On Tue, 28 Jan 2020, ToddAndMargo via perl6-users wrote:
> This all came up when I tried to match
>
> RegSetValueExW(
> _In_ HKEY hKey,
> _In_opt_ LPCWSTR lpValueName,
> _Reserved_ DWORD Reserved,
> _In_ DWORD dwType,
> _In_reads_bytes_opt_(cbData) CONST BYTE * lpData,
> _In_ DWORD cbData
>
> where CbData can either be a UTF little endian C string,
> terminated by a nul or a four byte little endian
> unsigned integer (no two's complement allowed) depending
> on the value of lpValueName (REG_SZ, REG_DWORD, etc.)
>
> I wound up doing this:
>
> subset StrOrDword where Str | UInt;
> sub WinRegSetValue( WinRegHives $Hive, Str $SubKey, Str $KeyName, ValueNames
> $ValueType, StrOrDword $ValueData, Bool $Debug = False )
> returns DWORD is export( :WinRegSetValue ) {
Are you really 100% sure that you interpreted this API correctly? I see how
a DWORD cbData can be a four-byte unsigned integer: it gives the length of
lpData in bytes, as documented [1].
But then a DWORD is 4 bytes long. Reusing these 4 bytes for an alternative
interface where you may pass a UTF-whatever string that is at most 4 bytes
encoded, including the NUL terminator... seems too insane. And there is no
mention of that in the documentation page [1]. I do not think that cbData
is ever used for anything but to indicate the length of the buffer lpData.
It is lpData which can have a multitude of types (and serialization formats),
the intended one to be taken from the dwType argument (not lpValueName).
My advice is still the same I gave in my very first reply to this thread:
make your function a multi and write a candidate for each dwType. You have
to write different code for serializing an integer vs. a string to pass as
lpData anyway and the compiler can detect native types in multi dispatch
for you:
# REG_DWORD
multi WinRegSetValue(…, uint32 $data) {
use experimental :pack;
RegSetValueExW(…, REG_DWORD, pack("L", $data), 4)
}
# REG_SZ
multi WinRegSetValue(…, Str $data) {
my $blob = "$data\0".encode
RegSetValueExW(…, REG_SZ, $blob, $blob.bytes)
}
# REG_BINARY
multi WinRegSetValue(…, blob8 $data) {
RegSetValueExW(…, REG_BINARY, $data, $data.bytes)
}
Regards,
Tobias
[1]
https://docs.microsoft.com/en-us/windows/win32/api/winreg/nf-winreg-regsetvalueexw
--
"There's an old saying: Don't change anything... ever!" -- Mr. Monk
