libmemcached中的memcached_get()问题 [英] question with memcached_get() in libmemcached

问题描述

memcached_get (memcached_st *ptr,
               const char *key, size_t key_length,
               size_t *value_length,
               uint32_t *flags,
               memcached_return_t *error);

为什么需要在此处传递参数"size_t key_length"和"size_t * value_length"?我认为可以直接通过键获取值.

Why need to pass the params "size_t key_length" and "size_t *value_length" here ? I think the value can be fetched by key directly.

谁能帮助告诉我原因，谢谢.

who can help to tell me the reason, thanks.

推荐答案

key参数是指向要从内存缓存中获取信息的标识符的指针. key_length告诉memcached_get()函数您的标识符数据有多长时间.

The key parameter is a pointer to an identifier for the information you want to get from memcache. The key_length tells the memcached_get() function how long your identifier data is.

如果libmemcache API假定key参数所指向的数据是一个以NULL终止的字符串，那么我们就不需要传递key_length参数.但是通过不做这样的假设，API允许我们使用除以NULL终止的char字符串之外的其他数据作为键(例如，UTF-16字符串或二进制数字).

If the libmemcache API assumed that the data pointed to by the key parameter was a NULL-terminated string of characters, then we wouldn't need to also pass in the key_length parameter. But by not making that assumption the API allows us to use data other than NULL-terminated char strings as keys (for example, UTF-16 strings, or binary numbers).

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