[sgt/puzzles] / random.c

/*
 * random.c: Internal random number generator, guaranteed to work
 * the same way on all platforms. Used when generating an initial
 * game state from a random game seed; required to ensure that game
 * seeds can be exchanged between versions of a puzzle compiled for
 * different platforms.
 * 
 * The generator is based on SHA-1. This is almost certainly
 * overkill, but I had the SHA-1 code kicking around and it was
 * easier to reuse it than to do anything else!
 */

#include <assert.h>
#include <string.h>
#include <stdio.h>

#include "puzzles.h"

/* ----------------------------------------------------------------------
 * Core SHA algorithm: processes 16-word blocks into a message digest.
 */

#define rol(x,y) ( ((x) << (y)) | (((uint32)x) >> (32-y)) )

static void SHA_Core_Init(uint32 h[5])
{
    h[0] = 0x67452301;
    h[1] = 0xefcdab89;
    h[2] = 0x98badcfe;
    h[3] = 0x10325476;
    h[4] = 0xc3d2e1f0;
}

static void SHATransform(uint32 * digest, uint32 * block)
{
    uint32 w[80];
    uint32 a, b, c, d, e;
    int t;

    for (t = 0; t < 16; t++)
	w[t] = block[t];

    for (t = 16; t < 80; t++) {
	uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
	w[t] = rol(tmp, 1);
    }

    a = digest[0];
    b = digest[1];
    c = digest[2];
    d = digest[3];
    e = digest[4];

    for (t = 0; t < 20; t++) {
	uint32 tmp =
	    rol(a, 5) + ((b & c) | (d & ~b)) + e + w[t] + 0x5a827999;
	e = d;
	d = c;
	c = rol(b, 30);
	b = a;
	a = tmp;
    }
    for (t = 20; t < 40; t++) {
	uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1;
	e = d;
	d = c;
	c = rol(b, 30);
	b = a;
	a = tmp;
    }
    for (t = 40; t < 60; t++) {
	uint32 tmp = rol(a,
			 5) + ((b & c) | (b & d) | (c & d)) + e + w[t] +
	    0x8f1bbcdc;
	e = d;
	d = c;
	c = rol(b, 30);
	b = a;
	a = tmp;
    }
    for (t = 60; t < 80; t++) {
	uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6;
	e = d;
	d = c;
	c = rol(b, 30);
	b = a;
	a = tmp;
    }

    digest[0] += a;
    digest[1] += b;
    digest[2] += c;
    digest[3] += d;
    digest[4] += e;
}

/* ----------------------------------------------------------------------
 * Outer SHA algorithm: take an arbitrary length byte string,
 * convert it into 16-word blocks with the prescribed padding at
 * the end, and pass those blocks to the core SHA algorithm.
 */

void SHA_Init(SHA_State * s)
{
    SHA_Core_Init(s->h);
    s->blkused = 0;
    s->lenhi = s->lenlo = 0;
}

void SHA_Bytes(SHA_State * s, void *p, int len)
{
    unsigned char *q = (unsigned char *) p;
    uint32 wordblock[16];
    uint32 lenw = len;
    int i;

    /*
     * Update the length field.
     */
    s->lenlo += lenw;
    s->lenhi += (s->lenlo < lenw);

    if (s->blkused && s->blkused + len < 64) {
	/*
	 * Trivial case: just add to the block.
	 */
	memcpy(s->block + s->blkused, q, len);
	s->blkused += len;
    } else {
	/*
	 * We must complete and process at least one block.
	 */
	while (s->blkused + len >= 64) {
	    memcpy(s->block + s->blkused, q, 64 - s->blkused);
	    q += 64 - s->blkused;
	    len -= 64 - s->blkused;
	    /* Now process the block. Gather bytes big-endian into words */
	    for (i = 0; i < 16; i++) {
		wordblock[i] =
		    (((uint32) s->block[i * 4 + 0]) << 24) |
		    (((uint32) s->block[i * 4 + 1]) << 16) |
		    (((uint32) s->block[i * 4 + 2]) << 8) |
		    (((uint32) s->block[i * 4 + 3]) << 0);
	    }
	    SHATransform(s->h, wordblock);
	    s->blkused = 0;
	}
	memcpy(s->block, q, len);
	s->blkused = len;
    }
}

void SHA_Final(SHA_State * s, unsigned char *output)
{
    int i;
    int pad;
    unsigned char c[64];
    uint32 lenhi, lenlo;

