Struct olio::fs::ReadSlice
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pub struct ReadSlice<P> where
P: PosRead, { /* fields omitted */ }
Re-implements Read
and Seek
over PosRead
using only positioned
reads, and by maintaining instance independent start, end, and position.
PosRead
is implemented for any Borrow<File>
so
this can own via ReadSlice<File>
or use a shared reference, as in
ReadSlice<&File>
or ReadSlice<Arc<File>>
.
As compared with ReadPos
, ReadSlice
adds a
general start offset, and limits access to the start..end range. Seeks are
relative, so a seek to SeekFrom::Start(0)
is always the first byte of
the slice.
Fixed start
and end
offsets are passed on construction and used to
constrain reads and interpret SeekFrom::Start
and SeekFrom::End
. These
offsets are neither checked against nor updated from the inner PosRead
(for example via file metadata) and could deviate if concurrent writes or
truncation is possible. Reads beyond end
or the end of the inner
PosRead
will return 0 length. Seeking past the end is allowed by the
platforms for File
, and is also allowed for ReadSlice
.
Methods
impl<P> ReadSlice<P> where
P: PosRead,
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P: PosRead,
pub fn new(pos_read: P, start: u64, end: u64) -> Self
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New instance by PosRead
reference, fixed start and end offsets. The
initial position is at the start (relative offset 0).
pub fn len(&self) -> u64
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Return the total size of the slice in bytes. This is based on the
start and end offsets as constructed and can differ from the inner
PosRead
length.
pub fn is_empty(&self) -> bool
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Return true
if length is 0.
pub fn tell(&self) -> u64
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Return the current instance position, relative to the slice. This is a
convenience shorthand for seek(SeekFrom::Current(0))
, is infallable,
and does not require a mutable reference.
impl<P> ReadSlice<P> where
P: PosRead + Clone,
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P: PosRead + Clone,
ⓘImportant traits for ReadSlice<P>pub fn subslice(&self, start: u64, end: u64) -> ReadSlice<P>
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Return a new and independent ReadSlice
by clone of the inner
PosRead
, for the range of byte offsets start..end
which are
relative to, and must be fully contained by self. This implementation
panics on overflow, if start..end is not fully contained, or if
start is greater-than end.
impl<P> ReadSlice<P> where
P: PosRead + Borrow<File>,
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P: PosRead + Borrow<File>,
pub fn mem_map(&self) -> Result<Mmap, Error>
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Return a new read-only memory map handle Mmap
for the complete
region of the underlying File
, from start to end.
Trait Implementations
impl<P: Debug> Debug for ReadSlice<P> where
P: PosRead,
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P: PosRead,
fn fmt(&self, __arg_0: &mut Formatter) -> Result
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Formats the value using the given formatter. Read more
impl<P> Clone for ReadSlice<P> where
P: PosRead + Clone,
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P: PosRead + Clone,
fn clone(&self) -> Self
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Return a new, independent ReadSlice
by clone of the inner PosRead
,
with the same start and end as self, and positioned at start.
fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl<P> PosRead for ReadSlice<P> where
P: PosRead,
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P: PosRead,
fn pread(&self, buf: &mut [u8], offset: u64) -> Result<usize>
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Read bytes, starting at the specified offset, into the specified buffer and return the number of bytes read. The offset is from the start of the underlying file or file range. Reads beyond the end of available bytes will return 0 length. The position of the underlying file pointer (aka cursor) is not used. It is platform dependent whether the underlying file pointer is modified by this operation. Read more
impl<P> Read for ReadSlice<P> where
P: PosRead,
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P: PosRead,
fn read(&mut self, buf: &mut [u8]) -> Result<usize>
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Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
unsafe fn initializer(&self) -> Initializer
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read_initializer
)Determines if this Read
er can work with buffers of uninitialized memory. Read more
fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>
1.0.0[src]
Read all bytes until EOF in this source, placing them into buf
. Read more
fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>
1.0.0[src]
Read all bytes until EOF in this source, appending them to buf
. Read more
fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>
1.6.0[src]
Read the exact number of bytes required to fill buf
. Read more
fn by_ref(&mut self) -> &mut Self
1.0.0[src]
Creates a "by reference" adaptor for this instance of Read
. Read more
fn bytes(self) -> Bytes<Self>
1.0.0[src]
Transforms this Read
instance to an [Iterator
] over its bytes. Read more
fn chars(self) -> Chars<Self>
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🔬 This is a nightly-only experimental API. (io
)
the semantics of a partial read/write of where errors happen is currently unclear and may change
Transforms this Read
instance to an [Iterator
] over [char
]s. Read more
fn chain<R>(self, next: R) -> Chain<Self, R> where
R: Read,
1.0.0[src]
R: Read,
Creates an adaptor which will chain this stream with another. Read more
fn take(self, limit: u64) -> Take<Self>
1.0.0[src]
Creates an adaptor which will read at most limit
bytes from it. Read more
impl<P> Seek for ReadSlice<P> where
P: PosRead,
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P: PosRead,