Files
adler32
aho_corasick
approx
arrayvec
ascii
backtrace
backtrace_sys
base64
bitflags
brotli2
brotli_sys
bstr
buf_redux
byteorder
bytes
cfg_if
chrono
chunked_transfer
color_quant
cookie
cookie_store
crc32fast
crossbeam_deque
crossbeam_epoch
crossbeam_queue
crossbeam_utils
csv
csv_core
csv_user_import
deflate
diesel
associations
connection
expression
expression_methods
macros
migration
mysql
query_builder
query_dsl
query_source
sql_types
type_impls
types
diesel_derives
diesel_migrations
dirs
dotenv
dtoa
either
encoding_rs
error_chain
failure
failure_derive
filetime
flate2
fnv
foreign_types
foreign_types_shared
futures
futures_cpupool
gif
google_signin
gzip_header
h2
http
http_body
httparse
hyper
hyper_rustls
hyper_tls
idna
image
indexmap
inflate
iovec
itoa
jpeg_decoder
language_tags
lazy_static
libc
lock_api
log
lzw
matches
memchr
memoffset
migrations_internals
migrations_macros
mime
mime_guess
miniz_oxide
mio
multipart
mysqlclient_sys
native_tls
net2
nodrop
num_cpus
num_derive
num_integer
num_iter
num_rational
num_traits
openssl
openssl_probe
openssl_sys
ordered_float
owning_ref
parking_lot
parking_lot_core
percent_encoding
phf
phf_shared
png
proc_macro2
publicsuffix
quick_error
quote
r2d2
rand
rand_chacha
rand_core
rand_hc
rand_isaac
rand_jitter
rand_os
rand_pcg
rand_xorshift
rayon
rayon_core
regex
regex_automata
regex_syntax
remove_dir_all
reqwest
ring
rouille
rustc_demangle
rustls
rusttype
ryu
safemem
scheduled_thread_pool
scoped_threadpool
scopeguard
sct
serde
serde_derive
serde_json
serde_urlencoded
sha1
simplelog
siphasher
slab
smallvec
stable_deref_trait
stb_truetype
string
syn
synom
synstructure
tempdir
term
thread_local
threadpool
tiff
time
tiny_http
tokio
tokio_buf
tokio_current_thread
tokio_executor
tokio_io
tokio_reactor
tokio_sync
tokio_tcp
tokio_threadpool
tokio_timer
traitobject
try_from
try_lock
twoway
typeable
unicase
unicode_bidi
unicode_normalization
unicode_xid
untrusted
url
uuid
want
webdev_lib
webpki
webpki_roots
 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
// Copyright 2016 Brian Smith.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

use crate::error;

/// XXX: When `const_fn` is implemented then make the value private to force
/// the constructors to be used.
#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd)]
pub struct BitLength(pub usize);

// Lengths measured in bits, where all arithmetic is guaranteed not to
// overflow.
impl BitLength {
    #[inline]
    pub fn from_usize_bits(bits: usize) -> BitLength { BitLength(bits) }

    #[inline]
    pub fn from_usize_bytes(bytes: usize) -> Result<BitLength, error::Unspecified> {
        let bits = bytes.checked_mul(8).ok_or(error::Unspecified)?;
        Ok(BitLength::from_usize_bits(bits))
    }

    #[inline]
    pub fn half_rounded_up(&self) -> BitLength {
        let round_up = self.0 & 1;
        BitLength((self.0 / 2) + round_up)
    }

    #[inline]
    pub fn as_usize_bits(&self) -> usize { self.0 }

    #[inline]
    pub fn as_usize_bytes_rounded_up(&self) -> usize {
        // Equivalent to (self.0 + 7) / 8, except with no potential for
        // overflow and without branches.

        // Branchless round_up = if self.0 & 0b111 != 0 { 1 } else { 0 };
        let round_up = ((self.0 >> 2) | (self.0 >> 1) | self.0) & 1;

        (self.0 / 8) + round_up
    }

    #[inline]
    pub fn try_sub(self, other: BitLength) -> Result<BitLength, error::Unspecified> {
        let sum = self.0.checked_sub(other.0).ok_or(error::Unspecified)?;
        Ok(BitLength(sum))
    }
}

pub const ONE: BitLength = BitLength(1);