大家来看看这段c语言中的一些用法！！！

lijun0623 · 发表于 2006-3-14 22:08:37

这个define也太。。。。。

make_ ## 是什么意思
多次出现的##是什么意思，我查不到啊

#define HASH_CODE(HASH, HASH_KEY, HASH_VALUE, KEY_HASH, KEY_NEQ, KEY_COPY,  \
   KEY_FREE, NULL_VALUE, VALUE_FREE)       \
\
/* HASH_HEADER(HASH, HASH_KEY, HASH_VALUE); */ \
\
HASH make_ ## HASH(size_t initial_size) \
{ \
  HASH ht; \
  ht = (HASH) MALLOC(sizeof(struct HASH ## _table)); \
  ht->tablesize = preferred_size(initial_size); \
  ht->size = 0; \
  ht->table = (HASH ## _cell_ptr *) \
CALLOC(ht->tablesize, (size_t) sizeof(HASH ## _cell_ptr)); \
  return ht; \
}    \
      \
size_t HASH ## _size(HASH ht) \
{                            \
  return ht->size;          \
}                            \
\
    \
static void HASH ## _resize(HASH ht) \
{ \
  HASH ## _cell_ptr *oldtable = ht->table; \
  size_t oldtablesize = ht->tablesize; \
  size_t tablesize = preferred_size(ht->size); \
  size_t i; \
  HASH ## _cell_ptr p, nextp; \
    \
  ht->tablesize = tablesize; \
  ht->table = (HASH ## _cell_ptr *) \
CALLOC(tablesize, (size_t) sizeof(HASH ## _cell_ptr)); \
    \
  for (i=0; i<oldtablesize; i++) \
for (p = oldtable; p; p = nextp) { \
   nextp = p->next; \
   p->next = ht->table[p->hashedkey%tablesize]; \
   ht->table[p->hashedkey%tablesize] = p; \
} \
    \
  FREE(oldtable); \
} \
\
HASH ## _cell_ptr HASH ## _find(HASH ht, const HASH_KEY key) \
{ \
  size_t hashedkey = KEY_HASH(key); \
  size_t hashedkeymod = hashedkey%ht->tablesize; \
  HASH ## _cell_ptr p = ht->table[hashedkeymod]; \
    \
  while (p && (p->hashedkey != hashedkey || KEY_NEQ(key, p->key))) \
p = p->next; \
\
  if (p) \
return p; \
  else { \
if (ht->size++ >= HASH_EXPAND_LOAD_FACTOR*ht->tablesize) { \
   HASH ## _resize(ht); \
   hashedkeymod = hashedkey%ht->tablesize; \
} \
p = MALLOC(sizeof(struct HASH ## _cell)); \
p->hashedkey = hashedkey; \
p->key = KEY_COPY(key); \
p->value = NULL_VALUE; \
p->next = ht->table[hashedkeymod]; \
ht->table[hashedkeymod] = p; \
return p; \
}} \
    \
HASH_VALUE *HASH ## _valuep(HASH ht, const HASH_KEY key)       \
{ \
  return(&(HASH ## _find(ht, key)->value)); \
} \
\
HASH_VALUE HASH ## _ref(const HASH ht, const HASH_KEY key) \
{ \
  size_t hashedkey = KEY_HASH(key); \
  HASH ## _cell_ptr p = ht->table[hashedkey%ht->tablesize]; \
\
  while (p && (p->hashedkey != hashedkey || KEY_NEQ(key, p->key))) \
p = p->next; \
\
  return p ? p->value : NULL_VALUE; \
} \
\
HASH_VALUE HASH ## _set(HASH ht, HASH_KEY key, HASH_VALUE value) \
{ \
  HASH ## _cell_ptr p = HASH ## _find(ht, key); \
  HASH_VALUE oldvalue = p->value; \
  p->value = value; \
  return oldvalue; \
} \
\
HASH_VALUE HASH ## _delete(HASH ht, HASH_KEY key)    \
{    \
  HASH_VALUE oldvalue;  \
  size_t hashedkey = KEY_HASH(key);    \
  HASH ## _cell_ptr    *p  = ht->table + hashedkey%ht->tablesize;    \
      \
  while ( *p &&       \
      ((*p)->hashedkey != hashedkey || KEY_NEQ(key, (*p)->key)) )  \
p = &((*p)->next); \
      \
  if (*p) {    \
oldvalue = (*p)->value;    \
*p = (*p)->next; \
KEY_FREE((*p)->key);       \
FREE(*p); \
      \
if (--ht->size < ht->tablesize/HASH_CONTRACT_LOAD_FACTOR) \
   HASH ## _resize(ht);    \
return oldvalue; \
  } \
  else          \
return NULL_VALUE; \
}          \
             \
    \
void free_ ## HASH(HASH ht) \
{ \
  HASH ## _cell_ptr p, q; \
  size_t  i; \
    \
  for (i = 0; i < ht->tablesize; i++) \
for (p = ht->table; p; p = q) { \
   q = p->next; \
   KEY_FREE(p->key); \
   VALUE_FREE(p->value); \
   FREE(p); \
} \
  FREE(ht->table); \
  FREE(ht); \
} \
    \
/*************************************************************************** \
*                                                                      * \
*                         hash iteration                               * \
*                                                                      * \
***************************************************************************/ \
    \
    \
HASH ## it HASH ## it_init(HASH ht) \
{ \
  struct HASH ## it hit = {0, NULL_VALUE, ht, NULL, 0}; \
  return HASH ## it_next(hit); \
} \
\
HASH ## it HASH ## it_next(HASH ## it hit0) \
{ \
  if (hit0.next) { \
hit0.key = hit0.next->key; \
hit0.value = hit0.next->value; \
hit0.next = hit0.next->next; \
return hit0; \
  } \
  else { \
size_t i = hit0.index; \
size_t tablesize = hit0.ht->tablesize; \
HASH ## _cell_ptr *table = hit0.ht->table; \
while (i < tablesize && !table) \
   i++; \
if (i==tablesize) { \
   hit0.ht = NULL; \
   return hit0; \
} \
else { \
   hit0.key = table->key; \
   hit0.value = table->value; \
   hit0.next = table->next; \
   hit0.index = i+1; \
   return hit0; \
}}} \
    \
int HASH ## it_ok(HASH ## it hit) \
{ \
  return hit.ht!=NULL; \
}

