Merge pull request #15 from cketti/remove_platform_test

Remove `PlatformComparisonTest` & change `CommonCodePoints.toChars()` behavior

Author: cketti

build.gradle.kts

@@ -28,9 +28,6 @@ kotlin {
         compilations.all {
             kotlinOptions.jvmTarget = "1.8"
         }
-        testRuns["test"].executionTask.configure {
-            useJUnitPlatform()
-        }
     }
 
     linuxArm64()
@@ -67,10 +64,6 @@ kotlin {
         val commonImplementation by creating {
             dependsOn(commonMain)
         }
-
-        val jvmTest by getting {
-            dependsOn(commonImplementation)
-        }
     }
 
     targets.onEach {

src/commonImplementation/kotlin/CommonCodePoints.kt

@@ -54,19 +54,24 @@ object CommonCodePoints {
     }
 
     fun toChars(codePoint: Int, destination: CharArray, offset: Int): Int {
-        val size = destination.size
-        if (offset >= 0) {
-            if (isBmpCodePoint(codePoint)) {
-                if (offset < size) {
-                    destination[offset] = codePoint.toChar()
-                    return 1
-                }
-            } else if (offset < size - 1) {
-                destination[offset] = highSurrogate(codePoint)
-                destination[offset + 1] = lowSurrogate(codePoint)
-                return 2
-            }
+        if (isBmpCodePoint(codePoint)) {
+            destination.setSafe(offset, codePoint.toChar())
+            return 1
+        } else {
+            // When writing the low surrogate succeeds but writing the high surrogate fails (offset = -1), the 
+            // destination will be modified even though the method throws. This feels wrong, but matches the behavior
+            // of the Java stdlib implementation.
+            destination.setSafe(offset + 1, lowSurrogate(codePoint))
+            destination.setSafe(offset, highSurrogate(codePoint))
+            return 2
         }
-        throw IndexOutOfBoundsException("Size: $size, offset: $offset")
+    }
+    
+    private fun CharArray.setSafe(index: Int, value: Char) {
+        if (index !in this.indices) {
+            throw IndexOutOfBoundsException("Size: $size, offset: $index")
+        }
+
+        this[index] = value
     }
 }

src/commonTest/kotlin/CodePointsTest.kt

@@ -140,7 +140,8 @@ class CodePointsTest {
         assertFailsWith<IndexOutOfBoundsException> {
             CodePoints.toChars("\uD83E\uDD95".codePointAt(0), chars, -1)
         }
-        assertContentEquals(charArrayOf('z', 'z'), chars)
+        // We're bug-compatible with the Java stdlib implementation 
+        assertContentEquals(charArrayOf('\uDD95', 'z'), chars)
     }
 
     @Test

src/commonTest/kotlin/StringExtensionsTest.kt

@@ -2,6 +2,7 @@ package de.cketti.codepoints
 
 import kotlin.test.assertEquals
 import kotlin.test.Test
+import kotlin.test.assertFailsWith
 
 class StringExtensionsTest {
     @Test
@@ -120,4 +121,34 @@ class StringExtensionsTest {
         assertEquals(0, "\uD83E\uDD95\uD83E\uDD96".offsetByCodePoints(index = 3, codePointOffset = -2))
         assertEquals(0, "\uD83E\uDD95\uD83E\uDD96".offsetByCodePoints(index = 1, codePointOffset = -1))
     }
+
+    @Test
+    fun offsetByCodePoints_with_invalid_index() {
+        assertFailsWith<IndexOutOfBoundsException> {
+            "a".offsetByCodePoints(index = -1, codePointOffset = 0)
+        }
+
+        assertFailsWith<IndexOutOfBoundsException> {
+            "a".offsetByCodePoints(index = 2, codePointOffset = 0)
+        }
+    }
+
+    @Test
+    fun offsetByCodePoints_with_invalid_codePointOffset() {
+        assertFailsWith<IndexOutOfBoundsException> {
+            "a".offsetByCodePoints(index = 0, codePointOffset = 2)
+        }
+
+        assertFailsWith<IndexOutOfBoundsException> {
+            "a".offsetByCodePoints(index = 1, codePointOffset = -2)
+        }
+
+        assertFailsWith<IndexOutOfBoundsException> {
+            "\uD83E\uDD95".offsetByCodePoints(index = 0, codePointOffset = 2)
+        }
+
+        assertFailsWith<IndexOutOfBoundsException> {
+            "\uD83E\uDD95".offsetByCodePoints(index = 2, codePointOffset = -2)
+        }
+    }
 }