cpython/Python/mystrtoul.c

// strtol() and strtoul(), renamed to avoid conflicts.
//
// API:
//
// - PyOS_strtol(): convert string to C long integer.
// - PyOS_strtoul(): convert string to C unsigned long integer.

#include "Python.h"
#include "pycore_long.h"          // _PyLong_DigitValue

#if defined(__sgi) && !defined(_SGI_MP_SOURCE)
#define _SGI_MP_SOURCE
#endif

/* strtol and strtoul, renamed to avoid conflicts */


#ifdef HAVE_ERRNO_H
#  include <errno.h>              // errno
#endif

/* Static overflow check values for bases 2 through 36.
 * smallmax[base] is the largest unsigned long i such that
 * i * base doesn't overflow unsigned long.
 */
static const unsigned long smallmax[] = …;

/* maximum digits that can't ever overflow for bases 2 through 36,
 * calculated by [int(math.floor(math.log(2**32, i))) for i in range(2, 37)].
 * Note that this is pessimistic if sizeof(long) > 4.
 */
#if SIZEOF_LONG == 4
static const int digitlimit[] = {
    0,  0, 32, 20, 16, 13, 12, 11, 10, 10,  /*  0 -  9 */
    9,  9,  8,  8,  8,  8,  8,  7,  7,  7,  /* 10 - 19 */
    7,  7,  7,  7,  6,  6,  6,  6,  6,  6,  /* 20 - 29 */
    6,  6,  6,  6,  6,  6,  6};             /* 30 - 36 */
#elif SIZEOF_LONG == 8
/* [int(math.floor(math.log(2**64, i))) for i in range(2, 37)] */
static const int digitlimit[] = …;             /* 30 - 36 */
#else
#  error "Need table for SIZEOF_LONG"
#endif

/*
**      strtoul
**              This is a general purpose routine for converting
**              an ascii string to an integer in an arbitrary base.
**              Leading white space is ignored.  If 'base' is zero
**              it looks for a leading 0b, 0o or 0x to tell which
**              base.  If these are absent it defaults to 10.
**              Base must be 0 or between 2 and 36 (inclusive).
**              If 'ptr' is non-NULL it will contain a pointer to
**              the end of the scan.
**              Errors due to bad pointers will probably result in
**              exceptions - we don't check for them.
*/
unsigned long
PyOS_strtoul(const char *str, char **ptr, int base)
{ … }

/* Checking for overflow in PyOS_strtol is a PITA; see comments
 * about PY_ABS_LONG_MIN in longobject.c.
 */
#define PY_ABS_LONG_MIN …

long
PyOS_strtol(const char *str, char **ptr, int base)
{ … }