/*
* Routines to provide a memory-efficient hashtable.
*
- * Copyright (C) 2007-2008 Wayne Davison
+ * Copyright (C) 2007-2020 Wayne Davison
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
struct hashtable *hashtable_create(int size, int key64)
{
+ int req = size;
struct hashtable *tbl;
int node_size = key64 ? sizeof (struct ht_int64_node)
: sizeof (struct ht_int32_node);
/* Pick a power of 2 that can hold the requested size. */
if (size & (size-1) || size < 16) {
- int req = size;
size = 16;
while (size < req)
size *= 2;
}
- if (!(tbl = new(struct hashtable))
- || !(tbl->nodes = new_array0(char, size * node_size)))
- out_of_memory("hashtable_create");
+ tbl = new(struct hashtable);
+ tbl->nodes = new_array0(char, size * node_size);
tbl->size = size;
tbl->entries = 0;
tbl->node_size = node_size;
- tbl->key64 = key64;
+ tbl->key64 = key64 ? 1 : 0;
+
+ if (DEBUG_GTE(HASH, 1)) {
+ char buf[32];
+ if (req != size)
+ snprintf(buf, sizeof buf, "req: %d, ", req);
+ else
+ *buf = '\0';
+ rprintf(FINFO, "[%s] created hashtable %lx (%ssize: %d, keys: %d-bit)\n",
+ who_am_i(), (long)tbl, buf, size, key64 ? 64 : 32);
+ }
return tbl;
}
void hashtable_destroy(struct hashtable *tbl)
{
+ if (DEBUG_GTE(HASH, 1)) {
+ rprintf(FINFO, "[%s] destroyed hashtable %lx (size: %d, keys: %d-bit)\n",
+ who_am_i(), (long)tbl, tbl->size, tbl->key64 ? 64 : 32);
+ }
free(tbl->nodes);
free(tbl);
}
-/* This returns the node for the indicated key, either newly created or
- * already existing. Returns NULL if not allocating and not found. */
-void *hashtable_find(struct hashtable *tbl, int64 key, int allocate_if_missing)
+/* Returns the node that holds the indicated key if it exists. When it does not
+ * exist, it returns either NULL (when data_when_new is NULL), or it returns a
+ * new node with its node->data set to the indicated value.
+ *
+ * If your code doesn't know the data value for a new node in advance (usually
+ * because it doesn't know if a node is new or not) you should pass in a unique
+ * (non-0) value that you can use to check if the returned node is new. You can
+ * then overwrite the data with any value you want (even 0) since it only needs
+ * to be different than whatever data_when_new value you use later on.
+ *
+ * This return is a void* just because it might be pointing at a ht_int32_node
+ * or a ht_int64_node, and that makes the caller's assignment a little easier. */
+void *hashtable_find(struct hashtable *tbl, int64 key, void *data_when_new)
{
int key64 = tbl->key64;
struct ht_int32_node *node;
uint32 ndx;
- if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
+ if (key64 ? key == 0 : (int32)key == 0) {
+ rprintf(FERROR, "Internal hashtable error: illegal key supplied!\n");
+ exit_cleanup(RERR_MESSAGEIO);
+ }
+
+ if (data_when_new && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
void *old_nodes = tbl->nodes;
int size = tbl->size * 2;
int i;
- if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
- out_of_memory("hashtable_node");
+ tbl->nodes = new_array0(char, size * tbl->node_size);
tbl->size = size;
tbl->entries = 0;
+ if (DEBUG_GTE(HASH, 1)) {
+ rprintf(FINFO, "[%s] growing hashtable %lx (size: %d, keys: %d-bit)\n",
+ who_am_i(), (long)tbl, size, key64 ? 64 : 32);
+ }
+
for (i = size / 2; i-- > 0; ) {
struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
int64 move_key = HT_KEY(move_node, key64);
if (move_key == 0)
continue;
- node = hashtable_find(tbl, move_key, 1);
- node->data = move_node->data;
+ if (move_node->data)
+ hashtable_find(tbl, move_key, move_node->data);
+ else {
+ node = hashtable_find(tbl, move_key, "");
+ node->data = 0;
+ }
}
free(old_nodes);
uchar buf[4], *keyp = buf;
int i;
- SIVAL(buf, 0, key);
+ SIVALu(buf, 0, key);
for (ndx = 0, i = 0; i < 4; i++) {
ndx += keyp[i];
ndx += (ndx << 10);
if (nkey == key)
return node;
if (nkey == 0) {
- if (!allocate_if_missing)
+ if (!data_when_new)
return NULL;
break;
}
if (key64)
((struct ht_int64_node*)node)->key = key;
else
- node->key = key;
+ node->key = (int32)key;
+ node->data = data_when_new;
tbl->entries++;
return node;
}
+
+#ifndef WORDS_BIGENDIAN
+# define HASH_LITTLE_ENDIAN 1
+# define HASH_BIG_ENDIAN 0
+#else
+# define HASH_LITTLE_ENDIAN 0
+# define HASH_BIG_ENDIAN 1
+#endif
+
+/*
+ -------------------------------------------------------------------------------
+ lookup3.c, by Bob Jenkins, May 2006, Public Domain.
