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bitstring ()
  • >> bitstring (3) ( FreeBSD man: Библиотечные вызовы )

  • BSD mandoc
     

    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>
    bitstr_t * bit_alloc (int nbits);
    void bit_decl (bitstr_t *name int nbits);
    void bit_clear (bitstr_t *name int bit);
    void bit_ffc (bitstr_t *name int nbits int *value);
    void bit_ffs (bitstr_t *name int nbits int *value);
    void bit_nclear (bitstr_t *name int start int stop);
    void bit_nset (bitstr_t *name int start int stop);
    void bit_set (bitstr_t *name int bit);
    int bitstr_size (int nbits);
    int bit_test (bitstr_t *name int bit);
     

    DESCRIPTION

    These macros operate on strings of bits.

    The macro bit_alloc ();
    returns a pointer of type ``Fa bitstr_t * '' to sufficient space to store Fa nbits bits, or NULL if no space is available.

    The macro bit_decl ();
    allocates sufficient space to store Fa nbits bits on the stack.

    The macro bitstr_size ();
    returns the number of elements of type Fa bitstr_t necessary to store Fa nbits bits. This is useful for copying bit strings.

    The macros bit_clear ();
    and bit_set ();
    clear or set the zero-based numbered bit Fa bit , in the bit string name

    The bit_nset ();
    and bit_nclear ();
    macros set or clear the zero-based numbered bits from Fa start through Fa stop in the bit string name

    The bit_test ();
    macro evaluates to non-zero if the zero-based numbered bit Fa bit of bit string Fa name is set, and zero otherwise.

    The bit_ffs ();
    macro stores in the location referenced by Fa value the zero-based number of the first bit set in the array of Fa nbits bits referenced by Fa name . If no bits are set, the location referenced by Fa value is set to -1.

    The macro bit_ffc ();
    stores in the location referenced by Fa value the zero-based number of the first bit not set in the array of Fa nbits bits referenced by Fa name . If all bits are set, the location referenced by Fa value is set to -1.

    The arguments to these macros are evaluated only once and may safely have side effects.  

    EXAMPLES

    #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)  

    HISTORY

    The bitstring functions first appeared in BSD 4.4


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    EXAMPLES
    SEE ALSO
    HISTORY


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