Merge branch 'dj-formatting'

src/swab.rs

@@ -25,19 +25,23 @@ use std::{
 };
 
 extern crate getopt;
-use getopt::GetOpt;
-
 extern crate sysexits;
-use sysexits::{ EX_OK, EX_OSERR, EX_USAGE };
-
 extern crate strerror;
+
+use getopt::GetOpt;
+use sysexits::{ EX_IOERR, EX_OK, EX_OSERR, EX_USAGE };
 use strerror::StrError;
 
-fn oserr(s: &str, e: Error) -> ExitCode {
-	eprintln!("{}: {}", s, e.strerror());
+fn oserr(argv0: &str, e: Error) -> ExitCode {
+	eprintln!("{}: {}", argv0, e.strerror());
 	ExitCode::from(EX_OSERR as u8)
 }
 
+fn ioerr(argv0: &str, e: Error) -> ExitCode {
+	eprintln!("{}: {}", argv0, e.strerror());
+	ExitCode::from(EX_IOERR as u8)
+}
+
 fn usage(s: &str) -> ExitCode {
 	eprintln!("Usage: {} [-w word_size]", s);
 	ExitCode::from(EX_USAGE as u8)
@@ -45,12 +49,11 @@ fn usage(s: &str) -> ExitCode {
 
 fn main() -> ExitCode {
 	let argv = args().collect::<Vec<String>>();
-	let mut buf: Vec<u8> = Vec::new();
+	let mut buf: Vec<u8> = Vec::new(); // holds the sequence getting swabbed
 	let mut input = stdin();
 	let mut output = stdout().lock();
-
 	let mut optind: usize = 1;   // argv[0]
-	let mut wordsize: usize = 2; // Equivalent to dd(1p).
+	let mut wordsize: usize = 2; // default; mimics dd(1p) conv=swab
 
 	while let Some(opt) = argv.getopt("w:") {
 		match opt.opt() {
@@ -73,17 +76,19 @@ fn main() -> ExitCode {
 
 	loop {
 		match input.read(&mut buf) {
-			Ok(0) => break ExitCode::from(EX_OK as u8),
-			Ok(v) if v == wordsize => {
+			Ok(0) => break ExitCode::from(EX_OK as u8), // read nothing; bye
+			Ok(v) if v == wordsize => { // read full block; swab
 				let (left, right) = buf.split_at(v/2);
+
 				if let Err(e) = output.write(&right)
 						.and_then(|_| output.write(&left)) {
-					break oserr(&argv[0], e)
+					break ioerr(&argv[0], e);
 				}
+
 			},
-			Ok(v) => {
+			Ok(v) => { // partial read; partially write
 				if let Err(e) = output.write(&buf[..v]) {
-					break oserr(&argv[0], e)
+					break ioerr(&argv[0], e);
 				}
 			},
 			Err(e) => break oserr(&argv[0], e)