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Change Schema to be implemented by a dedicated type instead of its element type.

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Tangent 128 2017-01-17 03:00:09 -05:00
parent 8b0021e3eb
commit 6ab32205bb
1 changed files with 12 additions and 7 deletions
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19
src/lib.rs
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@ -93,17 +93,22 @@ pub fn decode_tag(bytes: &[u8]) -> Result<Option<(u64, Varint, usize)>, Error> {
} }
} }
pub trait Schema<'a>: Sized { pub trait Schema<'a> {
type Element;
fn should_unwrap(element_id: u64) -> bool; fn should_unwrap(element_id: u64) -> bool;
fn decode<'b: 'a>(element_id: u64, bytes: &'b[u8]) -> Result<Self, Error>; fn decode<'b: 'a>(element_id: u64, bytes: &'b[u8]) -> Result<Self::Element, Error>;
} }
pub struct Webm;
#[derive(Debug, PartialEq)] #[derive(Debug, PartialEq)]
pub enum WebmElement<'a> { pub enum WebmElement<'a> {
Unknown(u64, &'a[u8]) Unknown(u64, &'a[u8])
} }
impl<'a> Schema<'a> for WebmElement<'a> { impl<'a> Schema<'a> for Webm {
type Element = WebmElement<'a>;
fn should_unwrap(element_id: u64) -> bool { fn should_unwrap(element_id: u64) -> bool {
false false
} }
@ -114,12 +119,12 @@ impl<'a> Schema<'a> for WebmElement<'a> {
} }
} }
pub fn decode_element<'a, 'b: 'a, T: Schema<'a>>(bytes: &'b[u8]) -> Result<Option<(T, usize)>, Error> { pub fn decode_element<'a, 'b: 'a, T: Schema<'a>>(bytes: &'b[u8]) -> Result<Option<(T::Element, usize)>, Error> {
match decode_tag(bytes) { match decode_tag(bytes) {
Ok(None) => Ok(None), Ok(None) => Ok(None),
Err(err) => Err(err), Err(err) => Err(err),
Ok(Some((element_id, payload_size_tag, tag_size))) => { Ok(Some((element_id, payload_size_tag, tag_size))) => {
let should_unwrap = <T as Schema>::should_unwrap(element_id); let should_unwrap = T::should_unwrap(element_id);
let payload_size = match (should_unwrap, payload_size_tag) { let payload_size = match (should_unwrap, payload_size_tag) {
(true, _) => 0, (true, _) => 0,
@ -133,7 +138,7 @@ pub fn decode_element<'a, 'b: 'a, T: Schema<'a>>(bytes: &'b[u8]) -> Result<Optio
return Ok(None); return Ok(None);
} }
match Schema::decode(element_id, &bytes[tag_size..element_size]) { match T::decode(element_id, &bytes[tag_size..element_size]) {
Ok(element) => Ok(Some((element, element_size))), Ok(element) => Ok(Some((element, element_size))),
Err(error) => Err(error) Err(error) => Err(error)
} }
@ -212,7 +217,7 @@ mod tests {
#[test] #[test]
fn decode_sanity_test() { fn decode_sanity_test() {
let decoded = decode_element(TEST_FILE); let decoded = decode_element::<Webm>(TEST_FILE);
if let Ok(Some((WebmElement::Unknown(tag, slice), element_size))) = decoded { if let Ok(Some((WebmElement::Unknown(tag, slice), element_size))) = decoded {
assert_eq!(tag, 0x0A45DFA3); // EBML tag, sans the length indicator bit assert_eq!(tag, 0x0A45DFA3); // EBML tag, sans the length indicator bit
assert_eq!(slice.len(), 31); // known header payload length assert_eq!(slice.len(), 31); // known header payload length