Optimized version of leftpad in plain C

#include <string.h>

static const char*
string_add(const char* first, const char* second)
{
const char* result = malloc(strlen(first) + strlen(second) + 1);
strcat(result, first);
strcat(result, second);
return result;
}

const char*
leftpad(const char* str, size_t len, char ch)
{
int i = -1;

if (ch == 0) ch = ' ';

int len = strlen(str);

while (++i < len) {
char buf[2] = { 0 };
buf[0] = ch;
str = string_add(buf, str);
}

return str;
}

>>101
Granted, the Unicode spec is complex. But you can use UTF-8 as an encoding without having to worry about most of the additional technical standards. I mean, you should probably at least normalize input when saving it to a persistent store, but hell - you can just ignore it and fail hard on all kinds of foreign language edge cases like all American software. UTF-8 don't care.