Node:Conversion Specifier Options,
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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.
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.
unsigned int wide
- This flag is set if the stream is wide oriented.
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.
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