Conversion Specifier Options

If you define a meaning for `%A', what if the template contains `%+23A' or `%-#A'? To implement a sensible meaning for these, the handler when called needs to be able to get the options specified in the template.

Both the handler-function and arginfo-function accept an argument that points to a struct printf_info, which contains information about the options appearing in an instance of the conversion specifier. This data type is declared in the header file `printf.h'.

Type: struct printf_info

This structure is used to pass information about the options appearing in an instance of a conversion specifier in a printf template string to the handler and arginfo functions for that specifier. It contains the following members:

int prec

This is the precision specified. The value is -1 if no precision was specified. If the precision was given as `*', the printf_info structure passed to the handler function contains the actual value retrieved from the argument list. But the structure passed to the arginfo function contains a value of INT_MIN, since the actual value is not known.

int width

This is the minimum field width specified. The value is 0 if no width was specified. If the field width was given as `*', the printf_info structure passed to the handler function contains the actual value retrieved from the argument list. But the structure passed to the arginfo function contains a value of INT_MIN, since the actual value is not known.

wchar_t spec

This is the conversion specifier character specified. It's stored in the structure so that you can register the same handler function for multiple characters, but still have a way to tell them apart when the handler function is called.

unsigned int is_long_double

This is a boolean that is true if the `L', `ll', or `q' type modifier was specified. For integer conversions, this indicates long long int, as opposed to long double for floating point conversions.

unsigned int is_char

This is a boolean that is true if the `hh' type modifier was specified.

unsigned int is_short

This is a boolean that is true if the `h' type modifier was specified.

unsigned int is_long

This is a boolean that is true if the `l' type modifier was specified.

unsigned int alt

This is a boolean that is true if the `#' flag was specified.

unsigned int space

This is a boolean that is true if the ` ' flag was specified.

unsigned int left

This is a boolean that is true if the `-' flag was specified.

unsigned int showsign

This is a boolean that is true if the `+' flag was specified.

unsigned int group

This is a boolean that is true if the `'' flag was specified.

unsigned int extra

This flag has a special meaning depending on the context. It could be used freely by the user-defined handlers but when called from the printf function this variable always contains the value 0.

wchar_t pad

This is the character to use for padding the output to the minimum field width. The value is '0' if the `0' flag was specified, and ' ' otherwise.

Go to the first, previous, next, last section, table of contents.