#include <memory.h>
#include "sha256.h"

const static uint32_t SHA256K[64] = {
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 
    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

uint32_t sha256_rr(uint32_t a, int c) {
    return ((a&((1<<c)-1))<<(32-c)) | (a>>c); }

void sha256_be(uint8_t *w) {
    int i;
    for (i=0; i<64; i+=4) {
        uint32_t tmp = 0;
        *(uint32_t*)(w+i) = w[i+3] | w[i+2]<<8 | w[i+1]<<16 | w[i]<<24;
    }
}

void sha256_inner( uint32_t *H, uint32_t *w ) {
        
    uint32_t i,
        a = H[0], b = H[1], c = H[2], d = H[3],
        e = H[4], f = H[5], g = H[6], h = H[7];
   
    sha256_be((uint8_t*)w);

    for (i=16;i<64;i++) {
        uint32_t s0,s1;
        s0 = sha256_rr(w[i - 15],  7) ^ sha256_rr(w[i - 15], 18) ^ (w[i - 15] >>  3);
        s1 = sha256_rr(w[i -  2], 17) ^ sha256_rr(w[i -  2], 19) ^ (w[i -  2] >> 10);
        w[i] = w[i-16] + s0 + w[i-7] + s1;
    }

    for (i=0;i<64;i++) {
        uint32_t s0,ma,t2,s1,ch,t1;
        s0 = sha256_rr(a,2) ^ sha256_rr(a,13) ^ sha256_rr(a,22);
        ma = (a & b) ^ (a & c) ^ (b & c);
        t2 = s0 + ma;
        s1 = sha256_rr(e,6) ^ sha256_rr(e,11) ^ sha256_rr(e,25);
        ch = (e & f) ^ ((~e) & g);
        t1 = h + s1 + ch + SHA256K[i] + w[i];
        h=g,g=f,f=e,e=d+t1,d=c,c=b,b=a,a=t1+t2;
    }

    H[0] += a; H[1] += b; H[2] += c; H[3] += d;
    H[4] += e; H[5] += f; H[6] += g; H[7] += h;
}


uint32_t *sha256( uint8_t *hash, uint8_t *buffer, int length ) {

    int i,restlength;
    uint64_t hashlen = length * ((uint64_t)8);
    uint8_t w[256];

    uint32_t H[8] = {
        0x6a09e667, 0xbb67ae85, 
        0x3c6ef372, 0xa54ff53a, 
        0x510e527f, 0x9b05688c, 
        0x1f83d9ab, 0x5be0cd19 };

    for (i=0; i<length-64; i+=64) {
        memcpy(w,buffer+i,64);
        sha256_inner(H,(uint32_t*)w);
    }

    restlength = length - i;
    memset(w,0,64);
    memcpy(w,buffer+i,restlength);
    w[restlength++] = 0x80;

    if (restlength > 56) {
        sha256_inner(H,(uint32_t*)w);
        memset(w,0,64);
    }

    w[56] = (uint8_t) ((hashlen >> 0x38) & 0xFF);
    w[57] = (uint8_t) ((hashlen >> 0x30) & 0xFF);
    w[58] = (uint8_t) ((hashlen >> 0x28) & 0xFF);
    w[59] = (uint8_t) ((hashlen >> 0x20) & 0xFF);
    w[60] = (uint8_t) ((hashlen >> 0x18) & 0xFF);
    w[61] = (uint8_t) ((hashlen >> 0x10) & 0xFF);
    w[62] = (uint8_t) ((hashlen >> 0x08) & 0xFF);
    w[63] = (uint8_t) ((hashlen        ) & 0xFF);

    sha256_inner(H,(uint32_t*)w);
    return memcpy(hash, H, 32);
}