一个简单的HashMap C语言实现

一个简单的HashMap C语言实现

cheungmine 

用C语言实现一个简单实用的hashmap，具有一定的实际意义。尤其我们不想使用STL里面的map<...>类的时候。我实现的这个hashmap，用来做key---value的映射，key必须是有效的字符串，value是调用者分配的任意类型的数据。这个hashmap适合在一些简单的场合下，消耗极少的资源。

首先定义头文件如下：

/*
  
 * hashmap.h
 *        Generic hash map: key(string)-value(any type).
 *        cheungmine 
 *      Sep. 22, 2007.  All rights reserved.
 
  */
  
#ifndef HASHMAP_H_INCLUDED

  #define
   HASHMAP_H_INCLUDED
  

#include 
  "
  unistd.h
  "
  


  /*
   You should always use 1024 
  */
  

  #define
       HASHMAP_SIZE    1024
  


  /*
   Opaque struct pointer to _hash_map_t 
  */
  
typedef 
  struct
      _hash_map_t
  *
          hash_map;

typedef 
  void
  (
  *
  pfcb_hmap_value_free)(
  void
  *
   value);


  /*
   An example of free value function implemented by caller:
void my_hmap_free_value(void* pv)
{
    free(pv);
}

  */
  



  /*
   Create before use. eg:
 * hash_map  hm;
 * hmap_create (&hm, HASHMAP_SIZE);
 * assert (hm);     // out of memory if hm==NULL 
 * void* mydata=malloc(n);
 * hmap_insert(hm, "shanghai", -1, mydata);
   ...
 * hmap_destroy(hm, my_hmap_free_value);
 
  */
  

  extern
   
  void
   
hmap_create(hash_map 
  *
  hmap, 
  int
   size);


  /*
   Destroy after use 
  */
  

  extern
   
  void
   
hmap_destroy(hash_map hmap, pfcb_hmap_value_free);


  /*
   Insert a key-value into hash map. value is a pointer to callee-allocated memory 
  */
  

  extern
   
  void
   
hmap_insert(hash_map hmap, 
  const
   
  char
  *
   key, 
  int
   key_len
  /*
   -1 for strlen to be called 
  */
  , 
  void
  *
   value);


  /*
   Search a hash map for value of given key string 
  */
  

  extern
   
  void
  *
    
hmap_search(hash_map hmap, 
  const
   
  char
    
  *
  key);



  #endif
    /* HASHMAP_H_INCLUDED */
   
 
实现文件如下：
 
 
/*
  
 * hashmap.c
 *        Generic hashmap implementation. 
 *      a map for pair of key-value. key must be a null-end string, value is any type of data.
 *        cheungmine 
 *      Sep. 22, 2007.  All rights reserved.
 
  */
  

#include 
  "
  hashmap.h
  "
  
#include 
  "
  list.h
  "
  

typedef 
  struct
   _hash_map_t
{
    size_t            size;
    listnode_t
  **
      key;
    listnode_t
  **
      value;
}hash_map_t;


  /*
   Hash a string, return a hash key 
  */
  

  static
   
  ulong
    hash_string(
  const
   
  char
    
  *
  s, 
  int
   len)
{
    
  ulong
   h 
  =
   
  0
  ;
    
  int
     i 
  =
   
  0
  ;
    assert (s);
    
  if
   (len 
  <
   
  0
  )
        len 
  =
   (s
  ?
   (
  int
  )strlen(s): 
  0
  );
    
  while
  (i
  ++
   
  <
   len) { h 
  =
   
  17
  *
  h 
  +
   
  *
  s
  ++
  ; }
    
  return
   h;    
}


  static
   
  void
   _free_map_key(listnode_t
  *
   node)
{
    listnode_t    
  *
  old;
    
  while
  (node)
    {        
        old 
  =
   node;
        node 
  =
   node
  ->
  next;
        
        free(old
  ->
  data);        
        free (old);
    }
}


  static
   
  void
   _free_map_value(listnode_t
  *
   node, pfcb_hmap_value_free pfunc)
{
    listnode_t    
  *
  old;
    
  while
  (node)
    {        
        old 
  =
   node;
        node 
  =
   node
  ->
  next;
        
        
  if
   (pfunc)
            (
  *
  pfunc)(old
  ->
  data);        
        free (old);
    }
}