    if (s->blkused >= 56)
	pad = 56 + 64 - s->blkused;
    else
	pad = 56 - s->blkused;

    lenhi = (s->lenhi << 3) | (s->lenlo >> (32 - 3));
    lenlo = (s->lenlo << 3);

    memset(c, 0, pad);
    c[0] = 0x80;
    SHA_Bytes(s, &c, pad);

    c[0] = (unsigned char)((lenhi >> 24) & 0xFF);
    c[1] = (unsigned char)((lenhi >> 16) & 0xFF);
    c[2] = (unsigned char)((lenhi >> 8) & 0xFF);
    c[3] = (unsigned char)((lenhi >> 0) & 0xFF);
    c[4] = (unsigned char)((lenlo >> 24) & 0xFF);
    c[5] = (unsigned char)((lenlo >> 16) & 0xFF);
    c[6] = (unsigned char)((lenlo >> 8) & 0xFF);
    c[7] = (unsigned char)((lenlo >> 0) & 0xFF);

    SHA_Bytes(s, &c, 8);

    for (i = 0; i < 5; i++) {
	output[i * 4] = (unsigned char)((s->h[i] >> 24) & 0xFF);
	output[i * 4 + 1] = (unsigned char)((s->h[i] >> 16) & 0xFF);
	output[i * 4 + 2] = (unsigned char)((s->h[i] >> 8) & 0xFF);
	output[i * 4 + 3] = (unsigned char)((s->h[i]) & 0xFF);
    }
}

void SHA_Simple(void *p, int len, unsigned char *output)
{
    SHA_State s;

    SHA_Init(&s);
    SHA_Bytes(&s, p, len);
    SHA_Final(&s, output);
}

/* ----------------------------------------------------------------------
 * The random number generator.
 */

struct random_state {
    unsigned char seedbuf[40];
    unsigned char databuf[20];
    int pos;
};

random_state *random_init(char *seed, int len)
{
    random_state *state;

    state = snew(random_state);

    SHA_Simple(seed, len, state->seedbuf);
    SHA_Simple(state->seedbuf, 20, state->seedbuf + 20);
    SHA_Simple(state->seedbuf, 40, state->databuf);
    state->pos = 0;

    return state;
}

unsigned long random_bits(random_state *state, int bits)
{
    unsigned long ret = 0;
    int n;

    for (n = 0; n < bits; n += 8) {
	if (state->pos >= 20) {
	    int i;

	    for (i = 0; i < 20; i++) {
		if (state->seedbuf[i] != 0xFF) {
		    state->seedbuf[i]++;
		    break;
		} else
		    state->seedbuf[i] = 0;
	    }
	    SHA_Simple(state->seedbuf, 40, state->databuf);
	    state->pos = 0;
	}
	ret = (ret << 8) | state->databuf[state->pos++];
    }

    /*
     * `(1 << bits) - 1' is not good enough, since if bits==32 on a
     * 32-bit machine, behaviour is undefined and Intel has a nasty
     * habit of shifting left by zero instead. We'll shift by
     * bits-1 and then separately shift by one.
     */
    ret &= (1 << (bits-1)) * 2 - 1;
    return ret;
}

unsigned long random_upto(random_state *state, unsigned long limit)
{
    int bits = 0;
    unsigned long max, divisor, data;

    while ((limit >> bits) != 0)
	bits++;

    bits += 3;
    assert(bits < 32);

    max = 1L << bits;
    divisor = max / limit;
    max = limit * divisor;

    do {
	data = random_bits(state, bits);
    } while (data >= max);

    return data / divisor;
}

void random_free(random_state *state)
{
    sfree(state);
}

char *random_state_encode(random_state *state)
{
    char retbuf[256];
    int len = 0, i;

    for (i = 0; i < lenof(state->seedbuf); i++)
	len += sprintf(retbuf+len, "%02x", state->seedbuf[i]);
    for (i = 0; i < lenof(state->databuf); i++)
	len += sprintf(retbuf+len, "%02x", state->databuf[i]);
    len += sprintf(retbuf+len, "%02x", state->pos);

    return dupstr(retbuf);
}

random_state *random_state_decode(char *input)
{
    random_state *state;
    int pos, byte, digits;

    state = snew(random_state);

    memset(state->seedbuf, 0, sizeof(state->seedbuf));
    memset(state->databuf, 0, sizeof(state->databuf));
    state->pos = 0;

