SHA1.java
/*
* Copyright (C) 2017, Google Inc. and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.util.sha1;
import static java.lang.Integer.lowestOneBit;
import static java.lang.Integer.numberOfTrailingZeros;
import static java.lang.Integer.rotateLeft;
import static java.lang.Integer.rotateRight;
import java.text.MessageFormat;
import java.util.Arrays;
import org.eclipse.jgit.internal.JGitText;
import org.eclipse.jgit.lib.MutableObjectId;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.util.NB;
import org.eclipse.jgit.util.SystemReader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Pure Java implementation of SHA-1 from FIPS 180-1 / RFC 3174.
*
* <p>
* See <a href="https://tools.ietf.org/html/rfc3174">RFC 3174</a>.
* <p>
* Unlike MessageDigest, this implementation includes the algorithm used by
* {@code sha1dc} to detect cryptanalytic collision attacks against SHA-1, such
* as the one used by <a href="https://shattered.it/">SHAttered</a>. See
* <a href="https://github.com/cr-marcstevens/sha1collisiondetection">
* sha1collisiondetection</a> for more information.
* <p>
* When detectCollision is true (default), this implementation throws
* {@link org.eclipse.jgit.util.sha1.Sha1CollisionException} from any digest
* method if a potential collision was detected.
*
* @since 4.7
*/
public class SHA1 {
private static final Logger LOG = LoggerFactory.getLogger(SHA1.class);
private static final boolean DETECT_COLLISIONS;
static {
SystemReader sr = SystemReader.getInstance();
String v = sr.getProperty("org.eclipse.jgit.util.sha1.detectCollision"); //$NON-NLS-1$
DETECT_COLLISIONS = v != null ? Boolean.parseBoolean(v) : true;
}
/**
* Create a new context to compute a SHA-1 hash of data.
*
* @return a new context to compute a SHA-1 hash of data.
*/
public static SHA1 newInstance() {
return new SHA1();
}
private final State h = new State();
private final int[] w = new int[80];
/** Buffer to accumulate partial blocks to 64 byte alignment. */
private final byte[] buffer = new byte[64];
/** Total number of bytes in the message. */
private long length;
private boolean detectCollision = DETECT_COLLISIONS;
private boolean foundCollision;
private final int[] w2 = new int[80];
private final State state58 = new State();
private final State state65 = new State();
private final State hIn = new State();
private final State hTmp = new State();
private SHA1() {
h.init();
}
/**
* Enable likely collision detection.
* <p>
* Default is {@code true}.
* <p>
* May also be set by system property:
* {@code -Dorg.eclipse.jgit.util.sha1.detectCollision=true}.
*
* @param detect
* a boolean.
* @return {@code this}
*/
public SHA1 setDetectCollision(boolean detect) {
detectCollision = detect;
return this;
}
/**
* Update the digest computation by adding a byte.
*
* @param b a byte.
*/
public void update(byte b) {
int bufferLen = (int) (length & 63);
length++;
buffer[bufferLen] = b;
if (bufferLen == 63) {
compress(buffer, 0);
}
}
/**
* Update the digest computation by adding bytes to the message.
*
* @param in
* input array of bytes.
*/
public void update(byte[] in) {
update(in, 0, in.length);
}
/**
* Update the digest computation by adding bytes to the message.
*
* @param in
* input array of bytes.
* @param p
* offset to start at from {@code in}.
* @param len
* number of bytes to hash.
*/
public void update(byte[] in, int p, int len) {
// SHA-1 compress can only process whole 64 byte blocks.
// Hold partial updates in buffer, whose length is the low bits.
int bufferLen = (int) (length & 63);
length += len;
if (bufferLen > 0) {
int n = Math.min(64 - bufferLen, len);
System.arraycopy(in, p, buffer, bufferLen, n);
p += n;
len -= n;
if (bufferLen + n < 64) {
return;
}
compress(buffer, 0);
}
while (len >= 64) {
compress(in, p);
p += 64;
len -= 64;
}
if (len > 0) {
System.arraycopy(in, p, buffer, 0, len);
}
}
private void compress(byte[] block, int p) {
initBlock(block, p);
int ubcDvMask = detectCollision ? UbcCheck.check(w) : 0;
compress();
while (ubcDvMask != 0) {
int b = numberOfTrailingZeros(lowestOneBit(ubcDvMask));
UbcCheck.DvInfo dv = UbcCheck.DV[b];
for (int i = 0; i < 80; i++) {
w2[i] = w[i] ^ dv.dm[i];
}
recompress(dv.testt);
if (eq(hTmp, h)) {
foundCollision = true;
break;
}
ubcDvMask &= ~(1 << b);
}
}
private void initBlock(byte[] block, int p) {
for (int t = 0; t < 16; t++) {
w[t] = NB.decodeInt32(block, p + (t << 2));
}
// RFC 3174 6.1.b, extend state vector to 80 words.
for (int t = 16; t < 80; t++) {
int x = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
w[t] = rotateLeft(x, 1); // S^1(...)
