Struct mmap_bitvec::MmapBitVec

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pub struct MmapBitVec {
    pub mmap: MmapKind,
    pub size: usize,
    /* private fields */
}

Expand description

Bit vector backed by a mmap-ed file

Examples

use mmap_bitvec::{BitVector, MmapBitVec};

let mut bv = MmapBitVec::from_memory(128).unwrap();
bv.set_range_bytes(2..12, &[0b10, 0b01101101]);
assert_eq!(bv.get_range(2..12), 0b1001101101);

Fields

mmap: MmapKind

The mmap we are using, either a mutable or read-only one

size: usize

Number of bits in the bitvector

Implementations

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impl MmapBitVec

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pub fn create<P: AsRef<Path>>(
 filename: P,
 size: usize,
 magic: Option<[u8; 2]>,
 header: &[u8]
) -> Result<Self, Error>

Creates a new MmapBitVec file

The overall size of bit vector (in bits) and a fixed-size header must also be provided (although the header can be 0-length).

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pub fn open(
 filename: P,
 magic: Option<&[u8; 2]>,
 read_only: bool
) -> Result<Self, Error>where
 P: AsRef<Path>,

Opens an existing MmapBitVec file

If magic bytes are passed to indicate file type, they are checked against the file.

The header size must be specified (as it isn’t stored in the file to allow the magic bytes to be set) and there is an optional read_only property that will lock the underlying mmap from writing.

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pub fn open_no_header(filename: P, offset: usize) -> Result<Self, Error>where
P: AsRef<Path>,

Opens a MmapBitVec file that doesn’t have our “standard” file header format TODO: what is the standard file header? if we put in the docstring on the struct we can say to refer to that here

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pub fn from_memory(size: usize) -> Result<Self, Error>

Creates an in-memory MmapBitVec (not backed by a file).

Note that unlike the create and open no header is set. The MmapBitVec is also read/write by default.

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pub fn save_to_disk<P: AsRef<Path>>(
 &self,
 filename: P,
 magic: Option<[u8; 2]>,
 header: &[u8]
) -> Result<(), Error>

Save in-memory mmap bitvector to disk. This is a no-op if the mmap is already file-backed.

Returns the header

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pub fn get_range_bytes(&self, r: Range<usize>) -> Vec<u8>

Read/copy an unaligned chunk of the MmapBitVec

Panics

Explicitly panics if the end location, r.end, is outside the bounds of the bit vector. A panic may also occur if r.start is greater than r.end.

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pub fn set_range_bytes(&mut self, r: Range<usize>, x: &[u8])

Set an unaligned range of bits in the bit vector from a byte slice.

Note this operation ORs the passed byteslice and the existing bitmask.

Explicitly panics if the end location, r.end, is outside the bounds of the bit vector or if the byte slice passed in is a different size from the range specified. A panic may also occur if r.start is greater than r.end.

Trait Implementations

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impl BitVector for MmapBitVec

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fn get(&self, i: usize) -> bool

Check a single value in the MmapBitVec, returning its true/false status

Panics

Panics if the location, i, is outside the bounds of the bit vector

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fn set(&mut self, i: usize, x: bool)

Set a single bit in the bit vector

Panics

Panics if the location, i, is outside the bounds of the bit vector

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fn size(&self) -> usize

Returns the length (in bits) of the bit vector

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fn rank(&self, r: Range<usize>) -> usize

Return the number of set bits in the range r

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fn select(&self, n: usize, start: usize) -> Option<usize>

Return the position of the nth set bit with start treated as the 0th position, or None if there is no set bit

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fn get_range(&self, r: Range<usize>) -> u128

Read an unaligned chunk of the MmapBitVec into a u128

Panics

Explicitly panics if the end location, r.end, is outside the bounds of the bit vector or if the range specified is greater than 128 bits. (Use get_range_bytes instead if you need to read larger chunks) A panic will also occur when r.start is greater than r.end.

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fn set_range(&mut self, r: Range<usize>, x: u128)

Set an unaligned range of bits using a u64.

Note this operation ORs the passed u64 and the existing bitmask

Panics

Explicitly panics if the end location, r.end, is outside the bounds of the bit vector. A panic will also occur when r.start is greater than r.end.

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