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Remove unnecessary array access from SHA1

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Provides a very small speedup.
This commit is contained in:
Brian Anderson 2011-05-11 01:02:27 -04:00
parent e35984b6c6
commit 7e7d134e3c
1 changed files with 15 additions and 14 deletions
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29
src/lib/SHA1.rs
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@ -31,6 +31,11 @@ state type sha1 = state obj {
const uint digest_buf_len = 5;
const uint msg_block_len = 64;
const u32 k0 = 0x5A827999u32;
const u32 k1 = 0x6ED9EBA1u32;
const u32 k2 = 0x8F1BBCDCu32;
const u32 k3 = 0xCA62C1D6u32;
// Builds a sha1 object
fn mk_sha1() -> sha1 {
@ -69,22 +74,18 @@ fn mk_sha1() -> sha1 {
// FIXME: Make precondition
assert (Vec.len(st.h) == digest_buf_len);
// Constants
auto k = vec(0x5A827999u32,
0x6ED9EBA1u32,
0x8F1BBCDCu32,
0xCA62C1D6u32);
let int t; // Loop counter
let vec[mutable u32] w = Vec.init_elt_mut[u32](0u32, 80u);
// Initialize the first 16 words of the vector w
t = 0;
while (t < 16) {
w.(t) = (st.msg_block.(t * 4) as u32) << 24u32;
w.(t) = w.(t) | ((st.msg_block.(t * 4 + 1) as u32) << 16u32);
w.(t) = w.(t) | ((st.msg_block.(t * 4 + 2) as u32) << 8u32);
w.(t) = w.(t) | (st.msg_block.(t * 4 + 3) as u32);
auto tmp;
tmp = (st.msg_block.(t * 4) as u32) << 24u32;
tmp = tmp | ((st.msg_block.(t * 4 + 1) as u32) << 16u32);
tmp = tmp | ((st.msg_block.(t * 4 + 2) as u32) << 8u32);
tmp = tmp | (st.msg_block.(t * 4 + 3) as u32);
w.(t) = tmp;
t += 1;
}
@ -106,7 +107,7 @@ fn mk_sha1() -> sha1 {
t = 0;
while (t < 20) {
temp = circular_shift(5u32, a)
+ ((b & c) | ((~b) & d)) + e + w.(t) + k.(0);
+ ((b & c) | ((~b) & d)) + e + w.(t) + k0;
e = d;
d = c;
c = circular_shift(30u32, b);
@ -117,7 +118,7 @@ fn mk_sha1() -> sha1 {
while (t < 40) {
temp = circular_shift(5u32, a)
+ (b ^ c ^ d) + e + w.(t) + k.(1);
+ (b ^ c ^ d) + e + w.(t) + k1;
e = d;
d = c;
c = circular_shift(30u32, b);
@ -128,7 +129,7 @@ fn mk_sha1() -> sha1 {
while (t < 60) {
temp = circular_shift(5u32, a)
+ ((b & c) | (b & d) | (c & d)) + e + w.(t) + k.(2);
+ ((b & c) | (b & d) | (c & d)) + e + w.(t) + k2;
e = d;
d = c;
c = circular_shift(30u32, b);
@ -139,7 +140,7 @@ fn mk_sha1() -> sha1 {
while (t < 80) {
temp = circular_shift(5u32, a)
+ (b ^ c ^ d) + e + w.(t) + k.(3);
+ (b ^ c ^ d) + e + w.(t) + k3;
e = d;
d = c;
c = circular_shift(30u32, b);