1 files changed, 63 insertions, 0 deletions
diff --git a/lib/text_roll.sh b/lib/text_roll.sh
new file mode 100644
index 0000000..e53247f
--- /dev/null
+++ b/lib/text_roll.sh
@@ -0,0 +1,63 @@
+# Rolling anything what you want.
+# arg1: text to roll.
+# arg2: max length to display.
+# arg3: roll speed in characters per second.
+roll_text() {
+	local text="$1"  # Text to print
+
+	if [ -z "$text" ]; then
+		return;
+	fi
+
+	local max_len="10"	# Default max length.
+
+	if [ -n "$2" ]; then
+		max_len="$2"
+	fi
+
+	local speed="1"  # Default roll speed in chars per second.
+
+	if [ -n "$3" ]; then
+		speed="$3"
+	fi
+
+	# Skip rolling if the output is less than max_len.
+	if [ "${#text}" -le "$max_len" ]; then
+		echo "$text"
+		return
+	fi
+
+	# Anything starting with 0 is an Octal number in Shell,C or Perl,
+	# so we must explicitly state the base of a number using base#number
+	local offset=$((10#$(date +%s) * ${speed} % ${#text}))
+
+	# Truncate text.
+	text=${text:offset}
+
+	local char	# Character.
+	local bytes # The bytes of one character.
+	local index
+
+	for ((index=0; index < max_len; index++)); do
+		char=${text:index:1}
+		bytes=$(echo -n $char | wc -c)
+		# The character will takes twice space
+		# of an alphabet if (bytes > 1).
+		if ((bytes > 1)); then
+			max_len=$((max_len - 1))
+		fi
+	done
+
+	text=${text:0:max_len}
+
+	#echo "index=${index} max=${max_len} len=${#text}"
+	# How many spaces we need to fill to keep
+	# the length of text that will be shown?
+	local fill_count=$((${index} - ${#text}))
+
+	for ((index=0; index < fill_count; index++)); do
+		text="${text} "
+	done
+
+	echo "${text}"
+}