    byte = digits = 0;
    pos = 0;
    while (*input) {
	int v = *input++;

	if (v >= '0' && v <= '9')
	    v = v - '0';
	else if (v >= 'A' && v <= 'F')
	    v = v - 'A' + 10;
	else if (v >= 'a' && v <= 'f')
	    v = v - 'a' + 10;
	else
	    v = 0;

	byte = (byte << 4) | v;
	digits++;

	if (digits == 2) {
	    /*
	     * We have a byte. Put it somewhere.
	     */
	    if (pos < lenof(state->seedbuf))
		state->seedbuf[pos++] = byte;
	    else if (pos < lenof(state->seedbuf) + lenof(state->databuf))
		state->databuf[pos++ - lenof(state->seedbuf)] = byte;
	    else if (pos == lenof(state->seedbuf) + lenof(state->databuf) &&
		     byte <= lenof(state->databuf))
		state->pos = byte;
	    byte = digits = 0;
	}
    }

    return state;
}
Commit	Line	Data
720a8fb7	1	/*
	2	* random.c: Internal random number generator, guaranteed to work
	3	* the same way on all platforms. Used when generating an initial
	4	* game state from a random game seed; required to ensure that game
	5	* seeds can be exchanged between versions of a puzzle compiled for
	6	* different platforms.
	7	*
	8	* The generator is based on SHA-1. This is almost certainly
	9	* overkill, but I had the SHA-1 code kicking around and it was
	10	* easier to reuse it than to do anything else!
	11	*/
	12
	13	#include <assert.h>
2ef96bd6	14	#include <string.h>
c380832d	15	#include <stdio.h>
720a8fb7	16
	17	#include "puzzles.h"
	18
720a8fb7	19	/* ----------------------------------------------------------------------
	20	* Core SHA algorithm: processes 16-word blocks into a message digest.
	21	*/
	22
	23	#define rol(x,y) ( ((x) << (y)) \| (((uint32)x) >> (32-y)) )
	24
	25	static void SHA_Core_Init(uint32 h[5])
	26	{
	27	h[0] = 0x67452301;
	28	h[1] = 0xefcdab89;
	29	h[2] = 0x98badcfe;
	30	h[3] = 0x10325476;
	31	h[4] = 0xc3d2e1f0;
	32	}
	33
	34	static void SHATransform(uint32 * digest, uint32 * block)
	35	{
	36	uint32 w[80];
	37	uint32 a, b, c, d, e;
	38	int t;
	39
	40	for (t = 0; t < 16; t++)
	41	w[t] = block[t];
	42
	43	for (t = 16; t < 80; t++) {
	44	uint32 tmp = w[t - 3] ^ w[t - 8] ^ w[t - 14] ^ w[t - 16];
	45	w[t] = rol(tmp, 1);
	46	}
	47
	48	a = digest[0];
	49	b = digest[1];
	50	c = digest[2];
	51	d = digest[3];
	52	e = digest[4];
	53
	54	for (t = 0; t < 20; t++) {
	55	uint32 tmp =
	56	rol(a, 5) + ((b & c) \| (d & ~b)) + e + w[t] + 0x5a827999;
	57	e = d;
	58	d = c;
	59	c = rol(b, 30);
	60	b = a;
	61	a = tmp;
	62	}
	63	for (t = 20; t < 40; t++) {
	64	uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0x6ed9eba1;
	65	e = d;
	66	d = c;
	67	c = rol(b, 30);
	68	b = a;
	69	a = tmp;
	70	}
	71	for (t = 40; t < 60; t++) {
	72	uint32 tmp = rol(a,
	73	5) + ((b & c) \| (b & d) \| (c & d)) + e + w[t] +
	74	0x8f1bbcdc;
	75	e = d;
	76	d = c;
	77	c = rol(b, 30);
	78	b = a;
	79	a = tmp;
	80	}
	81	for (t = 60; t < 80; t++) {
	82	uint32 tmp = rol(a, 5) + (b ^ c ^ d) + e + w[t] + 0xca62c1d6;
83	e = d;
84	d = c;
85	c = rol(b, 30);
86	b = a;
87	a = tmp;
88	}
89
90	digest[0] += a;
91	digest[1] += b;
92	digest[2] += c;
93	digest[3] += d;
94	digest[4] += e;
95	}
96
97	/* ----------------------------------------------------------------------
98	* Outer SHA algorithm: take an arbitrary length byte string,
