/*
lonesha256.h - Portable, endian-proof, single-file, single-function sha256 implementation, originally based on LibTomCrypt

To the extent possible under law, the author(s) have dedicated all copyright and related and neighboring
rights to this software to the public domain worldwide. This software is distributed without any warranty.
You should have received a copy of the CC0 Public Domain Dedication along with this software.
If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
*/

/*
lonesha256 supports the following three configurations:
#define LONESHA256_EXTERN
    Default, should be used when using lonesha256 in multiple compilation units within the same project.
#define LONESHA256_IMPLEMENTATION
    Must be defined in exactly one source file within a project for lonesha256 to be found by the linker.
#define LONESHA256_STATIC
    Defines the lonesha256() function as static, useful if lonesha256 is only used in a single compilation unit.

lonesha256 function:
(static|extern) int lonesha256 (unsigned char out[32], const unsigned char* in, size_t len)
    writes the sha256 hash of the first "len" bytes in buffer "in" to buffer "out"
    returns 0 on success, may return non-zero in future versions to indicate error
*/

//header section
#ifndef LONESHA256_H
#define LONESHA256_H

//process configuration
#ifdef LONESHA256_STATIC
    #define LONESHA256_IMPLEMENTATION
    #define LSHA256DEF static
#else //LONESHA256_EXTERN
    #define LSHA256DEF extern
#endif

//includes
#include <stddef.h> //size_t

//lonesha256 declaration
LSHA256DEF int lonesha256(unsigned char[32], const unsigned char*, size_t);

#endif //LONESHA256_H

//implementation section
#ifdef LONESHA256_IMPLEMENTATION
#undef LONESHA256_IMPLEMENTATION

//macros
#define S(x, n) (((((uint32_t)(x)&0xFFFFFFFFUL)>>(uint32_t)((n)&31))|((uint32_t)(x)<<(uint32_t)((32-((n)&31))&31)))&0xFFFFFFFFUL)
#define R(x, n) (((x)&0xFFFFFFFFUL)>>(n))
#define Gamma0(x) (S(x, 7) ^ S(x, 18) ^ R(x, 3))
#define Gamma1(x) (S(x, 17) ^ S(x, 19) ^ R(x, 10))
#define RND(a,b,c,d,e,f,g,h,i) \
    t0 = h + (S(e, 6) ^ S(e, 11) ^ S(e, 25)) + (g ^ (e & (f ^ g))) + K[i] + W[i]; \
    t1 = (S(a, 2) ^ S(a, 13) ^ S(a, 22)) + (((a | b) & c) | (a & b)); \
    d += t0; \
    h  = t0 + t1;
#define STORE32H(x, y) \
    (y)[0] = (unsigned char)(((x)>>24)&255); (y)[1] = (unsigned char)(((x)>>16)&255); \
    (y)[2] = (unsigned char)(((x)>>8)&255); (y)[3] = (unsigned char)((x)&255);
#define LOAD32H(x, y) \
    x = ((uint32_t)((y)[0]&255)<<24)|((uint32_t)((y)[1]&255)<<16)|((uint32_t)((y)[2]&255)<<8)|((uint32_t)((y)[3]&255));
#define STORE64H(x, y) \
    (y)[0] = (unsigned char)(((x)>>56)&255); (y)[1] = (unsigned char)(((x)>>48)&255); \
    (y)[2] = (unsigned char)(((x)>>40)&255); (y)[3] = (unsigned char)(((x)>>32)&255); \
    (y)[4] = (unsigned char)(((x)>>24)&255); (y)[5] = (unsigned char)(((x)>>16)&255); \
    (y)[6] = (unsigned char)(((x)>>8)&255); (y)[7] = (unsigned char)((x)&255);
#define SHA256_COMPRESS(buff) \
    for (int i = 0; i < 8; i++) S[i] = sha256_state[i]; \
    for (int i = 0; i < 16; i++) LOAD32H(W[i], buff + (4*i)); \
    for (int i = 16; i < 64; i++) W[i] = Gamma1(W[i-2]) + W[i-7] + Gamma0(W[i-15]) + W[i-16]; \
    for (int i = 0; i < 64; i++) { \
        RND(S[0],S[1],S[2],S[3],S[4],S[5],S[6],S[7],i); \
        t = S[7]; S[7] = S[6]; S[6] = S[5]; S[5] = S[4]; \
        S[4] = S[3]; S[3] = S[2]; S[2] = S[1]; S[1] = S[0]; S[0] = t; \
    } \
    for (int i = 0; i < 8; i++) sha256_state[i] = sha256_state[i] + S[i];

//includes
#include <stdint.h> //uint32_t, uint64_t
#include <string.h> //memcpy

//lonesha256 function
LSHA256DEF int lonesha256 (unsigned char out[32], const unsigned char* in, size_t len) {
    //writes the sha256 hash of the first "len" bytes in buffer "in" to buffer "out"
    //returns 0 on success, may return non-zero in future versions to indicate error
    const uint32_t K[64] = {
        0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL,
        0x3956c25bUL, 0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL,
        0xd807aa98UL, 0x12835b01UL, 0x243185beUL, 0x550c7dc3UL,
        0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL, 0xc19bf174UL,
        0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL,
        0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL,
        0x983e5152UL, 0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL,
        0xc6e00bf3UL, 0xd5a79147UL, 0x06ca6351UL, 0x14292967UL,
        0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL, 0x53380d13UL,
        0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
        0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL,
        0xd192e819UL, 0xd6990624UL, 0xf40e3585UL, 0x106aa070UL,
        0x19a4c116UL, 0x1e376c08UL, 0x2748774cUL, 0x34b0bcb5UL,
        0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL, 0x682e6ff3UL,
        0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
        0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL
    };
    uint64_t sha256_length = 0;
    uint32_t sha256_state[8] = {
        0x6A09E667UL, 0xBB67AE85UL, 0x3C6EF372UL, 0xA54FF53AUL,
        0x510E527FUL, 0x9B05688CUL, 0x1F83D9ABUL, 0x5BE0CD19UL
    }, S[8], W[64], t0, t1, t;
    unsigned char sha256_buf[64];
    //process input in 64 byte chunks
    while (len >= 64) {
       SHA256_COMPRESS(in);
       sha256_length += 64 * 8;
       in += 64;
       len -= 64;
    }
    //copy remaining bytes into sha256_buf
    memcpy(sha256_buf, in, len);
    //finish up (len now number of bytes in sha256_buf)
    sha256_length += len * 8;
    sha256_buf[len++] = 0x80;
    //pad then compress if length is above 56 bytes
    if (len > 56) {
        while (len < 64) sha256_buf[len++] = 0;
        SHA256_COMPRESS(sha256_buf);
        len = 0;
    }
    //pad up to 56 bytes
    while (len < 56) sha256_buf[len++] = 0;
    //store length and compress
    STORE64H(sha256_length, sha256_buf + 56);
    SHA256_COMPRESS(sha256_buf);
    //copy output
    for (int i = 0; i < 8; i++) {
        STORE32H(sha256_state[i], out + 4*i);
    }
    //return
    return 0;
}

#endif //LONESHA256_IMPLEMENTATION
