计算 md5

代码从polarssl中扒来的，略作改动，md5.h & md5.cpp 如下

#ifndef POLARSSL_MD5_H
#define POLARSSL_MD5_H

#include <string>
#include <stdint.h>

class md5
{
public:    
    void    string_md5(const unsigned char *input, size_t ilen, unsigned char output[16]);

    // open file failed return -1;
    int        file_md5(const char *path, unsigned char output[16]);

private:
    typedef struct
    {
        uint32_t total[2];          /*!< number of bytes processed  */
        uint32_t state[4];          /*!< intermediate digest state  */
        unsigned char buffer[64];   /*!< data block being processed */

        unsigned char ipad[64];     /*!< HMAC: inner padding        */
        unsigned char opad[64];     /*!< HMAC: outer padding        */
    }
    md5_context;

    void md5_init(md5_context *ctx);

    void md5_free(md5_context *ctx);

    void md5_starts(md5_context *ctx);

    void md5_update(md5_context *ctx, const unsigned char *input, size_t ilen);

    void md5_finish(md5_context *ctx, unsigned char output[16]);

    void md5_process(md5_context *ctx, const unsigned char data[64]);
};

#endif // POLARSSL_MD5_H

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

/*
* 32-bit integer manipulation macros (little endian)
*/
#ifndef GET_UINT32_LE
#define GET_UINT32_LE(n,b,i)                            
{                                                       
    (n) = ( (uint32_t) (b)[(i)    ]       )             
        | ( (uint32_t) (b)[(i) + 1] <<  8 )             
        | ( (uint32_t) (b)[(i) + 2] << 16 )             
        | ( (uint32_t) (b)[(i) + 3] << 24 );            
}
#endif

#ifndef PUT_UINT32_LE
#define PUT_UINT32_LE(n,b,i)                            
{                                                       
    (b)[(i)    ] = (unsigned char) ( (n)       );       
    (b)[(i) + 1] = (unsigned char) ( (n) >>  8 );       
    (b)[(i) + 2] = (unsigned char) ( (n) >> 16 );       
    (b)[(i) + 3] = (unsigned char) ( (n) >> 24 );       
}
#endif

void md5::md5_init(md5_context *ctx)
{
    memset(ctx, 0, sizeof(md5_context));
}

void md5::md5_free(md5_context *ctx)
{
    if (ctx == NULL)
        return;
        
    size_t    n = sizeof(md5_context);
    volatile unsigned char *p = (unsigned char*)ctx; while (n--) *p++ = 0;
}

/*
* MD5 context setup
*/
void md5::md5_starts(md5_context *ctx)
{
    ctx->total[0] = 0;
    ctx->total[1] = 0;

    ctx->state[0] = 0x67452301;
    ctx->state[1] = 0xEFCDAB89;
    ctx->state[2] = 0x98BADCFE;
    ctx->state[3] = 0x10325476;
}

void md5::md5_process(md5_context *ctx, const unsigned char data[64])
{
    uint32_t X[16], A, B, C, D;

    GET_UINT32_LE(X[0], data, 0);
    GET_UINT32_LE(X[1], data, 4);
    GET_UINT32_LE(X[2], data, 8);
    GET_UINT32_LE(X[3], data, 12);
    GET_UINT32_LE(X[4], data, 16);
    GET_UINT32_LE(X[5], data, 20);
    GET_UINT32_LE(X[6], data, 24);
    GET_UINT32_LE(X[7], data, 28);
    GET_UINT32_LE(X[8], data, 32);
    GET_UINT32_LE(X[9], data, 36);
    GET_UINT32_LE(X[10], data, 40);
    GET_UINT32_LE(X[11], data, 44);
    GET_UINT32_LE(X[12], data, 48);
    GET_UINT32_LE(X[13], data, 52);
    GET_UINT32_LE(X[14], data, 56);
    GET_UINT32_LE(X[15], data, 60);

#define S(x,n) ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)))

