path: root/gnu/usr.bin/cvs/lib/hash.c

/*
 * Copyright (c) 1992, Brian Berliner and Jeff Polk
 * 
 * You may distribute under the terms of the GNU General Public License as
 * specified in the README file that comes with the CVS 1.4 kit.
 * 
 * Polk's hash list manager.  So cool.
 */

#include "cvs.h"

#ifndef lint
static char rcsid[] = "$CVSid: @(#)hash.c 1.19 94/09/23 $";
USE(rcsid)
#endif

/* global caches */
static List *listcache = NULL;
static Node *nodecache = NULL;

static void freenode_mem PROTO((Node * p));

/* hash function */
static int
hashp (key)
    char *key;
{
    unsigned int h = 0;
    unsigned int g;

    while (*key != 0)
    {
	h = (h << 4) + *key++;
	if ((g = h & 0xf0000000) != 0)
	    h = (h ^ (g >> 24)) ^ g;
    }

    return (h % HASHSIZE);
}

/*
 * create a new list (or get an old one from the cache)
 */
List *
getlist ()
{
    int i;
    List *list;
    Node *node;

    if (listcache != NULL)
    {
	/* get a list from the cache and clear it */
	list = listcache;
	listcache = listcache->next;
	list->next = (List *) NULL;
	for (i = 0; i < HASHSIZE; i++)
	    list->hasharray[i] = (Node *) NULL;
    }
    else
    {
	/* make a new list from scratch */
	list = (List *) xmalloc (sizeof (List));
	memset ((char *) list, 0, sizeof (List));
	node = getnode ();
	list->list = node;
	node->type = HEADER;
	node->next = node->prev = node;
    }
    return (list);
}

/*
 * free up a list
 */
void
dellist (listp)
    List **listp;
{
    int i;
    Node *p;

    if (*listp == (List *) NULL)
	return;

    p = (*listp)->list;

    /* free each node in the list (except header) */
    while (p->next != p)
	delnode (p->next);

    /* free any list-private data, without freeing the actual header */
    freenode_mem (p);

    /* free up the header nodes for hash lists (if any) */
    for (i = 0; i < HASHSIZE; i++)
    {
	if ((p = (*listp)->hasharray[i]) != (Node *) NULL)
	{
	    /* put the nodes into the cache */
	    p->type = UNKNOWN;
	    p->next = nodecache;
	    nodecache = p;
	}
    }

    /* put it on the cache */
    (*listp)->next = listcache;
    listcache = *listp;
    *listp = (List *) NULL;
}

/*
 * get a new list node
 */
Node *
getnode ()
{
    Node *p;

    if (nodecache != (Node *) NULL)
    {
	/* get one from the cache */
	p = nodecache;
	nodecache = p->next;
    }
    else
    {
	/* make a new one */
	p = (Node *) xmalloc (sizeof (Node));
    }

    /* always make it clean */
    memset ((char *) p, 0, sizeof (Node));
    p->type = UNKNOWN;

    return (p);
}

/*
 * remove a node from it's list (maybe hash list too) and free it
 */
void
delnode (p)
    Node *p;
{
    if (p == (Node *) NULL)
	return;

    /* take it out of the list */
    p->next->prev = p->prev;
    p->prev->next = p->next;

    /* if it was hashed, remove it from there too */
    if (p->hashnext != (Node *) NULL)
    {
	p->hashnext->hashprev = p->hashprev;
	p->hashprev->hashnext = p->hashnext;
    }

    /* free up the storage */
    freenode (p);
}

/*
 * free up the storage associated with a node
 */
static void
freenode_mem (p)
    Node *p;
{
    if (p->delproc != (void (*) ()) NULL)
	p->delproc (p);			/* call the specified delproc */
    else
    {
	if (p->data != NULL)		/* otherwise free() it if necessary */
	    free (p->data);
    }
    if (p->key != NULL)			/* free the key if necessary */
	free (p->key);

    /* to be safe, re-initialize these */
    p->key = p->data = (char *) NULL;
    p->delproc = (void (*) ()) NULL;
}

/*
 * free up the storage associated with a node and recycle it
 */
void
freenode (p)
    Node *p;
{
    /* first free the memory */
    freenode_mem (p);

    /* then put it in the cache */
    p->type = UNKNOWN;
    p->next = nodecache;
    nodecache = p;
}

