Add option to use std::string_view

src/source/CppMarshal.scala

@@ -72,7 +72,9 @@ class CppMarshal(spec: Spec) extends Marshal(spec) {
       case "i8" | "i16" | "i32" | "i64" => List(ImportRef("<cstdint>"))
       case _ => List()
     }
-    case MString => List(ImportRef("<string>"))
+    case MString => 
+      val includes = List(ImportRef("<string>"))
+      if (spec.cppUseStringView) ImportRef("<string_view>") :: includes else includes
     case MDate => List(ImportRef("<chrono>"))
     case MBinary => List(ImportRef("<vector>"), ImportRef("<cstdint>"))
     case MOptional => List(ImportRef(spec.cppOptionalHeader))
@@ -258,10 +260,15 @@ class CppMarshal(spec: Spec) extends Marshal(spec) {
 
   // this can be used in c++ generation to know whether a const& should be applied to the parameter or not
   private def toCppParamType(tm: MExpr, namespace: Option[String] = None, scopeSymbols: Seq[String] = Seq()): String = {
-    val cppType = toCppType(tm, namespace, scopeSymbols)
-    val refType = "const " + cppType + " &"
-    val valueType = cppType
-    if(byValue(tm)) valueType else refType
+    tm.base match {
+      case MString if spec.cppUseStringView => 
+        if (spec.cppUseWideStrings) "std::wstring_view" else "std::string_view"
+      case _ =>
+        val cppType = toCppType(tm, namespace, scopeSymbols)
+        val refType = "const " + cppType + " &"
+        val valueType = cppType
+        if(byValue(tm)) valueType else refType
+    }
   }
 
   private def moveOnly(tm: MExpr): Boolean = tm.base match {

src/source/Main.scala

@@ -42,6 +42,7 @@ object Main {
     var cppNnCheckExpression: Option[String] = None
     var cppUseWideStrings: Boolean = false
     var cppLegacyRecords: Boolean = false
+    var cppUseStringView: Boolean = false
     var javaOutFolder: Option[File] = None
     var javaPackage: Option[String] = None
     var javaClassAccessModifier: JavaAccessModifier.Value = JavaAccessModifier.Public
@@ -191,6 +192,8 @@ object Main {
         .text("Use wide strings in C++ code (default: false)")
       opt[Boolean]( "cpp-legacy-records").valueName("<true/false>").foreach(x => cppLegacyRecords = x)
         .text("Use legacy record behavior for C++ code (default: false)")
+      opt[Boolean]( "cpp-use-string-view").valueName("<true/false>").foreach(x => cppUseStringView = x)
+        .text("Use std::string_view for string parameters in C++ code (default: false)")
       note("")
       opt[File]("jni-out").valueName("<out-folder>").foreach(x => jniOutFolder = Some(x))
         .text("The folder for the JNI C++ output files (Generator disabled if unspecified).")
@@ -438,6 +441,7 @@ object Main {
       cppNnCheckExpression,
       cppUseWideStrings,
       cppLegacyRecords,
+      cppUseStringView,
       jniOutFolder,
       jniHeaderOutFolder,
       jniIncludePrefix,

src/source/generator.scala

@@ -60,6 +60,7 @@ package object generatorTools {
                    cppNnCheckExpression: Option[String],
                    cppUseWideStrings: Boolean,
                    cppLegacyRecords: Boolean,
+                   cppUseStringView: Boolean,
                    jniOutFolder: Option[File],
                    jniHeaderOutFolder: Option[File],
                    jniIncludePrefix: String,

test-suite/djinni/all.djinni

@@ -3,6 +3,7 @@
 @import "enum_flags.djinni"
 @import "constant_enum.djinni"
 @import "data_ref_view.djinni"
+@import "string_view_test.djinni"
 