#define P(a,b,c,d,k,s,t)                                
    {                                                       
    a += F(b,c,d) + X[k] + t; a = S(a,s) + b;           
    }

    A = ctx->state[0];
    B = ctx->state[1];
    C = ctx->state[2];
    D = ctx->state[3];

#define F(x,y,z) (z ^ (x & (y ^ z)))

    P(A, B, C, D, 0, 7, 0xD76AA478);
    P(D, A, B, C, 1, 12, 0xE8C7B756);
    P(C, D, A, B, 2, 17, 0x242070DB);
    P(B, C, D, A, 3, 22, 0xC1BDCEEE);
    P(A, B, C, D, 4, 7, 0xF57C0FAF);
    P(D, A, B, C, 5, 12, 0x4787C62A);
    P(C, D, A, B, 6, 17, 0xA8304613);
    P(B, C, D, A, 7, 22, 0xFD469501);
    P(A, B, C, D, 8, 7, 0x698098D8);
    P(D, A, B, C, 9, 12, 0x8B44F7AF);
    P(C, D, A, B, 10, 17, 0xFFFF5BB1);
    P(B, C, D, A, 11, 22, 0x895CD7BE);
    P(A, B, C, D, 12, 7, 0x6B901122);
    P(D, A, B, C, 13, 12, 0xFD987193);
    P(C, D, A, B, 14, 17, 0xA679438E);
    P(B, C, D, A, 15, 22, 0x49B40821);

#undef F

#define F(x,y,z) (y ^ (z & (x ^ y)))

    P(A, B, C, D, 1, 5, 0xF61E2562);
    P(D, A, B, C, 6, 9, 0xC040B340);
    P(C, D, A, B, 11, 14, 0x265E5A51);
    P(B, C, D, A, 0, 20, 0xE9B6C7AA);
    P(A, B, C, D, 5, 5, 0xD62F105D);
    P(D, A, B, C, 10, 9, 0x02441453);
    P(C, D, A, B, 15, 14, 0xD8A1E681);
    P(B, C, D, A, 4, 20, 0xE7D3FBC8);
    P(A, B, C, D, 9, 5, 0x21E1CDE6);
    P(D, A, B, C, 14, 9, 0xC33707D6);
    P(C, D, A, B, 3, 14, 0xF4D50D87);
    P(B, C, D, A, 8, 20, 0x455A14ED);
    P(A, B, C, D, 13, 5, 0xA9E3E905);
    P(D, A, B, C, 2, 9, 0xFCEFA3F8);
    P(C, D, A, B, 7, 14, 0x676F02D9);
    P(B, C, D, A, 12, 20, 0x8D2A4C8A);

#undef F

#define F(x,y,z) (x ^ y ^ z)

    P(A, B, C, D, 5, 4, 0xFFFA3942);
    P(D, A, B, C, 8, 11, 0x8771F681);
    P(C, D, A, B, 11, 16, 0x6D9D6122);
    P(B, C, D, A, 14, 23, 0xFDE5380C);
    P(A, B, C, D, 1, 4, 0xA4BEEA44);
    P(D, A, B, C, 4, 11, 0x4BDECFA9);
    P(C, D, A, B, 7, 16, 0xF6BB4B60);
    P(B, C, D, A, 10, 23, 0xBEBFBC70);
    P(A, B, C, D, 13, 4, 0x289B7EC6);
    P(D, A, B, C, 0, 11, 0xEAA127FA);
    P(C, D, A, B, 3, 16, 0xD4EF3085);
    P(B, C, D, A, 6, 23, 0x04881D05);
    P(A, B, C, D, 9, 4, 0xD9D4D039);
    P(D, A, B, C, 12, 11, 0xE6DB99E5);
    P(C, D, A, B, 15, 16, 0x1FA27CF8);
    P(B, C, D, A, 2, 23, 0xC4AC5665);

#undef F

#define F(x,y,z) (y ^ (x | ~z))

