x/mobile/bind: support slices of structs

Adds code generation for supporting slices of structs in gobind.

Fixes golang/go#13445

NOTE: This PR isn't quite done yet, I'm having some trouble getting the testing environment set up. It seems like the default test environment is a bit outdated? In any case, could I use this PR's CI to iterate on test failures? Open to other suggestions as well.

bind/gen.go

@@ -402,6 +402,11 @@ func (g *Generator) cgoType(t types.Type) string {
 			default:
 				g.errorf("unsupported slice type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				return "nrefnumslice"
+			}
 		default:
 			g.errorf("unsupported slice type: %s", t)
 		}
@@ -507,6 +512,11 @@ func (g *Generator) isSupported(t types.Type) bool {
 		switch e := t.Elem().(type) {
 		case *types.Basic:
 			return e.Kind() == types.Uint8
+		case *types.Pointer:
+			switch f := e.Elem().(type) {
+			case *types.Named:
+				return g.validPkg(f.Obj().Pkg())
+			}
 		}
 	case *types.Pointer:
 		switch t := t.Elem().(type) {

bind/gengo.go

@@ -119,6 +119,13 @@ func (g *goGen) genWrite(toVar, fromVar string, t types.Type, mode varMode) {
 			default:
 				g.errorf("unsupported type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("%s := toRefNumSlice(%s)\n", toVar, fromVar)
+			default:
+				g.errorf("unsupported type: %s", t)
+			}
 		default:
 			g.errorf("unsupported type: %s", t)
 		}
@@ -403,6 +410,13 @@ func (g *goGen) genRead(toVar, fromVar string, typ types.Type, mode varMode) {
 			default:
 				g.errorf("unsupported type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("%s := fromRefNumSlice(%s)\n", toVar, fromVar)
+			default:
+				g.errorf("unsupported type: %s", t)
+			}
 		default:
 			g.errorf("unsupported type: %s", t)
 		}

bind/genjava.go

@@ -135,6 +135,13 @@ func (j *javaClassInfo) toJavaType(T types.Type) *java.Type {
 			case types.Uint8: // Byte.
 				return &java.Type{Kind: java.Array, Elem: &java.Type{Kind: java.Byte}}
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				if isJavaType(e) {
+					return &java.Type{Kind: java.Array, Elem: &java.Type{Kind: java.Object, Class: classNameFor(e)}}
+				}
+			}
 		}
 		return nil
 	case *types.Named:
@@ -641,8 +648,18 @@ func (g *JavaGen) jniType(T types.Type) string {
 			return "TODO"
 		}
 	case *types.Slice:
-		return "jbyteArray"
-
+		switch e := T.Elem().(type) {
+		case *types.Basic:
+			switch e.Kind() {
+			case types.Uint8: // Byte.
+				return "jbyteArray"
+			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				return "jobjectArray"
+			}
+		}
 	case *types.Pointer:
 		if _, ok := T.Elem().(*types.Named); ok {
 			return g.jniType(T.Elem())
@@ -915,6 +932,13 @@ func (g *JavaGen) genJavaToC(varName string, t types.Type, mode varMode) {
 			default:
 				g.errorf("unsupported type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("nobjectarray _%s = go_seq_from_java_objectarray(env, %s, %d);\n", varName, varName, toCFlag(mode == modeRetained))
+			default:
+				g.errorf("unsupported type: %s", t)
+			}
 		default:
 			g.errorf("unsupported type: %s", t)
 		}
@@ -952,6 +976,13 @@ func (g *JavaGen) genCToJava(toName, fromName string, t types.Type, mode varMode
 			default:
 				g.errorf("unsupported type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("jobjectArray %s = go_seq_to_java_objectarray(env, %s, %d);\n", toName, fromName, toCFlag(mode == modeRetained))
+			default:
+				g.errorf("unsupported type: %s", t)
+			}
 		default:
 			g.errorf("unsupported type: %s", t)
 		}

