Question

#include <stdio.h>
#include <stdlib.h>
#include <search.h>
#include <assert.h>

char *data[] = { "alpha", "bravo", "charlie", "delta",
      "echo", "foxtrot", "golf", "hotel", "india", "juliet",
      "kilo", "lima", "mike", "november", "oscar", "papa",
      "quebec", "romeo", "sierra", "tango", "uniform",
      "victor", "whisky", "x-ray", "yankee", "zulu"
       };

int
main(void)
{
    ENTRY e, **ep;
    struct hsearch_data *htab;
    int i;
    int resultOfHcreate_r;
    resultOfHcreate_r=hcreate_r(30,htab);
    assert(resultOfHcreate_r!=0);
    hdestroy_r(htab);
    exit(EXIT_SUCCESS);
}

hcreate_r

中的

错误

如何使用此hcreate_r？

和其他问题是：

您是否可以使用GNU扩展C库示例？我认为GNU扩展C库的文档编写的知识不够。

我对如何使用扩展C库有很多疑问。

Answer 1

首先，您需要添加#define _GNU_SOURCE宏才能正确访问GNU扩展。即：

#define _GNU_SOURCE
#include <search.h>

然后你需要了解文档：的的

的

功能：int hcreate_r（size_t nel，struct hsearch_data * htab）

The hcreate_r function initializes the object pointed to by htab to contain a hashing table with at least nel elements. So this function is equivalent to the hcreate function except that the initialized data structure is controlled by the user. This allows having more than one hashing table at one time. The memory necessary for the struct hsearch_data object can be allocated dynamically. It must be initialized with zero before calling this function. The return value is non-zero if the operation was successful. If the return value is zero, something went wrong, which probably means the programs ran out of memory.

的
因此，与hcreate不同，您正在提供散列表数据结构。此外，这些结构应初始化为零。那么你可能想做这样的事情：

//dynamically create a single table of 30 elements 
htab=calloc(1,sizeof(struct hsearch_data));
resultOfHcreate_r=hcreate_r(30,htab);

//do some stuff

//dispose of the hash table and free heap memory
hdestroy_r(htab);
free(htab)

如何使用GNU hcreate_r

1 个答案: