WindowsEnvironStrings

const WindowsEnvironStrings = struct {
    PATH: ?[:0]const u16 = null,
    PATHEXT: ?[:0]const u16 = null,

    fn scan() WindowsEnvironStrings {
        const peb = windows.peb();
        assert(windows.ntdll.RtlEnterCriticalSection(peb.FastPebLock) == .SUCCESS);
        defer assert(windows.ntdll.RtlLeaveCriticalSection(peb.FastPebLock) == .SUCCESS);
        const ptr = peb.ProcessParameters.Environment;

        var result: WindowsEnvironStrings = .{};
        var i: usize = 0;
        while (ptr[i] != 0) {
            const key_start = i;

            // There are some special environment variables that start with =,
            // so we need a special case to not treat = as a key/value separator
            // if it's the first character.
            // https://devblogs.microsoft.com/oldnewthing/20100506-00/?p=14133
            if (ptr[key_start] == '=') i += 1;

            while (ptr[i] != 0 and ptr[i] != '=') : (i += 1) {}
            const key_w = ptr[key_start..i];

            if (ptr[i] == '=') i += 1;

            const value_start = i;
            while (ptr[i] != 0) : (i += 1) {}
            const value_w = ptr[value_start..i :0];

            i += 1; // skip over null byte

            inline for (@typeInfo(WindowsEnvironStrings).@"struct".field_names) |field_name| {
                const field_name_w = comptime std.unicode.wtf8ToWtf16LeStringLiteral(field_name);
                if (windows.eqlIgnoreCaseWtf16(key_w, field_name_w)) @field(result, field_name) = value_w;
            }
        }

        return result;
    }
}