a C standard library for fx Casio calculators
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fxlibc/src/libc/string/strcat.c

50 lines
1.4 KiB

#include <string.h>
/*
** The strcat() function appends the src string to the dest string,
** overwriting the terminating null byte ('\0') at the end of dest, and then
** adds a terminating null byte. The strings may not overlap, and the dest
** string must have enough space for the result. If dest is not large enough,
** program behavior is unpredictable; buffer overruns are a favorite avenue for
** attacking secure programs.
**
** TODO: use the DMA !
** TODO: look at the DSP ?
*/
char *strcat(char *dest, char const *src)
{
size_t i;
size_t start;
if (src == NULL || dest == NULL)
return (0);
i = -1;
start = -1;
while (dest[++start] != '\0') ;
while (src[++i] != '\0')
dest[start + i] = src[i];
dest[i + start] = '\0';
return (dest);
}
/*
** The strncat() function is similar, except that:
** * it will use at most n bytes from src; and
** * src does not need to be null-terminated if it contains n or more bytes.
**
** As with strcat(), the resulting string in dest is always null-terminated.
**
** If src contains n or more bytes, strncat() writes n+1 bytes to dest (n from
** src plus the terminating null byte). Therefore, the size of dest must be at
** least strlen(dest)+n+1.
*/
char *strncat(char *dest, const char *src, size_t n)
{
size_t dest_len = strlen(dest);
size_t i;
for (i = 0; i < n && src[i] != '\0'; i++)
dest[dest_len + i] = src[i];
dest[dest_len + i] = '\0';
return (dest);
}