1 unstable release
0.4.0 | Aug 7, 2024 |
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#971 in Encoding
12KB
206 lines
four-cc
Representation of four-character-codes.
lib.rs
:
Newtype wrapper providing a convenient representation of four-character-code values.
Using this type in a public APIs as an alternative to simply passing the equivalent u32
makes the value's expected use explicit.
Creating a FourCC value
use four_cc::FourCC;
let uuid = FourCC(*b"uuid");
// using Into
let code: FourCC = b"uuid".into();
assert_eq!(uuid, code);
From a slice
let data = b"moofftyp";
let code = FourCC::from(&data[0..4]); // would panic if fewer than 4 bytes
assert_eq!(FourCC(*b"moof"), code);
From a u32
let data: u32 = 0x6d6f6f66;
let code = FourCC::from(data);
assert_eq!(FourCC(*b"moof"), code);
// conversion back into a u32
let converted: u32 = code.into();
assert_eq!(data, converted);
Constants
FourCC values can be used in const expressions
const UUID: FourCC = FourCC(*b"uuid");
Matching
You can use FourCC values in match patterns as long as you define constants to match against,
const UUID: FourCC = FourCC(*b"uuid");
const MOOV: FourCC = FourCC(*b"moov");
match other_value {
MOOV => println!("movie"),
UUID => println!("unique identifier"),
// compiler will not accept: FourCC(*b"trun") => println!("track fragment run"),
_ => println!("Other value; scary stuff")
}
Invalid literal values
If the literal has other than four bytes, compilation will fail
let bad_fourcc = FourCC(*b"uuid123");
// -> expected an array with a fixed size of 4 elements, found one with 7 elements
Note the FourCC value may contain non-printable byte values, including the byte-value zero.
Debug display
let uuid = FourCC(*b"uuid");
println!("it's {:?}", uuid); // produces: it's FourCC{uuid}
Note that if the FourCC bytes are not able to be converted to UTF8, then a fallback
representation will be used (as it would be surprising for format!()
to panic).
let uuid = FourCC(*b"u\xFFi\0");
println!("it's {:?}", uuid); // produces: it's FourCC{u\xffi\x00}
Dependencies
~0–490KB