Struct HPFile

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pub struct HPFile { /* private fields */ }

Expand description

Head-prunable file

Implementations§

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impl HPFile

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pub fn new( wr_buf_size: i64, segment_size: i64, dir_name: String, directio: bool, ) -> Result<HPFile>

Create a HPFile with a directory. If this directory was used by an old HPFile, the old HPFile must have the same segment_size as this one.

§Parameters

wr_buf_size: The write buffer used in append will not exceed this size
segment_size: The target size of the small files
dir_name: The name of the directory used to store the small files
directio: Enable directio for readonly files (only use this feature on Linux)

§Returns

A Result which is:

Ok: A successfully initialized HPFile
Err: Encounted some file system error.

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pub fn empty() -> HPFile

Create an empty HPFile that has no function and can only be used as placeholder.

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pub fn is_empty(&self) -> bool

Returns whether this HPFile is empty.

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pub fn size(&self) -> i64

Returns the size of the virtual large file, including the non-flushed bytes

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pub fn size_on_disk(&self) -> i64

Returns the flushed size of the virtual large file

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pub fn truncate(&self, size: i64) -> Result<()>

Truncate the file to make it smaller

§Parameters

size: the size of the virtual large file after truncation. It must be smaller than the original size.

§Returns

A Result which is:

Ok: It’s truncated successfully
Err: Encounted some file system error.

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pub fn flush(&self, buffer: &mut Vec<u8>, eof: bool) -> Result<()>

Flush the remained data in buffer into file system

§Parameters

buffer: the write buffer, which is used by the client to call append.
eof: indicates if this is the end of file. If so, padding may be added for alignment.

§Returns

A Result which is:

Ok: It’s flushed successfully
Err: Encounted some file system error.

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pub fn close(&self)

Close the opened small files

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pub fn get_file_and_pos(&self, offset: i64) -> (Arc<(File, bool)>, i64)

Returns the corresponding file and in-file position given a logical offset. When we use io_uring to read data from HPFile, the underlying segment files must be exposed.

§Parameters

offset: a logical offset of this HPFile

§Returns

A tuple. Its first entry is the underlying File and its readonly attribute, and its sencond entry is the position within this underlying File.

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pub fn read_at(&self, bz: &mut [u8], offset: i64) -> Result<usize>

Read data from file at offset to fill bz

§Parameters

offset: the start position of a byteslice that was written before

§Returns

A Result which is:

Ok: Number of bytes that was filled into bz
Err: Encounted some file system error.

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pub fn read_range(&self, buf: &mut [u8], offset: i64) -> Result<()>

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pub fn read_at_with_pre_reader( &self, buf: &mut Vec<u8>, num_bytes: usize, offset: i64, pre_reader: &mut PreReader, ) -> Result<usize>

Read at most num_bytes from file at offset to fill buf

§Parameters

buf: a vector to be filled
num_bytes: the wanted number of bytes to be read
offset: the start position of a byteslice that was written before
pre_reader: a PreReader used to take advantage of spatial locality

§Returns

A Result which is:

Ok: Number of bytes that was filled into buf
Err: Encounted some file system error.

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pub fn append(&self, bz: &[u8], buffer: &mut Vec<u8>) -> Result<i64>

Append a byteslice to the file. This byteslice may be temporarily held in buffer before flushing.

§Parameters

bz: the byteslice to append. It cannot be longer than wr_buf_size specified in HPFile::new.
buffer: the write buffer. It will never be larger than wr_buf_size.