/*
Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.
*/

/*
 * Implementation of the Secure Hashing Algorithm (SHA-256)
 *
 * Generates a 256 bit message digest. It should be impossible to come
 * come up with two messages that hash to the same value ("collision free").
 *
 * For use with byte-oriented messages only. Could/Should be speeded
 * up by unwinding loops in HASH_transform(), and assembly patches.
 */
/* SU=m, m is Stack Usage */

#include "amcl.h"

#define H0 0x6A09E667L
#define H1 0xBB67AE85L
#define H2 0x3C6EF372L
#define H3 0xA54FF53AL
#define H4 0x510E527FL
#define H5 0x9B05688CL
#define H6 0x1F83D9ABL
#define H7 0x5BE0CD19L

static const unsign32 K[64]={
0x428a2f98L,0x71374491L,0xb5c0fbcfL,0xe9b5dba5L,0x3956c25bL,0x59f111f1L,0x923f82a4L,0xab1c5ed5L,
0xd807aa98L,0x12835b01L,0x243185beL,0x550c7dc3L,0x72be5d74L,0x80deb1feL,0x9bdc06a7L,0xc19bf174L,
0xe49b69c1L,0xefbe4786L,0x0fc19dc6L,0x240ca1ccL,0x2de92c6fL,0x4a7484aaL,0x5cb0a9dcL,0x76f988daL,
0x983e5152L,0xa831c66dL,0xb00327c8L,0xbf597fc7L,0xc6e00bf3L,0xd5a79147L,0x06ca6351L,0x14292967L,
0x27b70a85L,0x2e1b2138L,0x4d2c6dfcL,0x53380d13L,0x650a7354L,0x766a0abbL,0x81c2c92eL,0x92722c85L,
0xa2bfe8a1L,0xa81a664bL,0xc24b8b70L,0xc76c51a3L,0xd192e819L,0xd6990624L,0xf40e3585L,0x106aa070L,
0x19a4c116L,0x1e376c08L,0x2748774cL,0x34b0bcb5L,0x391c0cb3L,0x4ed8aa4aL,0x5b9cca4fL,0x682e6ff3L,
0x748f82eeL,0x78a5636fL,0x84c87814L,0x8cc70208L,0x90befffaL,0xa4506cebL,0xbef9a3f7L,0xc67178f2L};

#define PAD  0x80
#define ZERO 0

/* functions */

#define S(n,x) (((x)>>n) | ((x)<<(32-n)))
#define R(n,x) ((x)>>n)

#define Ch(x,y,z)  ((x&y)^(~(x)&z))
#define Maj(x,y,z) ((x&y)^(x&z)^(y&z))
#define Sig0(x)    (S(2,x)^S(13,x)^S(22,x))
#define Sig1(x)    (S(6,x)^S(11,x)^S(25,x))
#define theta0(x)  (S(7,x)^S(18,x)^R(3,x))
#define theta1(x)  (S(17,x)^S(19,x)^R(10,x))

/* SU= 72 */
static void HASH_transform(hash *sh)
{ /* basic transformation step */
    unsign32 a,b,c,d,e,f,g,h,t1,t2;
    int j;
    for (j=16;j<64;j++)
        sh->w[j]=theta1(sh->w[j-2])+sh->w[j-7]+theta0(sh->w[j-15])+sh->w[j-16];

    a=sh->h[0]; b=sh->h[1]; c=sh->h[2]; d=sh->h[3];
    e=sh->h[4]; f=sh->h[5]; g=sh->h[6]; h=sh->h[7];

    for (j=0;j<64;j++)
    { /* 64 times - mush it up */
        t1=h+Sig1(e)+Ch(e,f,g)+K[j]+sh->w[j];
        t2=Sig0(a)+Maj(a,b,c);
        h=g; g=f; f=e;
        e=d+t1;
        d=c;
        c=b;
        b=a;
        a=t1+t2;
    }

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

/* Initialise Hash function */
void HASH_init(hash *sh)
{ /* re-initialise */
    int i;
    for (i=0;i<64;i++) sh->w[i]=0L;
    sh->length[0]=sh->length[1]=0L;
    sh->h[0]=H0;
    sh->h[1]=H1;
    sh->h[2]=H2;
    sh->h[3]=H3;
    sh->h[4]=H4;
    sh->h[5]=H5;
    sh->h[6]=H6;
    sh->h[7]=H7;
}

/* process a single byte */
void HASH_process(hash *sh,int byte)
{ /* process the next message byte */
    int cnt;
//printf("byt= %x\n",byte);
    cnt=(int)((sh->length[0]/32)%16);

    sh->w[cnt]<<=8;
    sh->w[cnt]|=(unsign32)(byte&0xFF);

    sh->length[0]+=8;
    if (sh->length[0]==0L) { sh->length[1]++; sh->length[0]=0L; }
    if ((sh->length[0]%512)==0) HASH_transform(sh);
}

/* SU= 24 */
/* Generate 32-byte Hash */
void HASH_hash(hash *sh,char digest[32])
{ /* pad message and finish - supply digest */
    int i;
    unsign32 len0,len1;
    len0=sh->length[0];
    len1=sh->length[1];
    HASH_process(sh,PAD);
    while ((sh->length[0]%512)!=448) HASH_process(sh,ZERO);
    sh->w[14]=len1;
    sh->w[15]=len0;
    HASH_transform(sh);
    for (i=0;i<32;i++)
    { /* convert to bytes */
        digest[i]=(char)((sh->h[i/4]>>(8*(3-i%4))) & 0xffL);
    }
    HASH_init(sh);
}

/* test program: should produce digest  */

//248d6a61 d20638b8 e5c02693 0c3e6039 a33ce459 64ff2167 f6ecedd4 19db06c1

/*
#include <stdio.h>
#include "amcl.h"

char test[]="abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq";

int main()
{
    char digest[32];
    int i;
    hash sh;
    HASH_init(&sh);
    for (i=0;test[i]!=0;i++)
		HASH_process(&sh,test[i]);

    HASH_hash(&sh,digest);
    for (i=0;i<32;i++) printf("%02x",(unsigned char)digest[i]);
    printf("\n");
    return 0;
}

*/