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string provides a minimal set of string utilities for bare-metal use. It is compiled with -nostdlib and therefore cannot include the standard <string.h>. Only the operations actually required by the OS are implemented.
This library does not expose strlen, strcpy, strcmp, memset, or memcpy. The sole function is my_strncpy, which covers the one safe-copy use case needed in the project.

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my_strncpy

char *my_strncpy(char *dest, const char *src, size_t n);
Copies at most n characters from src into dest. If src is shorter than n characters, the remainder of dest is filled with null bytes. The destination is always null-padded up to n bytes, but it is not guaranteed to be null-terminated when src is exactly n characters long.

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Parameters

ParameterTypeDescription
destchar *Destination buffer. Must have room for at least n bytes.
srcconst char *Source string to copy from.
nsize_tMaximum number of characters to copy.

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Return value

Returns dest.

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Implementation

char *my_strncpy(char *dest, const char *src, size_t n) {
    size_t i;
    for(i = 0; i < n && src[i] != '\0'; i++) {
        dest[i] = src[i];
    }
    for(; i < n; i++) {
        dest[i] = '\0';
    }
    return dest;
}

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Usage example

#include "string.h"

char buf[16];
my_strncpy(buf, "hello", sizeof(buf));
// buf == "hello\0\0\0\0\0\0\0\0\0\0\0"
If src is exactly n characters long with no null terminator, dest will not be null-terminated. Always ensure the destination buffer is at least n + 1 bytes when treating the result as a C string, or keep src shorter than n.

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