From 51538fd5c367977136c555188f2f08e24134dd56 Mon Sep 17 00:00:00 2001
From: Karchnu <karchnu@karchnu.fr>
Date: Wed, 26 Jan 2022 12:27:41 +0100
Subject: [PATCH] Remove xxd dep & '\'. Change fun. names. </d/n in while read
 block. Comments.

---
 get-tracks.sh | 77 +++++++++++++++++++++++++++------------------------
 1 file changed, 41 insertions(+), 36 deletions(-)

diff --git a/get-tracks.sh b/get-tracks.sh
index 33f7166..95a6c97 100755
--- a/get-tracks.sh
+++ b/get-tracks.sh
@@ -1,7 +1,8 @@
 #!/usr/bin/env sh
 
-# From a single byte in hexadecimal per line
-# to lines ending with 0a (hex for '\n').
+# From a single byte in hexadecimal per line to lines ending with 0a
+# (hex for '\n'). Ex: 61 62 63 0a
+# Required to easily match (and remove) multi-byte characters.
 regroup_lines() awk '
 	BEGIN {
 		line_start=1
@@ -32,25 +33,40 @@ simple_quote()                sed "s/e2 80 99/27/g"
 # From / to '-'
 replace_slashes()             sed "s/2f/2d/g"
 
+remove_backslashes()          sed "s/5c//g"
+
 remove_multibyte_characters() sed "s/e2 80 .. //g"
 
+uppercase()                   tr "[a-z]" "[A-Z]"
+
+# One column decimal to plain text.
+from_dec()                    awk '{ printf ("%c", $1 + 0) }'
+
+# Replace spaces by line returns, outputs a single column.
+spaces_to_line_returns()      tr " " "\n"
+
 # Convert input into hexadecimal and a single byte per line.
-to_hex_one_column()           xxd -p -c 1
+to_hex_one_column() { od -An -tx1 | awk '{for(i=1;i<=NF;i++){ print $i }}'; }
 
-# Reverse hexadecimal to original value.
-from_hex()                    xxd -p -r
+# One column hexa to one column decimal.
+hex_to_dec() { { echo "obase=10;ibase=16;" ; cat ; } | bc ; }
 
-# Remove non ascii characters, convert "’" to "'", or remove invalid filename characters.
+# Reverse hexadecimal (with space separators) to original value.
+from_hex() { spaces_to_line_returns | uppercase | hex_to_dec | from_dec; }
+
+# Remove non ascii, backslashes and invalid filename characters,
+# convert "’" to "'", "/" to " - ".
 to_ascii(){
-	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 "'".
-		replace_slashes | # Replace / by ' - ', since it isn't a valid filename character.
+	to_hex_one_column | # Input to hexadecimal, 1-byte representation per line.
+		regroup_lines | # From 1-byte to x-byte lines with space separators.
+		simple_quote |  # From "’" to "'".
+		replace_slashes | # From / to '-'.
 		remove_multibyte_characters | # Remove non ascii values.
-		from_hex # Convert back from hex.
+		remove_backslashes | # Can mess with the script.
+		from_hex # Convert back from hex (x-byte per line, space separator).
 }
 
-process_end_of_songs() awk -v NONUMBER="$NONUMBER" -v SEPARATOR="$SEPARATOR" '
+comp_end_of_tracks() awk -v NONUMBER="$NONUMBER" -v SEPARATOR="$SEPARATOR" '
 	BEGIN {
 		OFS="	"
 	}
@@ -106,7 +122,7 @@ first_column_to_seconds() awk '
 	'
 
 # Get a more usable time representation for the beginning and the end of songs.
-process_time_file(){ to_ascii | first_column_to_seconds | process_end_of_songs ; }
+get_timestamps(){ to_ascii | first_column_to_seconds | comp_end_of_tracks; }
 
 run_ffmpeg(){
 	file=$1
@@ -139,15 +155,15 @@ run_ffmpeg(){
 	esac
 
 	if [ "$SIMULATION" = "" ]; then
-		$(< /dev/null ffmpeg $LOG_LEVEL $FROM $TO -i "$INPUT_FILE" "$OUTPUT_FILE")
+		ffmpeg $LOG_LEVEL $FROM $TO -i "$INPUT_FILE" "$OUTPUT_FILE"
 	fi
 }
 
-rip(){
+extraction(){
 	audio_file="$1"
 	time_file="$2"
 
-	process_time_file < "$time_file" | while read LINE; do
+	get_timestamps < "$time_file" | while read LINE; do
 		track_start=$(echo $LINE | cut -d ' ' -f 1)
 		track_end=$(echo $LINE | cut -d ' ' -f 2)
 		track_title=$(echo $LINE | cut -d ' ' -f 3-)
@@ -156,7 +172,12 @@ rip(){
 			track_end=""
 		fi
 
-		run_ffmpeg "${audio_file}" "${track_start}" "${track_end}" "${track_title}.${FORMAT}"
+		# Input is /dev/null, otherwise subshells will take the output
+		# of "get_timestamps" as input.
+		# Be careful: "while read X" is a dangerous shell design.
+		< /dev/null run_ffmpeg "${audio_file}" \
+			"${track_start}" "${track_end}" \
+			"${track_title}.${FORMAT}"
 	done
 }
 
@@ -192,11 +213,6 @@ Environment variables:
 END
 }
 
-if [ $# -lt 1 ]; then
-	usage
-	exit 0
-fi
-
 header(){
 	if [ "$HEADERS" = "1" ]; then
 		echo $*
@@ -237,20 +253,9 @@ if [ "$SIMULATION" != "" ]; then
 	header "SIMULATION envvar is set: this is a simulation."
 fi
 
-</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
-	exit 1
-fi
-
-</dev/null xxd -r >/dev/null 2>/dev/null
-if [ $? -ne 0 ]; then
-	echo "xxd: you don't have an xxd program with '-r' option." 1>&2
-	exit 1
-fi
-
 case $# in
-	1) process_time_file < "$1" ;;
-	2) rip "$1" "$2" ;;
+	0) usage; exit 0;;
+	1) get_timestamps < "$1" ;;
+	2) extraction "$1" "$2" ;;
 	*) usage 1>&2 ; exit 1 ;;
 esac