Prepends @len bytes of @val to @string. Because @len is provided, @val may contain embedded nuls and need not be nul-terminated.
Since this function does not stop at nul bytes, it is the caller's responsibility to ensure that @val has at least @len addressable bytes.
bytes to prepend
number of bytes in @val to prepend
Return: @string
See Implementation
Prepends @len bytes of @val to @string. Because @len is provided, @val may contain embedded nuls and need not be nul-terminated.
Since this function does not stop at nul bytes, it is the caller's responsibility to ensure that @val has at least @len addressable bytes.