该文件是线程私有数据的实现。在线程tcb里有一个数组，保存了一系列的键对值。从而实现了线程的私有数据存储。线程想拥有自己的数据时，首先获取一个键，然后在tcb中保存一个键对值即可。
代码语言：javascript复制/
/* Thread-specific data */
#include <errno.h>
#include <stddef.h>
#include "pthread.h"
#include "internals.h"
typedef void (*destr_function)(void *);
/* Table of keys. */
struct pthread_key_struct {
int in_use; /* already allocated? */
destr_function destr; /* destruction routine */
};
static struct pthread_key_struct pthread_keys[PTHREAD_KEYS_MAX] =
{ { 0, NULL } };
/* Mutex to protect access to pthread_keys */
static pthread_mutex_t pthread_keys_mutex = PTHREAD_MUTEX_INITIALIZER;
/* Create a new key */
// 创建一个key
int __pthread_key_create(pthread_key_t * key, destr_function destr)
{
int i;
// 加锁
pthread_mutex_lock(&pthread_keys_mutex);
// 从列表中找一项空闲的
for (i = 0; i < PTHREAD_KEYS_MAX; i ) {
if (! pthread_keys[i].in_use) {
pthread_keys[i].in_use = 1;
pthread_keys[i].destr = destr;
// 找到则解锁并返回键值
pthread_mutex_unlock(&pthread_keys_mutex);
*key = i;
return 0;
}
}
// 找不到则解锁
pthread_mutex_unlock(&pthread_keys_mutex);
return EAGAIN;
}
weak_alias (__pthread_key_create, pthread_key_create)
/* Delete a key */
// 删除一个键对应的项
int pthread_key_delete(pthread_key_t key)
{
pthread_mutex_lock(&pthread_keys_mutex);
if (key >= PTHREAD_KEYS_MAX || !pthread_keys[key].in_use) {
pthread_mutex_unlock(&pthread_keys_mutex);
return EINVAL;
}
pthread_keys[key].in_use = 0;
pthread_keys[key].destr = NULL;
pthread_mutex_unlock(&pthread_keys_mutex);
return 0;
}
/* Set the value of a key */
// 关联键对应的值
int __pthread_setspecific(pthread_key_t key, const void * pointer)
{
pthread_t self = thread_self();
if (key >= PTHREAD_KEYS_MAX) return EINVAL;
self->p_specific[key] = (void *) pointer;
return 0;
}
weak_alias (__pthread_setspecific, pthread_setspecific)
/* Get the value of a key */
void * __pthread_getspecific(pthread_key_t key)
{
pthread_t self = thread_self();
if (key >= PTHREAD_KEYS_MAX)
return NULL;
else
return self->p_specific[key];
}
weak_alias (__pthread_getspecific, pthread_getspecific)
/* Call the destruction routines on all keys */
// 逐个调用pthread_keys数组中的destr函数，并以线程关联的value为参数
void __pthread_destroy_specifics()
{
int i;
pthread_t self = thread_self();
destr_function destr;
void * data;
for (i = 0; i < PTHREAD_KEYS_MAX; i ) {
// 销毁时执行的函数
destr = pthread_keys[i].destr;
// 获取键对应的值
data = self->p_specific[i];
// 执行
if (destr != NULL && data != NULL) destr(data);
}
}