}
}
private void compress() {
// Method 1 from RFC 3174 section 6.1.
// Method 2 (circular queue of 16 words) is slower.
int a = h.a, b = h.b, c = h.c, d = h.d, e = h.e;
// @formatter:off
e += s1(a, b, c, d,w[ 0]); b = rotateLeft( b, 30);
d += s1(e, a, b, c,w[ 1]); a = rotateLeft( a, 30);
c += s1(d, e, a, b,w[ 2]); e = rotateLeft( e, 30);
b += s1(c, d, e, a,w[ 3]); d = rotateLeft( d, 30);
a += s1(b, c, d, e,w[ 4]); c = rotateLeft( c, 30);
e += s1(a, b, c, d,w[ 5]); b = rotateLeft( b, 30);
d += s1(e, a, b, c,w[ 6]); a = rotateLeft( a, 30);
c += s1(d, e, a, b,w[ 7]); e = rotateLeft( e, 30);
b += s1(c, d, e, a,w[ 8]); d = rotateLeft( d, 30);
a += s1(b, c, d, e,w[ 9]); c = rotateLeft( c, 30);
e += s1(a, b, c, d,w[ 10]); b = rotateLeft( b, 30);
d += s1(e, a, b, c,w[ 11]); a = rotateLeft( a, 30);
c += s1(d, e, a, b,w[ 12]); e = rotateLeft( e, 30);
b += s1(c, d, e, a,w[ 13]); d = rotateLeft( d, 30);
a += s1(b, c, d, e,w[ 14]); c = rotateLeft( c, 30);
e += s1(a, b, c, d,w[ 15]); b = rotateLeft( b, 30);
d += s1(e, a, b, c,w[ 16]); a = rotateLeft( a, 30);
c += s1(d, e, a, b,w[ 17]); e = rotateLeft( e, 30);
b += s1(c, d, e, a,w[ 18]); d = rotateLeft( d, 30);
a += s1(b, c, d, e,w[ 19]); c = rotateLeft( c, 30);
e += s2(a, b, c, d,w[ 20]); b = rotateLeft( b, 30);
d += s2(e, a, b, c,w[ 21]); a = rotateLeft( a, 30);
c += s2(d, e, a, b,w[ 22]); e = rotateLeft( e, 30);
b += s2(c, d, e, a,w[ 23]); d = rotateLeft( d, 30);
a += s2(b, c, d, e,w[ 24]); c = rotateLeft( c, 30);
e += s2(a, b, c, d,w[ 25]); b = rotateLeft( b, 30);
d += s2(e, a, b, c,w[ 26]); a = rotateLeft( a, 30);
c += s2(d, e, a, b,w[ 27]); e = rotateLeft( e, 30);
b += s2(c, d, e, a,w[ 28]); d = rotateLeft( d, 30);
a += s2(b, c, d, e,w[ 29]); c = rotateLeft( c, 30);
e += s2(a, b, c, d,w[ 30]); b = rotateLeft( b, 30);
d += s2(e, a, b, c,w[ 31]); a = rotateLeft( a, 30);
c += s2(d, e, a, b,w[ 32]); e = rotateLeft( e, 30);
b += s2(c, d, e, a,w[ 33]); d = rotateLeft( d, 30);
a += s2(b, c, d, e,w[ 34]); c = rotateLeft( c, 30);
e += s2(a, b, c, d,w[ 35]); b = rotateLeft( b, 30);
d += s2(e, a, b, c,w[ 36]); a = rotateLeft( a, 30);
c += s2(d, e, a, b,w[ 37]); e = rotateLeft( e, 30);
b += s2(c, d, e, a,w[ 38]); d = rotateLeft( d, 30);
a += s2(b, c, d, e,w[ 39]); c = rotateLeft( c, 30);
e += s3(a, b, c, d,w[ 40]); b = rotateLeft( b, 30);
d += s3(e, a, b, c,w[ 41]); a = rotateLeft( a, 30);
c += s3(d, e, a, b,w[ 42]); e = rotateLeft( e, 30);
b += s3(c, d, e, a,w[ 43]); d = rotateLeft( d, 30);
a += s3(b, c, d, e,w[ 44]); c = rotateLeft( c, 30);
e += s3(a, b, c, d,w[ 45]); b = rotateLeft( b, 30);
d += s3(e, a, b, c,w[ 46]); a = rotateLeft( a, 30);
c += s3(d, e, a, b,w[ 47]); e = rotateLeft( e, 30);
