xnu-3789.1.32.tar.gz

[apple/xnu.git] / libsyscall / mach / mig_strncpy.c

diff --git a/libsyscall/mach/mig_strncpy.c b/libsyscall/mach/mig_strncpy.c
index ed17aaff2412394f459d919891c8d2af36e447ac..3bc188adf9d636591965e18f185782eea4faf346 100644 (file)
--- a/libsyscall/mach/mig_strncpy.c
+++ b/libsyscall/mach/mig_strncpy.c
@@ -92,3 +92,59 @@ mig_strncpy(
     *dest = '\0';
     return i;
 }
+
+/*
+ * mig_strncpy_zerofill -- Bounded string copy.  Does what the
+ * library routine strncpy OUGHT to do:  Copies the (null terminated)
+ * string in src into dest, a buffer of length len.  Assures that
+ * the copy is still null terminated and doesn't overflow the buffer,
+ * truncating the copy if necessary. If the string in src is smaller
+ * than given length len, it will zero fill the remaining bytes in dest.
+ *
+ * Parameters:
+ *
+ *     dest - Pointer to destination buffer.
+ *
+ *     src - Pointer to source string.
+ *
+ *     len - Length of destination buffer.
+ *
+ * Result:
+ *     length of string copied, INCLUDING the trailing 0.
+ */
+int
+mig_strncpy_zerofill(
+    char *dest,
+    const char *src,
+    int len)
+{
+       int i;
+       boolean_t terminated = FALSE;
+       int retval = 0;
+
+       if (len <= 0 || dest == 0) {
+               return 0;
+       }
+
+       if (src == 0) {
+               terminated = TRUE;
+       }
+
+       for (i = 1; i < len; i++) {
+               if (!terminated) {
+                       if (!(*dest++ = *src++)) {
+                               retval = i;
+                               terminated = TRUE;
+                       }
+               } else {
+                       *dest++ = '\0';
+               }
+       }
+
+       *dest = '\0';
+       if (!terminated) {
+               retval = i;
+       }
+
+       return retval;
+}