strcspn.c

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 Copyright (c) 2019 Walt Elam
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/***************************************************************************//**
 @file strcspn.c
 
 @brief Defines the strcspn function
*******************************************************************************/
#include <string.h>
 
/*******************************************************************************
 strcspn
*//**
 @brief Find the length of the span of complementary characters to s2 in s1
 @param *s1 String being searched
 @param *s2 String of characters not counted in the span being found
 
 The strcspn function computes the length of the maximum initial segment of
 the string pointed to by s1 which consists entirely of characters not from
 the string pointed to by s2.
 
 @return The length of the segment
*******************************************************************************/
size_t
strcspn(const char *s1, const char *s2)
{
 size_t len = 0;
 
 if (!s1)
 {
 return 0;
 }
 
 if (!s2)
 {
 return strlen(s1);
 }
 
 while (*s1 &&
 !strchr(s2, *s1++))
 {
 len++;
 }
 
 return len;
}