b += s3(c, d, e, a,w[ 48]); d = rotateLeft( d, 30);
a += s3(b, c, d, e,w[ 49]); c = rotateLeft( c, 30);
e += s3(a, b, c, d,w[ 50]); b = rotateLeft( b, 30);
d += s3(e, a, b, c,w[ 51]); a = rotateLeft( a, 30);
c += s3(d, e, a, b,w[ 52]); e = rotateLeft( e, 30);
b += s3(c, d, e, a,w[ 53]); d = rotateLeft( d, 30);
a += s3(b, c, d, e,w[ 54]); c = rotateLeft( c, 30);
e += s3(a, b, c, d,w[ 55]); b = rotateLeft( b, 30);
d += s3(e, a, b, c,w[ 56]); a = rotateLeft( a, 30);
c += s3(d, e, a, b,w[ 57]); e = rotateLeft( e, 30);
state58.save(a, b, c, d, e);
b += s3(c, d, e, a,w[ 58]); d = rotateLeft( d, 30);
a += s3(b, c, d, e,w[ 59]); c = rotateLeft( c, 30);
e += s4(a, b, c, d,w[ 60]); b = rotateLeft( b, 30);
d += s4(e, a, b, c,w[ 61]); a = rotateLeft( a, 30);
c += s4(d, e, a, b,w[ 62]); e = rotateLeft( e, 30);
b += s4(c, d, e, a,w[ 63]); d = rotateLeft( d, 30);
a += s4(b, c, d, e,w[ 64]); c = rotateLeft( c, 30);
state65.save(a, b, c, d, e);
e += s4(a, b, c, d,w[ 65]); b = rotateLeft( b, 30);
d += s4(e, a, b, c,w[ 66]); a = rotateLeft( a, 30);
c += s4(d, e, a, b,w[ 67]); e = rotateLeft( e, 30);
b += s4(c, d, e, a,w[ 68]); d = rotateLeft( d, 30);
a += s4(b, c, d, e,w[ 69]); c = rotateLeft( c, 30);
e += s4(a, b, c, d,w[ 70]); b = rotateLeft( b, 30);
d += s4(e, a, b, c,w[ 71]); a = rotateLeft( a, 30);
c += s4(d, e, a, b,w[ 72]); e = rotateLeft( e, 30);
b += s4(c, d, e, a,w[ 73]); d = rotateLeft( d, 30);
a += s4(b, c, d, e,w[ 74]); c = rotateLeft( c, 30);
e += s4(a, b, c, d,w[ 75]); b = rotateLeft( b, 30);
d += s4(e, a, b, c,w[ 76]); a = rotateLeft( a, 30);
c += s4(d, e, a, b,w[ 77]); e = rotateLeft( e, 30);
b += s4(c, d, e, a,w[ 78]); d = rotateLeft( d, 30);
a += s4(b, c, d, e,w[ 79]); c = rotateLeft( c, 30);
// @formatter:on
h.save(h.a + a, h.b + b, h.c + c, h.d + d, h.e + e);
}
private void recompress(int t) {
State s;
switch (t) {
case 58:
s = state58;
break;
case 65:
s = state65;
break;
default:
throw new IllegalStateException();
}
int a = s.a, b = s.b, c = s.c, d = s.d, e = s.e;
// @formatter:off
if (t == 65) {
{ c = rotateRight( c, 30); a -= s4(b, c, d, e,w2[ 64]);}
{ d = rotateRight( d, 30); b -= s4(c, d, e, a,w2[ 63]);}
{ e = rotateRight( e, 30); c -= s4(d, e, a, b,w2[ 62]);}
{ a = rotateRight( a, 30); d -= s4(e, a, b, c,w2[ 61]);}
{ b = rotateRight( b, 30); e -= s4(a, b, c, d,w2[ 60]);}
{ c = rotateRight( c, 30); a -= s3(b, c, d, e,w2[ 59]);}
{ d = rotateRight( d, 30); b -= s3(c, d, e, a,w2[ 58]);}
}
{ e = rotateRight( e, 30); c -= s3(d, e, a, b,w2[ 57]);}
{ a = rotateRight( a, 30); d -= s3(e, a, b, c,w2[ 56]);}
{ b = rotateRight( b, 30); e -= s3(a, b, c, d,w2[ 55]);}
{ c = rotateRight( c, 30); a -= s3(b, c, d, e,w2[ 54]);}
