contrib/maxlen.bash: also test dir and path length

Move the script from tests to contrib as it may now
be useful to somebody else.

https://github.com/rfjakob/gocryptfs/issues/552

contrib/maxlen.bash

@@ -0,0 +1,74 @@
+#!/bin/bash
+#
+# Find out the maximum supported filename length and print it.
+#
+# Part of the gocryptfs test suite
+# https://nuetzlich.net/gocryptfs/
+
+set -eu
+MYNAME=$(basename "$0")
+
+if [[ $# -ne 1 || $1 == -* ]]; then
+	echo "Usage: $MYNAME DIRECTORY"
+	exit 1
+fi
+
+cd "$1"
+echo "Testing $PWD"
+
+echo -n "  Maximum filename length: "
+# Add one character at a time until we hit an error
+NAME=""
+while true ; do
+	NEXT="${NAME}x"
+	if [[ -e $NEXT ]]; then
+		echo "error: file $NEXT already exists"
+		exit 1
+	fi
+	touch $NEXT 2> /dev/null || break
+	rm $NEXT
+	NAME="$NEXT"
+done
+echo "${#NAME}"
+
+echo -n "  Maximum dirname length:  "
+# Add one character at a time until we hit an error
+NAME=""
+while true ; do
+	NEXT="${NAME}x"
+	mkdir $NEXT 2> /dev/null || break
+	rmdir $NEXT
+	NAME="$NEXT"
+done
+MAX_DIRNAME=${#NAME}
+echo "${#NAME}"
+
+for CHARS_PER_SUBDIR in 1 10 100 $MAX_DIRNAME ; do
+	echo -n "  Maximum path length with $(printf %3d $CHARS_PER_SUBDIR) chars per subdir:     "
+	# Trick from https://stackoverflow.com/a/5349842/1380267
+	SUBDIR=$(printf 'x%.0s' $(seq 1 $CHARS_PER_SUBDIR))
+	mkdir "$SUBDIR"
+	P=$SUBDIR
+	# Create a deep path, one $SUBDIR at a time, until we hit an error
+	while true ; do
+		NEXT="$P/$SUBDIR"
+		mkdir "$NEXT" 2> /dev/null || break
+		P=$NEXT
+		echo -n -e "\b\b\b\b"
+		printf %4d ${#P}
+	done
+	# Then add one character at a time until we hit an error
+	NAME=""
+	while true ; do
+		NEXT="${NAME}x"
+		touch "$P/$NEXT" 2> /dev/null || break
+		NAME=$NEXT
+	done
+	if [[ $NAME != "" ]] ; then
+		P=$P/$NAME
+	fi
+	echo -n -e "\b\b\b\b"
+	printf %4d ${#P}
+	echo
+	rm -R "$SUBDIR"
+done

tests/maxlen.bash

@@ -1,18 +0,0 @@
-#!/bin/bash -eu
-#
-# Find out the maximum supported filename length and print it.
-#
-# Part of the gocryptfs test suite
-# https://nuetzlich.net/gocryptfs/
-
-NAME="maxlen."
-LEN=0
-
-while [ $LEN -le 10000 ]; do
-	touch $NAME 2> /dev/null || break
-	rm $NAME
-	LEN=${#NAME}
-	NAME="${NAME}x"
-done
-
-echo $LEN