echo_config_lib/
echo_config_lib_rust_config_lib_source.rs

1use fidl::unpersist;
2use fidl_cf_sc_internal_echoconfiglib::Config as FidlConfig;
3use fuchsia_inspect::Node;
4use fuchsia_runtime::{take_startup_handle, HandleInfo, HandleType};
5#[derive(Debug)]
6pub struct Config {
7    pub greeting: String,
8}
9impl Config {
10    pub fn take_from_startup_handle() -> Self {
11        let config_vmo: zx::Vmo =
12            take_startup_handle(HandleInfo::new(HandleType::ComponentConfigVmo, 0))
13                .expect("Config VMO handle must be provided and cannot already have been taken.")
14                .into();
15        let config_size =
16            config_vmo.get_content_size().expect("must be able to read config vmo content size");
17        assert_ne!(config_size, 0, "config vmo must be non-empty");
18        let config_bytes =
19            config_vmo.read_to_vec(0, config_size).expect("must be able to read config vmo");
20        let checksum_length = u16::from_le_bytes([config_bytes[0], config_bytes[1]]) as usize;
21        let fidl_start = 2 + checksum_length;
22        let observed_checksum = &config_bytes[2..fidl_start];
23        let expected_checksum = vec![
24            0x41, 0xf4, 0x61, 0xea, 0xf8, 0x03, 0x45, 0xc3, 0xfe, 0x80, 0xac, 0xc7, 0xe9, 0x26,
25            0x20, 0x20, 0x5a, 0x7b, 0x41, 0xc5, 0x0d, 0xe6, 0x30, 0xe5, 0xd8, 0x39, 0xad, 0xa2,
26            0x10, 0xa9, 0xc1, 0xca,
27        ];
28        assert_eq!(
29            observed_checksum, expected_checksum,
30            "checksum from config VMO does not match expected checksum"
31        );
32        let fidl_config: FidlConfig = unpersist(&config_bytes[fidl_start..])
33            .expect("must be able to parse bytes as config FIDL");
34        Self { greeting: fidl_config.greeting }
35    }
36    pub fn record_inspect(&self, inspector_node: &Node) {
37        inspector_node.record_string("greeting", &self.greeting);
38    }
39}