Merge pull request #1814 from uasi/from-cstr-len

Implement core::str::from_cstr_len with a test, close issue #1666

Author: brson

src/libcore/str.rs

@@ -17,6 +17,7 @@ export
    from_char,
    from_chars,
    from_cstr,
+   from_cstr_len,
    concat,
    connect,
 
@@ -210,6 +211,24 @@ unsafe fn from_cstr(cstr: sbuf) -> str {
     ret from_bytes(res);
 }
 
+/*
+Function: from_cstr_len
+
+Create a Rust string from a C string of the given length
+*/
+unsafe fn from_cstr_len(cstr: sbuf, len: uint) -> str {
+    let res = [];
+    let start = cstr;
+    let curr = start;
+    let i = 0u;
+    while i < len {
+        vec::push(res, *curr);
+        i += 1u;
+        curr = ptr::offset(start, i);
+    }
+    ret from_bytes(res);
+}
+
 /*
 Function: concat
 
@@ -1960,6 +1979,14 @@ mod tests {
         assert (c == "AAAAAAA");
     }
 
+    #[test]
+    fn test_from_cstr_len() unsafe {
+        let a = [65u8, 65u8, 65u8, 65u8, 65u8, 65u8, 65u8, 0u8];
+        let b = vec::to_ptr(a);
+        let c = from_cstr_len(b, 3u);
+        assert (c == "AAA");
+    }
+
     #[test]
     fn test_as_buf() unsafe {
         let a = "Abcdefg";