Introduce Common readln() and readlnOrNull() top-level functions #KT-48456

kotlin-native/runtime/src/main/cpp/Console.cpp

@@ -13,6 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <cstdio>
+
 #include "KAssert.h"
 #include "Memory.h"
 #include "Natives.h"
@@ -67,4 +69,35 @@ OBJ_GETTER0(Kotlin_io_Console_readLine) {
     RETURN_RESULT_OF(CreateStringFromCString, data);
 }
 
+OBJ_GETTER0(Kotlin_io_Console_readlnOrNull) {
+    KStdVector<char> data;
+    data.reserve(16);
+    bool isEOF = false;
+    bool isError = false;
+    {
+        kotlin::ThreadStateGuard guard(kotlin::ThreadState::kNative);
+        while (true) {
+            int result = fgetc(stdin);
+
+            if (result == EOF || result == '\n') {
+                isEOF = (result == EOF);
+                isError = (ferror(stdin) != 0);
+                break;
+            }
+
+            data.push_back(result);
+        }
+    }
+    if (isError) {
+        ThrowIllegalStateException();
+    }
+    if (!isEOF && !data.empty() && data.back() == '\r') { // CRLF
+        data.pop_back();
+    }
+    if (data.empty() && isEOF) {
+        RETURN_OBJ(nullptr);
+    }
+    RETURN_RESULT_OF(StringFromUtf8Buffer, data.data(), data.size());
+}
+
 } // extern "C"

kotlin-native/runtime/src/main/kotlin/kotlin/io/Console.kt

@@ -29,6 +29,29 @@ public actual fun println(message: Any?) {
 @GCUnsafeCall("Kotlin_io_Console_println0")
 public actual external fun println()
 
+/**
+ * Reads a line of input from the standard input stream and returns it,
+ * or throws a [RuntimeException] if EOF has already been reached when [readln] is called.
+ *
+ * LF or CRLF is treated as the line terminator. Line terminator is not included in the returned string.
+ *
+ * The input is interpreted as UTF-8. Invalid bytes are replaced by the replacement character '\uFFFD'.
+ */
+@SinceKotlin("1.6")
+public actual fun readln(): String = readlnOrNull() ?: throw ReadAfterEOFException("EOF has already been reached")
+
+/**
+ * Reads a line of input from the standard input stream and returns it,
+ * or return `null` if EOF has already been reached when [readlnOrNull] is called.
+ *
+ * LF or CRLF is treated as the line terminator. Line terminator is not included in the returned string.
+ *
+ * The input is interpreted as UTF-8. Invalid bytes are replaced by the replacement character '\uFFFD'.
+ */
+@SinceKotlin("1.6")
+@GCUnsafeCall("Kotlin_io_Console_readlnOrNull")
+public actual external fun readlnOrNull(): String?
+
 /**
  * Reads a line of input from the standard input stream.
  *