
String conversion and formatting
********************************

Functions for number conversion and formatted string output.

int PyOS_snprintf(char *str, size_t size, const char *format, ...)

   Output not more than *size* bytes to *str* according to the format
   string *format* and the extra arguments. See the Unix man page
   *snprintf(2)*.

int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)

   Output not more than *size* bytes to *str* according to the format
   string *format* and the variable argument list *va*. Unix man page
   *vsnprintf(2)*.

``PyOS_snprintf`` and ``PyOS_vsnprintf`` wrap the Standard C library
functions ``snprintf`` and ``vsnprintf``. Their purpose is to
guarantee consistent behavior in corner cases, which the Standard C
functions do not.

The wrappers ensure that *str*[*size*-1] is always ``'\0'`` upon
return. They never write more than *size* bytes (including the
trailing ``'\0'`` into str. Both functions require that ``str !=
NULL``, ``size > 0`` and ``format != NULL``.

If the platform doesn't have ``vsnprintf`` and the buffer size needed
to avoid truncation exceeds *size* by more than 512 bytes, Python
aborts with a *Py_FatalError*.

The return value (*rv*) for these functions should be interpreted as
follows:

* When ``0 <= rv < size``, the output conversion was successful and
  *rv* characters were written to *str* (excluding the trailing
  ``'\0'`` byte at *str*[*rv*]).

* When ``rv >= size``, the output conversion was truncated and a
  buffer with ``rv + 1`` bytes would have been needed to succeed.
  *str*[*size*-1] is ``'\0'`` in this case.

* When ``rv < 0``, "something bad happened." *str*[*size*-1] is
  ``'\0'`` in this case too, but the rest of *str* is undefined. The
  exact cause of the error depends on the underlying platform.

The following functions provide locale-independent string to number
conversions.

double PyOS_ascii_strtod(const char *nptr, char **endptr)

   Convert a string to a ``double``. This function behaves like the
   Standard C function ``strtod`` does in the C locale. It does this
   without changing the current locale, since that would not be
   thread-safe.

   ``PyOS_ascii_strtod`` should typically be used for reading
   configuration files or other non-user input that should be locale
   independent.

   New in version 2.4.

   See the Unix man page *strtod(2)* for details.

char * PyOS_ascii_formatd(char *buffer, size_t buf_len, const char *format, double d)

   Convert a ``double`` to a string using the ``'.'`` as the decimal
   separator. *format* is a ``printf``-style format string specifying
   the number format. Allowed conversion characters are ``'e'``,
   ``'E'``, ``'f'``, ``'F'``, ``'g'`` and ``'G'``.

   The return value is a pointer to *buffer* with the converted string
   or NULL if the conversion failed.

   New in version 2.4.

double PyOS_ascii_atof(const char *nptr)

   Convert a string to a ``double`` in a locale-independent way.

   New in version 2.4.

   See the Unix man page *atof(2)* for details.

char * PyOS_stricmp(char *s1, char *s2)

   Case insensitive comparison of strings. The function works almost
   identically to ``strcmp`` except that it ignores the case.

   New in version 2.6.

char * PyOS_strnicmp(char *s1, char *s2, Py_ssize_t  size)

   Case insensitive comparison of strings. The function works almost
   identically to ``strncmp`` except that it ignores the case.

   New in version 2.6.
