first ever correct use of strncpy

766ba5cc · rsc · aa6824ab · 766ba5cc · 766ba5cc · 766ba5cc
--- a/defs.h
+++ b/defs.h
@@ -127,6 +127,7 @@ void*           memset(void*, int, uint);
 char*           safestrcpy(char*, const char*, int);
 int             strlen(const char*);
 int             strncmp(const char*, const char*, uint);
+char*           strncpy(char*, const char*, int);

 // syscall.c
 int             argint(int, int*);

--- a/fs.c
+++ b/fs.c
@@ -455,15 +455,7 @@ writei(struct inode *ip, char *src, uint off, uint n)
 int
 namecmp(const char *s, const char *t)
 {
-  int i;
-  
-  for(i=0; i<DIRSIZ; i++){
-    if(s[i] != t[i])
-      return s[i] - t[i];
-    if(s[i] == 0)
-      break;
-  }
-  return 0;
+  return strncmp(s, t, DIRSIZ);
 }

 // Look for a directory entry in a directory.
@@ -500,18 +492,6 @@ dirlookup(struct inode *dp, char *name, uint *poff)
  return 0;
 }

-// Copy one name to another.
-static void
-namecpy(char *s, const char *t)
-{
-  int i;
-  
-  for(i=0; i<DIRSIZ && t[i]; i++)
-    s[i] = t[i];
-  for(; i<DIRSIZ; i++)
-    s[i] = 0;
-}
-
 // Write a new directory entry (name, ino) into the directory dp.
 int
 dirlink(struct inode *dp, char *name, uint ino)
@@ -534,7 +514,7 @@ dirlink(struct inode *dp, char *name, uint ino)
      break;
  }

-  namecpy(de.name, name);
+  strncpy(de.name, name, DIRSIZ);
  de.inum = ino;
  if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
    panic("dirwrite");

--- a/string.c
+++ b/string.c
@@ -56,8 +56,20 @@ strncmp(const char *p, const char *q, uint n)
    n--, p++, q++;
  if(n == 0)
    return 0;
-  else
-    return (int) ((uchar) *p - (uchar) *q);
+  return (uchar)*p - (uchar)*q;
+}
+
+char*
+strncpy(char *s, const char *t, int n)
+{
+  char *os;
+  
+  os = s;
+  while(n-- > 0 && (*s++ = *t++) != 0)
+    ;
+  while(n-- > 0)
+    *s++ = 0;
+  return os;
 }

 // Like strncpy but guaranteed to NUL-terminate.