Provide mechanisms to return strings (#324)

skiko/src/commonMain/kotlin/org/jetbrains/skia/ManagedString.kt

 package org.jetbrains.skia
 
+import org.jetbrains.skia.impl.*
 import org.jetbrains.skia.impl.Library.Companion.staticLoad
-import org.jetbrains.skia.impl.Managed
-import org.jetbrains.skia.impl.Stats
-import org.jetbrains.skia.impl.reachabilityBarrier
-import org.jetbrains.skia.impl.NativePointer
 
 class ManagedString internal constructor(ptr: NativePointer) : Managed(ptr, _FinalizerHolder.PTR) {
     companion object {
@@ -20,7 +17,10 @@ class ManagedString internal constructor(ptr: NativePointer) : Managed(ptr, _Fin
     override fun toString(): String {
         return try {
             Stats.onNativeCall()
-            _nToString(_ptr)
+            val size = _nStringSize(_ptr)
+            withResult(ByteArray(size)) {
+                _nStringData(_ptr, it, size)
+            }.decodeToString()
         } finally {
             reachabilityBarrier(this)
         }
@@ -61,8 +61,11 @@ private external fun ManagedString_nGetFinalizer(): NativePointer
 @ExternalSymbolName("org_jetbrains_skia_ManagedString__1nMake")
 private external fun _nMake(s: String?): NativePointer
 
-@ExternalSymbolName("org_jetbrains_skia_ManagedString__1nToString")
-private external fun _nToString(ptr: NativePointer): String
+@ExternalSymbolName("org_jetbrains_skia_ManagedString__nStringSize")
+private external fun _nStringSize(ptr: NativePointer): Int
+
+@ExternalSymbolName("org_jetbrains_skia_ManagedString__nStringData")
+private external fun _nStringData(ptr: NativePointer, result: InteropPointer, size: Int): String
 
 @ExternalSymbolName("org_jetbrains_skia_ManagedString__1nInsert")
 private external fun _nInsert(ptr: NativePointer, offset: Int, s: String?)

skiko/src/commonMain/kotlin/org/jetbrains/skia/impl/Native.kt

 package org.jetbrains.skia.impl
 
+import org.jetbrains.skia.ManagedString
+
 expect class NativePointer
 
 expect class InteropPointer
@@ -106,6 +108,12 @@ inline fun withResult(result: NativePointerArray, block: (InteropPointer) -> Uni
     result
 }
 
+@Suppress("NON_PUBLIC_CALL_FROM_PUBLIC_INLINE")
+inline fun withStringResult(block: () -> NativePointer): String {
+    val string = ManagedString(block())
+    return string.toString()
+}
+
 interface ArrayInteropDecoder<T> {
     fun getArrayElement(array: InteropPointer, index: Int): T
     fun getArraySize(array: InteropPointer): Int

skiko/src/commonTest/kotlin/org/jetbrains/skia/ManagedStringTest.kt

+package org.jetbrains.skia
+
+import org.jetbrains.skia.impl.withStringResult
+import org.jetbrains.skiko.tests.nativeStringByIndex
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class ManagedStringTest {
+    @Test
+    fun basicTest() {
+        val s1 = withStringResult {
+            nativeStringByIndex(0)
+        }
+        assertEquals("Hello", s1)
+        val s2 = withStringResult {
+            nativeStringByIndex(1)
+        }
+        assertEquals("Привет", s2)
+        val s3 = withStringResult {
+            nativeStringByIndex(2)
+        }
+        assertEquals("你好", s3)
+    }
+}

skiko/src/commonTest/kotlin/org/jetbrains/skiko/tests/TestHelpers.kt

@@ -2,6 +2,8 @@ package org.jetbrains.skiko.tests
 
 import org.jetbrains.skia.ExternalSymbolName
 import org.jetbrains.skia.impl.*
+import kotlin.test.Test
+import kotlin.test.assertEquals
 
 class TestHelpers {
 
@@ -54,3 +56,8 @@ private external fun _nFillIntArrayOf5(interopPointer: InteropPointer)
 
 @ExternalSymbolName("org_jetbrains_skiko_tests_TestHelpers__1nFillDoubleArrayOf5")
 private external fun _nFillDoubleArrayOf5(interopPointer: InteropPointer)
+
+@ExternalSymbolName("org_jetbrains_skiko_tests_TestHelpers__nStringByIndex")
+private external fun _nStringByIndex(index: Int): NativePointer
+
+internal fun nativeStringByIndex(index: Int): NativePointer = _nStringByIndex(index)
\ No newline at end of file

skiko/src/jsTest/kotlin/org/jetbrains/skia/impl/InteropScopeTests.kt

@@ -110,7 +110,7 @@ class InteropScopeTests {
                 it + 1
             }.map {
                 val charArray = CharArray(2)
-                (npa[it] as InteropPointer).fromInterop(charArray)
+                npa[it].fromInterop(charArray)
                 charArray.concatToString()
             }.take(3).toList().toTypedArray()
 

skiko/src/jvmMain/cpp/common/ManagedString.cc

@@ -17,10 +17,20 @@ extern "C" JNIEXPORT jlong JNICALL Java_org_jetbrains_skia_ManagedStringKt__1nMa
     return reinterpret_cast<jlong>(text);
 }
 
