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

Functions for number conversion and formatted string output.

int PyOS_snprintf(char *str, size_t size, const char *format, ...)
    * Part of the Stable ABI.*

   Output not more than *size* bytes to *str* according to the format
   string *format* and the extra arguments. See the Unix man page
   *snprintf(3)*.

int PyOS_vsnprintf(char *str, size_t size, const char *format, va_list va)
    * Part of the Stable ABI.*

   Output not more than *size* bytes to *str* according to the format
   string *format* and the variable argument list *va*. Unix man page
   *vsnprintf(3)*.

"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", "format != NULL" and "size < INT_MAX". Note that this means there
is no equivalent to the C99 "n = snprintf(NULL, 0, ...)" which would
determine the necessary buffer size.

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", the output conversion failed and "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.

unsigned long PyOS_strtoul(const char *str, char **ptr, int base)
    * Part of the Stable ABI.*

   Convert the initial part of the string in "str" to an unsigned long
   value according to the given "base", which must be between "2" and
   "36" inclusive, or be the special value "0".

   Leading white space and case of characters are 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.

   If the converted value falls out of range of corresponding return
   type, range error occurs ("errno" is set to "ERANGE") and
   "ULONG_MAX" is returned.  If no conversion can be performed, "0" is
   returned.

   See also the Unix man page *strtoul(3)*.

   Added in version 3.2.

long PyOS_strtol(const char *str, char **ptr, int base)
    * Part of the Stable ABI.*

   Convert the initial part of the string in "str" to an long value
   according to the given "base", which must be between "2" and "36"
   inclusive, or be the special value "0".

   Same as "PyOS_strtoul()", but return a long value instead and
   "LONG_MAX" on overflows.

   See also the Unix man page *strtol(3)*.

   Added in version 3.2.

double PyOS_string_to_double(const char *s, char **endptr, PyObject *overflow_exception)
    * Part of the Stable ABI.*

   Convert a string "s" to a double, raising a Python exception on
   failure.  The set of accepted strings corresponds to the set of
   strings accepted by Python’s "float()" constructor, except that "s"
   must not have leading or trailing whitespace. The conversion is
   independent of the current locale.

   If "endptr" is "NULL", convert the whole string.  Raise
   "ValueError" and return "-1.0" if the string is not a valid
   representation of a floating-point number.

   If endptr is not "NULL", convert as much of the string as possible
   and set "*endptr" to point to the first unconverted character.  If
   no initial segment of the string is the valid representation of a
   floating-point number, set "*endptr" to point to the beginning of
   the string, raise ValueError, and return "-1.0".

   If "s" represents a value that is too large to store in a float
   (for example, ""1e500"" is such a string on many platforms) then if
   "overflow_exception" is "NULL" return "Py_HUGE_VAL" (with an
   appropriate sign) and don’t set any exception.  Otherwise,
   "overflow_exception" must point to a Python exception object; raise
   that exception and return "-1.0".  In both cases, set "*endptr" to
   point to the first character after the converted value.

   If any other error occurs during the conversion (for example an
   out-of-memory error), set the appropriate Python exception and
   return "-1.0".

   Added in version 3.1.

char *PyOS_double_to_string(double val, char format_code, int precision, int flags, int *ptype)
    * Part of the Stable ABI.*

   Convert a double *val* to a string using supplied *format_code*,
   *precision*, and *flags*.

   *format_code* must be one of "'e'", "'E'", "'f'", "'F'", "'g'",
   "'G'" or "'r'".  For "'r'", the supplied *precision* must be 0 and
   is ignored.  The "'r'" format code specifies the standard "repr()"
   format.

   *flags* can be zero or more of the following values or-ed together:

   Py_DTSF_SIGN

      Always precede the returned string with a sign character, even
      if *val* is non-negative.

   Py_DTSF_ADD_DOT_0

      Ensure that the returned string will not look like an integer.

   Py_DTSF_ALT

      Apply “alternate” formatting rules. See the documentation for
      the "PyOS_snprintf()" "'#'" specifier for details.

   Py_DTSF_NO_NEG_0

      Negative zero is converted to positive zero.

      Added in version 3.11.

   If *ptype* is non-"NULL", then the value it points to will be set
   to one of the following constants depending on the type of *val*:

   +----------------------------------------------------+----------------------------------------------------+
   | **ptype*                                           | type of *val*                                      |
   |====================================================|====================================================|
   | Py_DTST_FINITE                                     | finite number                                      |
   +----------------------------------------------------+----------------------------------------------------+
   | Py_DTST_INFINITE                                   | infinite number                                    |
   +----------------------------------------------------+----------------------------------------------------+
   | Py_DTST_NAN                                        | not a number                                       |
   +----------------------------------------------------+----------------------------------------------------+

   The return value is a pointer to *buffer* with the converted string
   or "NULL" if the conversion failed. The caller is responsible for
   freeing the returned string by calling "PyMem_Free()".

   Added in version 3.1.

int PyOS_mystricmp(const char *str1, const char *str2)
int PyOS_mystrnicmp(const char *str1, const char *str2, Py_ssize_t size)
    * Part of the Stable ABI.*

   Case insensitive comparison of strings. These functions work almost
   identically to "strcmp()" and "strncmp()" (respectively), except
   that they ignore the case of ASCII characters.

   Return "0" if the strings are equal, a negative value if *str1*
   sorts lexicographically before *str2*, or a positive value if it
   sorts after.

   In the *str1* or *str2* arguments, a NUL byte marks the end of the
   string. For "PyOS_mystrnicmp()", the *size* argument gives the
   maximum size of the string, as if NUL was present at the index
   given by *size*.

   These functions do not use the locale.

int PyOS_stricmp(const char *str1, const char *str2)
int PyOS_strnicmp(const char *str1, const char *str2, Py_ssize_t size)

   Case insensitive comparison of strings.

   On Windows, these are aliases of "stricmp()" and "strnicmp()",
   respectively.

   On other platforms, they are aliases of "PyOS_mystricmp()" and
   "PyOS_mystrnicmp()", respectively.


Character classification and conversion
***************************************

The following macros provide locale-independent (unlike the C standard
library "ctype.h") character classification and conversion. The
argument must be a signed or unsigned char.

Py_ISALNUM(c)

   Return true if the character *c* is an alphanumeric character.

Py_ISALPHA(c)

   Return true if the character *c* is an alphabetic character ("a-z"
   and "A-Z").

Py_ISDIGIT(c)

   Return true if the character *c* is a decimal digit ("0-9").

Py_ISLOWER(c)

   Return true if the character *c* is a lowercase ASCII letter
   ("a-z").

Py_ISUPPER(c)

   Return true if the character *c* is an uppercase ASCII letter
   ("A-Z").

Py_ISSPACE(c)

   Return true if the character *c* is a whitespace character (space,
   tab, carriage return, newline, vertical tab, or form feed).

Py_ISXDIGIT(c)

   Return true if the character *c* is a hexadecimal digit ("0-9",
   "a-f", and "A-F").

Py_TOLOWER(c)

   Return the lowercase equivalent of the character *c*.

Py_TOUPPER(c)

   Return the uppercase equivalent of the character *c*.
