bitstr.doc

经过改进的C语言位操作功能

             bitstr.doc: documentation for the "bitstr" C routines

     The routines in bitstr.c and bitstr.h arose from an article on pages 34-
43 of the April, 1989 Computer Language issue. I thought that the routines 
given there were somewhat inefficient, and so I took the idea and rewrote the 
functions into much simpler (and, perhaps, less portable) versions.
     The idea behind the routines is to implement, in C, a way to store an 
array of "boolean" values, without using entire characters or even bitfields 
(whose values must be individually named). Three functions are included in 
bitstr.c: clear_bit(), set_bit(), and test_bit. In all three, there are two 
parameters: a pointer to one (or more) unsigned ints, and the bit number to be 
operated upon.
     The array of unsigned ints is the bit-array. The size of an unsigned int, 
in bits, is set to 16 in the US macro. Therefore, the number of data values 
able to be stored in a one-unsigned int-long array is 16. To store more than 
16 values, two or more unsigned ints may be declared, and the pointer should 
be passed to the first one.
     In memory, the bits are stored in a left-to-right fashion (bit 1 is on 
the left) -- at least on i80x86 CPUs, as the correctness of the routines 
depends on the orientation of the "(unsigned) 0x0001." Also, unsigned ints are 
used because they are, at least on the 8086, 8088, and 80286, the CPU internal 
bit width.
     I have strived to make these routines as bug-free as possible, and they 
have worked well in one of my large programming projects. However, if you do 
find an error (or just want to make comments, etc.), I can be contacted:

     Erik Mavrinac
     5333 Deerwood Dr.
     Shingle Springs, CA 95682

     CIS [73507,3523]