//===== Copyright © 1996-2005, Valve Corporation, All rights reserved. ======//
//
// Purpose: 
//
//===========================================================================//

#include "basetypes.h"
#include "commonmacros.h"
#include "checksum_md5.h"
#include <string.h>
#include <stdio.h>
#include "tier1/strtools.h"
#include "tier0/dbg.h"

// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"

// The four core functions - F1 is optimized somewhat
// #define F1(x, y, z) (x & y | ~x & z)
#define F1(x, y, z) (z ^ (x & (y ^ z)))
#define F2(x, y, z) F1(z, x, y)
#define F3(x, y, z) (x ^ y ^ z)
#define F4(x, y, z) (y ^ (x | ~z))

// This is the central step in the MD5 algorithm.
#define MD5STEP(f, w, x, y, z, data, s) \
        ( w += f(x, y, z) + data,  w = w<<s | w>>(32-s),  w += x )

//-----------------------------------------------------------------------------
// Purpose: The core of the MD5 algorithm, this alters an existing MD5 hash to
//  reflect the addition of 16 longwords of new data.  MD5Update blocks
//  the data and converts bytes into longwords for this routine.
// Input  : buf[4] - 
//			in[16] - 
// Output : static void
//-----------------------------------------------------------------------------
static void MD5Transform(unsigned int buf[4], unsigned int const in[16])
{
    register unsigned int a, b, c, d;

    a = buf[0];
    b = buf[1];
    c = buf[2];
    d = buf[3];

    MD5STEP(F1, a, b, c, d, in[0] + 0xd76aa478, 7);
    MD5STEP(F1, d, a, b, c, in[1] + 0xe8c7b756, 12);
    MD5STEP(F1, c, d, a, b, in[2] + 0x242070db, 17);
    MD5STEP(F1, b, c, d, a, in[3] + 0xc1bdceee, 22);
    MD5STEP(F1, a, b, c, d, in[4] + 0xf57c0faf, 7);
    MD5STEP(F1, d, a, b, c, in[5] + 0x4787c62a, 12);
    MD5STEP(F1, c, d, a, b, in[6] + 0xa8304613, 17);
    MD5STEP(F1, b, c, d, a, in[7] + 0xfd469501, 22);
    MD5STEP(F1, a, b, c, d, in[8] + 0x698098d8, 7);
    MD5STEP(F1, d, a, b, c, in[9] + 0x8b44f7af, 12);
    MD5STEP(F1, c, d, a, b, in[10] + 0xffff5bb1, 17);
    MD5STEP(F1, b, c, d, a, in[11] + 0x895cd7be, 22);
    MD5STEP(F1, a, b, c, d, in[12] + 0x6b901122, 7);
    MD5STEP(F1, d, a, b, c, in[13] + 0xfd987193, 12);
    MD5STEP(F1, c, d, a, b, in[14] + 0xa679438e, 17);
    MD5STEP(F1, b, c, d, a, in[15] + 0x49b40821, 22);

    MD5STEP(F2, a, b, c, d, in[1] + 0xf61e2562, 5);
    MD5STEP(F2, d, a, b, c, in[6] + 0xc040b340, 9);
    MD5STEP(F2, c, d, a, b, in[11] + 0x265e5a51, 14);
    MD5STEP(F2, b, c, d, a, in[0] + 0xe9b6c7aa, 20);
    MD5STEP(F2, a, b, c, d, in[5] + 0xd62f105d, 5);
    MD5STEP(F2, d, a, b, c, in[10] + 0x02441453, 9);
    MD5STEP(F2, c, d, a, b, in[15] + 0xd8a1e681, 14);
    MD5STEP(F2, b, c, d, a, in[4] + 0xe7d3fbc8, 20);
    MD5STEP(F2, a, b, c, d, in[9] + 0x21e1cde6, 5);
    MD5STEP(F2, d, a, b, c, in[14] + 0xc33707d6, 9);
    MD5STEP(F2, c, d, a, b, in[3] + 0xf4d50d87, 14);
    MD5STEP(F2, b, c, d, a, in[8] + 0x455a14ed, 20);
    MD5STEP(F2, a, b, c, d, in[13] + 0xa9e3e905, 5);
    MD5STEP(F2, d, a, b, c, in[2] + 0xfcefa3f8, 9);
    MD5STEP(F2, c, d, a, b, in[7] + 0x676f02d9, 14);
    MD5STEP(F2, b, c, d, a, in[12] + 0x8d2a4c8a, 20);

