From: Roy Marples <roy@marples.name>
Date: Sat, 7 Jun 2008 00:11:17 +0000 (+0000)
Subject: Add a function to test if a fd has data to be read.
X-Git-Tag: v4.0.2~294
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=751e2f818d970ca55fc094647df3ab9345ad3166;p=thirdparty%2Fdhcpcd.git

Add a function to test if a fd has data to be read.
---

diff --git a/common.c b/common.c
index 32df8844..7eeb1d9d 100644
--- a/common.c
+++ b/common.c
@@ -33,6 +33,7 @@
 #ifdef BSD
 #  include <paths.h>
 #endif
+#include <poll.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -150,6 +151,25 @@ close_fds(void)
 	return 0;
 }
 
+int
+fd_hasdata(int fd)
+{
+	struct pollfd fds;
+	int retval;
+
+	if (fd == -1)
+		return -1;
+	fds.fd = fd;
+	fds.events = POLLIN;
+	fds.revents = 0;
+	retval = poll(&fds, 1, 0);
+	if (retval == -1)
+		return -1;
+	if (retval > 0 && fds.revents & POLLIN)
+		return retval;
+	return 0;
+}
+
 int
 close_on_exec(int fd)
 {
diff --git a/common.h b/common.h
index 9df668a8..817ccaaa 100644
--- a/common.h
+++ b/common.h
@@ -35,6 +35,8 @@
 #include <stdio.h>
 #include <string.h>
 
+#define UNCONST(a)		((void *)(unsigned long)(const void *)(a))
+
 #if __GNUC__ > 2 || defined(__INTEL_COMPILER)
 # define _unused __attribute__((__unused__))
 #else
@@ -70,6 +72,7 @@ int closefrom(int);
 
 int close_fds(void);
 int close_on_exec(int);
+int fd_hasdata(int);
 ssize_t get_line(char **, size_t *, FILE *);
 int get_time(struct timeval *);
 time_t uptime(void);