bind/genobjc.go

@@ -696,6 +696,13 @@ func (g *ObjcGen) genWrite(varName string, t types.Type, mode varMode) {
 			default:
 				g.errorf("unsupported type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("nrefnumslice _%s = go_seq_from_objc_refnumarray(%s);\n", varName, varName)
+			default:
+				g.errorf("unsupported type: %s", t)
+			}
 		default:
 			g.errorf("unsupported type: %s", t)
 		}
@@ -763,6 +770,13 @@ func (g *ObjcGen) genRead(toName, fromName string, t types.Type, mode varMode) {
 			default:
 				g.errorf("unsupported type: %s", t)
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("NSArray *%s = go_seq_to_objc_refnumarray(%s);\n", toName, fromName)
+			default:
+				g.errorf("unsupported type: %s", t)
+			}
 		default:
 			g.errorf("unsupported type: %s", t)
 		}
@@ -1047,6 +1061,11 @@ func (g *ObjcGen) genRelease(varName string, t types.Type, mode varMode) {
 					g.Printf("}\n")
 				}
 			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				g.Printf("free(_%s.ptr);\n", varName)
+			}
 		}
 	}
 }
@@ -1344,10 +1363,17 @@ func (g *ObjcGen) objcType(typ types.Type) string {
 			return "TODO"
 		}
 	case *types.Slice:
-		elem := g.objcType(typ.Elem())
-		// Special case: NSData seems to be a better option for byte slice.
-		if elem == "byte" {
-			return "NSData* _Nullable"
+		switch e := typ.Elem().(type) {
+		case *types.Basic:
+			switch e.Kind() {
+			case types.Uint8:
+				return "NSData* _Nullable"
+			}
+		case *types.Pointer:
+			switch e.Elem().(type) {
+			case *types.Named:
+				return "NSArray* _Nullable"
+			}
 		}
 		// TODO(hyangah): support other slice types: NSArray or CFArrayRef.
 		// Investigate the performance implication.

bind/java/seq_android.c.support

@@ -93,6 +93,20 @@ jbyteArray go_seq_to_java_bytearray(JNIEnv *env, nbyteslice s, int copy) {
 	return res;
 }
 
+jobjectArray go_seq_to_java_objectarray(JNIEnv *env, nrefnumslice arr) {
+	if (arr.ptr == NULL) {
+		return NULL;
+	}
+	jobjectArray res = (*env)->NewObjectArray(env, arr.len, (*env)->FindClass(env, "java/lang/Object"), NULL);
+	if (res == NULL) {
+		LOG_FATAL("NewObjectArray failed");
+	}
+	for (int i = 0; i < arr.len; i++) {
+		(*env)->SetObjectArrayElement(env, res, i, go_seq_from_refnum(env, arr.ptr[i]));
+	}
+	return res;
+}
+
 #define surr1 0xd800
 #define surr2 0xdc00
 #define surr3 0xe000
@@ -224,6 +238,34 @@ nbyteslice go_seq_from_java_bytearray(JNIEnv *env, jbyteArray arr, int copy) {
 	return res;
 }
 
+nrefnumslice go_seq_from_java_objectarray(JNIEnv *env, jobjectArray arr) {
+	struct nrefnumslice res = {NULL, 0};
+	if (arr == NULL) {
+		return res;
+	}
+
+	jsize len = (*env)->GetArrayLength(env, arr);
+	if (len == 0) {
+		return res;
+	}
+	jint *ptr = (jint *)(*env)->GetPrimitiveArrayCritical(env, arr, NULL);
+	if (ptr == NULL) {
+		LOG_FATAL("GetPrimitiveArrayCritical failed");
+	}
+	void *refnums = (void *)malloc(len * sizeof(jint));
+	if (refnums == NULL) {
+		LOG_FATAL("malloc failed");
+	}
+	// convert to refnums
+	for (int i = 0; i < len; i++) {
+		refnums[i] = go_seq_to_refnum(env, (*env)->GetObjectArrayElement(env, arr, i));
+	}
+	res.ptr = refnums;
+	res.len = len;
+	(*env)->ReleasePrimitiveArrayCritical(env, arr, ptr, JNI_ABORT);
+	return res;
+}
+
 int32_t go_seq_to_refnum_go(JNIEnv *env, jobject o) {
 	if (o == NULL) {
 		return NULL_REFNUM;

