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feat: display in bits #110

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feat: display in bits #110

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72 changes: 61 additions & 11 deletions src/display.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,40 +2,54 @@ use core::{fmt, write};

use crate::ByteSize;

const KIB_BITS: u64 = crate::KIB * 8;
const KB_BITS: u64 = crate::KB * 8;

/// `ln(8196) ~= 6.931`
const LN_KIB_BITS: f64 = 9.010_913_347_279_289;
/// `ln(8000) ~= 6.931`
const LN_KB_BITS: f64 = 8.987_196_820_661_972;

/// Format / style to use when displaying a [`ByteSize`].
#[derive(Debug, Clone, Copy)]
pub(crate) enum Format {
Iec,
IecShort,
Si,
SiShort,
IecBits,
SiBits,
}

impl Format {
fn unit(self) -> u64 {
match self {
Format::Iec | Format::IecShort => crate::KIB,
Format::Si | Format::SiShort => crate::KB,
Format::IecBits => KIB_BITS,
Format::SiBits => KB_BITS,
}
}

fn unit_base(self) -> f64 {
match self {
Format::Iec | Format::IecShort => crate::LN_KIB,
Format::Si | Format::SiShort => crate::LN_KB,
Format::IecBits => LN_KIB_BITS,
Format::SiBits => LN_KB_BITS,
}
}

fn unit_prefixes(self) -> &'static [u8] {
match self {
Format::Iec | Format::IecShort => crate::UNITS_IEC.as_bytes(),
Format::Si | Format::SiShort => crate::UNITS_SI.as_bytes(),
Format::Iec | Format::IecShort | Format::IecBits => crate::UNITS_IEC.as_bytes(),
Format::Si | Format::SiShort | Self::SiBits => crate::UNITS_SI.as_bytes(),
}
}

fn unit_separator(self) -> &'static str {
match self {
Format::Iec | Format::Si => " ",
Format::Iec | Format::Si | Format::IecBits | Format::SiBits => " ",
Format::IecShort | Format::SiShort => "",
}
}
Expand All @@ -45,6 +59,8 @@ impl Format {
Format::Iec => "iB",
Format::Si => "B",
Format::IecShort | Format::SiShort => "",
Format::IecBits => "ib",
Format::SiBits => "b",
}
}
}
Expand Down Expand Up @@ -115,12 +131,33 @@ impl Display {
self.format = Format::SiShort;
self
}

/// Format as equivalent number of bits using IEC (binary) units.
///
/// E.g., `12.3 Mib`.
#[must_use]
pub fn iec_bits(mut self) -> Self {
self.format = Format::IecBits;
self
}

/// Format as equivalent number of bits using SI (decimal) units.
///
/// E.g., `12.3 Mb`.
#[must_use]
pub fn si_bits(mut self) -> Self {
self.format = Format::SiBits;
self
}
}

impl fmt::Display for Display {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let bytes = self.byte_size.as_u64();

let is_bits = matches!(self.format, Format::IecBits | Format::SiBits);
let bits_or_bytes = bytes * (is_bits as u64 * 8);

let unit = self.format.unit();
#[allow(unused_variables)] // used in std contexts
let unit_base = self.format.unit_base();
Expand All @@ -130,10 +167,14 @@ impl fmt::Display for Display {
let unit_suffix = self.format.unit_suffix();
let precision = f.precision().unwrap_or(1);

if bytes < unit {
write!(f, "{bytes}{unit_separator}B")?;
if bits_or_bytes < unit {
if is_bits {
write!(f, "{bits_or_bytes}{unit_separator}b")?;
} else {
write!(f, "{bits_or_bytes}{unit_separator}B")?;
}
} else {
let size = bytes as f64;
let size = bits_or_bytes as f64;

#[cfg(feature = "std")]
let exp = ideal_unit_std(size, unit_base);
Expand Down Expand Up @@ -215,6 +256,11 @@ mod tests {
}
}

#[track_caller]
fn assert_to_string(expected: &str, byte_size: ByteSize, format: Format) {
assert_eq!(expected, Display { byte_size, format }.to_string());
}

#[test]
fn to_string_iec() {
let display = Display {
Expand Down Expand Up @@ -260,11 +306,6 @@ mod tests {
assert_eq!("953.7M", display.to_string());
}

#[track_caller]
fn assert_to_string(expected: &str, byte_size: ByteSize, format: Format) {
assert_eq!(expected, Display { byte_size, format }.to_string());
}

#[test]
fn test_to_string_as() {
assert_to_string("215 B", ByteSize::b(215), Format::Iec);
Expand Down Expand Up @@ -295,6 +336,15 @@ mod tests {
assert_to_string("609.0 PB", ByteSize::pb(609), Format::Si);
}

#[test]
fn as_bits() {
assert_to_string("8 b", ByteSize(1), Format::IecBits);
assert_to_string("8 b", ByteSize(1), Format::SiBits);

assert_to_string("8.4 Kib", ByteSize(8555), Format::IecBits);
assert_to_string("8.6 kb", ByteSize(8555), Format::SiBits);
}

#[test]
fn precision() {
let size = ByteSize::mib(1908);
Expand Down
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