106 lines
2.6 KiB
C
106 lines
2.6 KiB
C
#include "../includes/hashtable.h"
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#include <stdlib.h>
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#include <string.h>
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#include <stdio.h>
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//Reference https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function#FNV-1a_hash
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//FNV = Fowler–Noll–Vo
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#define FNV_OFFSET 0xcbf29ce484222325 //Or 14695981039346656037 in decimal
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#define FNV_PRIME 0x100000001b3 //Or 1099511628211 in decimal
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#define DEFAULTHASHTABLESIZE 64
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Bucket* CreateBucket();
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void AddToBucket(char* key, char* text, Bucket* bucket);
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HashTable* CreateHashTable(void) {
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HashTable* table = calloc(1, sizeof(HashTable));
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table->Values = calloc(DEFAULTHASHTABLESIZE, sizeof(Bucket*));
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table->Capacity = DEFAULTHASHTABLESIZE;
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return table;
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}
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void AddItemToHashTable(char* key, char* item, HashTable* table) {
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//FNV-1a hash
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unsigned long long hash = FNV_OFFSET;
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for(int i = 0; i < strlen(key); i ++) {
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hash ^= key[i];
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hash *= FNV_PRIME;
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}
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unsigned int index = hash % table->Capacity;
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Bucket* bucket = table->Values[index];
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if (!bucket) table->Values[index] = CreateBucket();
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AddToBucket(key, item, table->Values[index]);
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}
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char* HashTableBucketLinearScan(char* key, Bucket* bucket) {
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for(int i = 0; i < bucket->Size; i++) {
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BucketKeyPair* pair = bucket->KeyPairs[i];
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if (strcmp(key, pair->Key) == 0) return pair->Value;
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}
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return NULL;
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}
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char* GetHashTableItem(char* key, HashTable* table) {
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unsigned long long hash = FNV_OFFSET;
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for(int i = 0; i < strlen(key); i ++) {
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hash ^= key[i];
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hash *= FNV_PRIME;
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}
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unsigned int index = hash % table->Capacity;
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Bucket* bucket = table->Values[index];
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if (!bucket) return NULL;
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if (bucket->Size == 1) return bucket->KeyPairs[0]->Value;
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return HashTableBucketLinearScan(key, bucket);
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}
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Bucket* CreateBucket() {
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Bucket* bucket = calloc(1, sizeof(Bucket));
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bucket->KeyPairs = calloc(16, sizeof(BucketKeyPair*));
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bucket->Capacity = 16;
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return bucket;
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}
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void AddToBucket(char* key, char* text, Bucket* bucket) {
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BucketKeyPair* keyPair = calloc(1, sizeof(BucketKeyPair));
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keyPair->Key = key;
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keyPair->Value = text;
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bucket->KeyPairs[bucket->Size] = keyPair;
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bucket->Size++;
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}
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void PrintHashTable(HashTable* table) {
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printf("Capacity %d\nBuckets:\n", table->Capacity);
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for(int i = 0; i < table->Capacity; i++) {
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Bucket* bucket = table->Values[i];
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if (!bucket) continue;
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printf("Bucket %d: \n", i+1);
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for(int j = 0; j < bucket->Size; j++) {
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printf("(%s) '%s'\n", bucket->KeyPairs[j]->Key, bucket->KeyPairs[j]->Value);
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}
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printf("\n");
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}
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} |