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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:18:56 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 16:18:56 +0000 |
commit | b7c15c31519dc44c1f691e0466badd556ffe9423 (patch) | |
tree | f944572f288bab482a615e09af627d9a2b6727d8 /src/util/peekfd.c | |
parent | Initial commit. (diff) | |
download | postfix-b7c15c31519dc44c1f691e0466badd556ffe9423.tar.xz postfix-b7c15c31519dc44c1f691e0466badd556ffe9423.zip |
Adding upstream version 3.7.10.upstream/3.7.10
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/util/peekfd.c')
-rw-r--r-- | src/util/peekfd.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/src/util/peekfd.c b/src/util/peekfd.c new file mode 100644 index 0000000..e9480a2 --- /dev/null +++ b/src/util/peekfd.c @@ -0,0 +1,89 @@ +/*++ +/* NAME +/* peekfd 3 +/* SUMMARY +/* determine amount of data ready to read +/* SYNOPSIS +/* #include <iostuff.h> +/* +/* ssize_t peekfd(fd) +/* int fd; +/* DESCRIPTION +/* peekfd() attempts to find out how many bytes are available to +/* be read from the named file descriptor. The result value is +/* the number of available bytes. +/* DIAGNOSTICS +/* peekfd() returns -1 in case of trouble. The global \fIerrno\fR +/* variable reflects the nature of the problem. +/* BUGS +/* On some systems, non-blocking read() may fail even after a +/* positive return from peekfd(). The smtp-sink program works +/* around this by using the readable() function instead. +/* 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 +/* +/* Wietse Venema +/* Google, Inc. +/* 111 8th Avenue +/* New York, NY 10011, USA +/*--*/ + +/* System library. */ + +#include <sys_defs.h> +#include <sys/ioctl.h> +#ifdef FIONREAD_IN_SYS_FILIO_H +#include <sys/filio.h> +#endif +#ifdef FIONREAD_IN_TERMIOS_H +#include <termios.h> +#endif +#include <unistd.h> + +#ifndef SHUT_RDWR +#define SHUT_RDWR 2 +#endif + +/* Utility library. */ + +#include "iostuff.h" + +/* peekfd - return amount of data ready to read */ + +ssize_t peekfd(int fd) +{ + + /* + * Anticipate a series of system-dependent code fragments. + */ +#ifdef FIONREAD + int count; + +#ifdef SUNOS5 + + /* + * With Solaris10, write_wait() hangs in poll() until timeout, when + * invoked after peekfd() has received an ECONNRESET error indication. + * This happens when a client sends QUIT and closes the connection + * immediately. + */ + if (ioctl(fd, FIONREAD, (char *) &count) < 0) { + (void) shutdown(fd, SHUT_RDWR); + return (-1); + } else { + return (count); + } +#else /* SUNOS5 */ + return (ioctl(fd, FIONREAD, (char *) &count) < 0 ? -1 : count); +#endif /* SUNOS5 */ +#else +#error "don't know how to look ahead" +#endif +} |