add safestrcpy

2 files changed, 17 insertions, 0 deletions

diff --git a/defs.h b/defs.h
index 31a3d75..8b2aac5 100644
--- a/defs.h
+++ b/defs.h
@@ -39,6 +39,7 @@ void* memset(void*, int, uint);
 int memcmp(const void*, const void*, uint);
 void* memmove(void*, const void*, uint);
 int strncmp(const char*, const char*, uint);
+char* safestrcpy(char*, const char*, int);
 
 // syscall.c
 void syscall(void);
diff --git a/string.c b/string.c
index 540a7d4..dc73266 100644
--- a/string.c
+++ b/string.c
@@ -57,3 +57,19 @@ strncmp(const char *p, const char *q, uint n)
   else
     return (int) ((uchar) *p - (uchar) *q);
 }
+
+// Like strncpy but guaranteed to NUL-terminate.
+char*
+safestrcpy(char *s, const char *t, int n)
+{
+  char *os;
+  
+  os = s;
+  if(n <= 0)
+    return os;
+  while(--n > 0 && (*s++ = *t++) != 0)
+    ;
+  *s = 0;
+  return os;
+}
+