/*
 * insert item p at end of list "list" (maybe hash it too) if hashing and it
 * already exists, return -1 and don't actually put it in the list
 * 
 * return 0 on success
 */
int
addnode (list, p)
    List *list;
    Node *p;
{
    int hashval;
    Node *q;

    if (p->key != NULL)			/* hash it too? */
    {
	hashval = hashp (p->key);
	if (list->hasharray[hashval] == NULL)	/* make a header for list? */
	{
	    q = getnode ();
	    q->type = HEADER;
	    list->hasharray[hashval] = q->hashnext = q->hashprev = q;
	}

	/* put it into the hash list if it's not already there */
	for (q = list->hasharray[hashval]->hashnext;
	     q != list->hasharray[hashval]; q = q->hashnext)
	{
	    if (strcmp (p->key, q->key) == 0)
		return (-1);
	}
	q = list->hasharray[hashval];
	p->hashprev = q->hashprev;
	p->hashnext = q;
	p->hashprev->hashnext = p;
	q->hashprev = p;
    }

    /* put it into the regular list */
    p->prev = list->list->prev;
    p->next = list->list;
    list->list->prev->next = p;
    list->list->prev = p;

    return (0);
}

/*
 * look up an entry in hash list table and return a pointer to the
 * node.  Return NULL on error or not found.
 */
Node *
findnode (list, key)
    List *list;
    char *key;
{
    Node *head, *p;

    if (list == (List *) NULL)
	return ((Node *) NULL);

    head = list->hasharray[hashp (key)];
    if (head == (Node *) NULL)
	return ((Node *) NULL);

    for (p = head->hashnext; p != head; p = p->hashnext)
	if (strcmp (p->key, key) == 0)
	    return (p);
    return ((Node *) NULL);
}

/*
 * walk a list with a specific proc
 */
int
walklist (list, proc, closure)
    List *list;
    int (*proc) ();
    void *closure;
{
    Node *head, *p;
    int err = 0;

    if (list == NULL)
	return (0);

    head = list->list;
    for (p = head->next; p != head; p = p->next)
	err += proc (p, closure);
    return (err);
}

/*
 * sort the elements of a list (in place)
 */
void
sortlist (list, comp)
    List *list;
    int (*comp) ();
{
    Node *head, *remain, *p, *q;

    /* save the old first element of the list */
    head = list->list;
    remain = head->next;

    /* make the header node into a null list of it's own */
    head->next = head->prev = head;

    /* while there are nodes remaining, do insert sort */
    while (remain != head)
    {
	/* take one from the list */
	p = remain;
	remain = remain->next;

	/* traverse the sorted list looking for the place to insert it */
	for (q = head->next; q != head; q = q->next)
	{
	    if (comp (p, q) < 0)
	    {
		/* p comes before q */
		p->next = q;
		p->prev = q->prev;
		p->prev->next = p;
		q->prev = p;
		break;
	    }
	}
	if (q == head)
	{
	    /* it belongs at the end of the list */
	    p->next = head;
	    p->prev = head->prev;
	    p->prev->next = p;
	    head->prev = p;
	}
    }
}

/* Debugging functions.  Quite useful to call from within gdb. */

char *
nodetypestring (type)
    Ntype type;
{
    switch (type) {
    case UNKNOWN:	return("UNKNOWN");
    case HEADER:	return("HEADER");
    case ENTRIES:	return("ENTRIES");
    case FILES:		return("FILES");
    case LIST:		return("LIST");
    case RCSNODE:	return("RCSNODE");
    case RCSVERS:	return("RCSVERS");
    case DIRS:		return("DIRS");
    case UPDATE:	return("UPDATE");
    case LOCK:		return("LOCK");
    case NDBMNODE:	return("NDBMNODE");
    }

    return("<trash>");
}

int
printnode (node, closure)
     Node *node;
     void *closure;
{
    if (node == NULL)
    {
	(void) printf("NULL node.\n");
	return(0);
    }

    (void) printf("Node at 0x%p: type = %s, key = 0x%p = \"%s\", data = 0x%p, next = 0x%p, prev = 0x%p\n",
	   node, nodetypestring(node->type), node->key, node->key, node->data, node->next, node->prev);

    return(0);
}

void
printlist (list)
    List *list;
{
    if (list == NULL)
    {
	(void) printf("NULL list.\n");
	return;
    }

    (void) printf("List at 0x%p: list = 0x%p, HASHSIZE = %d, next = 0x%p\n",
	   list, list->list, HASHSIZE, list->next);
    
    (void) walklist(list, printnode, NULL);

    return;
}