_PY_FUNCTION}}({{TYPE}} value, char format_char) {
+    // simple and conservative C string allocation on the stack: each byte gives at most 3 digits, plus sign
     char digits[sizeof({{TYPE}})*3+2];
-    int length = -1;
+    // dpos points to end of digits array + 1 at the beginning to allow for pre-decrement looping
+    char *dpos = digits + sizeof({{TYPE}})*3+2;
+    int length;
+    PyObject *uval;
+    {{TYPE}} remaining;
     const {{TYPE}} neg_one = ({{TYPE}}) -1, const_zero = ({{TYPE}}) 0;
     const int is_unsigned = neg_one > const_zero;
 
-    if (is_unsigned) {
-        if (sizeof({{TYPE}}) <= sizeof(unsigned int)) {
-            length = sprintf(digits, "%u", (unsigned int) value);
-        } else if (sizeof({{TYPE}}) <= sizeof(unsigned long)) {
-            length = sprintf(digits, "%lu", (unsigned long) value);
-        } else if (sizeof({{TYPE}}) <= sizeof(unsigned PY_LONG_LONG)) {
-            length = sprintf(digits, "%llu", (unsigned PY_LONG_LONG) value);
-        }
-    } else {
-        if (sizeof({{TYPE}}) <= sizeof(int)) {
-            length = sprintf(digits, "%d", (int) value);
-        } else if (sizeof({{TYPE}}) <= sizeof(long)) {
-            length = sprintf(digits, "%ld", (long) value);
-        } else if (sizeof({{TYPE}}) <= sizeof(PY_LONG_LONG)) {
-            length = sprintf(digits, "%lld", (PY_LONG_LONG) value);
+    // single character unicode strings are cached in CPython => use PyUnicode_FromOrdinal() for them
+    if (unlikely((is_unsigned || value >= const_zero) && (
+            (format_char == 'o') ? value <= 7 : (format_char == 'd') ? value <= 9 : value <= 15))) {
+        return PyUnicode_FromOrdinal(
+            ((int) value) + (((int) value) <= 9 ? '0' : (format_char == 'x' ? 'a' : 'A') - 10));
+    }
+
+    // surprise: even trivial sprintf() calls don't get optimised in gcc (4.8)
+    remaining = value;
+    length = 0;
+    while (remaining != 0) {
+        char digit;
+        switch (format_char) {
+        case 'o':
+            digit = '0' + abs(remaining % 8);
+            remaining = remaining / 8;
+            break;
+        case 'd':
+            digit = '0' + abs(remaining % 10);
+            remaining = remaining / 10;
+            break;
+        case 'x':
+        case 'X':
+            digit = '0' + abs(remaining % 16);
+            remaining = remaining / 16;
+            if (digit > '9')
+                digit = digit - '9' - 1 + (format_char == 'x' ? 'a' : 'A');
+            break;
+        default:
+            assert(0);
         }
+        *(--dpos) = digit;
+        ++length;
     }
-    if (unlikely(length < 0)) {
-        // huge integer type or (unlikely) error in sprintf() => use slow conversion
-        PyObject *pylong, *uval = NULL;
-        int one = 1; int little = (int)*(unsigned char *)&one;
-        unsigned char *bytes = (unsigned char *)&value;
-        pylong = _PyLong_FromByteArray(bytes, sizeof({{TYPE}}), little, !is_unsigned);
-        if (likely(pylong)) {
-#if PY_MAJOR_VERSION >= 3
-            uval = PyObject_Str(pylong);
+    if (!is_unsigned && value <= neg_one) {
+        *(--dpos) = '-';
+        ++length;
+    }
+
+#if CYTHON_COMPILING_IN_CPYTHON
+    {
+        int i;
+#if PY_MAJOR_VERSION > 3 || PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION >= 3
+        void *udata;
+        uval = PyUnicode_New(length, 127);
+        if (unlikely(!uval)) return NULL;
+        udata = PyUnicode_DATA(uval);
+        for (i=0; i<length; i++) {
+            PyUnicode_WRITE(PyUnicode_1BYTE_KIND, udata, i, dpos[i]);
+        }
 #else
-            uval = PyObject_Unicode(pylong);
-#endif
-            Py_DECREF(pylong);
+        Py_UNICODE *udata;
+        uval = PyUnicode_FromUnicode(NULL, length);
+        if (unlikely(!uval)) return uval;
+        udata = PyUnicode_AS_UNICODE(uval);
+        for (i=0; i<length; i++) {
+            udata[i] = dpos[i];
         }
+#endif
         return uval;
     }
-    return PyUnicode_DecodeASCII(digits, length, NULL);
+#else
+    return PyUnicode_DecodeASCII(dpos, length, NULL);
+#endif
 }
 
 

tests/run/fstring.pyx

@@ -32,7 +32,7 @@ def format2(ab, cd):
     return a, b, c
 
 
-def format_c_numbers(char c, short s, int n, long l, float f, double d):
+def format_c_numbers(signed char c, short s, int n, long l, float f, double d):
     """
     >>> s1, s2, s3, s4 = format_c_numbers(123, 135, 12, 12312312, 2.3456, 3.1415926)
     >>> print(s1)
@@ -44,6 +44,16 @@ def format_c_numbers(char c, short s, int n, long l, float f, double d):
     >>> print(s4)
     C 3.14
 
+    >>> s1, s2, s3, s4 = format_c_numbers(-123, -135, -12, -12312312, -2.3456, -3.1415926)
+    >>> print(s1)
+    -123-135-12312312-12-2.35
+    >>> print(s2)
+    -3.14-2.3
+    >>> print(s3)
+     -12f
+    >>> print(s4)
+    -C-3.14
+
     """
     s1 = f"{c}{s:4}{l}{n}{f:.3}"
     assert isinstance(s1, unicode), type(s1)