 @import "vendor/third-party/date.djinni"
 @import "third-party/duration.djinni"

test-suite/djinni/string_view_test.djinni

@@ -0,0 +1,6 @@
+# @flag "--cpp-use-string-view true"
+
+test_interface_with_string = interface +c {
+    # Method with string parameter to test string_view generation
+    process_string(message: string): string;
+}

test-suite/generated-src/cpp/test_interface_with_string.hpp

@@ -0,0 +1,19 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+#pragma once
+
+#include <string>
+
+namespace testsuite {
+
+/** @flag "--cpp-use-string-view true" */
+class TestInterfaceWithString {
+public:
+    virtual ~TestInterfaceWithString() = default;
+
+    /** Method with string parameter to test string_view generation */
+    virtual std::string process_string(const std::string & message) = 0;
+};
+
+} // namespace testsuite

test-suite/generated-src/inFileList.txt

@@ -26,6 +26,7 @@ djinni/constant_enum.djinni
 djinni/data_ref_view.djinni
 ../support-lib/dataref.yaml
 ../support-lib/dataview.yaml
+djinni/string_view_test.djinni
 djinni/vendor/third-party/date.djinni
 djinni/vendor/third-party/date.yaml
 djinni/vendor/third-party/duration.djinni

test-suite/generated-src/java/com/dropbox/djinni/test/TestInterfaceWithString.java

@@ -0,0 +1,38 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+package com.dropbox.djinni.test;
+
+import com.snapchat.djinni.NativeObjectManager;
+import java.util.concurrent.atomic.AtomicBoolean;
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+
+/** @flag "--cpp-use-string-view true" */
+public abstract class TestInterfaceWithString {
+    /** Method with string parameter to test string_view generation */
+    @Nonnull
+    public abstract String processString(@Nonnull String message);
+
+    public static final class CppProxy extends TestInterfaceWithString
+    {
+        private final long nativeRef;
+        private final AtomicBoolean destroyed = new AtomicBoolean(false);
+
+        private CppProxy(long nativeRef)
+        {
+            if (nativeRef == 0) throw new RuntimeException("nativeRef is zero");
+            this.nativeRef = nativeRef;
+            NativeObjectManager.register(this, nativeRef);
+        }
+        public static native void nativeDestroy(long nativeRef);
+
+        @Override
+        public String processString(String message)
+        {
+            assert !this.destroyed.get() : "trying to use a destroyed object";
+            return native_processString(this.nativeRef, message);
+        }
+        private native String native_processString(long _nativeRef, String message);
+    }
+}

test-suite/generated-src/jni/NativeTestInterfaceWithString.cpp

@@ -0,0 +1,30 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+#include "NativeTestInterfaceWithString.hpp"  // my header
+#include "Marshal.hpp"
+
+namespace djinni_generated {
+
+NativeTestInterfaceWithString::NativeTestInterfaceWithString() : ::djinni::JniInterface<::testsuite::TestInterfaceWithString, NativeTestInterfaceWithString>("com/dropbox/djinni/test/TestInterfaceWithString$CppProxy") {}
+
+NativeTestInterfaceWithString::~NativeTestInterfaceWithString() = default;
+
+
+CJNIEXPORT void JNICALL Java_com_dropbox_djinni_test_TestInterfaceWithString_00024CppProxy_nativeDestroy(JNIEnv* jniEnv, jobject /*this*/, jlong nativeRef)
+{
+    try {
+        delete reinterpret_cast<::djinni::CppProxyHandle<::testsuite::TestInterfaceWithString>*>(nativeRef);
+    } JNI_TRANSLATE_EXCEPTIONS_RETURN(jniEnv, )
+}
+
+CJNIEXPORT jstring JNICALL Java_com_dropbox_djinni_test_TestInterfaceWithString_00024CppProxy_native_1processString(JNIEnv* jniEnv, jobject /*this*/, jlong nativeRef, jstring j_message)
+{
+    try {
+        const auto& ref = ::djinni::objectFromHandleAddress<::testsuite::TestInterfaceWithString>(nativeRef);
+        auto r = ref->process_string(::djinni::String::toCpp(jniEnv, j_message));
+        return ::djinni::release(::djinni::String::fromCpp(jniEnv, r));
+    } JNI_TRANSLATE_EXCEPTIONS_RETURN(jniEnv, 0 /* value doesn't matter */)
+}
+
+} // namespace djinni_generated

