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
|
// SPDX-License-Identifier: MIT
//! Pure helpers used by the speedtester binary.
//!
//! Anything that does not require live I/O lives in this library crate so the
//! test suite can exercise it directly. The `main.rs` binary is a thin wrapper
//! that wires these helpers up to a hyper client.
/// Speed expressed in three units at once, all derived from a single
/// bytes-per-second figure using 1024-based (binary) division.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Speed {
/// Bytes per second (the raw figure passed to [`Speed::from_bps`]).
pub bps: u64,
/// Kibibytes per second (`bps / 1024`, rounded down).
pub kib_s: u64,
/// Mebibytes per second (`bps / 1024 / 1024`, rounded down).
pub mib_s: u64,
}
impl Speed {
/// Format `bytes_per_sec` into B/s, KiB/s, and MiB/s.
#[must_use]
pub const fn from_bps(bytes_per_sec: u64) -> Self {
Self {
bps: bytes_per_sec,
kib_s: bytes_per_sec / 1024,
mib_s: bytes_per_sec / (1024 * 1024),
}
}
}
/// Compute the list of `Range:` header values to use for parallel range
/// downloads.
///
/// Returns:
/// * `vec![None]` — a single sequential download with no range header — when
/// the server did not advertise a Content-Length, or `Content-Length: 0`.
/// This corresponds to the chunked / streaming fallback path.
/// * `vec![Some("bytes=A-B"), Some("bytes=C-D"), …]` — one entry per worker,
/// with the last entry's end-byte left empty (`"bytes=N-"`) so the final
/// worker reads to EOF and never misses a trailing remainder when
/// `content_length` is not evenly divisible by `cpu_count`.
///
/// `cpu_count` is clamped to at least 1 to avoid divide-by-zero and to match
/// the binary's runtime behaviour for single-CPU systems.
#[must_use]
pub fn compute_ranges(content_length: Option<u64>, cpu_count: u64) -> Vec<Option<String>> {
let cpu_count = cpu_count.max(1);
match content_length {
Some(cl) if cl > 0 => {
let bytes_per_cpu = cl / cpu_count;
(0..cpu_count)
.map(|i| {
let start = i * bytes_per_cpu;
let end = if i == cpu_count - 1 {
String::new()
} else {
format!("{}", (i + 1) * bytes_per_cpu - 1)
};
Some(format!("bytes={start}-{end}"))
})
.collect()
}
_ => vec![None],
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn speed_zero() {
let s = Speed::from_bps(0);
assert_eq!(
s,
Speed {
bps: 0,
kib_s: 0,
mib_s: 0
}
);
}
#[test]
fn speed_one_kib() {
let s = Speed::from_bps(1024);
assert_eq!(s.bps, 1024);
assert_eq!(s.kib_s, 1);
assert_eq!(s.mib_s, 0);
}
#[test]
fn speed_one_mib() {
let s = Speed::from_bps(1024 * 1024);
assert_eq!(s.bps, 1024 * 1024);
assert_eq!(s.kib_s, 1024);
assert_eq!(s.mib_s, 1);
}
#[test]
fn speed_sub_kib_rounds_down() {
let s = Speed::from_bps(1023);
assert_eq!(s.kib_s, 0);
assert_eq!(s.mib_s, 0);
}
#[test]
fn ranges_no_content_length_falls_back_to_single_streaming_worker() {
assert_eq!(compute_ranges(None, 24), vec![None]);
assert_eq!(compute_ranges(None, 1), vec![None]);
}
#[test]
fn ranges_zero_content_length_falls_back_to_single_streaming_worker() {
// Regression: the historical bug at this point produced N * file_size
// bytes of traffic because each worker computed `bytes=0-(u64::MAX)`.
assert_eq!(compute_ranges(Some(0), 24), vec![None]);
}
#[test]
fn ranges_even_split() {
let ranges = compute_ranges(Some(1024), 4);
assert_eq!(
ranges,
vec![
Some("bytes=0-255".to_string()),
Some("bytes=256-511".to_string()),
Some("bytes=512-767".to_string()),
// Last worker has open-ended end so any remainder is picked up.
Some("bytes=768-".to_string()),
]
);
}
#[test]
fn ranges_uneven_split_assigns_remainder_to_last_worker() {
// 1000 bytes across 3 workers: 1000/3 = 333 → workers cover
// 0-332, 333-665, 666-EOF (which is byte 999).
let ranges = compute_ranges(Some(1000), 3);
assert_eq!(
ranges,
vec![
Some("bytes=0-332".to_string()),
Some("bytes=333-665".to_string()),
Some("bytes=666-".to_string()),
]
);
}
#[test]
fn ranges_single_cpu_returns_one_open_range() {
let ranges = compute_ranges(Some(1_000_000), 1);
assert_eq!(ranges, vec![Some("bytes=0-".to_string())]);
}
#[test]
fn ranges_cpu_count_clamped_to_at_least_one() {
// Defensive: zero CPUs is non-sensical but must not panic.
let ranges = compute_ranges(Some(1024), 0);
assert_eq!(ranges, vec![Some("bytes=0-".to_string())]);
}
}
|
