libstddjb
libskarnet
skalibs
Software
skarnet.org

The bitarray library interface

The following functions are declared in the skalibs/bitarray.h header, and implemented in the libskarnet.a or libskarnet.so library.

General information

bitarray is a set of primitives to operate efficiently on large bitfields.

A bitfield is represented by a pre-allocated block of unsigned char; bitarray does not care if that block has been BSS-, stack- or heap-allocated. Bitfields that can grow in size should be stored in a stralloc.

Bits in a bitfield of length n are numbered from 0 to n-1.

Functions

unsigned int bitarray_div8 (unsigned int n)
Returns the minimum number of bytes needed to store a field of n bits.

void bitarray_clearsetn (unsigned char *s, unsigned int start, unsigned int len, int h)
Sets (if h is nonzero) or clears (if h is zero) len bits in field s, starting at bit start.

void bitarray_clearn (unsigned char *s, unsigned int start, unsigned int len)
Clears len bits in field s, starting at bit start.

void bitarray_setn (unsigned char *s, unsigned int start, unsigned int len)
Sets len bits in field s, starting at bit start.

int bitarray_peek (unsigned char const *s, unsigned int n)
Returns the value of the nth bit in field s.

void bitarray_poke (unsigned char *s, unsigned int n, int h)
Sets (if h is nonzero) or clears (if h is zero) the nth bit in field s.

void bitarray_clear (unsigned char *s, unsigned int n)
Clears the nth bit in field s.

void bitarray_set (unsigned char *s, unsigned int n)
Sets the nth bit in field s.

int bitarray_testandpoke (unsigned char *s, unsigned int n, int h)
Sets (if h is nonzero) or clears (if h is zero) the nth bit in field s, and returns the previous value of that bit.

int bitarray_testandclear (unsigned char *s, unsigned int n)
Clear the nth bit in field s, and returns the previous value of that bit.

int bitarray_testandset (unsigned char *s, unsigned int n)
Sets the nth bit in field s, and returns the previous value of that bit.

unsigned int bitarray_first (unsigned char const *s, unsigned int len, int h)
Returns the number of the first set (if h is nonzero) or clear (if h is zero) bit in s, len being the total number of bits. If all bits in s are the negation of h, then len is returned.

unsigned int bitarray_firstclear (unsigned char const *s, unsigned int len)
Returns the number of the first clear bit in s, len being the total number of bits. If all bits in s are set, len is returned.

unsigned int bitarray_firstset (unsigned char const *s, unsigned int len)
Returns the number of the first set bit in s, len being the total number of bits. If all bits in s are clear, len is returned.