99	* convert it into 16-word blocks with the prescribed padding at
100	* the end, and pass those blocks to the core SHA algorithm.
101	*/
102
7959b517	103	void SHA_Init(SHA_State * s)
720a8fb7	104	{
	105	SHA_Core_Init(s->h);
	106	s->blkused = 0;
	107	s->lenhi = s->lenlo = 0;
	108	}
	109
7959b517	110	void SHA_Bytes(SHA_State * s, void *p, int len)
720a8fb7	111	{
	112	unsigned char q = (unsigned char ) p;
	113	uint32 wordblock[16];
	114	uint32 lenw = len;
	115	int i;
	116
	117	/*
	118	* Update the length field.
	119	*/
	120	s->lenlo += lenw;
	121	s->lenhi += (s->lenlo < lenw);
	122
	123	if (s->blkused && s->blkused + len < 64) {
	124	/*
	125	* Trivial case: just add to the block.
	126	*/
	127	memcpy(s->block + s->blkused, q, len);
	128	s->blkused += len;
	129	} else {
	130	/*
	131	* We must complete and process at least one block.
	132	*/
	133	while (s->blkused + len >= 64) {
	134	memcpy(s->block + s->blkused, q, 64 - s->blkused);
	135	q += 64 - s->blkused;
	136	len -= 64 - s->blkused;
	137	/* Now process the block. Gather bytes big-endian into words */
	138	for (i = 0; i < 16; i++) {
	139	wordblock[i] =
	140	(((uint32) s->block[i * 4 + 0]) << 24) \|
	141	(((uint32) s->block[i * 4 + 1]) << 16) \|
	142	(((uint32) s->block[i * 4 + 2]) << 8) \|
	143	(((uint32) s->block[i * 4 + 3]) << 0);
	144	}
	145	SHATransform(s->h, wordblock);
	146	s->blkused = 0;
	147	}
	148	memcpy(s->block, q, len);
	149	s->blkused = len;
	150	}
	151	}
	152
7959b517	153	void SHA_Final(SHA_State * s, unsigned char *output)
720a8fb7	154	{
	155	int i;
	156	int pad;
	157	unsigned char c[64];
	158	uint32 lenhi, lenlo;
	159
	160	if (s->blkused >= 56)
	161	pad = 56 + 64 - s->blkused;
	162	else
	163	pad = 56 - s->blkused;
	164
	165	lenhi = (s->lenhi << 3) \| (s->lenlo >> (32 - 3));
	166	lenlo = (s->lenlo << 3);
	167
	168	memset(c, 0, pad);
	169	c[0] = 0x80;
	170	SHA_Bytes(s, &c, pad);
	171
03f856c4	172	c[0] = (unsigned char)((lenhi >> 24) & 0xFF);
	173	c[1] = (unsigned char)((lenhi >> 16) & 0xFF);
	174	c[2] = (unsigned char)((lenhi >> 8) & 0xFF);
	175	c[3] = (unsigned char)((lenhi >> 0) & 0xFF);
	176	c[4] = (unsigned char)((lenlo >> 24) & 0xFF);
	177	c[5] = (unsigned char)((lenlo >> 16) & 0xFF);
	178	c[6] = (unsigned char)((lenlo >> 8) & 0xFF);
	179	c[7] = (unsigned char)((lenlo >> 0) & 0xFF);
720a8fb7	180
	181	SHA_Bytes(s, &c, 8);
	182
	183	for (i = 0; i < 5; i++) {
03f856c4	184	output[i * 4] = (unsigned char)((s->h[i] >> 24) & 0xFF);
	185	output[i * 4 + 1] = (unsigned char)((s->h[i] >> 16) & 0xFF);
	186	output[i * 4 + 2] = (unsigned char)((s->h[i] >> 8) & 0xFF);
	187	output[i * 4 + 3] = (unsigned char)((s->h[i]) & 0xFF);
720a8fb7	188	}
	189	}
	190
7959b517	191	void SHA_Simple(void p, int len, unsigned char output)
720a8fb7	192	{
	193	SHA_State s;
	194
	195	SHA_Init(&s);
	196	SHA_Bytes(&s, p, len);
	197	SHA_Final(&s, output);
	198	}
	199
	200	/* ----------------------------------------------------------------------
	201	* The random number generator.
	202	*/
	203
	204	struct random_state {
	205	unsigned char seedbuf[40];
	206	unsigned char databuf[20];
	207	int pos;
	208	};
	209
	210	random_state random_init(char seed, int len)
	211	{
	212	random_state *state;
	213
