SHA-256 hash function

/* * An implementation of the SHA-256 hash function, this is endian neutral * so should work just about anywhere. * * This code works much like the MD5 code provided by RSA. You sha_init() * a "sha_state" then sha_process() the bytes you want and sha_done() to get * the output. * * Revised Code:  Complies to SHA-256 standard now. * * Tom St Denis * */#include <stdio.h>typedef struct {    unsigned int state[8], length, curlen;    unsigned char buf[64];} sha_state;/* the K array */static const unsigned int K[64] = {    0x428a2f98U, 0x71374491U, 0xb5c0fbcfU, 0xe9b5dba5U, 0x3956c25bU,    0x59f111f1U, 0x923f82a4U, 0xab1c5ed5U, 0xd807aa98U, 0x12835b01U,    0x243185beU, 0x550c7dc3U, 0x72be5d74U, 0x80deb1feU, 0x9bdc06a7U,    0xc19bf174U, 0xe49b69c1U, 0xefbe4786U, 0x0fc19dc6U, 0x240ca1ccU,    0x2de92c6fU, 0x4a7484aaU, 0x5cb0a9dcU, 0x76f988daU, 0x983e5152U,    0xa831c66dU, 0xb00327c8U, 0xbf597fc7U, 0xc6e00bf3U, 0xd5a79147U,    0x06ca6351U, 0x14292967U, 0x27b70a85U, 0x2e1b2138U, 0x4d2c6dfcU,    0x53380d13U, 0x650a7354U, 0x766a0abbU, 0x81c2c92eU, 0x92722c85U,    0xa2bfe8a1U, 0xa81a664bU, 0xc24b8b70U, 0xc76c51a3U, 0xd192e819U,    0xd6990624U, 0xf40e3585U, 0x106aa070U, 0x19a4c116U, 0x1e376c08U,    0x2748774cU, 0x34b0bcb5U, 0x391c0cb3U, 0x4ed8aa4aU, 0x5b9cca4fU,    0x682e6ff3U, 0x748f82eeU, 0x78a5636fU, 0x84c87814U, 0x8cc70208U,    0x90befffaU, 0xa4506cebU, 0xbef9a3f7U, 0xc67178f2UL};/* Various logical functions */#define Ch(x,y,z)    ((x & y) ^ (~x & z))#define Maj(x,y,z)  ((x & y) ^ (x & z) ^ (y & z))#define S(x, n)        (((x)>>((n)&31))|((x)<<(32-((n)&31))))#define R(x, n)        ((x)>>(n))#define Sigma0(x)    (S(x, 2) ^ S(x, 13) ^ S(x, 22))#define Sigma1(x)    (S(x, 6) ^ S(x, 11) ^ S(x, 25))#define Gamma0(x)    (S(x, 7) ^ S(x, 18) ^ R(x, 3))#define Gamma1(x)    (S(x, 17) ^ S(x, 19) ^ R(x, 10))/* compress 512-bits */static void sha_compress(sha_state * md){    unsigned int S[8], W[64], t0, t1;    int i;    /* copy state into S */    for (i = 0; i < 8; i++)        S[i] = md->state[i];    /* copy the state into 512-bits into W[0..15] */    for (i = 0; i < 16; i++)        W[i] = (((unsigned int) md->buf[(4 * i) + 0]) << 24) |            (((unsigned int) md->buf[(4 * i) + 1]) << 16) |            (((unsigned int) md->buf[(4 * i) + 2]) << 8) |            (((unsigned int) md->buf[(4 * i) + 3]));    /* fill W[16..63] */    for (i = 16; i < 64; i++)        W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) + W[i - 16];    /* Compress */    for (i = 0; i < 64; i++) {        t0 = S[7] + Sigma1(S[4]) + Ch(S[4], S[5], S[6]) + K[i] + W[i];        t1 = Sigma0(S[0]) + Maj(S[0], S[1], S[2]);        S[7] = S[6];        S[6] = S[5];        S[5] = S[4];        S[4] = S[3] + t0;        S[3] = S[2];        S[2] = S[1];        S[1] = S[0];        S[0] = t0 + t1;    }    /* feedback */    for (i = 0; i < 8; i++)        md->state[i] += S[i];}/* init the SHA state */void sha_init(sha_state * md){    md->curlen = md->length = 0;    md->state[0] = 0x6A09E667U;    md->state[1] = 0xBB67AE85U;    md->state[2] = 0x3C6EF372U;    md->state[3] = 0xA54FF53AU;    md->state[4] = 0x510E527FU;    md->state[5] = 0x9B05688CU;    md->state[6] = 0x1F83D9ABU;    md->state[7] = 0x5BE0CD19U;}void sha_process(sha_state * md, unsigned char *buf, int len){    while (len--) {        /* copy byte */        md->buf[md->curlen++] = *buf++;        /* is 64 bytes full? */        if (md->curlen == 64) {            sha_compress(md);            md->length += 512;            md->curlen = 0;        }    }}void sha_done(sha_state * md, unsigned char *hash){    int i;    /* increase the length of the message */    md->length += md->curlen * 8;    /* append the '1' bit */    md->buf[md->curlen++] = 0x80;    /* if the length is currenlly above 56 bytes we append zeros then compress.    Then we can fall back to padding zeros and length encoding like normal. */    if (md->curlen >= 56) {        for (; md->curlen < 64;)            md->buf[md->curlen++] = 0;        sha_compress(md);        md->curlen = 0;    }    /* pad upto 56 bytes of zeroes */    for (; md->curlen < 56;)        md->buf[md->curlen++] = 0;    /* since all messages are under 2^32 bits we mark the top bits zero */    for (i = 56; i < 60; i++)        md->buf[i] = 0;    /* append length */    for (i = 60; i < 64; i++)        md->buf[i] = (md->length >> ((63 - i) * 8)) & 255;    sha_compress(md);    /* copy output */    for (i = 0; i < 32; i++)        hash[i] = (md->state[i >> 2] >> (((3 - i) & 3) << 3)) & 255;}// sha-256 a block of memoryvoid SHA256_memory(unsigned char *buf, int len, unsigned char *hash){    sha_state md;    sha_init(&md);    sha_process(&md, buf, len);    sha_done(&md, hash);    memset(&md, 0, sizeof(md));}// sha-256 a file, return 1 if okint sha_file(unsigned char *filename, unsigned char *hash){    unsigned char buf[512];    int i;    FILE *in;    sha_state md;    sha_init(&md);    in = fopen(filename, "rb");    if (!in)        return 0;    do {        i = fread(buf, 1, 512, in);        sha_process(&md, buf, i);    }    while (i == 512);    sha_done(&md, hash);    fclose(in);    return 1;}