pub trait Decode {
type Item;
// Required methods
fn decode(&mut self, buf: &[u8], eos: Eos) -> Result<usize>;
fn finish_decoding(&mut self) -> Result<Self::Item>;
fn requiring_bytes(&self) -> ByteCount;
// Provided method
fn is_idle(&self) -> bool { ... }
}Expand description
This trait allows for decoding items from a byte sequence incrementally.
Required Associated Types§
Required Methods§
Sourcefn decode(&mut self, buf: &[u8], eos: Eos) -> Result<usize>
fn decode(&mut self, buf: &[u8], eos: Eos) -> Result<usize>
Consumes the given buffer (a part of a byte sequence), and proceeds the decoding process.
It returns the number of bytes consumed from the input buffer.
If an item is completely decoded, the next invocation of is_idle method will return true.
And if is_idle method returns true, decode method should consume no bytes.
The decoder must consume as many bytes in the buffer as possible.
If an item is not yet decoded but the number of consumed bytes in the last decode invocation
is smaller than the length of buf, it means the decoder has been suspended its work in any reasons.
In that case the decoder may require some instructions from clients to resume the work,
but its concrete method is beyond the scope of this trait.
§Errors
The following errors may be returned by the decoder:
ErrorKind::DecoderTerminated:- If all decodable items have been decoded,
the decoder must return this kind of error when
decodemethod is called.
- If all decodable items have been decoded,
the decoder must return this kind of error when
ErrorKind::UnexpectedEos:- The invocation of
eos.is_reached()returnstruedespite of the decoder requires more bytes to decode the next item.
- The invocation of
ErrorKind::InvalidInput:- Decoded items have invalid values
- Invalid parameters were given to decoders
ErrorKind::InconsistentState:- The state of the decoder bocame inconsistent
- This means the implementation contains a bug
ErrorKind::Other:- Other errors
Sourcefn finish_decoding(&mut self) -> Result<Self::Item>
fn finish_decoding(&mut self) -> Result<Self::Item>
Finishes the current decoding process and returns the decoded item.
§Errors
The following errors may be returned by the decoder:
ErrorKind::IncompleteDecoding:- The decoding process has not been completed
ErrorKind::DecoderTerminated:- The decoder has terminated (i.e., cannot decode any more items)
ErrorKind::InconsistentState:- The state of the decoder bocame inconsistent
- This means the implementation contains a bug
ErrorKind::Other:- Other errors
Sourcefn requiring_bytes(&self) -> ByteCount
fn requiring_bytes(&self) -> ByteCount
Returns the lower bound of the number of bytes needed to decode the next item.
If the decoder does not know the value, it will return ByteCount::Unknown
(e.g., null-terminated strings have no pre-estimable length).
If the decoder returns ByteCount::Finite(0), it means one of the followings:
- (a) There is an already decoded item
- The next invocation of
decode()will return it without consuming any bytes
- The next invocation of
- (b) There are no decodable items
- All decodable items have been decoded, and the decoder cannot do any further works
- In this case, the next invocation of
decodemethod will fail.
Provided Methods§
Sourcefn is_idle(&self) -> bool
fn is_idle(&self) -> bool
Returns true if there are no items to be decoded by the decoder
at the next invocation of decode method, otherwise false.
Typically, true means the decoder already has a decoded item and
it is waiting for finish_decoding to be called.
The default implementation returns the result of self.requiring_bytes() == ByteCount::Finite(0).