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Aminet - June 1993 [Walnut Creek].iso
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hash.lha
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hash.c
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C/C++ Source or Header
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1993-01-06
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3KB
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148 lines
/*
* HASH.C
* (c) 1992-3 J.Harper
*
* open hashing module
*/
#include "hash.h"
#include <string.h>
/*
* _very_ simple hash function
*/
static int
hash(char *name, int tabSize)
{
int total = 0;
char c;
while(c = *name++)
total += c;
return(total % tabSize);
}
/****** inserthash **********************************************************
*
* NAME
* inserthash -- link a hash node
*
* SYNOPSIS
* inserthash(hashTab, hashNode, tabSize)
*
* void inserthash(HASHNODE **, HASHNODE *, int);
*
* FUNCTION
* Links an initialized HASHNODE into a hash table, this node will
* be inserted before any other nodes with the same name. (ie, calls
* to inserthash() and removehash() nest).
*
* INPUTS
* hashTab -- pointer to an array containing tabSize number of
* pointers to HASHNODE's.
* hashNode -- initialized HASHNODE which is to be linked into the
* hashTab
* tabSize -- number of pointers in hashTab
*
* RESULT
* none.
*
* SEE ALSO
* hash.h, removehash(), findhash()
*
*****************************************************************************
*
*/
void
inserthash(HASHNODE **hashTab, HASHNODE *node, int tabSize)
{
HASHNODE *lastchain;
int index = hash(node->h_Name, tabSize);
lastchain = hashTab[index];
hashTab[index] = node;
node->h_Next = lastchain;
node->h_Prev = NULL;
if(lastchain)
lastchain->h_Prev = node;
}
/****** removehash **********************************************************
*
* NAME
* removehash -- unlink a hash node
*
* SYNOPSIS
* removehash(hashTab, hashNode, tabSize)
*
* void removehash(HASHNODE **, HASHNODE *, int);
*
* FUNCTION
* Unlinks hashNode from hashTable.
*
* INPUTS
* hashTab -- pointer to the hash table
* hashNode -- pointer to the hash node
* tabSize -- number of pointers in hashTab
*
* RESULT
* none.
*
* SEE ALSO
* hash.h, inserthash(), findhash()
*
*****************************************************************************
*
*/
void
removehash(HASHNODE **hashTab, HASHNODE *node, int tabSize)
{
HASHNODE *next = node->h_Next;
HASHNODE *prev = node->h_Prev;
if(!prev)
hashTab[hash(node->h_Name, tabSize)] = next;
else
prev->h_Next = next;
if(next)
next->h_Prev = prev;
}
/****** findhash ************************************************************
*
* NAME
* findhash -- find a hash entry
*
* SYNOPSIS
* hashNode = findhash(hashTab, name)
*
* HASHNODE *findhash(HASHNODE **, char *);
*
* FUNCTION
* Scans the specified hash table for the specified entry.
*
* INPUTS
* hashTab -- pointer to the hash table
* name -- name of node to find
* tabSize -- number of pointers in hashTab
*
* RESULT
* hashNode -- pointer to found node or NULL if no matching node
* could be found
*
* SEE ALSO
* hash.h, inserthash(), removehash()
*
*****************************************************************************
*
*/
HASHNODE *
findhash(HASHNODE **hashTab, char *name, int tabSize)
{
HASHNODE *node;
for(node = hashTab[hash(name, tabSize)]; node; node = node->h_Next)
{
if(!(stricmp(name, node->h_Name)))
break;
}
return(node);
}