libstddjb
libskarnet
skalibs
Software
skarnet.org

Formatting and scanning functions

The preferred skalibs way of converting objects to string for output is to use the various *_fmt functions available in skalibs/fmtscan.h and other object-specific headers. These functions take at least two parameters:

• The target buffer into which the formatted object will be written. This buffer must be large enough to hold the formatted object.
• The object that should be formatted into the buffer.

They return the number of bytes written into the buffer.

To ensure that the buffer is large enough, skalibs provides several x_FMT macros corresponding to the minimum buffer size necessary for formatting an object of type x to a string, including the terminating nul byte.

Conversely, to scan objects from a string, skalibs provides several *_scan functions. They take the same parameters as the *_fmt ones, with meaning reversed. They return the number of bytes read from the input buffer

Examples

 uint32_t u = ... ;
 char buf[UINT32_FMT] ;
 buf[uint32_fmt(buf, u)] = 0 ;

 char *buf = "123a" ;
 uint32_t u ;
 size_t p ;
 p = uint32_scan(buf, &u) ;
 // p is 3, u is 123

Functions

Formatting and scanning functions for the integer types can be found in skalibs/uint16h, skalibs/uint32.h and skalibs/uint64.h, those for standard unix types (such as pid_t or uid_t) can be found in skalibs/types.h. Other formatting functions can be found in skalibs/fmtscan.h.

size_t uint64_fmt_generic (char *s, uint64_t i, uint8_t b)
Write the representation in base b of integer i into the buffer pointed to by s. Returns the number of bytes written.

size_t uint640_fmt_generic (char *s, uint64_t i, size_t pad, uint8_t b)
Write the representation in base b of integer i into the buffer pointed to by s, padding if necessary with zeros to ensure the written string is at least pad bytes long. Returns the number of bytes written.

size_t uint64_scan_base (char const *s, uint64_t *i, uint8_t b)
Scan the first bytes of the buffer pointed to by s for an uint64_t exrpessed in base b and write it into i. Returns the number of bytes read.

The above are the most fundamental functions. Other functions are usually expressed in terms of these, or have self-explanatory prototypes.