README.md

In the files below, a.c is the original version.

Version b.c swaps the order of the functions and makes no other changes.

Version c.c adds a comment to Chunk_copy.

This is what you get if you merge b.c and c.c using Git's default diff algorithm.

int Chunk_bounds_check(Chunk *chunk, size_t start, size_t n)
{
    if (chunk == NULL) return 0;

<<<<<<<
    size_t length = chunk->length;
=======
    // copy the bytes
    memcpy(dst->data + dst_start, src->data + src_start, n);
>>>>>>>

    return start <= length && n <= length - start;
}

size_t Chunk_copy(Chunk *src, size_t src_start, Chunk *dst, size_t dst_start, size_t n)
{
    if (!Chunk_bounds_check(src, src_start, n)) return 0;
    if (!Chunk_bounds_check(dst, dst_start, n)) return 0;

    memcpy(dst->data + dst_start, src->data + src_start, n);

    return n;
}

a.c

size_t Chunk_copy(Chunk *src, size_t src_start, Chunk *dst, size_t dst_start, size_t n)
{
    if (!Chunk_bounds_check(src, src_start, n)) return 0;
    if (!Chunk_bounds_check(dst, dst_start, n)) return 0;

    memcpy(dst->data + dst_start, src->data + src_start, n);

    return n;
}

int Chunk_bounds_check(Chunk *chunk, size_t start, size_t n)
{
    if (chunk == NULL) return 0;

    size_t length = chunk->length;

    return start <= length && n <= length - start;
}

b.c

int Chunk_bounds_check(Chunk *chunk, size_t start, size_t n)
{
    if (chunk == NULL) return 0;

    size_t length = chunk->length;

    return start <= length && n <= length - start;
}

size_t Chunk_copy(Chunk *src, size_t src_start, Chunk *dst, size_t dst_start, size_t n)
{
    if (!Chunk_bounds_check(src, src_start, n)) return 0;
    if (!Chunk_bounds_check(dst, dst_start, n)) return 0;

    memcpy(dst->data + dst_start, src->data + src_start, n);

    return n;
}

c.c

size_t Chunk_copy(Chunk *src, size_t src_start, Chunk *dst, size_t dst_start, size_t n)
{
    if (!Chunk_bounds_check(src, src_start, n)) return 0;
    if (!Chunk_bounds_check(dst, dst_start, n)) return 0;

    // copy the bytes
    memcpy(dst->data + dst_start, src->data + src_start, n);

    return n;
}

int Chunk_bounds_check(Chunk *chunk, size_t start, size_t n)
{
    if (chunk == NULL) return 0;

    size_t length = chunk->length;

    return start <= length && n <= length - start;
}