Commit f3bed25c authored by simonm's avatar simonm

[project @ 1999-01-27 12:11:25 by simonm]

More missing files <sigh>
parent 1eada159
/*-----------------------------------------------------------------------------
* $Id: Hash.c,v 1.1 1999/01/27 12:11:25 simonm Exp $
*
* (c) The AQUA Project, Glasgow University, 1995-1998
* (c) The GHC Team, 1999
*
* Dynamically expanding linear hash tables, as described in
* Per-\AAke Larson, ``Dynamic Hash Tables,'' CACM 31(4), April 1988,
* pp. 446 -- 457.
* -------------------------------------------------------------------------- */
#include "Rts.h"
#include "Hash.h"
#include "RtsUtils.h"
#define HSEGSIZE 1024 /* Size of a single hash table segment */
/* Also the minimum size of a hash table */
#define HDIRSIZE 1024 /* Size of the segment directory */
/* Maximum hash table size is HSEGSIZE * HDIRSIZE */
#define HLOAD 5 /* Maximum average load of a single hash bucket */
#define HCHUNK (1024 * sizeof(W_) / sizeof(HashList))
/* Number of HashList cells to allocate in one go */
/* Linked list of (key, data) pairs for separate chaining */
struct hashlist {
StgWord key;
void *data;
struct hashlist *next; /* Next cell in bucket chain (same hash value) */
};
typedef struct hashlist HashList;
struct hashtable {
int split; /* Next bucket to split when expanding */
int max; /* Max bucket of smaller table */
int mask1; /* Mask for doing the mod of h_1 (smaller table) */
int mask2; /* Mask for doing the mod of h_2 (larger table) */
int kcount; /* Number of keys */
int bcount; /* Number of buckets */
HashList **dir[HDIRSIZE]; /* Directory of segments */
};
/* -----------------------------------------------------------------------------
* Hash first using the smaller table. If the bucket is less than the
* next bucket to be split, re-hash using the larger table.
* -------------------------------------------------------------------------- */
static int
hash(HashTable *table, W_ key)
{
int bucket;
/* Strip the boring zero bits */
key /= sizeof(StgWord);
/* Mod the size of the hash table (a power of 2) */
bucket = key & table->mask1;
if (bucket < table->split) {
/* Mod the size of the expanded hash table (also a power of 2) */
bucket = key & table->mask2;
}
return bucket;
}
/* -----------------------------------------------------------------------------
* Allocate a new segment of the dynamically growing hash table.
* -------------------------------------------------------------------------- */
static void
allocSegment(HashTable *table, int segment)
{
table->dir[segment] = stgMallocBytes(HSEGSIZE * sizeof(HashList *),
"allocSegment");
}
/* -----------------------------------------------------------------------------
* Expand the larger hash table by one bucket, and split one bucket
* from the smaller table into two parts. Only the bucket referenced
* by @table->split@ is affected by the expansion.
* -------------------------------------------------------------------------- */
static void
expand(HashTable *table)
{
int oldsegment;
int oldindex;
int newbucket;
int newsegment;
int newindex;
HashList *hl;
HashList *next;
HashList *old, *new;
if (table->split + table->max >= HDIRSIZE * HSEGSIZE)
/* Wow! That's big. Too big, so don't expand. */
return;
/* Calculate indices of bucket to split */
oldsegment = table->split / HSEGSIZE;
oldindex = table->split % HSEGSIZE;
newbucket = table->max + table->split;
/* And the indices of the new bucket */
newsegment = newbucket / HSEGSIZE;
newindex = newbucket % HSEGSIZE;
if (newindex == 0)
allocSegment(table, newsegment);
if (++table->split == table->max) {
table->split = 0;
table->max *= 2;
table->mask1 = table->mask2;
table->mask2 = table->mask2 << 1 | 1;
}
table->bcount++;
/* Split the bucket, paying no attention to the original order */
old = new = NULL;
for (hl = table->dir[oldsegment][oldindex]; hl != NULL; hl = next) {
next = hl->next;
if (hash(table, hl->key) == newbucket) {
hl->next = new;
new = hl;
} else {
hl->next = old;
old = hl;
}
}
table->dir[oldsegment][oldindex] = old;
table->dir[newsegment][newindex] = new;
return;
}
void *
lookupHashTable(HashTable *table, StgWord key)
{
int bucket;
int segment;
int index;
HashList *hl;
bucket = hash(table, key);
segment = bucket / HSEGSIZE;
index = bucket % HSEGSIZE;
for (hl = table->dir[segment][index]; hl != NULL; hl = hl->next)
if (hl->key == key)
return hl->data;
/* It's not there */
return NULL;
}
/* -----------------------------------------------------------------------------
* We allocate the hashlist cells in large chunks to cut down on malloc
* overhead. Although we keep a free list of hashlist cells, we make
* no effort to actually return the space to the malloc arena.