+
+ These are functions for producing 32-bit hashes for hash table lookup.
+ hash_word(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
+ are externally useful functions. Routines to test the hash are included
+ if SELF_TEST is defined. You can use this free for any purpose. It's in
+ the public domain. It has no warranty.
+
+ You probably want to use hashlittle(). hashlittle() and hashbig()
+ hash byte arrays. hashlittle() is is faster than hashbig() on
+ little-endian machines. Intel and AMD are little-endian machines.
+ On second thought, you probably want hashlittle2(), which is identical to
+ hashlittle() except it returns two 32-bit hashes for the price of one.
+ You could implement hashbig2() if you wanted but I haven't bothered here.
+
+ If you want to find a hash of, say, exactly 7 integers, do
+ a = i1; b = i2; c = i3;
+ mix(a,b,c);
+ a += i4; b += i5; c += i6;
+ mix(a,b,c);
+ a += i7;
+ final(a,b,c);
+ then use c as the hash value. If you have a variable length array of
+ 4-byte integers to hash, use hash_word(). If you have a byte array (like
+ a character string), use hashlittle(). If you have several byte arrays, or
+ a mix of things, see the comments above hashlittle().
+
+ Why is this so big? I read 12 bytes at a time into 3 4-byte integers,
+ then mix those integers. This is fast (you can do a lot more thorough
+ mixing with 12*3 instructions on 3 integers than you can with 3 instructions
+ on 1 byte), but shoehorning those bytes into integers efficiently is messy.
+*/
+
+#define hashsize(n) ((uint32_t)1<<(n))
+#define hashmask(n) (hashsize(n)-1)
+#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
+
+/*
+ -------------------------------------------------------------------------------
+ mix -- mix 3 32-bit values reversibly.
+
+ This is reversible, so any information in (a,b,c) before mix() is
+ still in (a,b,c) after mix().
+
+ If four pairs of (a,b,c) inputs are run through mix(), or through
+ mix() in reverse, there are at least 32 bits of the output that
+ are sometimes the same for one pair and different for another pair.
+ This was tested for:
+ * pairs that differed by one bit, by two bits, in any combination
+ of top bits of (a,b,c), or in any combination of bottom bits of
+ (a,b,c).
+ * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
+ the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
+ is commonly produced by subtraction) look like a single 1-bit
+ difference.
+ * the base values were pseudorandom, all zero but one bit set, or
+ all zero plus a counter that starts at zero.
+
+ Some k values for my "a-=c; a^=rot(c,k); c+=b;" arrangement that
+ satisfy this are
+ 4 6 8 16 19 4
+ 9 15 3 18 27 15
+ 14 9 3 7 17 3
+ Well, "9 15 3 18 27 15" didn't quite get 32 bits diffing
+ for "differ" defined as + with a one-bit base and a two-bit delta. I
+ used http://burtleburtle.net/bob/hash/avalanche.html to choose
+ the operations, constants, and arrangements of the variables.
+
+ This does not achieve avalanche. There are input bits of (a,b,c)
+ that fail to affect some output bits of (a,b,c), especially of a. The
+ most thoroughly mixed value is c, but it doesn't really even achieve
+ avalanche in c.
+
+ This allows some parallelism. Read-after-writes are good at doubling
+ the number of bits affected, so the goal of mixing pulls in the opposite
+ direction as the goal of parallelism. I did what I could. Rotates
+ seem to cost as much as shifts on every machine I could lay my hands
+ on, and rotates are much kinder to the top and bottom bits, so I used
+ rotates.