-extern "C" JNIEXPORT jobject JNICALL Java_org_jetbrains_skia_ManagedStringKt__1nToString
+extern "C" JNIEXPORT jint JNICALL Java_org_jetbrains_skia_ManagedStringKt__1nStringSize
   (JNIEnv* env, jclass jclass, jlong ptr) {
     SkString* instance = reinterpret_cast<SkString*>(static_cast<uintptr_t>(ptr));
-    return javaString(env, *instance);
+    return instance->size();
+}
+
+extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skia_ManagedStringKt__1nStringData
+  (JNIEnv* env, jclass jclass, jlong ptr, jbyteArray array, jint size) {
+    SkString* instance = reinterpret_cast<SkString*>(static_cast<uintptr_t>(ptr));
+    jbyte* bytes = env->GetByteArrayElements(array, NULL);
+    if (bytes != nullptr) {
+        memcpy(bytes, instance->c_str(), size);
+        env->ReleaseByteArrayElements(array, bytes, 0);
+    }
 }
 
 extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skia_ManagedStringKt__1nInsert

skiko/src/jvmTest/cpp/TestHelpers.cc

 #include <jni.h>
 
+#include "SkString.h"
+
 extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skiko_tests_TestHelpersKt__1nFillByteArrayOf5
 (JNIEnv* env, jclass jclass, jbyteArray jbarray) {
     jbyte *result_bytes = env->GetByteArrayElements(jbarray, NULL);
@@ -11,7 +13,6 @@ extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skiko_tests_TestHelpersKt__
     env->ReleaseByteArrayElements(jbarray, result_bytes, 0);
 }
 
-
 extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skiko_tests_TestHelpersKt__1nFillFloatArrayOf5
 (JNIEnv* env, jclass jclass, jfloatArray jfarray) {
     jfloat *result_float = env->GetFloatArrayElements(jfarray, NULL);
@@ -55,3 +56,18 @@ extern "C" JNIEXPORT void JNICALL Java_org_jetbrains_skiko_tests_TestHelpersKt__
     result_double[4] = 10000000.9991;
     env->ReleaseDoubleArrayElements(jdarray, result_double, 0);
 }
+
+static inline jlong ptrToJlong(void* ptr) {
+    return static_cast<jlong>(reinterpret_cast<uintptr_t>(ptr));
+}
+
+extern "C" JNIEXPORT jlong JNICALL Java_org_jetbrains_skiko_tests_TestHelpersKt__1nStringByIndex
+(JNIEnv* env, jclass jclass, jint index) {
+    switch (index) {
+        case 0: return ptrToJlong(new SkString("Hello"));
+        case 1: return ptrToJlong(new SkString("Привет"));
+        case 2: return ptrToJlong(new SkString("你好"));
+        default: return 0;
+    }
+}
+

skiko/src/nativeJsMain/cpp/ManagedString.cc

@@ -19,20 +19,17 @@ SKIKO_EXPORT KNativePointer org_jetbrains_skia_ManagedString__1nMake
     return reinterpret_cast<KNativePointer>(text);
 }
 
-SKIKO_EXPORT KInteropPointer org_jetbrains_skia_ManagedString__1nToString
+SKIKO_EXPORT KInt org_jetbrains_skia_ManagedString__nStringSize
   (KNativePointer ptr) {
-    TODO("implement org_jetbrains_skia_ManagedString__1nToString");
+    SkString* instance = reinterpret_cast<SkString*>(ptr);
+    return instance->size();
 }
-     
-#if 0 
-SKIKO_EXPORT KInteropPointer org_jetbrains_skia_ManagedString__1nToString
-  (KNativePointer ptr) {
-    SkString* instance = reinterpret_cast<SkString*>((ptr));
-    return javaString(env, *instance);
-}
-#endif
-
 
+SKIKO_EXPORT void org_jetbrains_skia_ManagedString__nStringData
+  (KNativePointer ptr, KByte* bytes, KInt size) {
+    SkString* instance = reinterpret_cast<SkString*>(ptr);
+    memcpy(bytes, instance->c_str(), size);
+}
 
 SKIKO_EXPORT void org_jetbrains_skia_ManagedString__1nInsert
   (KNativePointer ptr, KInt offset, KInteropPointer s) {

skiko/src/nativeJsTest/cpp/TestHelpers.cc

@@ -45,3 +45,12 @@ SKIKO_EXPORT void org_jetbrains_skiko_tests_TestHelpers__1nFillDoubleArrayOf5(KN
     doubles[3] = 3.1415;
     doubles[4] = 10000000.9991;
 }
+
+SKIKO_EXPORT KNativePointer org_jetbrains_skiko_tests_TestHelpers__nStringByIndex(KInt index) {
+    switch (index) {
+        case 0: return new SkString("Hello");
+        case 1: return new SkString("Привет");
+        case 2: return new SkString("你好");
+        default: TODO("unknown");
+    }
+}
\ No newline at end of file