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|
use std::io::{self, BufRead as _};
use std::str;
/// A single zsh extended history item.
#[derive(Debug)]
pub struct Item<'a> {
pub time: u64,
pub duration: u64,
pub cmd: &'a [u8],
}
impl Item<'_> {
/// Writes one item in the format b": <timestamp>:<duration>;<command>\n".
pub fn write<W: io::Write>(&self, out: &mut W) -> Result<(), Error> {
write!(out, ": {}:{};", self.time, self.duration)?;
out.write_all(self.cmd)?;
Ok(())
}
}
#[derive(Debug, thiserror::Error)]
pub enum Error {
#[error(transparent)]
Io(#[from] io::Error),
#[error(transparent)]
Utf8(#[from] str::Utf8Error),
#[error(transparent)]
Int(#[from] std::num::ParseIntError),
#[error("Format error: {0}")]
Format(String),
}
/// A reader that parses extended zsh history items from a stream.
/// It reuses an internal buffer so that items are yielded without copying.
pub struct Reader<R: io::Read> {
reader: io::BufReader<R>,
buf: Vec<u8>,
}
impl<R: io::Read> Reader<R> {
pub fn new(inner: R) -> Self {
Reader {
reader: io::BufReader::new(inner),
buf: Vec::with_capacity(1024),
}
}
/// Parses self.buf into an Item.
/// Expected format: b": <timestamp>:<duration>;<command>"
/// This method borrows from self.buf.
fn parse(&self) -> Result<Item<'_>, Error> {
let mut item = &self.buf[..];
if let Some(stripped) = item.strip_prefix(b":").or_else(|| item.strip_prefix(b"\\:")) {
item = stripped;
} else {
return Err(Error::Format(format!(
"Item does not start with ':' or '\\:' : {:?}",
str::from_utf8(&item)?
)));
}
item = item.strip_prefix(b" ").unwrap_or(item);
let colon_pos = item.iter().position(|&c| c == b':')
.ok_or_else(|| Error::Format("Missing colon between timestamp and duration.".into()))?;
let time: u64 = str::from_utf8(&item[..colon_pos])?.parse()?;
let remainder = &item[colon_pos + 1..];
let semi_pos = remainder.iter().position(|&c| c == b';')
.ok_or_else(|| Error::Format("Missing semicolon in item.".into()))?;
let duration: u64 = str::from_utf8(&remainder[..semi_pos])?.parse()?;
let cmd = &remainder[semi_pos + 1..];
Ok(Item { time, duration, cmd })
}
// Reads and returns the next item, or None on EOF.
pub fn read_item(&mut self) -> Result<Option<Item<'_>>, Error> {
self.buf.clear();
loop {
if self.reader.read_until(b'\n', &mut self.buf)? == 0 {
return if self.buf.is_empty() {
Ok(None)
} else {
Ok(Some(self.parse()?))
}
}
// If a command ends with a backslash, zsh makes sure to prepend a space, such that
// backslash-quoted newlines mean: command continues on next line.
if !self.buf.ends_with(b"\\\n") {
break;
}
}
Ok(Some(self.parse()?))
}
}
pub fn merge<R1: io::Read, R2: io::Read, R3: io::Read, W: io::Write>(
mut left: Reader<R1>,
mut right: Reader<R2>,
mut ancestor: Reader<R3>,
out: &mut W,
) -> Result<(), Error> {
// Get the first item from each stream.
let mut l = left.read_item()?;
let mut r = right.read_item()?;
let mut a = ancestor.read_item()?;
let out = &mut io::BufWriter::new(out);
// While any stream still has an item:
while l.is_some() || r.is_some() || a.is_some() {
// Determine the current earliest time over all non-None items.
let current_time = [l.as_ref(), r.as_ref(), a.as_ref()]
.iter()
.filter_map(|opt| opt.map(|i| i.time))
.min()
.unwrap();
// Grab the "chunk": all items whose time equals the current time.
// (After this step, each of left, right, and ancestor is either Some(item)
// with the current time or None.)
let l_chunk = l.as_ref().filter(|i| i.time == current_time);
let r_chunk = r.as_ref().filter(|i| i.time == current_time);
let a_chunk = a.as_ref().filter(|i| i.time == current_time);
match (l_chunk, r_chunk, a_chunk) {
// Case 1: Both left and right are present.
(Some(l), Some(r), a_opt) => {
if l.cmd == r.cmd {
// They agree: output it.
l.write(out)?;
} else {
// They differ. Check against ancestor.
if let Some(a) = a_opt {
if l.cmd == a.cmd && r.cmd != a.cmd {
r.write(out)?;
} else if r.cmd == a.cmd && l.cmd != a.cmd {
l.write(out)?;
} else {
// Otherwise both differ, so output both.
l.write(out)?;
r.write(out)?;
}
} else {
// No ancestor: output both.
l.write(out)?;
r.write(out)?;
}
}
}
// Case 2a: Left is present; right is missing.
(Some(l), None, a_opt) => {
if let Some(a) = a_opt {
if l.cmd == a.cmd {
// Left == ancestor: deletion.
} else {
l.write(out)?;
}
} else {
l.write(out)?;
}
}
// Case 2b: Right is present; left is missing.
(None, Some(r), a_opt) => {
if let Some(a) = a_opt {
if r.cmd == a.cmd {
} else {
r.write(out)?;
}
} else {
r.write(out)?;
}
}
// Case 3: Neither left nor right have a item.
(None, None, Some(_)) => {
// Interpret as a deletion.
}
(None, None, None) => unreachable!(),
}
// Advance the readers.
if l_chunk.is_some() {
l = left.read_item()?;
}
if r_chunk.is_some() {
r = right.read_item()?;
}
if a_chunk.is_some() {
a = ancestor.read_item()?;
}
}
Ok(())
}
|