    MD5STEP(F3, a, b, c, d, in[5] + 0xfffa3942, 4);
    MD5STEP(F3, d, a, b, c, in[8] + 0x8771f681, 11);
    MD5STEP(F3, c, d, a, b, in[11] + 0x6d9d6122, 16);
    MD5STEP(F3, b, c, d, a, in[14] + 0xfde5380c, 23);
    MD5STEP(F3, a, b, c, d, in[1] + 0xa4beea44, 4);
    MD5STEP(F3, d, a, b, c, in[4] + 0x4bdecfa9, 11);
    MD5STEP(F3, c, d, a, b, in[7] + 0xf6bb4b60, 16);
    MD5STEP(F3, b, c, d, a, in[10] + 0xbebfbc70, 23);
    MD5STEP(F3, a, b, c, d, in[13] + 0x289b7ec6, 4);
    MD5STEP(F3, d, a, b, c, in[0] + 0xeaa127fa, 11);
    MD5STEP(F3, c, d, a, b, in[3] + 0xd4ef3085, 16);
    MD5STEP(F3, b, c, d, a, in[6] + 0x04881d05, 23);
    MD5STEP(F3, a, b, c, d, in[9] + 0xd9d4d039, 4);
    MD5STEP(F3, d, a, b, c, in[12] + 0xe6db99e5, 11);
    MD5STEP(F3, c, d, a, b, in[15] + 0x1fa27cf8, 16);
    MD5STEP(F3, b, c, d, a, in[2] + 0xc4ac5665, 23);

    MD5STEP(F4, a, b, c, d, in[0] + 0xf4292244, 6);
    MD5STEP(F4, d, a, b, c, in[7] + 0x432aff97, 10);
    MD5STEP(F4, c, d, a, b, in[14] + 0xab9423a7, 15);
    MD5STEP(F4, b, c, d, a, in[5] + 0xfc93a039, 21);
    MD5STEP(F4, a, b, c, d, in[12] + 0x655b59c3, 6);
    MD5STEP(F4, d, a, b, c, in[3] + 0x8f0ccc92, 10);
    MD5STEP(F4, c, d, a, b, in[10] + 0xffeff47d, 15);
    MD5STEP(F4, b, c, d, a, in[1] + 0x85845dd1, 21);
    MD5STEP(F4, a, b, c, d, in[8] + 0x6fa87e4f, 6);
    MD5STEP(F4, d, a, b, c, in[15] + 0xfe2ce6e0, 10);
    MD5STEP(F4, c, d, a, b, in[6] + 0xa3014314, 15);
    MD5STEP(F4, b, c, d, a, in[13] + 0x4e0811a1, 21);
    MD5STEP(F4, a, b, c, d, in[4] + 0xf7537e82, 6);
    MD5STEP(F4, d, a, b, c, in[11] + 0xbd3af235, 10);
    MD5STEP(F4, c, d, a, b, in[2] + 0x2ad7d2bb, 15);
    MD5STEP(F4, b, c, d, a, in[9] + 0xeb86d391, 21);

    buf[0] += a;
    buf[1] += b;
    buf[2] += c;
    buf[3] += d;
}

//-----------------------------------------------------------------------------
// Purpose: Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious initialization constants.

// Input  : *ctx - 
//-----------------------------------------------------------------------------
void MD5Init(MD5Context_t *ctx)
{
    ctx->buf[0] = 0x67452301;
    ctx->buf[1] = 0xefcdab89;
    ctx->buf[2] = 0x98badcfe;
    ctx->buf[3] = 0x10325476;

    ctx->bits[0] = 0;
    ctx->bits[1] = 0;
}

//-----------------------------------------------------------------------------
// Purpose: Update context to reflect the concatenation of another buffer full of bytes.
// Input  : *ctx - 
//			*buf - 
//			len - 
//-----------------------------------------------------------------------------
void MD5Update(MD5Context_t *ctx, unsigned char const *buf, unsigned int len)
{
    unsigned int t;