test-suite/generated-src/jni/NativeTestInterfaceWithString.hpp

@@ -0,0 +1,32 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+#pragma once
+
+#include "djinni_support.hpp"
+#include "test_interface_with_string.hpp"
+
+namespace djinni_generated {
+
+class NativeTestInterfaceWithString final : ::djinni::JniInterface<::testsuite::TestInterfaceWithString, NativeTestInterfaceWithString> {
+public:
+    using CppType = std::shared_ptr<::testsuite::TestInterfaceWithString>;
+    using CppOptType = std::shared_ptr<::testsuite::TestInterfaceWithString>;
+    using JniType = jobject;
+
+    using Boxed = NativeTestInterfaceWithString;
+
+    ~NativeTestInterfaceWithString();
+
+    static CppType toCpp(JNIEnv* jniEnv, JniType j) { return ::djinni::JniClass<NativeTestInterfaceWithString>::get()._fromJava(jniEnv, j); }
+    static ::djinni::LocalRef<JniType> fromCppOpt(JNIEnv* jniEnv, const CppOptType& c) { return {jniEnv, ::djinni::JniClass<NativeTestInterfaceWithString>::get()._toJava(jniEnv, c)}; }
+    static ::djinni::LocalRef<JniType> fromCpp(JNIEnv* jniEnv, const CppType& c) { return fromCppOpt(jniEnv, c); }
+
+private:
+    NativeTestInterfaceWithString();
+    friend ::djinni::JniClass<NativeTestInterfaceWithString>;
+    friend ::djinni::JniInterface<::testsuite::TestInterfaceWithString, NativeTestInterfaceWithString>;
+
+};
+
+} // namespace djinni_generated

test-suite/generated-src/objc/DBTestInterfaceWithString+Private.h

@@ -0,0 +1,31 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+#include "test_interface_with_string.hpp"
+#include <memory>
+
+static_assert(__has_feature(objc_arc), "Djinni requires ARC to be enabled for this file");
+
+@class DBTestInterfaceWithString;
+
+namespace djinni_generated {
+
+class TestInterfaceWithString
+{
+public:
+    using CppType = std::shared_ptr<::testsuite::TestInterfaceWithString>;
+    using CppOptType = std::shared_ptr<::testsuite::TestInterfaceWithString>;
+    using ObjcType = DBTestInterfaceWithString*;
+
+    using Boxed = TestInterfaceWithString;
+
+    static CppType toCpp(ObjcType objc);
+    static ObjcType fromCppOpt(const CppOptType& cpp);
+    static ObjcType fromCpp(const CppType& cpp) { return fromCppOpt(cpp); }
+
+private:
+    class ObjcProxy;
+};
+
+} // namespace djinni_generated
+

test-suite/generated-src/objc/DBTestInterfaceWithString+Private.mm

@@ -0,0 +1,60 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+#import "DBTestInterfaceWithString+Private.h"
+#import "DBTestInterfaceWithString.h"
+#import "DJICppWrapperCache+Private.h"
+#import "DJIError.h"
+#import "DJIMarshal+Private.h"
+#include <exception>
+#include <stdexcept>
+#include <utility>
+
+static_assert(__has_feature(objc_arc), "Djinni requires ARC to be enabled for this file");
+
+@interface DBTestInterfaceWithString ()
+
+- (id)initWithCpp:(const std::shared_ptr<::testsuite::TestInterfaceWithString>&)cppRef;
+
+@end
+
+@implementation DBTestInterfaceWithString {
+    ::djinni::CppProxyCache::Handle<std::shared_ptr<::testsuite::TestInterfaceWithString>> _cppRefHandle;
+}
+
+- (id)initWithCpp:(const std::shared_ptr<::testsuite::TestInterfaceWithString>&)cppRef
+{
+    if (self = [super init]) {
+        _cppRefHandle.assign(cppRef);
+    }
+    return self;
+}
+
+- (nonnull NSString *)processString:(nonnull NSString *)message {
+    try {
+        auto objcpp_result_ = _cppRefHandle.get()->process_string(::djinni::String::toCpp(message));
+        return ::djinni::String::fromCpp(objcpp_result_);
+    } DJINNI_TRANSLATE_EXCEPTIONS()
+}
+
+namespace djinni_generated {
+
+auto TestInterfaceWithString::toCpp(ObjcType objc) -> CppType
+{
+    if (!objc) {
+        return nullptr;
+    }
+    return objc->_cppRefHandle.get();
+}
+
+auto TestInterfaceWithString::fromCppOpt(const CppOptType& cpp) -> ObjcType
+{
+    if (!cpp) {
+        return nil;
+    }
+    return ::djinni::get_cpp_proxy<DBTestInterfaceWithString>(cpp);
+}
+
+} // namespace djinni_generated
+
+@end

test-suite/generated-src/objc/DBTestInterfaceWithString.h

@@ -0,0 +1,13 @@
+// AUTOGENERATED FILE - DO NOT MODIFY!
+// This file was generated by Djinni from string_view_test.djinni
+
+#import <Foundation/Foundation.h>
+
+
+/** @flag "--cpp-use-string-view true" */
+@interface DBTestInterfaceWithString : NSObject
+
+/** Method with string parameter to test string_view generation */
+- (nonnull NSString *)processString:(nonnull NSString *)message;
+
+@end