	214	state = snew(random_state);
	215
	216	SHA_Simple(seed, len, state->seedbuf);
	217	SHA_Simple(state->seedbuf, 20, state->seedbuf + 20);
	218	SHA_Simple(state->seedbuf, 40, state->databuf);
	219	state->pos = 0;
	220
	221	return state;
	222	}
	223
	224	unsigned long random_bits(random_state *state, int bits)
	225	{
48d70ca9	226	unsigned long ret = 0;
720a8fb7	227	int n;
	228
	229	for (n = 0; n < bits; n += 8) {
	230	if (state->pos >= 20) {
	231	int i;
	232
	233	for (i = 0; i < 20; i++) {
	234	if (state->seedbuf[i] != 0xFF) {
	235	state->seedbuf[i]++;
	236	break;
	237	} else
	238	state->seedbuf[i] = 0;
	239	}
	240	SHA_Simple(state->seedbuf, 40, state->databuf);
	241	state->pos = 0;
	242	}
	243	ret = (ret << 8) \| state->databuf[state->pos++];
	244	}
	245
48d70ca9	246	/*
	247	* `(1 << bits) - 1' is not good enough, since if bits==32 on a
	248	* 32-bit machine, behaviour is undefined and Intel has a nasty
	249	* habit of shifting left by zero instead. We'll shift by
	250	* bits-1 and then separately shift by one.
	251	*/
	252	ret &= (1 << (bits-1)) * 2 - 1;
720a8fb7	253	return ret;
	254	}
	255
	256	unsigned long random_upto(random_state *state, unsigned long limit)
	257	{
	258	int bits = 0;
	259	unsigned long max, divisor, data;
	260
	261	while ((limit >> bits) != 0)
	262	bits++;
	263
	264	bits += 3;
	265	assert(bits < 32);
	266
ab53eb64	267	max = 1L << bits;
720a8fb7	268	divisor = max / limit;
	269	max = limit * divisor;
	270
	271	do {
	272	data = random_bits(state, bits);
	273	} while (data >= max);
	274
	275	return data / divisor;
	276	}
	277
	278	void random_free(random_state *state)
	279	{
	280	sfree(state);
	281	}
c380832d	282
	283	char random_state_encode(random_state state)
	284	{
	285	char retbuf[256];
	286	int len = 0, i;
	287
	288	for (i = 0; i < lenof(state->seedbuf); i++)
	289	len += sprintf(retbuf+len, "%02x", state->seedbuf[i]);
	290	for (i = 0; i < lenof(state->databuf); i++)
	291	len += sprintf(retbuf+len, "%02x", state->databuf[i]);
	292	len += sprintf(retbuf+len, "%02x", state->pos);
	293
	294	return dupstr(retbuf);
	295	}
	296
	297	random_state random_state_decode(char input)
	298	{
	299	random_state *state;
	300	int pos, byte, digits;
	301
	302	state = snew(random_state);
	303
	304	memset(state->seedbuf, 0, sizeof(state->seedbuf));
	305	memset(state->databuf, 0, sizeof(state->databuf));
	306	state->pos = 0;
	307
	308	byte = digits = 0;
	309	pos = 0;
	310	while (*input) {
	311	int v = *input++;
	312
	313	if (v >= '0' && v <= '9')
	314	v = v - '0';
	315	else if (v >= 'A' && v <= 'F')
	316	v = v - 'A' + 10;
	317	else if (v >= 'a' && v <= 'f')
	318	v = v - 'a' + 10;
	319	else
	320	v = 0;
	321
	322	byte = (byte << 4) \| v;
	323	digits++;
	324
	325	if (digits == 2) {
	326	/*
	327	* We have a byte. Put it somewhere.
	328	*/
	329	if (pos < lenof(state->seedbuf))
	330	state->seedbuf[pos++] = byte;
	331	else if (pos < lenof(state->seedbuf) + lenof(state->databuf))
	332	state->databuf[pos++ - lenof(state->seedbuf)] = byte;
	333	else if (pos == lenof(state->seedbuf) + lenof(state->databuf) &&
	334	byte <= lenof(state->databuf))
	335	state->pos = byte;
	336	byte = digits = 0;
	337	}
	338	}
	339
	340	return state;
	341	}