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#include "md5.h"
#include <stdio.h>
#include <string.h>

/*
 * This code implements the MD5 message-digest algorithm.
 * The algorithm is due to Ron Rivest. This code was
 * written by Colin Plumb in 1993, no copyright is claimed.
 * This code is in the public domain; do with it what you wish.
 *
 * Equivalent code is available from RSA Data Security, Inc.
 * This code has been tested against that, and is equivalent,
 * except that you don't need to include two pages of legalese
 * with every copy.
 *
 * To compute the message digest of a chunk of bytes, declare an
 * MD5Context structure, pass it to MD5Init, call MD5Update as
 * needed on buffers full of bytes, and then call MD5Final, which
 * will fill a supplied 16-byte array with the digest.
 *
 */

/* md5.h */
typedef unsigned int uint32;

struct MD5Context
{
	uint32 buf[4];
	uint32 bits[2];
	unsigned char in[64];
};

void MD5Init (struct MD5Context*);
void MD5Update (struct MD5Context*, unsigned const char*, unsigned);
void MD5Final (unsigned char digest[16], struct MD5Context*);
void MD5Transform (uint32 buf[4], uint32 const in[16]);

/*
 * This is needed to make RSAREF happy on some MS-DOS compilers.
 */

typedef struct MD5Context MD5_CTX;

/* md5.c */

/*
 * Note: this code is harmless on little-endian machines.
 */
static void byteReverse (unsigned char* buf, unsigned longs)
{
	uint32 t;

	do
	{
		t = (uint32) ( (unsigned) buf[3] << 8 | buf[2]) << 16 |
			( (unsigned) buf[1] << 8 | buf[0]);
		* (uint32*) buf = t;
		buf += 4;
	}
	while (--longs);
}

static void putu32 (uint32 data, unsigned char* addr)
{
	addr[0] = (unsigned char) data;
	addr[1] = (unsigned char) (data >> 8);
	addr[2] = (unsigned char) (data >> 16);
	addr[3] = (unsigned char) (data >> 24);
}

/*
 * Start MD5 accumulation. Set bit count to 0 and buffer to mysterious
 * initialization constants.
 */
void MD5Init (struct MD5Context* ctx)
{
	ctx->buf[0] = 0x67452301U;
	ctx->buf[1] = 0xefcdab89U;
	ctx->buf[2] = 0x98badcfeU;
	ctx->buf[3] = 0x10325476U;

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

/*
 * Update context to reflect the concatenation of another buffer full
 * of bytes.
 */
void MD5Update (struct MD5Context* ctx, unsigned const char* buf, unsigned len)
{
	uint32 t;

	/* Update bitcount */

	t = ctx->bits[0];

	if ( (ctx->bits[0] = t + ( (uint32) 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, (uint32*) 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, (uint32*) ctx->in);
		buf += 64;
		len -= 64;
	}

	/* Handle any remaining bytes of data. */

	memcpy (ctx->in, buf, len);
}

/*
 * Final wrapup - pad to 64-byte boundary with the bit pattern
 * 1 0* (64-bit count of bits processed, MSB-first)
 */
void MD5Final (unsigned char digest[16], struct MD5Context* 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, (uint32*) 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 */
	putu32 (ctx->bits[0], ctx->in + (14 * 4));
	putu32 (ctx->bits[1], ctx->in + (15 * 4));

	MD5Transform (ctx->buf, (uint32*) ctx->in);
	byteReverse ( (unsigned char*) ctx->buf, 4);
	memcpy (digest, ctx->buf, 16);
	// memset (ctx, 0, sizeof (ctx)); /* In case it's sensitive */
	ctx = NULL; // GCC doesn't like the line above.
}

/* 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 )

/*
 * 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.
 */
void MD5Transform (uint32 buf[4], uint32 const in[16])
{
	uint32 a, b, c, d;

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

	MD5STEP (F1, a, b, c, d, in[0] + 0xd76aa478U, 7);
	MD5STEP (F1, d, a, b, c, in[1] + 0xe8c7b756U, 12);
	MD5STEP (F1, c, d, a, b, in[2] + 0x242070dbU, 17);
	MD5STEP (F1, b, c, d, a, in[3] + 0xc1bdceeeU, 22);
	MD5STEP (F1, a, b, c, d, in[4] + 0xf57c0fafU, 7);
	MD5STEP (F1, d, a, b, c, in[5] + 0x4787c62aU, 12);
	MD5STEP (F1, c, d, a, b, in[6] + 0xa8304613U, 17);
	MD5STEP (F1, b, c, d, a, in[7] + 0xfd469501U, 22);
	MD5STEP (F1, a, b, c, d, in[8] + 0x698098d8U, 7);
	MD5STEP (F1, d, a, b, c, in[9] + 0x8b44f7afU, 12);
	MD5STEP (F1, c, d, a, b, in[10] + 0xffff5bb1U, 17);
	MD5STEP (F1, b, c, d, a, in[11] + 0x895cd7beU, 22);
	MD5STEP (F1, a, b, c, d, in[12] + 0x6b901122U, 7);
	MD5STEP (F1, d, a, b, c, in[13] + 0xfd987193U, 12);
	MD5STEP (F1, c, d, a, b, in[14] + 0xa679438eU, 17);
	MD5STEP (F1, b, c, d, a, in[15] + 0x49b40821U, 22);

