Struct deepmesa_encoding::prefix::delta::DeltaEncoder[][src]

pub struct DeltaEncoder { /* fields omitted */ }
Expand description

Encodes unsigned values using Delta Encoding.

Each value is encoded in two parts - a length and an offset. The length is encoded in Gamma and the offset is the binary representation with the leading 1 removed.

Examples

decimal 2 = 0000_0010
encoding for decimal 2 = 100_0

decimal 13 = 0000_1101
encoding for decimal 13 = 10_1_101

The delta encoder, encodes the data in a BitVector. The .encode() accepts a u128 value and pushes encoded bits to the BitVector.

The encoder maintains a count of number of values encoded (.elements()), the number of bits used to encode those elements (.encoded_len()) and the compression ratio (.comp_ratio()). The compression ratio is the average number of bits per value needed to encode all the values.

Examples

use deepmesa::encoding::DeltaEncoder;

let mut de = DeltaEncoder::new();

// encode 2
de.encode(2);
assert_eq!(de.elements(), 1);
assert_eq!(de.encoded_len(), 2);
assert_eq!(de.comp_ratio(), 2.0);

// Get the underlying BitVector.
let encoded = de.encoded();
assert_eq!(encoded.read_u8(0), (0b00, 2));

// encode 13
de.encode(13);
assert_eq!(de.elements(), 2);
assert_eq!(de.encoded_len(), 8);
assert_eq!(de.comp_ratio(), 4.0);

let encoded = de.encoded();
assert_eq!(encoded.read_u16(2), (0b101_101, 6));

Encoded bits can be decoded using the DeltaDecoder.

Implementations

Creates a new DeltaEncoder with the underlying BitVector initialized with a capacity of 1024 bits. .

Creates a new DeltaEncoder with the underlying BitVector initialized with the specified capacity_bits;

Encodes the specified u128 val

Returns an immutable reference to the underlying BitVector containing the encoded bits.

Returns the length in bits of the underlying BitVector containing the encoded bits.

Returns the number of elements encoded in the underlying BitVector.

Returns the compression ratio of the encoded elements. This is simply the .encoded_len() divided by the number of .elements();

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