Merge pull request #25 from JakeWharton/jw.zero.2023-03-07

Ensure `codePointCount` can be called on zero-width range

Author: cketti

kotlin-codepoints/src/commonMain/kotlin/CharSequenceExtensions.kt

@@ -91,7 +91,7 @@ fun CharSequence.codePointCount(beginIndex: Int, endIndex: Int): Int {
 
     var index = beginIndex
     var count = 0
-    do {
+    while (index < endIndex) {
         val firstChar = this[index]
         index++
         if (firstChar.isHighSurrogate() && index < endIndex) {
@@ -102,7 +102,7 @@ fun CharSequence.codePointCount(beginIndex: Int, endIndex: Int): Int {
         }
 
         count++
-    } while (index < endIndex)
+    }
 
     return count
 }

kotlin-codepoints/src/commonTest/kotlin/CharSequenceExtensionsTest.kt

@@ -61,6 +61,9 @@ class CharSequenceExtensionsTest {
 
     @Test
     fun codePointCount() {
+        assertEquals(0, "".codePointCount(beginIndex = 0, endIndex = 0))
+        assertEquals(0, "abc".codePointCount(beginIndex = 1, endIndex = 1))
+
         assertEquals(3, "abc".codePointCount(beginIndex = 0, endIndex = 3))
         assertEquals(2, "a\uFFFF".codePointCount(beginIndex = 0, endIndex = 2))
         assertEquals(1, "\uD83E\uDD95".codePointCount(beginIndex = 0, endIndex = 2))