_lsearch

2015-06-09

Performs a linear search for a value; adds to end of list if not found. A more secure version of this function is available; see _lsearch_s.

void *_lsearch(
   const void *key,
   void *base,
   unsigned int *num,
   unsigned int width,
   int (__cdecl *compare)(const void *, const void *) 
);

参数

key
Object to search for.
base
Pointer to the base of array to be searched.
num
Number of elements.
width
Width of each array element.
compare
Pointer to the comparison routine. The first parameter is a pointer to the key for search. The second parameter is a pointer to an array element to be compared with the key.

返回值

If the key is found, _lsearch returns a pointer to the element of the array at base that matches key. If the key is not found, _lsearch returns a pointer to the newly added item at the end of the array.

备注

The _lsearch function performs a linear search for the value key in an array of num elements, each of width bytes. Unlike bsearch, _lsearch does not require the array to be sorted. If key is not found, _lsearch adds it to the end of the array and increments num.

The compare argument is a pointer to a user-supplied routine that compares two array elements and returns a value specifying their relationship. _lsearch calls the compare routine one or more times during the search, passing pointers to two array elements on each call. compare must compare the elements and return either nonzero (meaning the elements are different) or 0 (meaning the elements are identical).

此函数验证其参数。 If compare, key or num is NULL, or if base is NULL and *num is nonzero, or if width is less than zero, the invalid parameter handler is invoked, as described in 参数验证. 如果允许执行继续，errno设置为EINVAL，并且函数返回NULL。

要求

例程	必需的标头
_lsearch	<search.h>

有关更多兼容性信息，请参见“简介”中的兼容性。

示例

// crt_lsearch.c
#include <search.h>
#include <string.h>
#include <stdio.h>

int compare( const void *arg1, const void *arg2 );

int main(void)
{
   char * wordlist[4] = { "hello", "thanks", "bye" };
                            // leave room to grow...
   int n = 3;
   char **result;
   char *key = "extra";
   int i;

   printf( "wordlist before _lsearch:" );
   for( i=0; i<n; ++i ) printf( " %s", wordlist[i] );
   printf( "\n" );

   result = (char **)_lsearch( &key, wordlist, 
                      &n, sizeof(char *), compare );

   printf( "wordlist after _lsearch:" );
   for( i=0; i<n; ++i ) printf( " %s", wordlist[i] );
   printf( "\n" );
}

int compare(const void *arg1, const void *arg2 )
{
   return( _stricmp( * (char**)arg1, * (char**)arg2 ) );
}