+ -------------------------------------------------------------------------------
+*/
+#define mix(a,b,c) \
+{ \
+ a -= c; a ^= rot(c, 4); c += b; \
+ b -= a; b ^= rot(a, 6); a += c; \
+ c -= b; c ^= rot(b, 8); b += a; \
+ a -= c; a ^= rot(c,16); c += b; \
+ b -= a; b ^= rot(a,19); a += c; \
+ c -= b; c ^= rot(b, 4); b += a; \
+}
+
+/*
+ -------------------------------------------------------------------------------
+ final -- final mixing of 3 32-bit values (a,b,c) into c
+
+ Pairs of (a,b,c) values differing in only a few bits will usually
+ produce values of c that look totally different. This was tested for
+ * pairs that differed by one bit, by two bits, in any combination
+ of top bits of (a,b,c), or in any combination of bottom bits of
+ (a,b,c).
+ * "differ" is defined as +, -, ^, or ~^. For + and -, I transformed
+ the output delta to a Gray code (a^(a>>1)) so a string of 1's (as
+ is commonly produced by subtraction) look like a single 1-bit
+ difference.
+ * the base values were pseudorandom, all zero but one bit set, or
+ all zero plus a counter that starts at zero.
+
+ These constants passed:
+ 14 11 25 16 4 14 24
+ 12 14 25 16 4 14 24
+ and these came close:
+ 4 8 15 26 3 22 24
+ 10 8 15 26 3 22 24
+ 11 8 15 26 3 22 24
+ -------------------------------------------------------------------------------
+*/
+#define final(a,b,c) \
+{ \
+ c ^= b; c -= rot(b,14); \
+ a ^= c; a -= rot(c,11); \
+ b ^= a; b -= rot(a,25); \
+ c ^= b; c -= rot(b,16); \
+ a ^= c; a -= rot(c,4); \
+ b ^= a; b -= rot(a,14); \
+ c ^= b; c -= rot(b,24); \
+}
+
+
+/*
+ -------------------------------------------------------------------------------
+ hashlittle() -- hash a variable-length key into a 32-bit value
+ k : the key (the unaligned variable-length array of bytes)
+ length : the length of the key, counting by bytes
+ val2 : IN: can be any 4-byte value OUT: second 32 bit hash.
+ Returns a 32-bit value. Every bit of the key affects every bit of
+ the return value. Two keys differing by one or two bits will have
+ totally different hash values. Note that the return value is better
+ mixed than val2, so use that first.
+
+ The best hash table sizes are powers of 2. There is no need to do
+ mod a prime (mod is sooo slow!). If you need less than 32 bits,
+ use a bitmask. For example, if you need only 10 bits, do
+ h = (h & hashmask(10));
+ In which case, the hash table should have hashsize(10) elements.
+
+ If you are hashing n strings (uint8_t **)k, do it like this:
+ for (i=0, h=0; i<n; ++i) h = hashlittle( k[i], len[i], h);
+
+ By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
+ code any way you wish, private, educational, or commercial. It's free.
+
+ Use for hash table lookup, or anything where one collision in 2^^32 is
+ acceptable. Do NOT use for cryptographic purposes.
+ -------------------------------------------------------------------------------
+*/
+
+uint32_t hashlittle(const void *key, size_t length)
+{
+ uint32_t a,b,c; /* internal state */
+ union { const void *ptr; size_t i; } u; /* needed for Mac Powerbook G4 */
+
+ /* Set up the internal state */
+ a = b = c = 0xdeadbeef + ((uint32_t)length);
+
+ u.ptr = key;
+ if (HASH_LITTLE_ENDIAN && ((u.i & 0x3) == 0)) {
+ const uint32_t *k = (const uint32_t *)key; /* read 32-bit chunks */
+ const uint8_t *k8;
+
+ /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
+ while (length > 12)
+ {
+ a += k[0];
+ b += k[1];
+ c += k[2];
+ mix(a,b,c);
