Method proxyval

Tools/gdb/libpython.py:907–952

Python's Include/cpython/longinterpr.h has this declaration: typedef struct _PyLongValue { uintptr_t lv_tag; /* Number of digits, sign and flags */ digit ob_digit[1]; } _PyLongValue; struct _longobject { P

(self, visited)

    _typename = 'PyLongObject'

    def proxyval(self, visited):
        '''
        Python's Include/cpython/longinterpr.h has this declaration:

            typedef struct _PyLongValue {
                uintptr_t lv_tag; /* Number of digits, sign and flags */
                digit ob_digit[1];
            } _PyLongValue;

            struct _longobject {
                PyObject_HEAD
                _PyLongValue long_value;
            };

        with this description:
            The absolute value of a number is equal to
                SUM(for i=0 through ndigits-1) ob_digit[i] * 2**(PyLong_SHIFT*i)
            The sign of the value is stored in the lower 2 bits of lv_tag.
                - 0: Positive
                - 1: Zero
                - 2: Negative
            The third lowest bit of lv_tag is set to 1 for the small ints and 0 otherwise.

        where SHIFT can be either:
            #define PyLong_SHIFT        30
            #define PyLong_SHIFT        15
        '''
        long_value = self.field('long_value')
        lv_tag = int(long_value['lv_tag'])
        size = lv_tag >> 3
        if size == 0:
            return 0

        ob_digit = long_value['ob_digit']

        if gdb.lookup_type('digit').sizeof == 2:
            SHIFT = 15
        else:
            SHIFT = 30

        digits = [int(ob_digit[i]) * 2**(SHIFT*i)
                  for i in safe_range(size)]
        result = sum(digits)
        if (lv_tag & 3) == 2:
            result = -result
        return result

    def write_repr(self, out, visited):
        # Write this out as a Python int literal