// md2.cpp - modified by Wei Dai from Sun Microsystems's md2.c

/*
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*/

#include "pch.h"
#include "md2.h"

NAMESPACE_BEGIN(CryptoPP)

MD2::MD2()
	: buf(64)
{
	Init();
}

void MD2::Init()
{
	memset(buf, 0, 64);
	len = 0;
}

void MD2::Update(const byte *input, unsigned int length)
{
	while (length)
	{
		unsigned int lenInc = STDMIN(length, 16-len);
		memcpy(buf+len+16, input, lenInc);
		input += lenInc;
		length -= lenInc;
		len += lenInc;

		if (len == 16)
		{
			Transform();
			len = 0;
		}
	}
}

void MD2::Final(byte *hash)
{
	byte space = 16 - len; // Amount of padding

	// Pad with "space" bytes of value "space"
	memset(buf+16+len, space, space);
	Transform();

	// Append checksum
	memcpy(buf+16, buf+48, 16);
	// The transform redundantly updates the checksum, but it's not worth optimizing away.
	Transform();

	// Copy hash out
	memcpy(hash, buf, 16);

	Init();
}

void MD2::Transform()
{
	static const byte permutation[256] = {
		 41, 46, 67,201,162,216,124,  1, 61, 54, 84,161,236,240,  6, 19,
		 98,167,  5,243,192,199,115,140,152,147, 43,217,188, 76,130,202,
		 30,155, 87, 60,253,212,224, 22,103, 66,111, 24,138, 23,229, 18,
		190, 78,196,214,218,158,222, 73,160,251,245,142,187, 47,238,122,
		169,104,121,145, 21,178,  7, 63,148,194, 16,137, 11, 34, 95, 33,
		128,127, 93,154, 90,144, 50, 39, 53, 62,204,231,191,247,151,  3,
		255, 25, 48,179, 72,165,181,209,215, 94,146, 42,172, 86,170,198,
		 79,184, 56,210,150,164,125,182,118,252,107,226,156,116,  4,241,
		 69,157,112, 89,100,113,135, 32,134, 91,207,101,230, 45,168,  2,
		 27, 96, 37,173,174,176,185,246, 28, 70, 97,105, 52, 64,126, 15,
		 85, 71,163, 35,221, 81,175, 58,195, 92,249,206,186,197,234, 38,
		 44, 83, 13,110,133, 40,132,  9,211,223,205,244, 65,129, 77, 82,
		106,220, 55,200,108,193,171,250, 36,225,123,  8, 12,189,177, 74,
		120,136,149,139,227, 99,232,109,233,203,213,254, 59,  0, 29, 57,
		242,239,183, 14,102, 88,208,228,166,119,114,248,235,117, 75, 10,
		 49, 68, 80,180,143,237, 31, 26,219,153,141, 51,159, 17,131, 20
	};

	// Fill in the temp buf
	unsigned int i;
	for (i = 0; i < 16; i++)
			buf[i+32] = buf[i+16] ^ buf[i];

	// Update the checksum in the last 16 bytes of the buf
	byte t = buf[63];
	for (i = 0; i < 16; i++)
		t = buf[48+i] ^= permutation[buf[16+i] ^ t];

	// 18 passes of encryption over the first 48 bytes of the buf
	t = 0;
	for (i = 0; i < 18; i++)
	{
		for (unsigned int j = 0; j < 48; j++)
			t = buf[j] ^= permutation[t];
		t += i;
	}
}

NAMESPACE_END