	MD5STEP (F2, a, b, c, d, in[1] + 0xf61e2562U, 5);
	MD5STEP (F2, d, a, b, c, in[6] + 0xc040b340U, 9);
	MD5STEP (F2, c, d, a, b, in[11] + 0x265e5a51U, 14);
	MD5STEP (F2, b, c, d, a, in[0] + 0xe9b6c7aaU, 20);
	MD5STEP (F2, a, b, c, d, in[5] + 0xd62f105dU, 5);
	MD5STEP (F2, d, a, b, c, in[10] + 0x02441453U, 9);
	MD5STEP (F2, c, d, a, b, in[15] + 0xd8a1e681U, 14);
	MD5STEP (F2, b, c, d, a, in[4] + 0xe7d3fbc8U, 20);
	MD5STEP (F2, a, b, c, d, in[9] + 0x21e1cde6U, 5);
	MD5STEP (F2, d, a, b, c, in[14] + 0xc33707d6U, 9);
	MD5STEP (F2, c, d, a, b, in[3] + 0xf4d50d87U, 14);
	MD5STEP (F2, b, c, d, a, in[8] + 0x455a14edU, 20);
	MD5STEP (F2, a, b, c, d, in[13] + 0xa9e3e905U, 5);
	MD5STEP (F2, d, a, b, c, in[2] + 0xfcefa3f8U, 9);
	MD5STEP (F2, c, d, a, b, in[7] + 0x676f02d9U, 14);
	MD5STEP (F2, b, c, d, a, in[12] + 0x8d2a4c8aU, 20);

	MD5STEP (F3, a, b, c, d, in[5] + 0xfffa3942U, 4);
	MD5STEP (F3, d, a, b, c, in[8] + 0x8771f681U, 11);
	MD5STEP (F3, c, d, a, b, in[11] + 0x6d9d6122U, 16);
	MD5STEP (F3, b, c, d, a, in[14] + 0xfde5380cU, 23);
	MD5STEP (F3, a, b, c, d, in[1] + 0xa4beea44U, 4);
	MD5STEP (F3, d, a, b, c, in[4] + 0x4bdecfa9U, 11);
	MD5STEP (F3, c, d, a, b, in[7] + 0xf6bb4b60U, 16);
	MD5STEP (F3, b, c, d, a, in[10] + 0xbebfbc70U, 23);
	MD5STEP (F3, a, b, c, d, in[13] + 0x289b7ec6U, 4);
	MD5STEP (F3, d, a, b, c, in[0] + 0xeaa127faU, 11);
	MD5STEP (F3, c, d, a, b, in[3] + 0xd4ef3085U, 16);
	MD5STEP (F3, b, c, d, a, in[6] + 0x04881d05U, 23);
	MD5STEP (F3, a, b, c, d, in[9] + 0xd9d4d039U, 4);
	MD5STEP (F3, d, a, b, c, in[12] + 0xe6db99e5U, 11);
	MD5STEP (F3, c, d, a, b, in[15] + 0x1fa27cf8U, 16);
	MD5STEP (F3, b, c, d, a, in[2] + 0xc4ac5665U, 23);

	MD5STEP (F4, a, b, c, d, in[0] + 0xf4292244U, 6);
	MD5STEP (F4, d, a, b, c, in[7] + 0x432aff97U, 10);
	MD5STEP (F4, c, d, a, b, in[14] + 0xab9423a7U, 15);
	MD5STEP (F4, b, c, d, a, in[5] + 0xfc93a039U, 21);
	MD5STEP (F4, a, b, c, d, in[12] + 0x655b59c3U, 6);
	MD5STEP (F4, d, a, b, c, in[3] + 0x8f0ccc92U, 10);
	MD5STEP (F4, c, d, a, b, in[10] + 0xffeff47dU, 15);
	MD5STEP (F4, b, c, d, a, in[1] + 0x85845dd1U, 21);
	MD5STEP (F4, a, b, c, d, in[8] + 0x6fa87e4fU, 6);
	MD5STEP (F4, d, a, b, c, in[15] + 0xfe2ce6e0U, 10);
	MD5STEP (F4, c, d, a, b, in[6] + 0xa3014314U, 15);
	MD5STEP (F4, b, c, d, a, in[13] + 0x4e0811a1U, 21);
	MD5STEP (F4, a, b, c, d, in[4] + 0xf7537e82U, 6);
	MD5STEP (F4, d, a, b, c, in[11] + 0xbd3af235U, 10);
	MD5STEP (F4, c, d, a, b, in[2] + 0x2ad7d2bbU, 15);
	MD5STEP (F4, b, c, d, a, in[9] + 0xeb86d391U, 21);

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

void CalculateMD5 (const unsigned char* buffer, int length, char* checksum)
{
	int i;
	struct MD5Context m_md5;
	unsigned char signature[16];

	MD5Init (&m_md5);
	MD5Update (&m_md5, buffer, length);
	MD5Final (signature, &m_md5);

	for (i = 0; i < 16; i++)
	{
		sprintf (checksum + i * 2, "%02x", signature[i]);
	}
}