Add a helper find_from_u8 function

1 files changed, 33 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index c8bb38f..9b59d02 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -79,6 +79,39 @@ fn find_from(line: &str, ix_start: usize, key: &str) -> Option<usize> {
     line[ix_start..].find(key).map(|v| ix_start + v)
 }
 
+fn find_from_u8(line: &[u8], ix_start: usize, key: &[u8]) -> Option<usize> {
+    assert!(key.len() > 0);
+    assert!(ix_start < line.len());
+    let ix_end = line.len() - key.len();
+    if ix_start <= ix_end {
+        for i in ix_start..ix_end {
+            if line[i] == key[0] {
+                let mut success = true;
+                for j in 1..key.len() {
+                    if line[i + j] != key[j] {
+                        success = false;
+                        break;
+                    }
+                }
+                if success {
+                    return Some(i);
+                }
+            }
+        }
+    }
+    None
+}
+
+#[test]
+fn test_find_from_u8() {
+    assert_eq!(find_from_u8(b"hello world", 0, b"hell"), Some(0));
+    assert_eq!(find_from_u8(b"hello world", 0, b"o"), Some(4));
+    assert_eq!(find_from_u8(b"hello world", 4, b"o"), Some(4));
+    assert_eq!(find_from_u8(b"hello world", 5, b"o"), Some(7));
+    assert_eq!(find_from_u8(b"hello world", 8, b"o"), None);
+    assert_eq!(find_from_u8(b"hello world", 10, b"d"), None);
+}
+
 impl<'a> MailHeader<'a> {
     pub fn get_key(&self) -> Result<String, MailParseError> {
         Ok(try!(encoding::all::ISO_8859_1.decode(self.key, encoding::DecoderTrap::Strict))