bind/java/seq_android.h

@@ -30,6 +30,10 @@ typedef struct nbyteslice {
 	void *ptr;
 	jsize len;
 } nbyteslice;
+typedef struct nrefnumslice {
+	void *ptr;
+	jsize len;
+} nrefnumslice;
 typedef jlong nint;
 
 extern void go_seq_dec_ref(int32_t ref);
@@ -47,6 +51,8 @@ extern jobject go_seq_get_exception(JNIEnv *env);
 
 extern jbyteArray go_seq_to_java_bytearray(JNIEnv *env, nbyteslice s, int copy);
 extern nbyteslice go_seq_from_java_bytearray(JNIEnv *env, jbyteArray s, int copy);
+extern jobjectArray go_seq_to_java_objectarray(JNIEnv *env, nrefnumslice arr);
+extern nrefnumslice go_seq_from_java_objectarray(JNIEnv *env, jobjectArray arr);
 extern void go_seq_release_byte_array(JNIEnv *env, jbyteArray arr, jbyte* ptr);
 
 extern jstring go_seq_to_java_string(JNIEnv *env, nstring str);

bind/objc/seq_darwin.h

@@ -34,6 +34,10 @@ typedef struct nbyteslice {
 	void *ptr;
 	int len;
 } nbyteslice;
+typedef struct nrefnumslice {
+  void *ptr;
+  int len;
+} nrefnumslice;
 typedef int nint;
 
 extern void init_seq();
@@ -55,9 +59,11 @@ extern GoSeqRef *go_seq_from_refnum(int32_t refnum);
 extern id go_seq_objc_from_refnum(int32_t refnum);
 
 extern nbyteslice go_seq_from_objc_bytearray(NSData *data, int copy);
+extern nrefnumslice go_seq_from_objc_objectarray(NSArray *arr);
 extern nstring go_seq_from_objc_string(NSString *s);
 
 extern NSData *go_seq_to_objc_bytearray(nbyteslice, int copy);
+extern NSArray *go_seq_to_objc_objectarray(nrefnumslice arr);
 extern NSString *go_seq_to_objc_string(nstring str);
 
 #endif // __GO_SEQ_DARWIN_HDR__

bind/testdata/structs.go

@@ -25,6 +25,38 @@ func IdentityWithError(s *S) (*S, error) {
 	return s, nil
 }
 
+func (s *S) Repeat(n int) []*S {
+	t := make([]*S, n)
+	for i := range t {
+		t[i] = s
+	}
+	return t
+}
+
+func (s *S) RepeatWithError(n int) ([]*S, error) {
+	return Repeat(s, n), nil
+}
+
+func Repeat(s *S, n int) []*S {
+	t := make([]*S, n)
+	for i := range t {
+		t[i] = s
+	}
+	return t
+}
+
+func RepeatWithError(s *S, n int) ([]*S, error) {
+	return Repeat(s, n), nil
+}
+
+func FirstSum(s []*S) float64 {
+	return s[0].Sum()
+}
+
+func FirstSumWithError(s []*S) (float64, error) {
+	return s[0].Sum(), nil
+}
+
 type (
 	S2 struct{}
 	I  interface {

bind/testdata/structs.java.golden

@@ -30,6 +30,8 @@ public final class S implements Seq.Proxy {
     public final native void setY(double v);
 
     public native S identity() throws Exception;
+    public native S[] repeat(long n);
+    public native S[] repeatWithError(long n) throws Exception;
     public native double sum();
     @Override public boolean equals(Object o) {
         if (o == null || !(o instanceof S)) {
@@ -176,7 +178,7 @@ import go.Seq;
 
 public abstract class Structs {
     static {
-        Seq.touch(); // for loading the native library
+    Seq.touch(); // for loading the native library
         _init();
     }
 
@@ -200,7 +202,10 @@ public abstract class Structs {
         public native void m();
     }
 
-
+    public static native double firstSum(S[] s);
+    public static native double firstSumWithError(S[] s) throws Exception;
     public static native S identity(S s);
     public static native S identityWithError(S s) throws Exception;
+    public static native S[] repeat(S s, long n);
+    public static native S[] repeatWithError(S s, long n) throws Exception;
 }