bf-tree 0.5.0

Bf-Tree is a modern read-write-optimized concurrent larger-than-memory range index in Rust from Microsoft Research.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141

// Copyright (c) Microsoft Corporation.
// Licensed under the MIT license.

use crate::nodes::leaf_node::OpType;

use super::LogEntryImpl;

pub(crate) struct WriteOp<'a> {
    pub(crate) key: &'a [u8],
    pub(crate) value: &'a [u8],
    pub(crate) op_type: OpType,
}

impl<'a> WriteOp<'a> {
    pub(crate) fn make_insert(key: &'a [u8], value: &'a [u8]) -> WriteOp<'a> {
        WriteOp {
            key,
            value,
            op_type: OpType::Insert,
        }
    }

    pub(crate) fn make_delete(key: &'a [u8]) -> WriteOp<'a> {
        WriteOp {
            key,
            value: &[],
            op_type: OpType::Delete,
        }
    }
}

impl<'a> LogEntryImpl<'a> for WriteOp<'a> {
    fn log_size(&self) -> usize {
        // layout:
        // key_size | value_size | op_type | key | value
        let key_size = self.key.len();
        let value_size = self.value.len();
        let op_type_size = std::mem::size_of::<OpType>();

        std::mem::size_of::<u16>()
            + std::mem::size_of::<u16>()
            + op_type_size
            + key_size
            + value_size
    }

    fn write_to_buffer(&self, buffer: &mut [u8]) {
        debug_assert_eq!(buffer.len(), self.log_size());
        let key_len = self.key.len() as u16;
        let val_len = self.value.len() as u16;
        let op_u8 = self.op_type as u8;
        buffer[0..2].copy_from_slice(key_len.to_le_bytes().as_ref());
        buffer[2..4].copy_from_slice(val_len.to_le_bytes().as_ref());
        buffer[4] = op_u8;

        let key_offset = 5 + self.key.len();
        buffer[5..key_offset].copy_from_slice(self.key);
        buffer[key_offset..].copy_from_slice(self.value);
    }

    fn read_from_buffer(buffer: &'a [u8]) -> WriteOp<'a> {
        let key_size = u16::from_le_bytes(buffer[0..2].try_into().unwrap()) as usize;
        let value_size = u16::from_le_bytes(buffer[2..4].try_into().unwrap()) as usize;
        let op_type = unsafe { std::mem::transmute::<u8, OpType>(buffer[4]) };
        let key = &buffer[5..5 + key_size];
        let value = &buffer[5 + key_size..];
        assert_eq!(value.len(), value_size);
        WriteOp {
            key,
            value,
            op_type,
        }
    }
}

pub(crate) enum LogEntry<'a> {
    Write(WriteOp<'a>),
    Split(SplitOp),
}

#[repr(u8)]
enum LogEntryTagVal {
    Write = 0,
    Split = 1,
}

impl LogEntryTagVal {
    fn size() -> usize {
        std::mem::size_of::<u8>()
    }
}

impl<'a> From<&LogEntry<'a>> for LogEntryTagVal {
    fn from(entry: &LogEntry<'a>) -> Self {
        match entry {
            LogEntry::Write(_) => LogEntryTagVal::Write,
            LogEntry::Split(_) => LogEntryTagVal::Split,
        }
    }
}

impl From<u8> for LogEntryTagVal {
    fn from(val: u8) -> Self {
        match val {
            0 => LogEntryTagVal::Write,
            1 => LogEntryTagVal::Split,
            _ => unreachable!(),
        }
    }
}

pub(crate) struct SplitOp {}

impl<'a> LogEntryImpl<'a> for LogEntry<'a> {
    fn log_size(&self) -> usize {
        let tag_size = LogEntryTagVal::size();
        let data_size = match self {
            LogEntry::Write(op) => op.log_size(),
            LogEntry::Split(_) => todo!(),
        };
        tag_size + data_size
    }

    fn write_to_buffer(&self, buffer: &mut [u8]) {
        buffer[0] = LogEntryTagVal::from(self) as u8;
        match self {
            LogEntry::Write(op) => op.write_to_buffer(&mut buffer[1..]),
            LogEntry::Split(_) => {
                todo!()
            }
        }
    }

    fn read_from_buffer(buffer: &'a [u8]) -> Self {
        let tag = LogEntryTagVal::from(buffer[0]);
        match tag {
            LogEntryTagVal::Write => LogEntry::Write(WriteOp::read_from_buffer(&buffer[1..])),
            LogEntryTagVal::Split => LogEntry::Split(SplitOp {}),
        }
    }
}