Mockup of the new package os interface (incomplete and non-functioning)

core/os/os2/env_windows.odin

@@ -0,0 +1,80 @@
+//+private
+package os2
+
+import "core:mem"
+import win32 "core:sys/windows"
+
+_lookup_env :: proc(key: string, allocator := context.allocator) -> (value: string, found: bool) {
+	if key == "" {
+		return;
+	}
+	wkey := win32.utf8_to_wstring(key);
+	b := make([dynamic]u16, 100, context.temp_allocator);
+	for {
+		n := win32.GetEnvironmentVariableW(wkey, raw_data(b), u32(len(b)));
+		if n == 0 {
+			err := win32.GetLastError();
+			if err == win32.ERROR_ENVVAR_NOT_FOUND {
+				return "", false;
+			}
+		}
+
+		if n <= u32(len(b)) {
+			value = win32.utf16_to_utf8(b[:n], allocator);
+			found = true;
+			return;
+		}
+
+		resize(&b, len(b)*2);
+	}
+}
+
+_set_env :: proc(key, value: string) -> bool {
+	k := win32.utf8_to_wstring(key);
+	v := win32.utf8_to_wstring(value);
+
+	return bool(win32.SetEnvironmentVariableW(k, v));
+}
+
+_unset_env :: proc(key: string) -> bool {
+	k := win32.utf8_to_wstring(key);
+	return bool(win32.SetEnvironmentVariableW(k, nil));
+}
+
+_clear_env :: proc() {
+	envs := environ(context.temp_allocator);
+	for env in envs {
+		for j in 1..<len(env) {
+			if env[j] == '=' {
+				unset_env(env[0:j]);
+				break;
+			}
+		}
+	}
+}
+
+_environ :: proc(allocator := context.allocator) -> []string {
+	envs := win32.GetEnvironmentStringsW();
+	if envs == nil {
+		return nil;
+	}
+	defer win32.FreeEnvironmentStringsW(envs);
+
+	r := make([dynamic]string, 0, 50, allocator);
+	for from, i, p := 0, 0, envs; true; i += 1 {
+		c := (^u16)(uintptr(p) + uintptr(i*2))^;
+		if c == 0 {
+			if i <= from {
+				break;
+			}
+			w := mem.slice_ptr(mem.ptr_offset(p, from), i-from);
+
+			append(&r, win32.utf16_to_utf8(w, allocator));
+			from = i + 1;
+		}
+	}
+
+	return r[:];
+}
+
+