// Package misc provides miscellaneous functions.
package misc

import (
	"errors"
	"strings"
)

// Copy_map the map src to dst without clearing existing items in dst.
func Copy_map[K comparable, V any](dst map[K]V, src map[K]V) {
	for k, v := range src {
		dst[k] = v
	}
}

// String_to_byte_ptr returns a pointer to the first byte of a string. It
// ensures that the returned pointer is null-terminated.
func String_to_byte_ptr(s string) (*byte, error) {
	// If the string already contains a null then whoever attempts to
	// interpret this as a null-terminated string won't be able to see the
	// whole string. This is probably not expected by the caller.
	if strings.IndexByte(s, 0) != -1 {
		return nil, Err_null_byte
	}
	buf := make([]byte, len(s)+1) // Zeros them out...
	copy(buf, s)                  // ... so the last byte would be null.
	return &buf[0], nil
}

var Err_null_byte = errors.New("string contains null byte")