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<sys/select.h>: add docs, and a warning against using select().

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Test: N/A
Change-Id: I596d63f2c8039434e2b8023eefb944da5c4bbb40
This commit is contained in:
Elliott Hughes 2019-10-02 14:12:31 -07:00
parent 822beaeeac
commit cfac8d0074
1 changed files with 49 additions and 5 deletions
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54
libc/include/sys/select.h
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@ -26,8 +26,12 @@
* SUCH DAMAGE.
*/
#ifndef _SYS_SELECT_H_
#define _SYS_SELECT_H_
#pragma once
/**
* @file sys/select.h
* @brief Wait for events on a set of file descriptors (but use <poll.h> instead).
*/
#include <sys/cdefs.h>
#include <sys/types.h>
@ -39,9 +43,17 @@ __BEGIN_DECLS
typedef unsigned long fd_mask;
/**
* The limit on the largest fd that can be used with this API.
* Use <poll.h> instead.
*/
#define FD_SETSIZE 1024
#define NFDBITS (8 * sizeof(fd_mask))
/**
* The type of a file descriptor set. Limited to 1024 fds.
* Use <poll.h> instead.
*/
typedef struct {
fd_mask fds_bits[FD_SETSIZE/NFDBITS];
} fd_set;
@ -67,21 +79,53 @@ int __FD_ISSET_chk(int, const fd_set*, size_t) __INTRODUCED_IN(21);
#define __FD_SET(fd, set) (__FDS_BITS(fd_set*,set)[__FDELT(fd)] |= __FDMASK(fd))
#define __FD_ISSET(fd, set) ((__FDS_BITS(const fd_set*,set)[__FDELT(fd)] & __FDMASK(fd)) != 0)
#if __ANDROID_API__ >= __ANDROID_API_L__
/** Removes `fd` from the given set. Use <poll.h> instead. */
#define FD_CLR(fd, set) __FD_CLR_chk(fd, set, __bos(set))
/** Adds `fd` to the given set. Use <poll.h> instead. */
#define FD_SET(fd, set) __FD_SET_chk(fd, set, __bos(set))
/** Tests whether `fd` is in the given set. Use <poll.h> instead. */
#define FD_ISSET(fd, set) __FD_ISSET_chk(fd, set, __bos(set))
#else
/** Removes `fd` from the given set. Use <poll.h> instead. */
#define FD_CLR(fd, set) __FD_CLR(fd, set)
/** Adds `fd` to the given set. Use <poll.h> instead. */
#define FD_SET(fd, set) __FD_SET(fd, set)
/** Tests whether `fd` is in the given set. Use <poll.h> instead. */
#define FD_ISSET(fd, set) __FD_ISSET(fd, set)
#endif /* __ANDROID_API >= 21 */
/**
* [select(2)](http://man7.org/linux/man-pages/man2/select.2.html) waits on a
* set of file descriptors. Use poll() instead.
*
* Returns the number of ready file descriptors on success, 0 for timeout,
* and returns -1 and sets `errno` on failure.
*/
int select(int __fd_count, fd_set* __read_fds, fd_set* __write_fds, fd_set* __exception_fds, struct timeval* __timeout);
/**
* [pselect(2)](http://man7.org/linux/man-pages/man2/select.2.html) waits on a
* set of file descriptors. Use ppoll() instead.
*
* Returns the number of ready file descriptors on success, 0 for timeout,
* and returns -1 and sets `errno` on failure.
*/
int pselect(int __fd_count, fd_set* __read_fds, fd_set* __write_fds, fd_set* __exception_fds, const struct timespec* __timeout, const sigset_t* __mask);
/**
* [pselect64(2)](http://man7.org/linux/man-pages/man2/select.2.html) waits on a
* set of file descriptors. Use ppoll64() instead.
*
* Returns the number of ready file descriptors on success, 0 for timeout,
* and returns -1 and sets `errno` on failure.
*
* Available since API level 28.
*/
int pselect64(int __fd_count, fd_set* __read_fds, fd_set* __write_fds, fd_set* __exception_fds, const struct timespec* __timeout, const sigset64_t* __mask) __INTRODUCED_IN(28);
__END_DECLS
#endif