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ntypes.h
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1994-02-01
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/*
* Select uses bit masks of file descriptors in longs.
* These macros manipulate such bit fields (the filesystem macros use chars).
* FD_SETSIZE may be defined by the user, but the default here
* should be >= NOFILE (param.h).
*/
#define MAX_NOFILE 32
#define NBBY 8
#ifndef FD_SETSIZE
#define FD_SETSIZE MAX_NOFILE
#endif /* FD_SETSIZE */
/* How many things we'll allow select to use. 0 if unlimited */
#define MAXSELFD MAX_NOFILE
typedef long fd_mask;
#define NFDBITS (sizeof(fd_mask) * NBBY) /* bits per mask (power of 2!)*/
#define NFDSHIFT 5 /* Shift based on above */
#ifndef howmany
#define howmany(x, y) (((x)+((y)-1))/(y))
#endif /* howmany */
typedef struct fd_set {
fd_mask fds_bits[howmany(FD_SETSIZE, NFDBITS)];
} fd_set;
#define FD_SET(n, p) ((p)->fds_bits[(n)/NFDBITS] |= (1 << ((n) % NFDBITS)))
#define FD_CLR(n, p) ((p)->fds_bits[(n)/NFDBITS] &= ~(1 << ((n) % NFDBITS)))
#define FD_ISSET(n, p) ((p)->fds_bits[(n)/NFDBITS] & (1 << ((n) % NFDBITS)))
#define FD_ZERO(p) bzero((char *)(p), sizeof(*(p)))