/*

 * Copyright (C) the libgit2 contributors. All rights reserved.

 *

 * This file is part of libgit2, distributed under the GNU GPL v2 with

 * a Linking Exception. For full terms see the included COPYING file.

 */

#include "common.h"

#include "hash.h"

#include "hash/hash_generic.h"

#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))

/*

 * Force usage of rol or ror by selecting the one with the smaller constant.

 * It _can_ generate slightly smaller code (a constant of 1 is special), but

 * perhaps more importantly it's possibly faster on any uarch that does a

 * rotate with a loop.

 */

#define SHA_ASM(op, x, n) (__extension__ ({ unsigned int __res; __asm__(op " %1,%0":"=r" (__res):"i" (n), "0" (x)); __res; }))

#define SHA_ROL(x,n)	SHA_ASM("rol", x, n)

#define SHA_ROR(x,n)	SHA_ASM("ror", x, n)

#else

#define SHA_ROT(X,l,r)	(((X) << (l)) | ((X) >> (r)))

#define SHA_ROL(X,n)	SHA_ROT(X,n,32-(n))

#define SHA_ROR(X,n)	SHA_ROT(X,32-(n),n)

#endif

/*

 * If you have 32 registers or more, the compiler can (and should)

 * try to change the array[] accesses into registers. However, on

 * machines with less than ~25 registers, that won't really work,

 * and at least gcc will make an unholy mess of it.

 *

 * So to avoid that mess which just slows things down, we force

 * the stores to memory to actually happen (we might be better off

 * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as

 * suggested by Artur Skawina - that will also make gcc unable to

 * try to do the silly "optimize away loads" part because it won't

 * see what the value will be).

 *

 * Ben Herrenschmidt reports that on PPC, the C version comes close

 * to the optimized asm with this (ie on PPC you don't want that

 * 'volatile', since there are lots of registers).

 *

 * On ARM we get the best code generation by forcing a full memory barrier

 * between each SHA_ROUND, otherwise gcc happily get wild with spilling and

 * the stack frame size simply explode and performance goes down the drain.

 */

#if defined(__i386__) || defined(__x86_64__)

 #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))

#elif defined(__GNUC__) && defined(__arm__)

 #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)

#else

 #define setW(x, val) (W(x) = (val))

#endif

/*

 * Performance might be improved if the CPU architecture is OK with

 * unaligned 32-bit loads and a fast ntohl() is available.

 * Otherwise fall back to byte loads and shifts which is portable,

 * and is faster on architectures with memory alignment issues.

 */

#if defined(__i386__) || defined(__x86_64__) || \

	defined(_M_IX86) || defined(_M_X64) || \

	defined(__ppc__) || defined(__ppc64__) || \

	defined(__powerpc__) || defined(__powerpc64__) || \

	defined(__s390__) || defined(__s390x__)

#define get_be32(p)	ntohl(*(const unsigned int *)(p))

#define put_be32(p, v)	do { *(unsigned int *)(p) = htonl(v); } while (0)

#else

#define get_be32(p)	( \

	(*((const unsigned char *)(p) + 0) << 24) | \

	(*((const unsigned char *)(p) + 1) << 16) | \

	(*((const unsigned char *)(p) + 2) << 8) | \

	(*((const unsigned char *)(p) + 3) << 0) )

#define put_be32(p, v)	do { \

	unsigned int __v = (v); \

	*((unsigned char *)(p) + 0) = __v >> 24; \

	*((unsigned char *)(p) + 1) = __v >> 16; \

	*((unsigned char *)(p) + 2) = __v >> 8; \

	*((unsigned char *)(p) + 3) = __v >> 0; } while (0)

#endif

/* This "rolls" over the 512-bit array */

#define W(x) (array[(x)&15])

/*

 * Where do we get the source from? The first 16 iterations get it from

 * the input data, the next mix it from the 512-bit array.

 */

#define SHA_SRC(t) get_be32(data + t)

#define SHA_MIX(t) SHA_ROL(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1)

#define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \

	unsigned int TEMP = input(t); setW(t, TEMP); \

	E += TEMP + SHA_ROL(A,5) + (fn) + (constant); \

	B = SHA_ROR(B, 2); } while (0)

#define T_0_15(t, A, B, C, D, E) SHA_ROUND(t, SHA_SRC, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E )

#define T_16_19(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E )

#define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0x6ed9eba1, A, B, C, D, E )

#define T_40_59(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, ((B&C)+(D&(B^C))) , 0x8f1bbcdc, A, B, C, D, E )

#define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0xca62c1d6, A, B, C, D, E )

static void hash__block(git_hash_ctx *ctx, const unsigned int *data)

{

	unsigned int A,B,C,D,E;

	unsigned int array[16];

	A = ctx->H[0];

	B = ctx->H[1];

	C = ctx->H[2];

	D = ctx->H[3];

	E = ctx->H[4];

	/* Round 1 - iterations 0-16 take their input from 'data' */

	T_0_15( 0, A, B, C, D, E);

	T_0_15( 1, E, A, B, C, D);

	T_0_15( 2, D, E, A, B, C);

	T_0_15( 3, C, D, E, A, B);

	T_0_15( 4, B, C, D, E, A);

	T_0_15( 5, A, B, C, D, E);

	T_0_15( 6, E, A, B, C, D);

	T_0_15( 7, D, E, A, B, C);

	T_0_15( 8, C, D, E, A, B);

	T_0_15( 9, B, C, D, E, A);

	T_0_15(10, A, B, C, D, E);

	T_0_15(11, E, A, B, C, D);

	T_0_15(12, D, E, A, B, C);