{ d = rotateRight( d, 30); b -= s3(c, d, e, a,w2[ 53]);}
{ e = rotateRight( e, 30); c -= s3(d, e, a, b,w2[ 52]);}
{ a = rotateRight( a, 30); d -= s3(e, a, b, c,w2[ 51]);}
{ b = rotateRight( b, 30); e -= s3(a, b, c, d,w2[ 50]);}
{ c = rotateRight( c, 30); a -= s3(b, c, d, e,w2[ 49]);}
{ d = rotateRight( d, 30); b -= s3(c, d, e, a,w2[ 48]);}
{ e = rotateRight( e, 30); c -= s3(d, e, a, b,w2[ 47]);}
{ a = rotateRight( a, 30); d -= s3(e, a, b, c,w2[ 46]);}
{ b = rotateRight( b, 30); e -= s3(a, b, c, d,w2[ 45]);}
{ c = rotateRight( c, 30); a -= s3(b, c, d, e,w2[ 44]);}
{ d = rotateRight( d, 30); b -= s3(c, d, e, a,w2[ 43]);}
{ e = rotateRight( e, 30); c -= s3(d, e, a, b,w2[ 42]);}
{ a = rotateRight( a, 30); d -= s3(e, a, b, c,w2[ 41]);}
{ b = rotateRight( b, 30); e -= s3(a, b, c, d,w2[ 40]);}
{ c = rotateRight( c, 30); a -= s2(b, c, d, e,w2[ 39]);}
{ d = rotateRight( d, 30); b -= s2(c, d, e, a,w2[ 38]);}
{ e = rotateRight( e, 30); c -= s2(d, e, a, b,w2[ 37]);}
{ a = rotateRight( a, 30); d -= s2(e, a, b, c,w2[ 36]);}
{ b = rotateRight( b, 30); e -= s2(a, b, c, d,w2[ 35]);}
{ c = rotateRight( c, 30); a -= s2(b, c, d, e,w2[ 34]);}
{ d = rotateRight( d, 30); b -= s2(c, d, e, a,w2[ 33]);}
{ e = rotateRight( e, 30); c -= s2(d, e, a, b,w2[ 32]);}
{ a = rotateRight( a, 30); d -= s2(e, a, b, c,w2[ 31]);}
{ b = rotateRight( b, 30); e -= s2(a, b, c, d,w2[ 30]);}
{ c = rotateRight( c, 30); a -= s2(b, c, d, e,w2[ 29]);}
{ d = rotateRight( d, 30); b -= s2(c, d, e, a,w2[ 28]);}
{ e = rotateRight( e, 30); c -= s2(d, e, a, b,w2[ 27]);}
{ a = rotateRight( a, 30); d -= s2(e, a, b, c,w2[ 26]);}
{ b = rotateRight( b, 30); e -= s2(a, b, c, d,w2[ 25]);}
{ c = rotateRight( c, 30); a -= s2(b, c, d, e,w2[ 24]);}
{ d = rotateRight( d, 30); b -= s2(c, d, e, a,w2[ 23]);}
{ e = rotateRight( e, 30); c -= s2(d, e, a, b,w2[ 22]);}
{ a = rotateRight( a, 30); d -= s2(e, a, b, c,w2[ 21]);}
{ b = rotateRight( b, 30); e -= s2(a, b, c, d,w2[ 20]);}
{ c = rotateRight( c, 30); a -= s1(b, c, d, e,w2[ 19]);}
{ d = rotateRight( d, 30); b -= s1(c, d, e, a,w2[ 18]);}
{ e = rotateRight( e, 30); c -= s1(d, e, a, b,w2[ 17]);}
{ a = rotateRight( a, 30); d -= s1(e, a, b, c,w2[ 16]);}
{ b = rotateRight( b, 30); e -= s1(a, b, c, d,w2[ 15]);}
{ c = rotateRight( c, 30); a -= s1(b, c, d, e,w2[ 14]);}
{ d = rotateRight( d, 30); b -= s1(c, d, e, a,w2[ 13]);}
{ e = rotateRight( e, 30); c -= s1(d, e, a, b,w2[ 12]);}
{ a = rotateRight( a, 30); d -= s1(e, a, b, c,w2[ 11]);}
{ b = rotateRight( b, 30); e -= s1(a, b, c, d,w2[ 10]);}
{ c = rotateRight( c, 30); a -= s1(b, c, d, e,w2[ 9]);}
{ d = rotateRight( d, 30); b -= s1(c, d, e, a,w2[ 8]);}
{ e = rotateRight( e, 30); c -= s1(d, e, a, b,w2[ 7]);}
