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#[macro_use]
extern crate uucore;
use std::io::{self, Write};
use std::iter::Peekable;
use std::str::Chars;
const SYNTAX: &str = "[OPTIONS]... [STRING]...";
const SUMMARY: &str = "display a line of text";
const HELP: &str = r#"
Echo the STRING(s) to standard output.
If -e is in effect, the following sequences are recognized:
\\\\ backslash
\\a alert (BEL)
\\b backspace
\\c produce no further output
\\e escape
\\f form feed
\\n new line
\\r carriage return
\\t horizontal tab
\\v vertical tab
\\0NNN byte with octal value NNN (1 to 3 digits)
\\xHH byte with hexadecimal value HH (1 to 2 digits)
"#;
fn parse_code(
input: &mut Peekable<Chars>,
base: u32,
max_digits: u32,
bits_per_digit: u32,
) -> Option<char> {
let mut ret = 0x8000_0000;
for _ in 0..max_digits {
match input.peek().and_then(|c| c.to_digit(base)) {
Some(n) => ret = (ret << bits_per_digit) | n,
None => break,
}
input.next();
}
std::char::from_u32(ret)
}
fn print_escaped(input: &str, mut output: impl Write) -> io::Result<bool> {
let mut should_stop = false;
let mut buffer = ['\\'; 2];
let mut iter = input.chars().peekable();
while let Some(mut c) = iter.next() {
let mut start = 1;
if c == '\\' {
if let Some(next) = iter.next() {
c = match next {
'\\' => '\\',
'a' => '\x07',
'b' => '\x08',
'c' => {
should_stop = true;
break;
}
'e' => '\x1b',
'f' => '\x0c',
'n' => '\n',
'r' => '\r',
't' => '\t',
'v' => '\x0b',
'x' => parse_code(&mut iter, 16, 2, 4).unwrap_or_else(|| {
start = 0;
next
}),
'0' => parse_code(&mut iter, 8, 3, 3).unwrap_or_else(|| {
start = 0;
next
}),
_ => {
start = 0;
next
}
};
}
}
buffer[1] = c;
for ch in &buffer[start..] {
write!(output, "{}", ch)?;
}
}
Ok(should_stop)
}
pub fn uumain(args: impl uucore::Args) -> i32 {
let args = args.collect_str();
let matches = app!(SYNTAX, SUMMARY, HELP)
.optflag("n", "", "do not output the trailing newline")
.optflag("e", "", "enable interpretation of backslash escapes")
.optflag(
"E",
"",
"disable interpretation of backslash escapes (default)",
)
.parse(args);
let no_newline = matches.opt_present("n");
let escaped = matches.opt_present("e");
match execute(no_newline, escaped, matches.free) {
Ok(_) => 0,
Err(f) => {
show_error!("{}", f);
1
}
}
}
fn execute(no_newline: bool, escaped: bool, free: Vec<String>) -> io::Result<()> {
let stdout = io::stdout();
let mut output = stdout.lock();
for (i, input) in free.iter().enumerate() {
if i > 0 {
write!(output, " ")?;
}
if escaped {
let should_stop = print_escaped(&input, &mut output)?;
if should_stop {
break;
}
} else {
write!(output, "{}", input)?;
}
}
if !no_newline {
writeln!(output)?;
}
Ok(())
}