    /* Update bitcount */

    t = ctx->bits[0];
    if ((ctx->bits[0] = t + ((unsigned int) len << 3)) < t)
        ctx->bits[1]++;         /* Carry from low to high */
    ctx->bits[1] += len >> 29;

    t = (t >> 3) & 0x3f;        /* Bytes already in shsInfo->data */

    /* Handle any leading odd-sized chunks */

    if (t)
	{
        unsigned char *p = (unsigned char *) ctx->in + t;

        t = 64 - t;
        if (len < t)
		{
            memcpy(p, buf, len);
            return;
        }
        memcpy(p, buf, t);
        //byteReverse(ctx->in, 16);
        MD5Transform(ctx->buf, (unsigned int *) ctx->in);
        buf += t;
        len -= t;
    }
    /* Process data in 64-byte chunks */

    while (len >= 64)
	{
        memcpy(ctx->in, buf, 64);
        //byteReverse(ctx->in, 16);
        MD5Transform(ctx->buf, (unsigned int *) ctx->in);
        buf += 64;
        len -= 64;
    }

    /* Handle any remaining bytes of data. */
    memcpy(ctx->in, buf, len);
}

//-----------------------------------------------------------------------------
// Purpose: Final wrapup - pad to 64-byte boundary with the bit pattern 
// 1 0* (64-bit count of bits processed, MSB-first)
// Input  : digest[MD5_DIGEST_LENGTH] - 
//			*ctx - 
//-----------------------------------------------------------------------------
void MD5Final(unsigned char digest[MD5_DIGEST_LENGTH], MD5Context_t *ctx)
{
    unsigned count;
    unsigned char *p;

    /* Compute number of bytes mod 64 */
    count = (ctx->bits[0] >> 3) & 0x3F;

    /* Set the first char of padding to 0x80.  This is safe since there is
       always at least one byte free */
    p = ctx->in + count;
    *p++ = 0x80;

    /* Bytes of padding needed to make 64 bytes */
    count = 64 - 1 - count;

    /* Pad out to 56 mod 64 */
    if (count < 8)
	{
        /* Two lots of padding:  Pad the first block to 64 bytes */
        memset(p, 0, count);
        //byteReverse(ctx->in, 16);
        MD5Transform(ctx->buf, (unsigned int *) ctx->in);

        /* Now fill the next block with 56 bytes */
        memset(ctx->in, 0, 56);
    }
	else
	{
        /* Pad block to 56 bytes */
        memset(p, 0, count - 8);
    }
    //byteReverse(ctx->in, 14);

    /* Append length in bits and transform */
    ((unsigned int *) ctx->in)[14] = ctx->bits[0];
    ((unsigned int *) ctx->in)[15] = ctx->bits[1];

    MD5Transform(ctx->buf, (unsigned int *) ctx->in);
    //byteReverse((unsigned char *) ctx->buf, 4);
    memcpy(digest, ctx->buf, MD5_DIGEST_LENGTH);
    memset(ctx, 0, sizeof(ctx));        /* In case it's sensitive */
}

//-----------------------------------------------------------------------------
// Purpose: 
// Input  : *hash - 
//			hashlen - 
// Output : char
//-----------------------------------------------------------------------------
char *MD5_Print( unsigned char *hash, int hashlen )
{
	static char szReturn[64];

	Assert( hashlen <= 32 );

	Q_binarytohex( hash, hashlen, szReturn, sizeof( szReturn ) );
	return szReturn;
}

//-----------------------------------------------------------------------------
// Purpose: generate pseudo random number from a seed number
// Input  : seed number
// Output : pseudo random number
//-----------------------------------------------------------------------------
unsigned int MD5_PseudoRandom(unsigned int nSeed)
{
	MD5Context_t ctx;
	unsigned char digest[MD5_DIGEST_LENGTH]; // The MD5 Hash

	memset( &ctx, 0, sizeof( ctx ) );
		
	MD5Init(&ctx);
	MD5Update(&ctx, (unsigned char*)&nSeed, sizeof(nSeed) );
	MD5Final(digest, &ctx);

	return *(unsigned int*)(digest+6);	// use 4 middle bytes for random value
}