    P(A, B, C, D, 0, 6, 0xF4292244);
    P(D, A, B, C, 7, 10, 0x432AFF97);
    P(C, D, A, B, 14, 15, 0xAB9423A7);
    P(B, C, D, A, 5, 21, 0xFC93A039);
    P(A, B, C, D, 12, 6, 0x655B59C3);
    P(D, A, B, C, 3, 10, 0x8F0CCC92);
    P(C, D, A, B, 10, 15, 0xFFEFF47D);
    P(B, C, D, A, 1, 21, 0x85845DD1);
    P(A, B, C, D, 8, 6, 0x6FA87E4F);
    P(D, A, B, C, 15, 10, 0xFE2CE6E0);
    P(C, D, A, B, 6, 15, 0xA3014314);
    P(B, C, D, A, 13, 21, 0x4E0811A1);
    P(A, B, C, D, 4, 6, 0xF7537E82);
    P(D, A, B, C, 11, 10, 0xBD3AF235);
    P(C, D, A, B, 2, 15, 0x2AD7D2BB);
    P(B, C, D, A, 9, 21, 0xEB86D391);

#undef F

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

/*
* MD5 process buffer
*/
void md5::md5_update(md5_context *ctx, const unsigned char *input, size_t ilen)
{
    size_t fill;
    uint32_t left;

    if (ilen == 0)
        return;

    left = ctx->total[0] & 0x3F;
    fill = 64 - left;

    ctx->total[0] += (uint32_t)ilen;
    ctx->total[0] &= 0xFFFFFFFF;

    if (ctx->total[0] < (uint32_t)ilen)
        ctx->total[1]++;

    if (left && ilen >= fill)
    {
        memcpy((void *)(ctx->buffer + left), input, fill);
        md5_process(ctx, ctx->buffer);
        input += fill;
        ilen -= fill;
        left = 0;
    }

    while (ilen >= 64)
    {
        md5_process(ctx, input);
        input += 64;
        ilen -= 64;
    }

    if (ilen > 0)
    {
        memcpy((void *)(ctx->buffer + left), input, ilen);
    }
}

static const unsigned char md5_padding[64] =
{
    0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/*
* MD5 final digest
*/
void md5::md5_finish(md5_context *ctx, unsigned char output[16])
{
    uint32_t last, padn;
    uint32_t high, low;
    unsigned char msglen[8];

    high = (ctx->total[0] >> 29)
        | (ctx->total[1] << 3);
    low = (ctx->total[0] << 3);

    PUT_UINT32_LE(low, msglen, 0);
    PUT_UINT32_LE(high, msglen, 4);

    last = ctx->total[0] & 0x3F;
    padn = (last < 56) ? (56 - last) : (120 - last);

    md5_update(ctx, md5_padding, padn);
    md5_update(ctx, msglen, 8);

    PUT_UINT32_LE(ctx->state[0], output, 0);
    PUT_UINT32_LE(ctx->state[1], output, 4);
    PUT_UINT32_LE(ctx->state[2], output, 8);
    PUT_UINT32_LE(ctx->state[3], output, 12);
}

/*
* output = MD5( input buffer )
*/
void md5::string_md5(const unsigned char *input, size_t ilen, unsigned char output[16])
{
    md5_context ctx;

    md5_init(&ctx);
    md5_starts(&ctx);
    md5_update(&ctx, input, ilen);
    md5_finish(&ctx, output);
    md5_free(&ctx);
}

/*
* output = MD5( file contents )
*/
int md5::file_md5(const char *path, unsigned char output[16])
{
    FILE *f;
    size_t n;
    md5_context ctx;
    unsigned char buf[1024];

    if ((f = fopen(path, "rb")) == NULL)
        return    -1;

    md5_init(&ctx);
    md5_starts(&ctx);

    while ((n = fread(buf, 1, sizeof(buf), f)) > 0)
        md5_update(&ctx, buf, n);

    md5_finish(&ctx, output);
    md5_free(&ctx);

    if (ferror(f) != 0)
    {
        fclose(f);
        return    -1;
    }

    fclose(f);
    return(0);
}