From 0e8a90dd819ac19d2191a7b8077b336b136c6556 Mon Sep 17 00:00:00 2001
From: Karchnu <karchnu@karchnu.fr>
Date: Tue, 6 Apr 2021 16:09:15 +0200
Subject: [PATCH] Comments.

---
 get-tracks.sh | 55 ++++++++++++++++++++++++---------------------------
 1 file changed, 26 insertions(+), 29 deletions(-)

diff --git a/get-tracks.sh b/get-tracks.sh
index 5c21518..8f77430 100755
--- a/get-tracks.sh
+++ b/get-tracks.sh
@@ -1,31 +1,34 @@
 #!/usr/bin/env sh
 
+# From a single byte in hexadecimal per line
+# to lines ending with 0a (hex for '\n').
 regroup_lines(){
 	awk '
 	BEGIN {
-		first=1
+		line_start=1
 	}
 
 	{
-		if (first == 1)
+		if (line_start == 1)
 			line = $1;
 		else
 			line = line " " $1;
 
-		first = 0;
+		line_start = 0;
 		if ($1 == "0a") {
 			print line;
-			first = 1
+			line_start = 1
 		}
 	}
 
 	END {
-		if (first == 0)
+		if (line_start == 0)
 			print line
 	}
 	'
 }
 
+# From ’ to '
 simple_quote(){
 	sed "s/e2 80 99/27/g"
 }
@@ -34,20 +37,23 @@ remove_multibyte_characters(){
 	sed "s/e2 80 .. //g"
 }
 
-to_hex_one_colomun(){
+# Convert input into hexadecimal and a single byte per line.
+to_hex_one_column(){
 	xxd -p -c 1
 }
 
+# Reverse hexadecimal to original value.
 from_hex(){
 	xxd -p -r
 }
 
+# Remove non ascii characters, convert "’" to "'".
 to_ascii(){
-	to_hex_one_colomun |
-		regroup_lines |
-		simple_quote |
-		remove_multibyte_characters |
-		from_hex
+	to_hex_one_column | # Convert input into hexadecimal and a single byte per line.
+		regroup_lines | # Required to easily match multi-byte characters.
+		simple_quote |  # Convert "’" to "'".
+		remove_multibyte_characters | # Remove non ascii values.
+		from_hex # Convert back from hex.
 }
 
 process_durations(){
@@ -112,8 +118,7 @@ first_column_to_seconds(){
 
 # Get a more usable time representation for the beginning and the end of songs.
 process_time_file(){
-	time_file="$1"
-	to_ascii < "$time_file" | first_column_to_seconds | process_durations
+	to_ascii | first_column_to_seconds | process_durations
 }
 
 run_ffmpeg(){
@@ -159,7 +164,7 @@ rip(){
 	audio_file="$1"
 	time_file="$2"
 
-	process_time_file "$time_file" | while read LINE; do
+	process_time_file < "$time_file" | while read LINE; do
 		track_start_s=$(echo $LINE | cut -d ' ' -f 1)
 		track_end_s=$(echo $LINE | cut -d ' ' -f 2)
 		track_title=$(echo $LINE | cut -d ' ' -f 3-)
@@ -175,7 +180,7 @@ rip(){
 
 usage(){
 	echo "usage: $0 command"
-	echo "command: show <single-file-playlist> <song-list>"
+	echo "command: show <song-list>"
 	echo "command: rip  <single-file-playlist> <song-list>"
 	echo
 	echo "song-list line format example: 1:30 My second track of the playlist"
@@ -187,9 +192,9 @@ usage(){
 	echo "envvar: SEPARATOR [separator] (default: ' - '), write song number, with this separator"
 	echo "        example with SEPARATOR='_': song names will be 01_song.opus 02_song.opus…"
 	echo "envvar: VERBOSITY [0-3] (default: 1)"
-	echo "        verbosity 0: no output exept errors from ffmpeg"
-	echo "        verbosity 1: simple indications on the current track being extracted"
-	echo "        verbosity 2: print actual ffmpeg commands the script currently runs"
+	echo "        VERBOSITY 0: no output exept errors from ffmpeg"
+	echo "        VERBOSITY 1: simple indications on the current track being extracted"
+	echo "        VERBOSITY 2: print actual ffmpeg commands the script currently runs"
 }
 
 if [ $# -lt 1 ]; then
@@ -234,10 +239,6 @@ if [ "$SIMULATION" != "" ]; then
 	echo "SIMULATION envvar is set: this is a simulation."
 fi
 
-# soxi provides the total length of the music file.
-#which soxi 2>/dev/null
-#total_length=$(soxi -D "${audio_file}" | sed "s/\..*//") # integer values only
-
 </dev/null xxd -p >/dev/null 2>/dev/null
 if [ $? -ne 0 ]; then
 	echo "xxd: you don't have an xxd program with '-p' option." 1>&2
@@ -254,12 +255,12 @@ case "x-${command}" in
 	x-show)
 
 		# Takes the audio file in first parameter
-		if [ $# -ne 2 ]; then
-			echo "Usage: $0 show music-file time-stamps-file" >&2
+		if [ $# -ne 1 ]; then
+			echo "Usage: $0 show time-stamps-file" >&2
 			exit 1
 		fi
 
-		process_time_file "$2"
+		process_time_file < "$1"
 		;;
 
 	x-rip)
@@ -273,10 +274,6 @@ case "x-${command}" in
 		rip "$1" "$2"
 		;;
 
-	x-input)
-		to_ascii < "$1"
-		;;
-
 	*)
 		usage 1>&2
 		exit 1