如何在Linux中使用Hashtable存储数据_云计算

发布时间:2024-10-01 14:18

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在 Linux 中，你可以使用 C 语言的标准库函数 malloc() 和 free() 来动态地创建和释放 Hashtable。以下是一个简单的 Hashtable 实现示例：

首先，创建一个名为 hashtable.h 的头文件，用于声明 Hashtable 结构和相关函数原型：

#ifndefhashtable_h #define hashtable_h  #include <stdio.h> #include <stdlib.h> #include <string.h>  #define TABLE_SIZE 100  typedef struct Entry {     char *key;     char *value;     struct Entry *next; } Entry;  typedef struct {     Entry *entries[TABLE_SIZE]; } Hashtable;  Hashtable* createTable(); void freeTable(Hashtable *table); int hash(const char *key); void insert(Hashtable *table, const char *key, const char *value); char* get(Hashtable *table, const char *key); void remove(Hashtable *table, const char *key); void rehash(Hashtable *table);  #endif //hashtable_h

接下来，创建一个名为 hashtable.c 的源文件，用于实现 Hashtable 结构和相关函数：

#include "hashtable.h"  Hashtable* createTable() {     Hashtable *table = (Hashtable *)malloc(sizeof(Hashtable));     if (table == NULL) {         fprintf(stderr, "Failed to allocate memory for the table.\n");         exit(1);     }      for (int i = 0; i < TABLE_SIZE; i++) {         table->entries[i] = NULL;     }      return table; }  void freeTable(Hashtable *table) {     for (int i = 0; i < TABLE_SIZE; i++) {         Entry *entry = table->entries[i];         while (entry != NULL) {             Entry *temp = entry;             entry = entry->next;             free(temp->key);             free(temp->value);             free(temp);         }     }     free(table); }  int hash(const char *key) {     int hashValue = 0;     for (int i = 0; key[i] != '\0'; i++) {         hashValue = (hashValue * 31 + key[i]) % TABLE_SIZE;     }     return hashValue; }  void insert(Hashtable *table, const char *key, const char *value) {     int index = hash(key);     Entry *entry = table->entries[index];      if (entry == NULL) {         Entry *newEntry = (Entry *)malloc(sizeof(Entry));         newEntry->key = strdup(key);         newEntry->value = strdup(value);         newEntry->next = NULL;         table->entries[index] = newEntry;     } else {         while (entry != NULL) {             if (strcmp(entry->key, key) == 0) {                 free(entry->value);                 entry->value = strdup(value);                 return;             }             entry = entry->next;         }         Entry *newEntry = (Entry *)malloc(sizeof(Entry));         newEntry->key = strdup(key);         newEntry->value = strdup(value);         newEntry->next = table->entries[index];         table->entries[index] = newEntry;     } }  char* get(Hashtable *table, const char *key) {     int index = hash(key);     Entry *entry = table->entries[index];      while (entry != NULL) {         if (strcmp(entry->key, key) == 0) {             return entry->value;         }         entry = entry->next;     }      return NULL; }  void remove(Hashtable *table, const char *key) {     int index = hash(key);     Entry *entry = table->entries[index];     Entry **prev = &table->entries[index];      while (entry != NULL) {         if (strcmp(entry->key, key) == 0) {             *prev = entry->next;             free(entry->key);             free(entry->value);             free(entry);             return;         }         prev = &entry->next;         entry = entry->next;     } }  void rehash(Hashtable *table) {     Entry **oldEntries = table->entries;     int oldSize = TABLE_SIZE;      table = createTable();     for (int i = 0; i < oldSize; i++) {         Entry *entry = oldEntries[i];         while (entry != NULL) {             insert(table, entry->key, entry->value);             entry = entry->next;         }     }      free(oldEntries); }

编译并安装 Hashtable 库：

gcc -c hashtable.c -o hashtable.o sudo ld -shared hashtable.o -o libhashtable.so

在你的应用程序中使用 Hashtable 库：

#include <stdio.h> #include "hashtable.h"  int main() {     Hashtable *table = createTable();     insert(table, "key1", "value1");     insert(table, "key2", "value2");     printf("key1: %s\n", get(table, "key1"));     printf("key2: %s\n", get(table, "key2"));     remove(table, "key1");     printf("key1 (after removal): %s\n", get(table, "key1"));     freeTable(table);     return 0; }