+ length -= 12;
+ k += 3;
+ }
+
+ /*----------------------------- handle the last (probably partial) block */
+ k8 = (const uint8_t *)k;
+ switch(length)
+ {
+ case 12: c+=k[2]; b+=k[1]; a+=k[0]; break;
+ case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
+ case 10: c+=((uint32_t)k8[9])<<8; /* fall through */
+ case 9 : c+=k8[8]; /* fall through */
+ case 8 : b+=k[1]; a+=k[0]; break;
+ case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
+ case 6 : b+=((uint32_t)k8[5])<<8; /* fall through */
+ case 5 : b+=k8[4]; /* fall through */
+ case 4 : a+=k[0]; break;
+ case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
+ case 2 : a+=((uint32_t)k8[1])<<8; /* fall through */
+ case 1 : a+=k8[0]; break;
+ case 0 : return c;
+ }
+ } else if (HASH_LITTLE_ENDIAN && ((u.i & 0x1) == 0)) {
+ const uint16_t *k = (const uint16_t *)key; /* read 16-bit chunks */
+ const uint8_t *k8;
+
+ /*--------------- all but last block: aligned reads and different mixing */
+ while (length > 12)
+ {
+ a += k[0] + (((uint32_t)k[1])<<16);
+ b += k[2] + (((uint32_t)k[3])<<16);
+ c += k[4] + (((uint32_t)k[5])<<16);
+ mix(a,b,c);
+ length -= 12;
+ k += 6;
+ }
+
+ /*----------------------------- handle the last (probably partial) block */
+ k8 = (const uint8_t *)k;
+ switch(length)
+ {
+ case 12: c+=k[4]+(((uint32_t)k[5])<<16);
+ b+=k[2]+(((uint32_t)k[3])<<16);
+ a+=k[0]+(((uint32_t)k[1])<<16);
+ break;
+ case 11: c+=((uint32_t)k8[10])<<16; /* fall through */
+ case 10: c+=k[4];
+ b+=k[2]+(((uint32_t)k[3])<<16);
+ a+=k[0]+(((uint32_t)k[1])<<16);
+ break;
+ case 9 : c+=k8[8]; /* fall through */
+ case 8 : b+=k[2]+(((uint32_t)k[3])<<16);
+ a+=k[0]+(((uint32_t)k[1])<<16);
+ break;
+ case 7 : b+=((uint32_t)k8[6])<<16; /* fall through */
+ case 6 : b+=k[2];
+ a+=k[0]+(((uint32_t)k[1])<<16);
+ break;
+ case 5 : b+=k8[4]; /* fall through */
+ case 4 : a+=k[0]+(((uint32_t)k[1])<<16);
+ break;
+ case 3 : a+=((uint32_t)k8[2])<<16; /* fall through */
+ case 2 : a+=k[0];
+ break;
+ case 1 : a+=k8[0];
+ break;
+ case 0 : return c; /* zero length requires no mixing */
+ }
+
+ } else { /* need to read the key one byte at a time */
+ const uint8_t *k = (const uint8_t *)key;
+
+ /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
+ while (length > 12)
+ {
+ a += k[0];
+ a += ((uint32_t)k[1])<<8;
+ a += ((uint32_t)k[2])<<16;
+ a += ((uint32_t)k[3])<<24;
+ b += k[4];
+ b += ((uint32_t)k[5])<<8;
+ b += ((uint32_t)k[6])<<16;
+ b += ((uint32_t)k[7])<<24;
+ c += k[8];
+ c += ((uint32_t)k[9])<<8;
+ c += ((uint32_t)k[10])<<16;
+ c += ((uint32_t)k[11])<<24;
+ mix(a,b,c);
+ length -= 12;
+ k += 12;
+ }
+
+ /*-------------------------------- last block: affect all 32 bits of (c) */
+ switch(length) /* all the case statements fall through */
+ {
+ case 12: c+=((uint32_t)k[11])<<24;
+ /* FALLTHROUGH */
+ case 11: c+=((uint32_t)k[10])<<16;
+ /* FALLTHROUGH */
+ case 10: c+=((uint32_t)k[9])<<8;
+ /* FALLTHROUGH */
+ case 9 : c+=k[8];
+ /* FALLTHROUGH */
+ case 8 : b+=((uint32_t)k[7])<<24;
+ /* FALLTHROUGH */
+ case 7 : b+=((uint32_t)k[6])<<16;
+ /* FALLTHROUGH */
+ case 6 : b+=((uint32_t)k[5])<<8;
+ /* FALLTHROUGH */
+ case 5 : b+=k[4];
+ /* FALLTHROUGH */
+ case 4 : a+=((uint32_t)k[3])<<24;
+ /* FALLTHROUGH */
+ case 3 : a+=((uint32_t)k[2])<<16;
+ /* FALLTHROUGH */
+ case 2 : a+=((uint32_t)k[1])<<8;
+ /* FALLTHROUGH */
+ case 1 : a+=k[0];
+ break;
+ case 0 : return c;
+ }
+ }
+
+ final(a,b,c);
+ return c;
+}
git.samba.org / rsync.git / blobdiff