Struct body_image::BodyImage
source · pub struct BodyImage { /* private fields */ }
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
and supports
low-cost shallow Clone
via internal (atomic) reference
counting. BodyImage
is not Sync
(with the default mmap feature
enabled).
Implementations§
source§impl BodyImage
impl BodyImage
sourcepub fn empty() -> BodyImage
pub fn empty() -> BodyImage
Create new empty instance with no allocation. The state is
Ram
with a zero-capacity vector.
sourcepub unsafe fn from_file(file: File, length: u64) -> BodyImage
pub unsafe fn from_file(file: File, length: u64) -> BodyImage
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).
sourcepub fn from_slice<T>(bytes: T) -> BodyImagewhere
T: Into<Bytes>,
pub fn from_slice<T>(bytes: T) -> BodyImagewhere
T: Into<Bytes>,
Create new instance from a single byte slice.
sourcepub unsafe fn from_read_slice(rslice: ReadSlice) -> BodyImage
pub unsafe fn from_read_slice(rslice: ReadSlice) -> BodyImage
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).
sourcepub fn is_mem_map(&self) -> bool
pub fn is_mem_map(&self) -> bool
Return true if in state MemMap
.
sourcepub fn mem_map(&mut self) -> Result<&mut Self, BodyError>
pub fn mem_map(&mut self) -> Result<&mut Self, BodyError>
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.
sourcepub fn gather(&mut self) -> &mut Self
pub fn gather(&mut self) -> &mut Self
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.
sourcepub fn reader(&self) -> BodyReader<'_>
pub fn reader(&self) -> BodyReader<'_>
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.
sourcepub fn explode(self) -> ExplodedImage
pub fn explode(self) -> ExplodedImage
Consume self, exploding into an
ExplodedImage
variant.
sourcepub fn read_from(
r: &mut dyn Read,
len_estimate: u64,
tune: &Tunables
) -> Result<BodyImage, BodyError>
pub fn read_from(
r: &mut dyn Read,
len_estimate: u64,
tune: &Tunables
) -> Result<BodyImage, BodyError>
Given a Read
object, 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).