Add readlink0() and readlinkat0() which null terminate the data.

2 files changed, 21 insertions, 1 deletions

diff --git a/lib/lib.c b/lib/lib.c
index 66814a45..b742bd17 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -444,7 +444,8 @@ off_t fdlength(int fd)
 
 // Read contents of file as a single nul-terminated string.
 // measure file size if !len, allocate buffer if !buf
-// note: for existing buffers use len = size-1, will set buf[len] = 0
+// Existing buffers need len in *plen
+// Returns amount of data read in *plen
 char *readfileat(int dirfd, char *name, char *ibuf, off_t *plen)
 {
   off_t len, rlen;
@@ -1130,3 +1131,20 @@ struct group *bufgetgrgid(gid_t gid)
 
   return &list->gr;
 }
+
+// Always null terminates, returns 0 for failure, len for success
+int readlinkat0(int dirfd, char *path, char *buf, int len)
+{
+  if (!len) return 0;
+
+  len = readlinkat(dirfd, path, buf, len-1);
+  if (len<1) return 0;
+  buf[len] = 0;
+
+  return len;
+}
+
+int readlink0(char *path, char *buf, int len)
+{
+  return readlinkat0(AT_FDCWD, path, buf, len);
+}
diff --git a/lib/lib.h b/lib/lib.h
index f545a794..3088f252 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -207,6 +207,8 @@ int dev_major(int dev);
 int dev_makedev(int major, int minor);
 struct passwd *bufgetpwuid(uid_t uid);
 struct group *bufgetgrgid(gid_t gid);
+int readlinkat0(int dirfd, char *path, char *buf, int len);
+int readlink0(char *path, char *buf, int len);
 
 #define HR_SPACE 1 // Space between number and units
 #define HR_B     2 // Use "B" for single byte units