initial implementation of ttyname()

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@3173 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kernel/libroot/posix/unistd/Jamfile

@@ -19,6 +19,7 @@ KernelMergeObject posix_unistd.o :
 	<$(SOURCE_GRIST)>sleep.c
 	<$(SOURCE_GRIST)>terminal.c
 	<$(SOURCE_GRIST)>truncate.c
+	<$(SOURCE_GRIST)>ttyname.c
 	<$(SOURCE_GRIST)>usergroup.c
 	<$(SOURCE_GRIST)>usleep.c
 	<$(SOURCE_GRIST)>write.c

src/kernel/libroot/posix/unistd/ttyname.c

@@ -0,0 +1,79 @@
+/* 
+** Copyright 2003, Daniel Reinhold, [email protected]. All rights reserved.
+** Distributed under the terms of the OpenBeOS License.
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <dirent.h>
+#include <sys/stat.h>
+
+
+/* the root directory in /dev where all tty devices reside */
+#define DEV_TTY  "/dev/tt/"
+
+
+/*
+ * ttyname - return the full pathname of the tty device
+ *           (NULL if not a tty or an error occurs)
+ */
+char *
+ttyname (int fd)
+{
+	static char pathname[MAXPATHLEN];
+	
+	char  *stub = pathname + sizeof(DEV_TTY) - 1;
+	int   stubLen = sizeof(pathname) - sizeof(DEV_TTY);
+	
+	struct stat fdStat;
+	DIR   *dir;
+	bool  found = false;
+	
+	
+	// first, some sanity checks:
+	if (!isatty(fd))
+		return NULL;
+	
+	if (fstat(fd, &fdStat) < 0)
+		return NULL;
+	
+	if (!S_ISCHR(fdStat.st_mode))
+		return NULL;
+	
+	
+	// start with the root tty directory at /dev
+	strcpy(pathname, DEV_TTY);
+	
+	if ((dir = opendir(pathname)) != NULL) {
+		// find a matching entry in the directory:
+		//   we must match both the inode for the file 
+		//   and the device that the file resides on
+		
+		struct dirent *e;
+		struct stat entryStat;
+		
+		while ((e = readdir(dir)) != NULL) {
+			// try to match the file's inode
+			if (e->d_ino != fdStat.st_ino)
+				continue;
+			
+			// construct the entry's full filename and
+			// call stat() to retrieve the inode info
+			strncpy(stub, e->d_name, stubLen);
+			
+			if (stat(pathname, &entryStat) < 0)
+				continue;
+			
+			if (entryStat.st_ino == fdStat.st_ino &&
+			    entryStat.st_dev == fdStat.st_dev) {
+			    found = true;
+			    break;
+			}
+		}
+	
+		closedir(dir);
+	}
+	
+	return found ? pathname : NULL;
+}