Add __lp_line_count() function and tests

This functions as a "poor man's" "wc -l". It's faster, but due to shell
quirks, it can be more difficult to use. The trick is that, like
'wc -l', this function counts newline characters, which means if the
input string has none, it will return 0.

The double underscore ("__") marks the function as "private" or
Liquidprompt only. Themes and users should not use it, as it should only
be run when the current directory changes, and Liquidprompt will control
that.

liquidprompt

@@ -99,6 +99,13 @@ else
     return
 fi
 
+# Count the number of lines in the input string. A faster subsitute for 'wc -l'.
+# input: $1; a single string of input.
+# return: $count; the number of newline characters in the string.
+__lp_line_count() {
+  local var="${1//[!$'\n']}"
+  count=${#var}
+}
 
 # Store $2 (or $?) as a true/false value in variable named $1
 # $? is propagated

tests/test_utils.sh

@@ -0,0 +1,38 @@
+
+. ../liquidprompt --no-activate
+
+function test_line_count {
+  typeset test_string="a normal string"
+  __lp_line_count "$test_string"
+  assertEquals "normal 1 line string" $(printf %s "$test_string" | wc -l) $count
+
+  test_string="\
+    a
+    longer
+    string"
+  __lp_line_count "$test_string"
+  assertEquals "3 line string" $(printf %s "$test_string" | wc -l) $count
+
+  test_string="\
+    a
+
+    longer
+
+    string
+
+
+    with many consecutive breaks"
+  __lp_line_count "$test_string"
+  assertEquals "consecutive blank lines string" $(printf %s "$test_string" | wc -l) $count
+
+  test_string=""
+  __lp_line_count "$test_string"
+  assertEquals "null string" $(printf %s "$test_string" | wc -l) $count
+}
+
+if [ -n "${ZSH_VERSION-}" ]; then
+  SHUNIT_PARENT="$0"
+  setopt shwordsplit
+fi
+
+. ./shunit2