test-suite/generated-src/outFileList.txt

@@ -10,6 +10,7 @@ djinni-output-temp/cpp/record_with_duration_and_derivings.cpp
 djinni-output-temp/cpp/date_record.hpp
 djinni-output-temp/cpp/date_record.cpp
 djinni-output-temp/cpp/map_date_record.hpp
+djinni-output-temp/cpp/test_interface_with_string.hpp
 djinni-output-temp/cpp/DataRefTest.hpp
 djinni-output-temp/cpp/constant_enum.hpp
 djinni-output-temp/cpp/constant_with_enum.hpp
@@ -81,6 +82,7 @@ djinni-output-temp/java/TestDuration.java
 djinni-output-temp/java/RecordWithDurationAndDerivings.java
 djinni-output-temp/java/DateRecord.java
 djinni-output-temp/java/MapDateRecord.java
+djinni-output-temp/java/TestInterfaceWithString.java
 djinni-output-temp/java/DataRefTest.java
 djinni-output-temp/java/ConstantEnum.java
 djinni-output-temp/java/ConstantWithEnum.java
@@ -150,6 +152,8 @@ djinni-output-temp/jni/NativeDateRecord.hpp
 djinni-output-temp/jni/NativeDateRecord.cpp
 djinni-output-temp/jni/NativeMapDateRecord.hpp
 djinni-output-temp/jni/NativeMapDateRecord.cpp
+djinni-output-temp/jni/NativeTestInterfaceWithString.hpp
+djinni-output-temp/jni/NativeTestInterfaceWithString.cpp
 djinni-output-temp/jni/NativeDataRefTest.hpp
 djinni-output-temp/jni/NativeDataRefTest.cpp
 djinni-output-temp/jni/NativeConstantEnum.hpp
@@ -263,6 +267,7 @@ djinni-output-temp/objc/DBDateRecord.h
 djinni-output-temp/objc/DBDateRecord.mm
 djinni-output-temp/objc/DBMapDateRecord.h
 djinni-output-temp/objc/DBMapDateRecord.mm
+djinni-output-temp/objc/DBTestInterfaceWithString.h
 djinni-output-temp/objc/DBDataRefTest.h
 djinni-output-temp/objc/DBConstantEnum.h
 djinni-output-temp/objc/DBConstantWithEnum.h
@@ -355,6 +360,8 @@ djinni-output-temp/objc/DBDateRecord+Private.h
 djinni-output-temp/objc/DBDateRecord+Private.mm
 djinni-output-temp/objc/DBMapDateRecord+Private.h
 djinni-output-temp/objc/DBMapDateRecord+Private.mm
+djinni-output-temp/objc/DBTestInterfaceWithString+Private.h
+djinni-output-temp/objc/DBTestInterfaceWithString+Private.mm
 djinni-output-temp/objc/DBDataRefTest+Private.h
 djinni-output-temp/objc/DBDataRefTest+Private.mm
 djinni-output-temp/objc/DBConstantEnum+Private.h
@@ -471,6 +478,8 @@ djinni-output-temp/wasm/NativeDateRecord.hpp
 djinni-output-temp/wasm/NativeDateRecord.cpp
 djinni-output-temp/wasm/NativeMapDateRecord.hpp
 djinni-output-temp/wasm/NativeMapDateRecord.cpp
+djinni-output-temp/wasm/NativeTestInterfaceWithString.hpp
+djinni-output-temp/wasm/NativeTestInterfaceWithString.cpp
 djinni-output-temp/wasm/NativeDataRefTest.hpp
 djinni-output-temp/wasm/NativeDataRefTest.cpp
 djinni-output-temp/wasm/NativeConstantEnum.hpp

test-suite/generated-src/ts/test.ts

@@ -85,6 +85,12 @@ export interface /*record*/ MapDateRecord {
     datesById: Map<string, Date>;
 }
 
+/** @flag "--cpp-use-string-view true" */
+export interface TestInterfaceWithString {
+    /** Method with string parameter to test string_view generation */
+    processString(message: string): string;
+}
+
 export interface DataRefTest {
     sendData(data: Uint8Array): void;
     retriveAsBin(): Uint8Array;