Do not eagerly materialize native strings from 'char *'.

Author: fangerer

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/cext/CExtNodes.java

@@ -76,6 +76,7 @@
 import com.oracle.graal.python.builtins.objects.function.PKeyword;
 import com.oracle.graal.python.builtins.objects.ints.PInt;
 import com.oracle.graal.python.builtins.objects.module.PythonModule;
+import com.oracle.graal.python.builtins.objects.str.NativeCharSequence;
 import com.oracle.graal.python.builtins.objects.str.PString;
 import com.oracle.graal.python.builtins.objects.type.PythonAbstractClass;
 import com.oracle.graal.python.builtins.objects.type.PythonManagedClass;
@@ -891,13 +892,12 @@ public static AsCharPointerNode getUncached() {
     // -----------------------------------------------------------------------------------------------------------------
     @GenerateUncached
     public abstract static class FromCharPointerNode extends CExtBaseNode {
-        public abstract String execute(Object charPtr);
+        public abstract Object execute(Object charPtr);
 
         @Specialization
-        public String execute(Object charPtr,
-                        @Cached PCallCapiFunction callCstrToStringNode) {
-
-            return (String) callCstrToStringNode.call(FUN_PY_TRUFFLE_CSTR_TO_STRING, charPtr);
+        PString execute(Object charPtr,
+                        @Cached PythonObjectFactory factory) {
+            return factory.createString(new NativeCharSequence(charPtr));
         }
     }
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/str/NativeCharSequence.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * The Universal Permissive License (UPL), Version 1.0
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or
+ * data (collectively the "Software"), free of charge and under any and all
+ * copyright rights in the Software, and any and all patent rights owned or
+ * freely licensable by each licensor hereunder covering either (i) the
+ * unmodified Software as contributed to or provided by such licensor, or (ii)
+ * the Larger Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ *
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ *
+ * The above copyright notice and either this complete permission notice or at a
+ * minimum a reference to the UPL must be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.oracle.graal.python.builtins.objects.str;
+
+import com.oracle.graal.python.builtins.objects.cext.CExtNodes.PCallCapiFunction;
+import com.oracle.graal.python.builtins.objects.cext.NativeCAPISymbols;
+import org.graalvm.nativeimage.ImageInfo;
+
+import com.oracle.graal.python.nodes.PGuards;
+import com.oracle.graal.python.runtime.PythonOptions;
+import com.oracle.truffle.api.CompilerAsserts;
+import com.oracle.truffle.api.CompilerDirectives.TruffleBoundary;
+import com.oracle.truffle.api.profiles.ConditionProfile;
+
+public class NativeCharSequence implements CharSequence {
+
+    private final Object ptr;
+    private String materialized;
+
+    public NativeCharSequence(Object ptr) {
+        this.ptr = ptr;
+    }
+
+    @Override
+    public int length() {
+        return materialize().length();
+    }
+
+    @Override
+    public char charAt(int index) {
+        return materialize().charAt(index);
+    }
+
+    @Override
+    public CharSequence subSequence(int start, int end) {
+        return materialize().subSequence(start, end);
+    }
+
+    private String materialize() {
+        if(materialized == null) {
+            materialized = (String) PCallCapiFunction.getUncached().call(NativeCAPISymbols.FUN_PY_TRUFFLE_CSTR_TO_STRING, ptr);
+        }
+        return materialized;
+    }
+
+    @Override
+    public String toString() {
+        return materialize();
+    }
+}