130 lines
3.7 KiB
Rust
130 lines
3.7 KiB
Rust
// This file is part of Moonfire NVR, a security camera network video recorder.
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// Copyright (C) 2016 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
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// SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception.
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use nom::branch::alt;
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use nom::bytes::complete::{tag, take_while1};
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use nom::character::complete::space0;
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use nom::combinator::{map, map_res, opt};
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use nom::sequence::{delimited, tuple};
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use nom::IResult;
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use std::fmt::Write as _;
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static MULTIPLIERS: [(char, u64); 4] = [
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// (suffix character, power of 2)
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('T', 40),
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('G', 30),
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('M', 20),
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('K', 10),
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];
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/// Encodes a non-negative size into human-readable form.
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pub fn encode_size(mut raw: i64) -> String {
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let mut encoded = String::new();
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for &(c, n) in &MULTIPLIERS {
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if raw >= 1i64 << n {
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write!(&mut encoded, "{}{} ", raw >> n, c).unwrap();
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raw &= (1i64 << n) - 1;
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}
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}
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if raw > 0 || encoded.len() == 0 {
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write!(&mut encoded, "{}", raw).unwrap();
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} else {
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encoded.pop(); // remove trailing space.
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}
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encoded
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}
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fn decode_sizepart(input: &str) -> IResult<&str, i64> {
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map(
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tuple((
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map_res(take_while1(|c: char| c.is_ascii_digit()), |input: &str| {
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i64::from_str_radix(input, 10)
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}),
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opt(alt((
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nom::combinator::value(1 << 40, tag("T")),
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nom::combinator::value(1 << 30, tag("G")),
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nom::combinator::value(1 << 20, tag("M")),
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nom::combinator::value(1 << 10, tag("K")),
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))),
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)),
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|(n, opt_unit)| n * opt_unit.unwrap_or(1),
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)(input)
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}
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fn decode_size_internal(input: &str) -> IResult<&str, i64> {
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nom::multi::fold_many1(delimited(space0, decode_sizepart, space0), 0, |sum, i| {
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sum + i
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})(input)
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}
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/// Decodes a human-readable size as output by encode_size.
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pub fn decode_size(encoded: &str) -> Result<i64, ()> {
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let (remaining, decoded) = decode_size_internal(encoded).map_err(|_e| ())?;
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if !remaining.is_empty() {
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return Err(());
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}
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Ok(decoded)
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}
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/// Returns a hex-encoded version of the input.
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pub fn hex(raw: &[u8]) -> String {
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#[rustfmt::skip]
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const HEX_CHARS: [u8; 16] = [
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b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7',
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b'8', b'9', b'a', b'b', b'c', b'd', b'e', b'f',
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];
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let mut hex = Vec::with_capacity(2 * raw.len());
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for b in raw {
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hex.push(HEX_CHARS[((b & 0xf0) >> 4) as usize]);
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hex.push(HEX_CHARS[(b & 0x0f) as usize]);
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}
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unsafe { String::from_utf8_unchecked(hex) }
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}
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/// Returns [0, 16) or error.
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fn dehex_byte(hex_byte: u8) -> Result<u8, ()> {
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match hex_byte {
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b'0'..=b'9' => Ok(hex_byte - b'0'),
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b'a'..=b'f' => Ok(hex_byte - b'a' + 10),
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_ => Err(()),
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}
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}
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/// Returns a 20-byte raw form of the given hex string.
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/// (This is the size of a SHA1 hash, the only current use of this function.)
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pub fn dehex(hexed: &[u8]) -> Result<[u8; 20], ()> {
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if hexed.len() != 40 {
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return Err(());
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}
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let mut out = [0; 20];
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for i in 0..20 {
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out[i] = (dehex_byte(hexed[i << 1])? << 4) + dehex_byte(hexed[(i << 1) + 1])?;
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}
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Ok(out)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_decode() {
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assert_eq!(super::decode_size("100M").unwrap(), 100i64 << 20);
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assert_eq!(super::decode_size("100M 42").unwrap(), (100i64 << 20) + 42);
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}
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#[test]
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fn round_trip() {
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let s = "de382684a471f178e4e3a163762711b0653bfd83";
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let dehexed = dehex(s.as_bytes()).unwrap();
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assert_eq!(&hex(&dehexed[..]), s);
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}
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#[test]
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fn dehex_errors() {
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dehex(b"").unwrap_err();
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dehex(b"de382684a471f178e4e3a163762711b0653bfd8g").unwrap_err();
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}
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}
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