#define HASH_CODE_ADD(HASH, HASH_KEY, HASH_VALUE, KEY_HASH, KEY_NEQ, \
      KEY_COPY, KEY_FREE, NULL_VALUE, VALUE_FREE)    \
         \
HASH_CODE(HASH, HASH_KEY, HASH_VALUE, KEY_HASH, KEY_NEQ,             \
KEY_COPY, KEY_FREE, NULL_VALUE, VALUE_FREE)          \
                                                                     \
HASH_VALUE HASH ## _inc(HASH ht, const HASH_KEY key, HASH_VALUE inc) \
{                                                                   \
/*  size_t hashedkey = KEY_HASH(key); */ \
  HASH ## _cell_ptr p = HASH ## _find(ht, key); \
    \
  p->value += inc; \
  return p->value; \
}

弥敦路九号 · 发表于 2006-3-15 00:29:53

##就是连接符。你看这段代码

#include <stdio.h>
#define CAT_NUM(NUM1,NUM2) NUM1 ## NUM2
int
main()
{
printf("%d\n", CAT_NUM(12,34));
return 0;
}

复制代码

输出结果为 1234
直接用如下写法是会报参数NUM1NUM2未声明的
#define CAT_NUM(NUM1,NUM2) NUM1NUM2

bookstack · 发表于 2006-3-15 03:01:27

nngx, 为什么不用inline来实现阿？

gamedragon · 发表于 2006-3-15 08:59:54

inline无法实现##这种功能。

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