datasketches 0.3.0

A software library of stochastic streaming algorithms (a.k.a. sketches)
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

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! Raw byte and string hash value wrappers.
//!
//! [`RawBytes`] hashes byte and string inputs as raw bytes without Rust's slice or string length
//! prefix.
//!
//! Empty byte and string inputs have zero bytes to hash. Other datasketches implementations skip
//! empty strings before hashing, so check `is_empty` before updating a sketch when that behavior
//! matters.

use std::hash::Hasher;

use super::value::HashStrategy;
use super::value::Value;

/// A byte or string value wrapper that hashes raw bytes.
///
/// See the [module level documentation](super) for more.
pub type RawBytes<T> = Value<T, RawBytesStrategy>;

/// Hashing strategy for [`RawBytes`].
#[doc(hidden)]
pub struct RawBytesStrategy;

/// Create a raw-byte hashable value from a byte vector.
///
/// This hashes the vector contents without Rust's slice length prefix.
///
/// # Examples
///
/// ```
/// # use datasketches::hash_value::calculate_hash;
/// # use datasketches::hash_value::raw_bytes::{from_slice, from_vec};
/// assert_eq!(
///     calculate_hash(from_vec(b"abc".to_vec())),
///     calculate_hash(from_slice(b"abc"))
/// );
/// assert!(from_vec(vec![]).is_empty());
/// assert!(!from_vec(b"abc".to_vec()).is_empty());
/// ```
pub fn from_vec(v: Vec<u8>) -> RawBytes<Vec<u8>> {
    RawBytes::new(v)
}

/// Create a raw-byte hashable value from a string.
///
/// This hashes the UTF-8 bytes of the string without Rust's string length prefix.
///
/// # Examples
///
/// ```
/// # use datasketches::hash_value::calculate_hash;
/// # use datasketches::hash_value::raw_bytes::{from_str, from_string};
/// assert_eq!(
///     calculate_hash(from_string("abc".to_owned())),
///     calculate_hash(from_str("abc"))
/// );
/// assert!(from_string(String::new()).is_empty());
/// assert!(!from_string("abc".to_string()).is_empty());
/// ```
pub fn from_string(v: String) -> RawBytes<String> {
    RawBytes::new(v)
}

/// Create a raw-byte hashable value from a byte slice.
///
/// This hashes the slice contents without Rust's slice length prefix.
///
/// # Examples
///
/// ```
/// # use datasketches::hash_value::calculate_hash;
/// # use datasketches::hash_value::raw_bytes::{from_slice, from_vec};
/// assert_eq!(
///     calculate_hash(from_slice(b"abc")),
///     calculate_hash(from_vec(b"abc".to_vec()))
/// );
/// assert!(from_slice(&[]).is_empty());
/// assert!(!from_slice(b"abc").is_empty());
/// ```
pub fn from_slice(v: &[u8]) -> RawBytes<&[u8]> {
    RawBytes::new(v)
}

/// Create a raw-byte hashable value from a string slice.
///
/// This hashes the UTF-8 bytes of the string slice without Rust's string length prefix.
///
/// # Examples
///
/// ```
/// # use datasketches::hash_value::calculate_hash;
/// # use datasketches::hash_value::raw_bytes::{from_str, from_string};
/// assert_eq!(
///     calculate_hash(from_str("abc")),
///     calculate_hash(from_string("abc".to_owned()))
/// );
/// assert!(from_str("").is_empty());
/// assert!(!from_str("abc").is_empty());
/// ```
pub fn from_str(v: &str) -> RawBytes<&str> {
    RawBytes::new(v)
}

macro_rules! impl_raw_bytes {
    ($t:ty, |$v:ident| $as_slice:expr) => {
        impl HashStrategy<$t> for RawBytesStrategy {
            fn hash<H: Hasher>(value: &$t, state: &mut H) {
                let $v = value;
                let slice = $as_slice;
                state.write(slice);
            }
        }
    };
}

impl_raw_bytes!(Vec<u8>, |v| v.as_slice());
impl_raw_bytes!(&[u8], |v| v);
impl_raw_bytes!(String, |v| v.as_bytes());
impl_raw_bytes!(&str, |v| v.as_bytes());