Struct body_image::BodyImage [−][src]
pub struct BodyImage { /* fields omitted */ }
Expand description
A logical buffer of bytes, which may or may not be RAM resident.
Besides a few immediate/convenience constructors found here, use
BodySink
for the incremental or stream-oriented
collection of bytes to produce a BodyImage
.
A BodyImage
is always in one of the following states, as a buffering
strategy:
Ram
: A vector of zero, one, or many discontinuous (AKA scattered) byte
buffers in Random Access Memory. This state is also used to represent
an empty body (without allocation).
FsRead
: Body in a (temporary) file, ready for position based, sequential read.
MemMap
: Body in a memory mapped file, ready for random access read (default
mmap feature)
All states support concurrent reads. BodyImage
is Send
, Sync
, and
supports low-cost shallow Clone
via internal (atomic) reference
counting.
Implementations
Create new empty instance with no allocation. The state is
Ram
with a zero-capacity vector.
Create a new FsRead
instance based on an existing File
. The fixed
length is used to report BodyImage::len
and may be obtained using
File::metadata
. If the provided length is zero, this returns as per
BodyImage::empty()
instead. Attempts to read from the returned
BodyImage
can fail if the file is not open for read.
Safety
Use of this constructor is potentially unsafe when the mmap feature
enabled and once mem_map
is called:
-
The
mem_map
call will fail if the file is zero length or not open for read. -
Any concurrent writes to the file, or file system modifications while under use in
MemMap
state may lead to Undefined Behavior (UB).
Create new instance from a single byte slice.
Create a new instance based on a ReadSlice
. The BodyImage::len
will be as per ReadSlice::len
, and if zero, this returns as per
BodyImage::empty()
. Attempts to read from the returned
BodyImage
can fail if the file is not open for read.
Safety
Use of this constructor is potentially unsafe when the mmap feature
enabled and once mem_map
is called:
-
The
mem_map
call will fail if the file is zero length or not open for read. -
Any concurrent writes to the file, or file system modifications while under use in
MemMap
state may lead to Undefined Behavior (UB).
Return true if in state MemMap
.
If FsRead
, convert to MemMap
by memory mapping the file.
Under normal construction via BodySink
in FsWrite
state, this
method is safe, because no other thread or process has access to the
underlying file. Note the potential safety requirements via
from_file
however.
If Ram
with 2 or more buffers, gather by copying into a single
contiguous buffer with the same total length. No-op for other
states. Buffers are eagerly dropped as they are copied. Possibly in
combination with mem_map
, this can be used to ensure Cursor
(and
&[u8]
slice) access via reader
, at the cost of the copy.
pub fn reader(&self) -> BodyReader<'_>ⓘNotable traits for BodyReader<'a>impl<'a> Read for BodyReader<'a>
pub fn reader(&self) -> BodyReader<'_>ⓘNotable traits for BodyReader<'a>impl<'a> Read for BodyReader<'a>
impl<'a> Read for BodyReader<'a>
Return a new BodyReader
enum over self. The enum provides a
consistent Read
reference, or can be destructured for access to
the specific concrete types.
Consume self, exploding into an ExplodedImage
variant.
Given a Read
reference, a length estimate in bytes and Tunables
,
read and prepare a new BodyImage
. Tunables
, the estimate and
actual length read will determine which buffering strategy is
used. The length estimate provides a hint to use the file system from
the start, which is more optimal than writing out accumulated Ram
buffers later. If the length can’t be estimated, use zero (0).
The Read
is passed by reference for backward compatibility with its
original non-generic form as &mut dyn Read
. C-RW-VALUE prefers
pass by value, but this would now be a breaking change.
Write self to out
and return length. If FsRead
this is performed
using std::io::copy
with ReadPos
as input.
The Write
is passed by reference for backward compatibility with its
original non-generic form as &mut dyn Write
. C-RW-VALUE prefers
pass by value, but this would now be a breaking change.
std::io::copy
is presumably in the same position.
Trait Implementations
Auto Trait Implementations
impl RefUnwindSafe for BodyImage
impl UnwindSafe for BodyImage
Blanket Implementations
Mutably borrows from an owned value. Read more