pub struct Partial<I> { /* private fields */ }
Expand description
Mark the input as a partial buffer for streaming input.
Complete input means that we already have all of the data. This will be the common case with small files that can be read entirely to memory.
In contrast, streaming input assumes that we might not have all of the data. This can happen with some network protocol or large file parsers, where the input buffer can be full and need to be resized or refilled.
ErrMode::Incomplete
will report how much more data is needed.Parser::complete_err
transformErrMode::Incomplete
toErrMode::Backtrack
See also StreamIsPartial
to tell whether the input supports complete or partial parsing.
See also [Special Topics: Parsing Partial Input][crate::_topic::partial].
Example
Here is how it works in practice:
fn take_partial(i: Partial<&[u8]>) -> IResult<Partial<&[u8]>, &[u8]> {
bytes::take(4u8).parse_next(i)
}
fn take_complete(i: &[u8]) -> IResult<&[u8], &[u8]> {
bytes::take(4u8).parse_next(i)
}
// both parsers will take 4 bytes as expected
assert_eq!(take_partial(Partial::new(&b"abcde"[..])), Ok((Partial::new(&b"e"[..]), &b"abcd"[..])));
assert_eq!(take_complete(&b"abcde"[..]), Ok((&b"e"[..], &b"abcd"[..])));
// if the input is smaller than 4 bytes, the partial parser
// will return `Incomplete` to indicate that we need more data
assert_eq!(take_partial(Partial::new(&b"abc"[..])), Err(ErrMode::Incomplete(Needed::new(1))));
// but the complete parser will return an error
assert_eq!(take_complete(&b"abc"[..]), Err(ErrMode::Backtrack(Error::new(&b"abc"[..], ErrorKind::Slice))));
// the alpha0 function recognizes 0 or more alphabetic characters
fn alpha0_partial(i: Partial<&str>) -> IResult<Partial<&str>, &str> {
character::alpha0(i)
}
fn alpha0_complete(i: &str) -> IResult<&str, &str> {
character::alpha0(i)
}
// if there's a clear limit to the recognized characters, both parsers work the same way
assert_eq!(alpha0_partial(Partial::new("abcd;")), Ok((Partial::new(";"), "abcd")));
assert_eq!(alpha0_complete("abcd;"), Ok((";", "abcd")));
// but when there's no limit, the partial version returns `Incomplete`, because it cannot
// know if more input data should be recognized. The whole input could be "abcd;", or
// "abcde;"
assert_eq!(alpha0_partial(Partial::new("abcd")), Err(ErrMode::Incomplete(Needed::new(1))));
// while the complete version knows that all of the data is there
assert_eq!(alpha0_complete("abcd"), Ok(("", "abcd")));
Implementations§
source§impl<I> Partial<I>where
I: StreamIsPartial,
impl<I> Partial<I>where
I: StreamIsPartial,
sourcepub fn into_inner(self) -> I
pub fn into_inner(self) -> I
Extract the original Stream
Trait Implementations§
source§impl<I, T> Compare<T> for Partial<I>where
I: Compare<T>,
impl<I, T> Compare<T> for Partial<I>where
I: Compare<T>,
source§fn compare(&self, t: T) -> CompareResult
fn compare(&self, t: T) -> CompareResult
Compares self to another value for equality
source§fn compare_no_case(&self, t: T) -> CompareResult
fn compare_no_case(&self, t: T) -> CompareResult
Compares self to another value for equality
independently of the case. Read more
source§impl<I, T> FindSlice<T> for Partial<I>where
I: FindSlice<T>,
impl<I, T> FindSlice<T> for Partial<I>where
I: FindSlice<T>,
source§fn find_slice(&self, substr: T) -> Option<usize>
fn find_slice(&self, substr: T) -> Option<usize>
Returns the offset of the slice if it is found
source§impl<I: Ord> Ord for Partial<I>
impl<I: Ord> Ord for Partial<I>
1.21.0 · source§fn max(self, other: Self) -> Selfwhere
Self: Sized,
fn max(self, other: Self) -> Selfwhere
Self: Sized,
Compares and returns the maximum of two values. Read more
source§impl<I: PartialEq> PartialEq<Partial<I>> for Partial<I>
impl<I: PartialEq> PartialEq<Partial<I>> for Partial<I>
source§impl<I: PartialOrd> PartialOrd<Partial<I>> for Partial<I>
impl<I: PartialOrd> PartialOrd<Partial<I>> for Partial<I>
1.0.0 · source§fn le(&self, other: &Rhs) -> bool
fn le(&self, other: &Rhs) -> bool
This method tests less than or equal to (for
self
and other
) and is used by the <=
operator. Read moresource§impl<I: Stream> Stream for Partial<I>
impl<I: Stream> Stream for Partial<I>
§type IterOffsets = <I as Stream>::IterOffsets
type IterOffsets = <I as Stream>::IterOffsets
Iterate with the offset from the current location
source§fn iter_offsets(&self) -> Self::IterOffsets
fn iter_offsets(&self) -> Self::IterOffsets
Iterate with the offset from the current location
source§fn eof_offset(&self) -> usize
fn eof_offset(&self) -> usize
Returns the offaet to the end of the input
source§fn next_token(&self) -> Option<(Self, Self::Token)>
fn next_token(&self) -> Option<(Self, Self::Token)>
Split off the next token from the input
source§fn offset_for<P>(&self, predicate: P) -> Option<usize>where
P: Fn(Self::Token) -> bool,
fn offset_for<P>(&self, predicate: P) -> Option<usize>where
P: Fn(Self::Token) -> bool,
Finds the offset of the next matching token
source§impl<I> StreamIsPartial for Partial<I>where
I: StreamIsPartial,
impl<I> StreamIsPartial for Partial<I>where
I: StreamIsPartial,
§type PartialState = bool
type PartialState = bool
Whether the stream is currently partial or complete
source§fn complete(&mut self) -> Self::PartialState
fn complete(&mut self) -> Self::PartialState
Mark the stream is complete
source§fn restore_partial(&mut self, state: Self::PartialState)
fn restore_partial(&mut self, state: Self::PartialState)
Restore the stream back to its previous state
source§fn is_partial_supported() -> bool
fn is_partial_supported() -> bool
Report whether the
Stream
is can ever be incompletesource§fn is_partial(&self) -> bool
fn is_partial(&self) -> bool
Report whether the
Stream
is currently incompletesource§impl<I> UpdateSlice for Partial<I>where
I: UpdateSlice,
impl<I> UpdateSlice for Partial<I>where
I: UpdateSlice,
source§fn update_slice(self, inner: Self::Slice) -> Self
fn update_slice(self, inner: Self::Slice) -> Self
Convert an
Output
type to be used as Stream