Node:Parsing a Template String, Next:Example of Parsing, Previous:Variable Arguments Output, Up:Formatted Output
You can use the function parse_printf_format
to obtain
information about the number and types of arguments that are expected by
a given template string. This function permits interpreters that
provide interfaces to printf
to avoid passing along invalid
arguments from the user's program, which could cause a crash.
All the symbols described in this section are declared in the header
file printf.h
.
size_t parse_printf_format (const char *template, size_t n, int *argtypes) | Function |
This function returns information about the number and types of
arguments expected by the printf template string template.
The information is stored in the array argtypes; each element of
this array describes one argument. This information is encoded using
the various PA_ macros, listed below.
The argument n specifies the number of elements in the array
argtypes. This is the maximum number of elements that
parse_printf_format will try to write.
parse_printf_format returns the total number of arguments required
by template. If this number is greater than n, then the
information returned describes only the first n arguments. If you
want information about additional arguments, allocate a bigger
array and call parse_printf_format again.
|
int PA_FLAG_MASK | Macro |
This macro is a bitmask for the type modifier flag bits. You can write
the expression (argtypes[i] & PA_FLAG_MASK) to extract just the
flag bits for an argument, or (argtypes[i] & ~PA_FLAG_MASK) to
extract just the basic type code.
|
PA_INT
int
.
PA_CHAR
int
, cast to char
.
PA_STRING
char *
, a null-terminated string.
PA_POINTER
void *
, an arbitrary pointer.
PA_FLOAT
float
.
PA_DOUBLE
double
.
PA_LAST
PA_LAST
. For example, if you have data types foo
and bar
with their own specialized printf
conversions,
you could define encodings for these types as:
#define PA_FOO PA_LAST #define PA_BAR (PA_LAST + 1)
PA_FLAG_PTR
PA_INT|PA_FLAG_PTR
represents the type int *
.
PA_FLAG_SHORT
short
. (This corresponds to the h
type modifier.)
PA_FLAG_LONG
long
. (This corresponds to the l
type modifier.)
PA_FLAG_LONG_LONG
long long
. (This corresponds to the L
type modifier.)
PA_FLAG_LONG_DOUBLE
PA_FLAG_LONG_LONG
, used by convention with
a base type of PA_DOUBLE
to indicate a type of long double
.