	T_0_15(13, C, D, E, A, B);

	T_0_15(14, B, C, D, E, A);

	T_0_15(15, A, B, C, D, E);

	/* Round 1 - tail. Input from 512-bit mixing array */

	T_16_19(16, E, A, B, C, D);

	T_16_19(17, D, E, A, B, C);

	T_16_19(18, C, D, E, A, B);

	T_16_19(19, B, C, D, E, A);

	/* Round 2 */

	T_20_39(20, A, B, C, D, E);

	T_20_39(21, E, A, B, C, D);

	T_20_39(22, D, E, A, B, C);

	T_20_39(23, C, D, E, A, B);

	T_20_39(24, B, C, D, E, A);

	T_20_39(25, A, B, C, D, E);

	T_20_39(26, E, A, B, C, D);

	T_20_39(27, D, E, A, B, C);

	T_20_39(28, C, D, E, A, B);

	T_20_39(29, B, C, D, E, A);

	T_20_39(30, A, B, C, D, E);

	T_20_39(31, E, A, B, C, D);

	T_20_39(32, D, E, A, B, C);

	T_20_39(33, C, D, E, A, B);

	T_20_39(34, B, C, D, E, A);

	T_20_39(35, A, B, C, D, E);

	T_20_39(36, E, A, B, C, D);

	T_20_39(37, D, E, A, B, C);

	T_20_39(38, C, D, E, A, B);

	T_20_39(39, B, C, D, E, A);

	/* Round 3 */

	T_40_59(40, A, B, C, D, E);

	T_40_59(41, E, A, B, C, D);

	T_40_59(42, D, E, A, B, C);

	T_40_59(43, C, D, E, A, B);

	T_40_59(44, B, C, D, E, A);

	T_40_59(45, A, B, C, D, E);

	T_40_59(46, E, A, B, C, D);

	T_40_59(47, D, E, A, B, C);

	T_40_59(48, C, D, E, A, B);

	T_40_59(49, B, C, D, E, A);

	T_40_59(50, A, B, C, D, E);

	T_40_59(51, E, A, B, C, D);

	T_40_59(52, D, E, A, B, C);

	T_40_59(53, C, D, E, A, B);

	T_40_59(54, B, C, D, E, A);

	T_40_59(55, A, B, C, D, E);

	T_40_59(56, E, A, B, C, D);

	T_40_59(57, D, E, A, B, C);

	T_40_59(58, C, D, E, A, B);

	T_40_59(59, B, C, D, E, A);

	/* Round 4 */

	T_60_79(60, A, B, C, D, E);

	T_60_79(61, E, A, B, C, D);

	T_60_79(62, D, E, A, B, C);

	T_60_79(63, C, D, E, A, B);

	T_60_79(64, B, C, D, E, A);

	T_60_79(65, A, B, C, D, E);

	T_60_79(66, E, A, B, C, D);

	T_60_79(67, D, E, A, B, C);

	T_60_79(68, C, D, E, A, B);

	T_60_79(69, B, C, D, E, A);

	T_60_79(70, A, B, C, D, E);

	T_60_79(71, E, A, B, C, D);

	T_60_79(72, D, E, A, B, C);

	T_60_79(73, C, D, E, A, B);

	T_60_79(74, B, C, D, E, A);

	T_60_79(75, A, B, C, D, E);

	T_60_79(76, E, A, B, C, D);

	T_60_79(77, D, E, A, B, C);

	T_60_79(78, C, D, E, A, B);

	T_60_79(79, B, C, D, E, A);

	ctx->H[0] += A;

	ctx->H[1] += B;

	ctx->H[2] += C;

	ctx->H[3] += D;

	ctx->H[4] += E;

}

int git_hash_init(git_hash_ctx *ctx)

{

	ctx->size = 0;

	/* Initialize H with the magic constants (see FIPS180 for constants) */

	ctx->H[0] = 0x67452301;

	ctx->H[1] = 0xefcdab89;

	ctx->H[2] = 0x98badcfe;

	ctx->H[3] = 0x10325476;

	ctx->H[4] = 0xc3d2e1f0;

	return 0;

}

int git_hash_update(git_hash_ctx *ctx, const void *data, size_t len)

{

	unsigned int lenW = ctx->size & 63;

	ctx->size += len;

	/* Read the data into W and process blocks as they get full */

	if (lenW) {

		unsigned int left = 64 - lenW;

		if (len < left)

			left = (unsigned int)len;

		memcpy(lenW + (char *)ctx->W, data, left);

		lenW = (lenW + left) & 63;

		len -= left;

		data = ((const char *)data + left);

		if (lenW)

			return 0;

		hash__block(ctx, ctx->W);

	}

	while (len >= 64) {

		hash__block(ctx, data);

		data = ((const char *)data + 64);

		len -= 64;

	}

	if (len)

		memcpy(ctx->W, data, len);

	return 0;

}

int git_hash_final(git_oid *out, git_hash_ctx *ctx)

{

	static const unsigned char pad[64] = { 0x80 };

	unsigned int padlen[2];

	int i;

	/* Pad with a binary 1 (ie 0x80), then zeroes, then length */

	padlen[0] = htonl((uint32_t)(ctx->size >> 29));

	padlen[1] = htonl((uint32_t)(ctx->size << 3));

	i = ctx->size & 63;

	git_hash_update(ctx, pad, 1+ (63 & (55 - i)));

	git_hash_update(ctx, padlen, 8);

	/* Output hash */

	for (i = 0; i < 5; i++)

		put_be32(out->id + i*4, ctx->H[i]);

	return 0;

}