* -------------------------------------------------------------------------- */
static HashList *freeList = NULL;
static HashList *
allocHashList(void)
{
HashList *hl, *p;
if ((hl = freeList) != NULL) {
freeList = hl->next;
} else {
hl = stgMallocBytes(HCHUNK * sizeof(HashList), "allocHashList");
freeList = hl + 1;
for (p = freeList; p < hl + HCHUNK - 1; p++)
p->next = p + 1;
p->next = NULL;
}
return hl;
}
static void
freeHashList(HashList *hl)
{
hl->next = freeList;
freeList = hl;
}
void
insertHashTable(HashTable *table, StgWord key, void *data)
{
int bucket;
int segment;
int index;
HashList *hl;
/* We want no duplicates */
ASSERT(lookupHashTable(table, key) == NULL);
/* When the average load gets too high, we expand the table */
if (++table->kcount >= HLOAD * table->bcount)
expand(table);
bucket = hash(table, key);
segment = bucket / HSEGSIZE;
index = bucket % HSEGSIZE;
hl = allocHashList();
hl->key = key;
hl->data = data;
hl->next = table->dir[segment][index];
table->dir[segment][index] = hl;
}
void *
removeHashTable(HashTable *table, StgWord key, void *data)
{
int bucket;
int segment;
int index;
HashList *hl;
HashList *prev = NULL;
bucket = hash(table, key);
segment = bucket / HSEGSIZE;
index = bucket % HSEGSIZE;
for (hl = table->dir[segment][index]; hl != NULL; hl = hl->next) {
if (hl->key == key && (data == NULL || hl->data == data)) {
if (prev == NULL)
table->dir[segment][index] = hl->next;
else
prev->next = hl->next;
table->kcount--;
return hl->data;
}
prev = hl;
}
/* It's not there */
ASSERT(data == NULL);
return NULL;
}
/* -----------------------------------------------------------------------------
* When we free a hash table, we are also good enough to free the
* data part of each (key, data) pair, as long as our caller can tell
* us how to do it.
* -------------------------------------------------------------------------- */
void
freeHashTable(HashTable *table, void (*freeDataFun)(void *) )
{
long segment;
long index;
HashList *hl;
HashList *next;
/* The last bucket with something in it is table->max + table->split - 1 */
segment = (table->max + table->split - 1) / HSEGSIZE;
index = (table->max + table->split - 1) % HSEGSIZE;
while (segment >= 0) {
while (index >= 0) {
for (hl = table->dir[segment][index]; hl != NULL; hl = next) {
next = hl->next;
if (freeDataFun != NULL)
(*freeDataFun)(hl->data);
freeHashList(hl);
}
index--;
}
free(table->dir[segment]);
segment--;
index = HSEGSIZE - 1;
}
free(table);
}
/* -----------------------------------------------------------------------------
* When we initialize a hash table, we set up the first segment as well,
* initializing all of the first segment's hash buckets to NULL.
* -------------------------------------------------------------------------- */
HashTable *
allocHashTable(void)
{
HashTable *table;
HashList **hb;
table = stgMallocBytes(sizeof(HashTable),"allocHashTable");
allocSegment(table, 0);
for (hb = table->dir[0]; hb < table->dir[0] + HSEGSIZE; hb++)
*hb = NULL;
table->split = 0;
table->max = HSEGSIZE;
table->mask1 = HSEGSIZE - 1;
table->mask2 = 2 * HSEGSIZE - 1;
table->kcount = 0;
table->bcount = HSEGSIZE;
return table;
}
/*-----------------------------------------------------------------------------
* $Id: Hash.h,v 1.1 1999/01/27 12:11:26 simonm Exp $
*
* (c) The GHC Team, 1999
*
* Prototypes for Hash.c
*
* -------------------------------------------------------------------------- */
typedef struct hashtable HashTable; /* abstract */
void * lookupHashTable ( HashTable *table, StgWord key );
void insertHashTable ( HashTable *table, StgWord key, void *data );
void * removeHashTable ( HashTable *table, StgWord key, void *data );
void freeHashTable ( HashTable *table, void (*freeDataFun)(void *) );
HashTable * allocHashTable ( void );
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