{ a = rotateRight( a, 30); d -= s1(e, a, b, c,w2[ 6]);}
{ b = rotateRight( b, 30); e -= s1(a, b, c, d,w2[ 5]);}
{ c = rotateRight( c, 30); a -= s1(b, c, d, e,w2[ 4]);}
{ d = rotateRight( d, 30); b -= s1(c, d, e, a,w2[ 3]);}
{ e = rotateRight( e, 30); c -= s1(d, e, a, b,w2[ 2]);}
{ a = rotateRight( a, 30); d -= s1(e, a, b, c,w2[ 1]);}
{ b = rotateRight( b, 30); e -= s1(a, b, c, d,w2[ 0]);}
hIn.save(a, b, c, d, e);
a = s.a; b = s.b; c = s.c; d = s.d; e = s.e;
if (t == 58) {
{ b += s3(c, d, e, a,w2[ 58]); d = rotateLeft( d, 30);}
{ a += s3(b, c, d, e,w2[ 59]); c = rotateLeft( c, 30);}
{ e += s4(a, b, c, d,w2[ 60]); b = rotateLeft( b, 30);}
{ d += s4(e, a, b, c,w2[ 61]); a = rotateLeft( a, 30);}
{ c += s4(d, e, a, b,w2[ 62]); e = rotateLeft( e, 30);}
{ b += s4(c, d, e, a,w2[ 63]); d = rotateLeft( d, 30);}
{ a += s4(b, c, d, e,w2[ 64]); c = rotateLeft( c, 30);}
}
{ e += s4(a, b, c, d,w2[ 65]); b = rotateLeft( b, 30);}
{ d += s4(e, a, b, c,w2[ 66]); a = rotateLeft( a, 30);}
{ c += s4(d, e, a, b,w2[ 67]); e = rotateLeft( e, 30);}
{ b += s4(c, d, e, a,w2[ 68]); d = rotateLeft( d, 30);}
{ a += s4(b, c, d, e,w2[ 69]); c = rotateLeft( c, 30);}
{ e += s4(a, b, c, d,w2[ 70]); b = rotateLeft( b, 30);}
{ d += s4(e, a, b, c,w2[ 71]); a = rotateLeft( a, 30);}
{ c += s4(d, e, a, b,w2[ 72]); e = rotateLeft( e, 30);}
{ b += s4(c, d, e, a,w2[ 73]); d = rotateLeft( d, 30);}
{ a += s4(b, c, d, e,w2[ 74]); c = rotateLeft( c, 30);}
{ e += s4(a, b, c, d,w2[ 75]); b = rotateLeft( b, 30);}
{ d += s4(e, a, b, c,w2[ 76]); a = rotateLeft( a, 30);}
{ c += s4(d, e, a, b,w2[ 77]); e = rotateLeft( e, 30);}
{ b += s4(c, d, e, a,w2[ 78]); d = rotateLeft( d, 30);}
{ a += s4(b, c, d, e,w2[ 79]); c = rotateLeft( c, 30);}
// @formatter:on
hTmp.save(hIn.a + a, hIn.b + b, hIn.c + c, hIn.d + d, hIn.e + e);
}
private static int s1(int a, int b, int c, int d, int w_t) {
return rotateLeft(a, 5)
// f: 0 <= t <= 19
+ ((b & c) | ((~b) & d))
+ 0x5A827999 + w_t;
}
private static int s2(int a, int b, int c, int d, int w_t) {
return rotateLeft(a, 5)
// f: 20 <= t <= 39
+ (b ^ c ^ d)
+ 0x6ED9EBA1 + w_t;
}
private static int s3(int a, int b, int c, int d, int w_t) {
return rotateLeft(a, 5)
// f: 40 <= t <= 59
+ ((b & c) | (b & d) | (c & d))
+ 0x8F1BBCDC + w_t;
}
private static int s4(int a, int b, int c, int d, int w_t) {
return rotateLeft(a, 5)
// f: 60 <= t <= 79
+ (b ^ c ^ d)
+ 0xCA62C1D6 + w_t;
}
private static boolean eq(State q, State r) {
return q.a == r.a
&& q.b == r.b
&& q.c == r.c
&& q.d == r.d
&& q.e == r.e;
}
private void finish() {
int bufferLen = (int) (length & 63);
if (bufferLen > 55) {
// Last block is too small; pad, compress, pad another block.
