/* Copyright 2004, 2005, 2006, 2007 Acegi Technology Pty Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.security.providers.encoding;

/**
 * Implementation of the MD4 message digest derived from the RSA Data Security, Inc, MD4 Message-Digest Algorithm.
 *
 * @author Alan Stewart
 */
class Md4 {
	private static final int BLOCK_SIZE = 64;
	private static final int HASH_SIZE = 16;
	private final byte[] buffer = new byte[BLOCK_SIZE];
	private int bufferOffset;
	private long byteCount;
	private int[] state = new int[4];
	private int[] tmp = new int[16];

	Md4() {
		reset();
	}

	public void reset() {
		bufferOffset = 0;
		byteCount = 0;
		state[0] = 0x67452301;
		state[1] = 0xEFCDAB89;
		state[2] = 0x98BADCFE;
		state[3] = 0x10325476;
	}

	public byte[] digest() {
		byte[] resBuf = new byte[HASH_SIZE];
		digest(resBuf, 0, HASH_SIZE);
		return resBuf;
	}

	private void digest(byte[] buffer, int off) {
		for (int i = 0; i < 4; i++) {
			for (int j = 0; j < 4; j++) {
				buffer[off + (i * 4 + j)] = (byte) (state[i] >>> (8 * j));
			}
		}
	}

	private void digest(byte[] buffer, int offset, int len) {
		this.buffer[this.bufferOffset++] = (byte) 0x80;
		int lenOfBitLen = 8;
		int C = BLOCK_SIZE - lenOfBitLen;
		if (this.bufferOffset > C) {
			while (this.bufferOffset < BLOCK_SIZE) {
				this.buffer[this.bufferOffset++] = (byte) 0x00;
			}
			update(this.buffer, 0);
			this.bufferOffset = 0;
		}

		while (this.bufferOffset < C) {
			this.buffer[this.bufferOffset++] = (byte) 0x00;
		}

		long bitCount = byteCount * 8;
		for (int i = 0; i < 64; i += 8) {
			this.buffer[this.bufferOffset++] = (byte) (bitCount >>> (i));
		}

		update(this.buffer, 0);
		digest(buffer, offset);
	}

	public void update(byte[] input, int offset, int length) {
		byteCount += length;
		int todo;
		while (length >= (todo = BLOCK_SIZE - this.bufferOffset)) {
			System.arraycopy(input, offset, this.buffer, this.bufferOffset, todo);
			update(this.buffer, 0);
			length -= todo;
			offset += todo;
			this.bufferOffset = 0;
		}

		System.arraycopy(input, offset, this.buffer, this.bufferOffset, length);
		bufferOffset += length;
	}

	private void update(byte[] block, int offset) {
		for (int i = 0; i < 16; i++) {
			tmp[i] = (block[offset++] & 0xFF) | (block[offset++] & 0xFF) << 8 | (block[offset++] & 0xFF) << 16 | (block[offset++] & 0xFF) << 24;
		}

		int A = state[0];
		int B = state[1];
		int C = state[2];
		int D = state[3];

		A = FF(A, B, C, D, tmp[0], 3);
		D = FF(D, A, B, C, tmp[1], 7);
		C = FF(C, D, A, B, tmp[2], 11);
		B = FF(B, C, D, A, tmp[3], 19);
		A = FF(A, B, C, D, tmp[4], 3);
		D = FF(D, A, B, C, tmp[5], 7);
		C = FF(C, D, A, B, tmp[6], 11);
		B = FF(B, C, D, A, tmp[7], 19);
		A = FF(A, B, C, D, tmp[8], 3);
		D = FF(D, A, B, C, tmp[9], 7);
		C = FF(C, D, A, B, tmp[10], 11);
		B = FF(B, C, D, A, tmp[11], 19);
		A = FF(A, B, C, D, tmp[12], 3);
		D = FF(D, A, B, C, tmp[13], 7);
		C = FF(C, D, A, B, tmp[14], 11);
		B = FF(B, C, D, A, tmp[15], 19);

		A = GG(A, B, C, D, tmp[0], 3);
		D = GG(D, A, B, C, tmp[4], 5);
		C = GG(C, D, A, B, tmp[8], 9);
		B = GG(B, C, D, A, tmp[12], 13);
		A = GG(A, B, C, D, tmp[1], 3);
		D = GG(D, A, B, C, tmp[5], 5);
		C = GG(C, D, A, B, tmp[9], 9);
		B = GG(B, C, D, A, tmp[13], 13);
		A = GG(A, B, C, D, tmp[2], 3);
		D = GG(D, A, B, C, tmp[6], 5);
		C = GG(C, D, A, B, tmp[10], 9);
		B = GG(B, C, D, A, tmp[14], 13);
		A = GG(A, B, C, D, tmp[3], 3);
		D = GG(D, A, B, C, tmp[7], 5);
		C = GG(C, D, A, B, tmp[11], 9);
		B = GG(B, C, D, A, tmp[15], 13);

		A = HH(A, B, C, D, tmp[0], 3);
		D = HH(D, A, B, C, tmp[8], 9);
		C = HH(C, D, A, B, tmp[4], 11);
		B = HH(B, C, D, A, tmp[12], 15);
		A = HH(A, B, C, D, tmp[2], 3);
		D = HH(D, A, B, C, tmp[10], 9);
		C = HH(C, D, A, B, tmp[6], 11);
		B = HH(B, C, D, A, tmp[14], 15);
		A = HH(A, B, C, D, tmp[1], 3);
		D = HH(D, A, B, C, tmp[9], 9);
		C = HH(C, D, A, B, tmp[5], 11);
		B = HH(B, C, D, A, tmp[13], 15);
		A = HH(A, B, C, D, tmp[3], 3);
		D = HH(D, A, B, C, tmp[11], 9);
		C = HH(C, D, A, B, tmp[7], 11);
		B = HH(B, C, D, A, tmp[15], 15);

		state[0] += A;
		state[1] += B;
		state[2] += C;
		state[3] += D;
	}

	private int FF(int a, int b, int c, int d, int x, int s) {
		int t = a + ((b & c) | (~b & d)) + x;
		return t << s | t >>> (32 - s);
	}

	private int GG(int a, int b, int c, int d, int x, int s) {
		int t = a + ((b & (c | d)) | (c & d)) + x + 0x5A827999;
		return t << s | t >>> (32 - s);
	}

	private int HH(int a, int b, int c, int d, int x, int s) {
		int t = a + (b ^ c ^ d) + x + 0x6ED9EBA1;
		return t << s | t >>> (32 - s);
	}
}
