A quick hashtable implementation in c.

hash.c

/* Read this comment first: https://gist.github.com/tonious/1377667#gistcomment-2277101
 * 2017-12-05
 * 
 *  -- T.
 */

#define _XOPEN_SOURCE 500 /* Enable certain library functions (strdup) on linux.  See feature_test_macros(7) */

#include <stdlib.h>
#include <stdio.h>
#include <limits.h>
#include <string.h>

struct entry_s {
	char *key;
	char *value;
	struct entry_s *next;
};

typedef struct entry_s entry_t;

struct hashtable_s {
	int size;
	struct entry_s **table;	
};

typedef struct hashtable_s hashtable_t;


/* Create a new hashtable. */
hashtable_t *ht_create( int size ) {

	hashtable_t *hashtable = NULL;
	int i;

	if( size < 1 ) return NULL;

	/* Allocate the table itself. */
	if( ( hashtable = malloc( sizeof( hashtable_t ) ) ) == NULL ) {
		return NULL;
	}

	/* Allocate pointers to the head nodes. */
	if( ( hashtable->table = malloc( sizeof( entry_t * ) * size ) ) == NULL ) {
		return NULL;
	}
	for( i = 0; i < size; i++ ) {
		hashtable->table[i] = NULL;
	}

	hashtable->size = size;

	return hashtable;	
}

/* Hash a string for a particular hash table. */
int ht_hash( hashtable_t *hashtable, char *key ) {

	unsigned long int hashval;
	int i = 0;

	/* Convert our string to an integer */
	while( hashval < ULONG_MAX && i < strlen( key ) ) {
		hashval = hashval << 8;
		hashval += key[ i ];
		i++;
	}

	return hashval % hashtable->size;
}

/* Create a key-value pair. */
entry_t *ht_newpair( char *key, char *value ) {
	entry_t *newpair;

	if( ( newpair = malloc( sizeof( entry_t ) ) ) == NULL ) {
		return NULL;
	}

	if( ( newpair->key = strdup( key ) ) == NULL ) {
		return NULL;
	}

	if( ( newpair->value = strdup( value ) ) == NULL ) {
		return NULL;
	}

	newpair->next = NULL;

	return newpair;
}

/* Insert a key-value pair into a hash table. */
void ht_set( hashtable_t *hashtable, char *key, char *value ) {
	int bin = 0;
	entry_t *newpair = NULL;
	entry_t *next = NULL;
	entry_t *last = NULL;

	bin = ht_hash( hashtable, key );

	next = hashtable->table[ bin ];

	while( next != NULL && next->key != NULL && strcmp( key, next->key ) > 0 ) {
		last = next;
		next = next->next;
	}

	/* There's already a pair.  Let's replace that string. */
	if( next != NULL && next->key != NULL && strcmp( key, next->key ) == 0 ) {

		free( next->value );
		next->value = strdup( value );

	/* Nope, could't find it.  Time to grow a pair. */
	} else {
		newpair = ht_newpair( key, value );

		/* We're at the start of the linked list in this bin. */
		if( next == hashtable->table[ bin ] ) {
			newpair->next = next;
			hashtable->table[ bin ] = newpair;
	
		/* We're at the end of the linked list in this bin. */
		} else if ( next == NULL ) {
			last->next = newpair;
	
		/* We're in the middle of the list. */
		} else  {
			newpair->next = next;
			last->next = newpair;
		}
	}
}

/* Retrieve a key-value pair from a hash table. */
char *ht_get( hashtable_t *hashtable, char *key ) {
	int bin = 0;
	entry_t *pair;

	bin = ht_hash( hashtable, key );

	/* Step through the bin, looking for our value. */
	pair = hashtable->table[ bin ];
	while( pair != NULL && pair->key != NULL && strcmp( key, pair->key ) > 0 ) {
		pair = pair->next;
	}

	/* Did we actually find anything? */
	if( pair == NULL || pair->key == NULL || strcmp( key, pair->key ) != 0 ) {
		return NULL;

	} else {
		return pair->value;
	}
	
}


int main( int argc, char **argv ) {

	hashtable_t *hashtable = ht_create( 65536 );

	ht_set( hashtable, "key1", "inky" );
	ht_set( hashtable, "key2", "pinky" );
	ht_set( hashtable, "key3", "blinky" );
	ht_set( hashtable, "key4", "floyd" );

	printf( "%s\n", ht_get( hashtable, "key1" ) );
	printf( "%s\n", ht_get( hashtable, "key2" ) );
	printf( "%s\n", ht_get( hashtable, "key3" ) );
	printf( "%s\n", ht_get( hashtable, "key4" ) );

	return 0;
}

@tonious, I'm just seeing this reply! Man, thanks for this, it's working great after tweaking it just a bit, have had no complaints so far!

@tonious I couldn't find the source of the reference of the relation between (inky, pinky, blinky) and floyd.Where did you get the reference from? (Google gives just instances of your code (thank you for it) which is spread all over the place)

https://pacman.fandom.com/wiki/Ghosts