buffer[bufferLen++] = (byte) 0x80;
Arrays.fill(buffer, bufferLen, 64, (byte) 0);
compress(buffer, 0);
Arrays.fill(buffer, 0, 56, (byte) 0);
} else {
// Last block can hold padding and length.
buffer[bufferLen++] = (byte) 0x80;
Arrays.fill(buffer, bufferLen, 56, (byte) 0);
}
// SHA-1 appends the length of the message in bits after the
// padding block (above). Here length is in bytes. Multiply by
// 8 by shifting by 3 as part of storing the 64 bit byte length
// into the two words expected in the trailer.
NB.encodeInt32(buffer, 56, (int) (length >>> (32 - 3)));
NB.encodeInt32(buffer, 60, (int) (length << 3));
compress(buffer, 0);
if (foundCollision) {
ObjectId id = h.toObjectId();
LOG.warn(MessageFormat.format(JGitText.get().sha1CollisionDetected,
id.name()));
throw new Sha1CollisionException(id);
}
}
/**
* Finish the digest and return the resulting hash.
* <p>
* Once {@code digest()} is called, this instance should be discarded.
*
* @return the bytes for the resulting hash.
* @throws org.eclipse.jgit.util.sha1.Sha1CollisionException
* if a collision was detected and safeHash is false.
*/
public byte[] digest() throws Sha1CollisionException {
finish();
byte[] b = new byte[20];
NB.encodeInt32(b, 0, h.a);
NB.encodeInt32(b, 4, h.b);
NB.encodeInt32(b, 8, h.c);
NB.encodeInt32(b, 12, h.d);
NB.encodeInt32(b, 16, h.e);
return b;
}
/**
* Finish the digest and return the resulting hash.
* <p>
* Once {@code digest()} is called, this instance should be discarded.
*
* @return the ObjectId for the resulting hash.
* @throws org.eclipse.jgit.util.sha1.Sha1CollisionException
* if a collision was detected and safeHash is false.
*/
public ObjectId toObjectId() throws Sha1CollisionException {
finish();
return h.toObjectId();
}
/**
* Finish the digest and return the resulting hash.
* <p>
* Once {@code digest()} is called, this instance should be discarded.
*
* @param id
* destination to copy the digest to.
* @throws org.eclipse.jgit.util.sha1.Sha1CollisionException
* if a collision was detected and safeHash is false.
*/
public void digest(MutableObjectId id) throws Sha1CollisionException {
finish();
id.set(h.a, h.b, h.c, h.d, h.e);
}
/**
* Check if a collision was detected.
*
* <p>
* This method only returns an accurate result after the digest was obtained
* through {@link #digest()}, {@link #digest(MutableObjectId)} or
* {@link #toObjectId()}, as the hashing function must finish processing to
* know the final state.
*
* @return {@code true} if a likely collision was detected.
*/
public boolean hasCollision() {
return foundCollision;
}
/**
* Reset this instance to compute another hash.
*
* @return {@code this}.
*/
public SHA1 reset() {
h.init();
length = 0;
foundCollision = false;
return this;
}
private static final class State {
int a;
int b;
int c;
int d;
int e;
final void init() {
// Magic initialization constants defined by FIPS180.
save(0x67452301, 0xEFCDAB89, 0x98BADCFE, 0x10325476, 0xC3D2E1F0);
}
final void save(int a1, int b1, int c1, int d1, int e1) {
a = a1;
b = b1;
c = c1;
d = d1;
e = e1;
}
ObjectId toObjectId() {
return new ObjectId(a, b, c, d, e);
}
}
}