/*++ /* NAME /* timed_read 3 /* SUMMARY /* read operation with pre-read timeout /* SYNOPSIS /* #include <iostuff.h> /* /* ssize_t timed_read(fd, buf, len, timeout, context) /* int fd; /* void *buf; /* size_t len; /* int timeout; /* void *context; /* DESCRIPTION /* timed_read() performs a read() operation when the specified /* descriptor becomes readable within a user-specified deadline. /* /* Arguments: /* .IP fd /* File descriptor in the range 0..FD_SETSIZE. /* .IP buf /* Read buffer pointer. /* .IP len /* Read buffer size. /* .IP timeout /* The deadline in seconds. If this is <= 0, the deadline feature /* is disabled. /* .IP context /* Application context. This parameter is unused. It exists only /* for the sake of VSTREAM compatibility. /* DIAGNOSTICS /* When the operation does not complete within the deadline, the /* result value is -1, and errno is set to ETIMEDOUT. /* All other returns are identical to those of a read(2) operation. /* LICENSE /* .ad /* .fi /* The Secure Mailer license must be distributed with this software. /* AUTHOR(S) /* Wietse Venema /* IBM T.J. Watson Research /* P.O. Box 704 /* Yorktown Heights, NY 10598, USA /*--*/ /* System library. */ #include <sys_defs.h> #include <unistd.h> #include <errno.h> /* Utility library. */ #include <msg.h> #include <iostuff.h> /* timed_read - read with deadline */ ssize_t timed_read(int fd, void *buf, size_t len, int timeout, void *unused_context) { ssize_t ret; /* * Wait for a limited amount of time for something to happen. If nothing * happens, report an ETIMEDOUT error. * * XXX Solaris 8 read() fails with EAGAIN after read-select() returns * success. */ for (;;) { #ifdef __APPLE_OS_X_SERVER__ if (unused_context) { if (timeout > 0 && read_wait_no_poll(fd, timeout) < 0) return (-1); } else { #endif /* __APPLE_OS_X_SERVER__ */ if (timeout > 0 && read_wait(fd, timeout) < 0) return (-1); #ifdef __APPLE_OS_X_SERVER__ } #endif /* __APPLE_OS_X_SERVER__ */ if ((ret = read(fd, buf, len)) < 0 && timeout > 0 && errno == EAGAIN) { msg_warn("read() returns EAGAIN on a readable file descriptor!"); msg_warn("pausing to avoid going into a tight select/read loop!"); sleep(1); continue; } else if (ret < 0 && errno == EINTR) { continue; } else { return (ret); } } }