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bitstring

NAME

bit_alloc, bit_clear, bit_decl, bit_ffs, bit_nclear, bit_nset, bit_set, bitstr_size, bit_test - bit-string manipulation macros

SYNOPSIS

 #include <bitstring.h>
 
 name = bit_alloc(nbits)
 bitstr_t *name;
 int nbits;
 
 bit_decl(name, nbits)
 bitstr_t name;
 int nbits;
 
 bit_clear(name, bit)
 bitstr_t name;
 int bit;
 
 bit_ffc(name, nbits, value)
 bitstr_t name;
 int nbits, *value;
 
 bit_ffs(name, nbits, value)
 bitstr_t name;
 int nbits, *value;
 
 bit_nclear(name, start, stop)
 bitstr_t name;
 int start, stop;
 
 bit_nset(name, start, stop)
 bitstr_t name;
 int start, stop;
 
 bit_set(name, bit)
 bitstr_t name;
 int bit;
 
 bitstr_size(nbits)
 int nbits;
 
 bit_test(name, bit)
 bitstr_t name;
 int bit;
 

DESCRIPTION

These macros operate on strings of bits.

Bit_alloc returns a pointer of type bitstr_t * to sufficient space to store nbits bits, or NULL if no space is available.

Bit_decl is a macro for allocating sufficient space to store nbits bits on the stack.

Bitstr_size returns the number of elements of type bitstr_t necessary to store nbits bits. This is useful for copying bit strings.

Bit_clear and bit_set clear or set the zero-based numbered bit bit, in the bit string name.

Bit_nset and bit_nclear set or clear the zero-based numbered bits from start to stop in the bit string name.

Bit_test evaluates to zero if the zero-based numbered bit bit of bit string name is set, and non-zero otherwise.

Bit_ffs sets *value to the zero-based number of the first bit set in the array of nbits bits referenced by name. If no bits are set, *value is set to -1.

Bit_ffc sets *value to the zero-based number of the first bit not set in the array of nbits bits referenced by name. If all bits are set, value is set to -1.

EXAMPLE

 #include <limits.h>
 #include <bitstring.h>
 
 #define LPR_BUSY_BIT            0
 #define LPR_FORMAT_BIT          1
 #define LPR_DOWNLOAD_BIT        2
 #define LPR_AVAILABLE_BIT       9
 #define LPR_MAX_BITS            10
 
 make_lpr_available()
 {
         bitstr_t bit_decl(bitlist, LPR_MAX_BITS);
         ...
         bit_nclear(bitlist, 0, LPR_MAX_BITS - 1);
         ...
         if (!bit_test(bitlist, LPR_BUSY_BIT)) {
                 bit_clear(bitlist, LPR_FORMAT_BIT);
                 bit_clear(bitlist, LPR_DOWNLOAD_BIT);
                 bit_set(bitlist, LPR_AVAILABLE_BIT);
         }
 }
 

SEE ALSO

malloc(3)