// SHA-256. Adapted from https://github.com/kalven/sha-2, which was adapted
// from LibTomCrypt. This code is Public Domain.

#if !defined(CONF_OPENSSL)

#include "hash_ctxt.h"

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

typedef uint32_t u32;
typedef uint64_t u64;
typedef SHA256_CTX sha256_state;

static const u32 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};

static u32 minimum(u32 x, u32 y)
{
	return x < y ? x : y;
}

static u32 load32(const unsigned char *y)
{
	return ((u32)y[0] << 24) | ((u32)y[1] << 16) | ((u32)y[2] << 8) | ((u32)y[3] << 0);
}

static void store64(u64 x, unsigned char *y)
{
	int i;
	for(i = 0; i != 8; ++i)
		y[i] = (x >> ((7 - i) * 8)) & 255;
}

static void store32(u32 x, unsigned char *y)
{
	int i;
	for(i = 0; i != 4; ++i)
		y[i] = (x >> ((3 - i) * 8)) & 255;
}

static u32 Ch(u32 x, u32 y, u32 z) { return z ^ (x & (y ^ z)); }
static u32 Maj(u32 x, u32 y, u32 z) { return ((x | y) & z) | (x & y); }
static u32 Rot(u32 x, u32 n) { return (x >> (n & 31)) | (x << (32 - (n & 31))); }
static u32 Sh(u32 x, u32 n) { return x >> n; }
static u32 Sigma0(u32 x) { return Rot(x, 2) ^ Rot(x, 13) ^ Rot(x, 22); }
static u32 Sigma1(u32 x) { return Rot(x, 6) ^ Rot(x, 11) ^ Rot(x, 25); }
static u32 Gamma0(u32 x) { return Rot(x, 7) ^ Rot(x, 18) ^ Sh(x, 3); }
static u32 Gamma1(u32 x) { return Rot(x, 17) ^ Rot(x, 19) ^ Sh(x, 10); }

static void sha_compress(sha256_state *md, const unsigned char *buf)
{
	u32 S[8], W[64], t0, t1, t;
	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] = load32(buf + (4 * i));

	// 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
#define RND(a, b, c, d, e, f, g, h, i) \
	{ \
		t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[i]; \
		t1 = Sigma0(a) + Maj(a, b, c); \
		d += t0; \
		h = t0 + t1; \
	}

	for(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;
	}

	// Feedback
	for(i = 0; i < 8; i++)
		md->state[i] = md->state[i] + S[i];
}

// Public interface

static void sha_init(sha256_state *md)
{
	md->curlen = 0;
	md->length = 0;
	md->state[0] = 0x6A09E667UL;
	md->state[1] = 0xBB67AE85UL;
	md->state[2] = 0x3C6EF372UL;
	md->state[3] = 0xA54FF53AUL;
	md->state[4] = 0x510E527FUL;
	md->state[5] = 0x9B05688CUL;
	md->state[6] = 0x1F83D9ABUL;
	md->state[7] = 0x5BE0CD19UL;
}

static void sha_process(sha256_state *md, const void *src, u32 inlen)
{
	const u32 block_size = 64;
	const unsigned char *in = (const unsigned char *)src;

	while(inlen > 0)
	{
		if(md->curlen == 0 && inlen >= block_size)
		{
			sha_compress(md, in);
			md->length += block_size * 8;
			in += block_size;
			inlen -= block_size;
		}
		else
		{
			u32 n = minimum(inlen, (block_size - md->curlen));
			memcpy(md->buf + md->curlen, in, n);
			md->curlen += n;
			in += n;
			inlen -= n;

			if(md->curlen == block_size)
			{
				sha_compress(md, md->buf);
				md->length += 8 * block_size;
				md->curlen = 0;
			}
		}
	}
}

static void sha_done(sha256_state *md, void *out)
{
	int i;

	// Increase the length of the message
	md->length += md->curlen * 8;

	// Append the '1' bit
	md->buf[md->curlen++] = (unsigned char)0x80;

	// If the length is currently 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)
	{
		while(md->curlen < 64)
			md->buf[md->curlen++] = 0;
		sha_compress(md, md->buf);
		md->curlen = 0;
	}

	// Pad up to 56 bytes of zeroes
	while(md->curlen < 56)
		md->buf[md->curlen++] = 0;

	// Store length
	store64(md->length, md->buf + 56);
	sha_compress(md, md->buf);

	// Copy output
	for(i = 0; i < 8; i++)
		store32(md->state[i], (unsigned char *)out + (4 * i));
}

void sha256_init(SHA256_CTX *ctxt)
{
	sha_init(ctxt);
}

void sha256_update(SHA256_CTX *ctxt, const void *data, size_t data_len)
{
	sha_process(ctxt, data, data_len);
}

SHA256_DIGEST sha256_finish(SHA256_CTX *ctxt)
{
	SHA256_DIGEST result;
	sha_done(ctxt, result.data);
	return result;
}

#endif