sst 0.24.0

SST provides a sorted string table abstraction.
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
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170

//! Reference types for comparing sst and block behavior.

use std::rc::Rc;

use super::{
    Cursor, Error, KeyRef, KeyValuePair, check_key_len, check_table_size, check_value_len,
};

////////////////////////////////////////// ReferenceTable //////////////////////////////////////////

/// A ReferenceTable provides the table interface as a comparison for specifying behavior.
#[derive(Clone, Debug, Default)]
pub struct ReferenceTable {
    entries: Rc<Vec<KeyValuePair>>,
}

impl ReferenceTable {
    /// Return a new cursor over this table.
    pub fn cursor(&self) -> ReferenceCursor {
        ReferenceCursor {
            entries: Rc::clone(&self.entries),
            index: -1,
        }
    }
}

///////////////////////////////////////// ReferenceBuilder /////////////////////////////////////////

/// A builder that returns a ReferenceTable.
#[derive(Clone, Debug, Default)]
pub struct ReferenceBuilder {
    entries: Vec<KeyValuePair>,
    approximate_size: usize,
}

impl ReferenceBuilder {
    /// The approximate size of the builder.
    pub fn approximate_size(&self) -> usize {
        self.approximate_size
    }

    /// Put a key in the reference builder.
    pub fn put(&mut self, key: &[u8], timestamp: u64, value: &[u8]) -> Result<(), Error> {
        check_key_len(key)?;
        check_value_len(value)?;
        self.approximate_size += key.len() + 8 + value.len();
        check_table_size(self.approximate_size)?;
        let kvp = KeyValuePair {
            key: key.into(),
            timestamp,
            value: Some(value.into()),
        };
        self.entries.push(kvp);
        Ok(())
    }

    /// Delete a key from the reference builder.
    pub fn del(&mut self, key: &[u8], timestamp: u64) -> Result<(), Error> {
        check_key_len(key)?;
        self.approximate_size += key.len() + 8;
        check_table_size(self.approximate_size)?;
        let kvp = KeyValuePair {
            key: key.into(),
            timestamp,
            value: None,
        };
        self.entries.push(kvp);
        Ok(())
    }

    /// Seal the reference builder and get a ReferenceTable.
    pub fn seal(self) -> Result<ReferenceTable, Error> {
        let mut entries = self.entries;
        entries.sort();
        Ok(ReferenceTable {
            entries: Rc::new(entries),
        })
    }
}

////////////////////////////////////////// ReferenceCursor /////////////////////////////////////////

/// A cursor over a reference table.
#[derive(Clone, Debug)]
pub struct ReferenceCursor {
    entries: Rc<Vec<KeyValuePair>>,
    index: isize,
}

impl Cursor for ReferenceCursor {
    fn seek_to_first(&mut self) -> Result<(), Error> {
        self.index = -1;
        Ok(())
    }

    fn seek_to_last(&mut self) -> Result<(), Error> {
        self.index = self.entries.len() as isize;
        Ok(())
    }

    fn seek(&mut self, key: &[u8]) -> Result<(), Error> {
        let target = KeyValuePair {
            key: key.into(),
            timestamp: u64::MAX,
            value: None,
        };
        self.index = match self.entries.binary_search(&target) {
            Ok(index) => index,
            Err(index) => index,
        } as isize;
        Ok(())
    }

    fn prev(&mut self) -> Result<(), Error> {
        self.index -= 1;
        if self.index < 0 {
            self.seek_to_first()
        } else {
            Ok(())
        }
    }

    fn next(&mut self) -> Result<(), Error> {
        self.index += 1;
        if self.index as usize >= self.entries.len() {
            self.seek_to_last()
        } else {
            Ok(())
        }
    }

    fn key(&self) -> Option<KeyRef<'_>> {
        if self.index < 0 || self.index as usize >= self.entries.len() {
            None
        } else {
            let kvp = &self.entries[self.index as usize];
            Some(KeyRef::from(kvp))
        }
    }

    fn value(&self) -> Option<&[u8]> {
        if self.index < 0 || self.index as usize >= self.entries.len() {
            None
        } else {
            let kvp = &self.entries[self.index as usize];
            kvp.value.as_deref()
        }
    }
}

impl From<ReferenceTable> for ReferenceCursor {
    fn from(table: ReferenceTable) -> Self {
        table.cursor()
    }
}

/////////////////////////////////////////////// tests //////////////////////////////////////////////

#[cfg(test)]
mod tables {
    use super::*;

    #[test]
    fn empty() {
        let table = ReferenceBuilder::default().seal().unwrap();
        let cursor = table.cursor();
        let got = cursor.key_value();
        assert_eq!(None, got);
    }
}