Struct winnow::stream::Partial

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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 transform [ErrMode::Incomplete] to [ErrMode::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<'s>(i: &mut Partial<&'s [u8]>) -> PResult<&'s [u8], InputError<Partial<&'s [u8]>>> {
  token::take(4u8).parse_next(i)
}

fn take_complete<'s>(i: &mut &'s [u8]) -> PResult<&'s [u8], InputError<&'s [u8]>> {
  token::take(4u8).parse_next(i)
}

// both parsers will take 4 bytes as expected
assert_eq!(take_partial.parse_peek(Partial::new(&b"abcde"[..])), Ok((Partial::new(&b"e"[..]), &b"abcd"[..])));
assert_eq!(take_complete.parse_peek(&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.parse_peek(Partial::new(&b"abc"[..])), Err(ErrMode::Incomplete(Needed::new(1))));

// but the complete parser will return an error
assert_eq!(take_complete.parse_peek(&b"abc"[..]), Err(ErrMode::Backtrack(InputError::new(&b"abc"[..], ErrorKind::Slice))));

// the alpha0 function takes 0 or more alphabetic characters
fn alpha0_partial<'s>(i: &mut Partial<&'s str>) -> PResult<&'s str, InputError<Partial<&'s str>>> {
  ascii::alpha0.parse_next(i)
}

fn alpha0_complete<'s>(i: &mut &'s str) -> PResult<&'s str, InputError<&'s str>> {
  ascii::alpha0.parse_next(i)
}

// if there's a clear limit to the taken characters, both parsers work the same way
assert_eq!(alpha0_partial.parse_peek(Partial::new("abcd;")), Ok((Partial::new(";"), "abcd")));
assert_eq!(alpha0_complete.parse_peek("abcd;"), Ok((";", "abcd")));

// but when there's no limit, the partial version returns `Incomplete`, because it cannot
// know if more input data should be taken. The whole input could be "abcd;", or
// "abcde;"
assert_eq!(alpha0_partial.parse_peek(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.parse_peek("abcd"), Ok(("", "abcd")));

Implementations§

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impl<I> Partial<I>
where I: StreamIsPartial,

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pub fn new(input: I) -> Self

Create a partial input

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pub fn into_inner(self) -> I

Extract the original Stream

Trait Implementations§

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impl<I> AsBStr for Partial<I>
where I: AsBStr,

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fn as_bstr(&self) -> &[u8]

Casts the input type to a byte slice
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impl<I> AsBytes for Partial<I>
where I: AsBytes,

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fn as_bytes(&self) -> &[u8]

Casts the input type to a byte slice
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impl<I: Clone> Clone for Partial<I>

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fn clone(&self) -> Partial<I>

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<I, T> Compare<T> for Partial<I>
where I: Compare<T>,

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fn compare(&self, t: T) -> CompareResult

Compares self to another value for equality
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impl<I: Debug> Debug for Partial<I>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<I> Default for Partial<I>

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fn default() -> Self

Returns the “default value” for a type. Read more
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impl<I> Deref for Partial<I>

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type Target = I

The resulting type after dereferencing.
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fn deref(&self) -> &Self::Target

Dereferences the value.
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impl<I: Display> Display for Partial<I>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<I, T> FindSlice<T> for Partial<I>
where I: FindSlice<T>,

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fn find_slice(&self, substr: T) -> Option<Range<usize>>

Returns the offset of the slice if it is found
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impl<I> Location for Partial<I>
where I: Location,

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fn location(&self) -> usize

Number of indices input has advanced since start of parsing
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impl<I> Offset<<Partial<I> as Stream>::Checkpoint> for Partial<I>
where I: Stream,

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fn offset_from(&self, other: &<Partial<I> as Stream>::Checkpoint) -> usize

Offset between the first byte of start and the first byte of selfa Read more
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impl<I> Offset for Partial<I>
where I: Stream,

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fn offset_from(&self, start: &Self) -> usize

Offset between the first byte of start and the first byte of selfa Read more
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impl<I: Ord> Ord for Partial<I>

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fn cmp(&self, other: &Partial<I>) -> Ordering

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl<I: PartialEq> PartialEq for Partial<I>

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fn eq(&self, other: &Partial<I>) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl<I: PartialOrd> PartialOrd for Partial<I>

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fn partial_cmp(&self, other: &Partial<I>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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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 more
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fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl<I> SliceLen for Partial<I>
where I: SliceLen,

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fn slice_len(&self) -> usize

Calculates the input length, as indicated by its name, and the name of the trait itself
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impl<I: Stream> Stream for Partial<I>

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type Token = <I as Stream>::Token

The smallest unit being parsed Read more
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type Slice = <I as Stream>::Slice

Sequence of Tokens Read more
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type IterOffsets = <I as Stream>::IterOffsets

Iterate with the offset from the current location
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type Checkpoint = Checkpoint<<I as Stream>::Checkpoint, Partial<I>>

A parse location within the stream
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fn iter_offsets(&self) -> Self::IterOffsets

Iterate with the offset from the current location
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fn eof_offset(&self) -> usize

Returns the offset to the end of the input
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fn next_token(&mut self) -> Option<Self::Token>

Split off the next token from the input
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fn offset_for<P>(&self, predicate: P) -> Option<usize>
where P: Fn(Self::Token) -> bool,

Finds the offset of the next matching token
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fn offset_at(&self, tokens: usize) -> Result<usize, Needed>

Get the offset for the number of tokens into the stream Read more
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fn next_slice(&mut self, offset: usize) -> Self::Slice

Split off a slice of tokens from the input Read more
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fn checkpoint(&self) -> Self::Checkpoint

Save the current parse location within the stream
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fn reset(&mut self, checkpoint: &Self::Checkpoint)

Revert the stream to a prior Self::Checkpoint Read more
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fn raw(&self) -> &dyn Debug

Return the inner-most stream
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fn finish(&mut self) -> Self::Slice

Advance to the end of the stream
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impl<I> StreamIsPartial for Partial<I>
where I: StreamIsPartial,

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type PartialState = bool

Whether the stream is currently partial or complete
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fn complete(&mut self) -> Self::PartialState

Mark the stream is complete
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fn restore_partial(&mut self, state: Self::PartialState)

Restore the stream back to its previous state
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fn is_partial_supported() -> bool

Report whether the Stream is can ever be incomplete
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fn is_partial(&self) -> bool

Report whether the Stream is currently incomplete
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impl<I> UpdateSlice for Partial<I>
where I: UpdateSlice,

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fn update_slice(self, inner: Self::Slice) -> Self

Convert an Output type to be used as Stream
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impl<I: Copy> Copy for Partial<I>

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impl<I: Eq> Eq for Partial<I>

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impl<I> StructuralPartialEq for Partial<I>

Auto Trait Implementations§

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impl<I> Freeze for Partial<I>
where I: Freeze,

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impl<I> RefUnwindSafe for Partial<I>
where I: RefUnwindSafe,

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impl<I> Send for Partial<I>
where I: Send,

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impl<I> Sync for Partial<I>
where I: Sync,

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impl<I> Unpin for Partial<I>
where I: Unpin,

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impl<I> UnwindSafe for Partial<I>
where I: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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default unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> CloneToUninit for T
where T: Copy,

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unsafe fn clone_to_uninit(&self, dst: *mut T)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dst. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T> ToString for T
where T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.