std: Constify the bytes sent to Sha1::input

We are of course never going to modify the data, and this change allows us to
accept data from to_bytes::IterBytes types.

Author: pkgw

src/libstd/sha1.rs

@@ -37,7 +37,7 @@ use core::vec;
 /// The SHA-1 interface
 trait Sha1 {
     /// Provide message input as bytes
-    fn input((&[u8]));
+    fn input((&[const u8]));
     /// Provide message input as string
     fn input_str((&str));
     /**
@@ -75,9 +75,9 @@ pub fn sha1() -> Sha1 {
          mut computed: bool,
          work_buf: @~[mut u32]};
 
-    fn add_input(st: &Sha1State, msg: &[u8]) {
+    fn add_input(st: &Sha1State, msg: &[const u8]) {
         assert (!st.computed);
-        for vec::each(msg) |element| {
+        for vec::each_const(msg) |element| {
             st.msg_block[st.msg_block_idx] = *element;
             st.msg_block_idx += 1u;
             st.len_low += 8u32;
@@ -243,7 +243,7 @@ pub fn sha1() -> Sha1 {
             self.h[4] = 0xC3D2E1F0u32;
             self.computed = false;
         }
-        fn input(msg: &[u8]) { add_input(&self, msg); }
+        fn input(msg: &[const u8]) { add_input(&self, msg); }
         fn input_str(msg: &str) {
             let bs = str::to_bytes(msg);
             add_input(&self, bs);