  /*
  =============================================================================
                            Public Functions
=============================================================================
  */
  

  /*
   Create before use 
  */
  

  void
   
hmap_create(hash_map 
  *
  hmap, 
  int
   size)
{
    (
  *
  hmap) 
  =
   (hash_map_t
  *
  ) malloc(
  sizeof
  (hash_map_t));
    (
  *
  hmap)
  ->
  size 
  =
   size;
    (
  *
  hmap)
  ->
  key 
  =
   (listnode_t
  **
  ) calloc(size, 
  sizeof
  (listnode_t
  *
  ));
    (
  *
  hmap)
  ->
  value 
  =
   (listnode_t
  **
  ) calloc(size, 
  sizeof
  (listnode_t
  *
  ));
}


  /*
   Destroy after use 
  */
  

  extern
   
  void
   
hmap_destroy(hash_map hmap, pfcb_hmap_value_free pfunc)
{
    size_t i;
    
  for
  (i
  =
  0
  ; i
  <
  hmap
  ->
  size; i
  ++
  ){
        _free_map_key(hmap
  ->
  key[i]);
        _free_map_value(hmap
  ->
  value[i], pfunc);
    }
    
    free(hmap
  ->
  key);
    free(hmap
  ->
  value);
    free(hmap);
}



  /*
   Insert a key-value into hash map. value is a pointer to callee-allocated memory 
  */
  

  void
   
hmap_insert(hash_map hmap, 
  const
   
  char
  *
   key, 
  int
   key_len, 
  void
  *
   value)
{
    listnode_t    
  *
  node_key, 
  *
  node_val;
    
  ulong
          h;
    
  char
          
  *
  s;
    assert (key);

    
  if
   (key_len
  <
  0
  ) key_len 
  =
   (
  int
  ) strlen (key);
    s 
  =
   (
  char
  *
  ) malloc (key_len
  +
  1
  );
    assert(s);


  #pragma
   warning(push)    /* C4996 */
  

  #pragma
   warning( disable : 4996 )
  
    strncpy (s, key, key_len);

  #pragma
   warning(pop)    /* C4996 */
  
    s[key_len] 
  =
   
  0
  ;
    
    node_key 
  =
   list_node_create ( (
  void
  *
  )s );
    node_val 
  =
   list_node_create ( value );
    assert(node_key 
  &&
   node_val);

    h 
  =
   hash_string (s, key_len) 
  %
   hmap
  ->
  size;

    node_key
  ->
  next 
  =
   hmap
  ->
  key[h];
    hmap
  ->
  key[h] 
  =
   node_key;
    
    node_val
  ->
  next 
  =
   hmap
  ->
  value[h];
    hmap
  ->
  value[h] 
  =
   node_val;
}


  /*
   Search a hash map for value of given key string 
  */
  

  void
  *
    
hmap_search(hash_map hmap, 
  const
   
  char
   
  *
  key)
{
    
  ulong
          h    
  =
   hash_string (key, 
  -
  1
  ) 
  %
   hmap
  ->
  size;
    listnode_t  
  *
  pk 
  =
   hmap
  ->
  key[h];
    listnode_t  
  *
  pv 
  =
   hmap
  ->
  value[h];

    
  while
   (pk)
    {
        
  if
   (strcmp(key, pk
  ->
  str) 
  ==
   
  0
  )
            
  return
   pv
  ->
  data;        
        pk 
  =
   pk
  ->
  next;
        pv 
  =
   pv
  ->
  next;
    }

    
  return
   NULL;
}

好了，其中用到的其他文件（unistd.h，list.h，list.c）看我下一篇文章！

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