Move JNIHelp to a C implementation

Completes the move to C for libnativehelper.

Reduces the size of libnativehelper_compat_c++.so as it
no longer statically links against lbc++:

  arm     125kB -> 14kB
  arm8    181kB -> 20kB
  x86     172kB -> 16kB
  x86_64  180kB -> 18kB

Marginal reduction in the size of libnativehelper.so.

Bug: 151443957
Test: m && boot
Test: ExpandableString_test
Change-Id: I562897337901131d3f855b66307bb2a12c04d477

Author: ohodson

ALog-priv.h

@@ -35,8 +35,8 @@
  */
 
 #ifndef ALOG
-#define ALOG(priority, tag, fmt...) \
-    __android_log_print(ANDROID_##priority, tag, fmt)
+#define ALOG(priority, tag, fmt, ...) \
+    __android_log_print(ANDROID_##priority, tag, fmt, __VA_ARGS__)
 #endif
 
 #ifndef ALOGV

Android.bp

@@ -12,6 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+cc_defaults {
+    name: "libnativehelper_defaults",
+    cflags: [
+        "-fvisibility=protected",
+        "-std=c11",
+    ],
+}
+
 cc_library_headers {
     name: "jni_headers",
     host_supported: true,
@@ -69,25 +77,24 @@ cc_library_headers {
 
 cc_library {
     name: "libnativehelper",
+    defaults: ["libnativehelper_defaults"],
     host_supported: true,
     srcs: [
         "DlHelp.c",
-        "JNIHelp.cpp",
+        "ExpandableString.c",
+        "JNIHelp.c",
         "JniConstants.c",
         "JniInvocation.c",
     ],
     shared_libs: ["liblog"],
-    cflags: [
-        "-Werror",
-        "-fvisibility=protected",
-    ],
     export_include_dirs: [
         "header_only_include",
         "include",
         "platform_include",
     ],
     header_libs: ["jni_headers"],
     export_header_lib_headers: ["jni_headers"],
+    stl: "none",
     stubs: {
         symbol_file: "libnativehelper.map.txt",
         versions: ["1"],
@@ -116,6 +123,7 @@ cc_library {
 
 cc_library_shared {
     name: "libnativehelper_compat_libc++",
+    defaults: ["libnativehelper_defaults"],
     header_libs: ["jni_headers"],
     cflags: ["-Werror"],
     export_header_lib_headers: ["jni_headers"],
@@ -129,14 +137,15 @@ cc_library_shared {
     ],
     srcs: [
         "DlHelp.c",
-        "JNIHelp.cpp",
+        "ExpandableString.c",
+        "JNIHelp.c",
         "JniConstants.c",
     ],
     shared_libs: [
         "liblog",
     ],
     sdk_version: "19",
-    stl: "c++_static",
+    stl: "none",
 }
 
 ndk_headers {

ExpandableString.c

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ExpandableString.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void ExpandableStringInitialize(struct ExpandableString *s) {
+    memset(s, 0, sizeof(*s));
+}
+
+void ExpandableStringRelease(struct ExpandableString* s) {
+    free(s->data);
+    memset(s, 0, sizeof(*s));
+}
+
+bool ExpandableStringAppend(struct ExpandableString* s, const char* text) {
+    size_t textSize = strlen(text);
+    size_t requiredSize = s->dataSize + textSize + 1;
+    char* data = (char*) realloc(s->data, requiredSize);
+    if (data == NULL) {
+        return false;
+    }
+    s->data = data;
+    memcpy(s->data + s->dataSize, text, textSize + 1);
+    s->dataSize += textSize;
+    return true;
+}
+
+bool ExpandableStringAssign(struct ExpandableString* s, const char* text) {
+    ExpandableStringRelease(s);
+    return ExpandableStringAppend(s, text);
+}

ExpandableString.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <sys/cdefs.h>
+
+#include <stdbool.h>
+#include <stddef.h>
+
+__BEGIN_DECLS
+
+struct ExpandableString {
+    size_t dataSize;  // The length of the C string data (not including the null-terminator).
+    char* data;       // The C string data.
+};
+
+// Initialize ExpandableString.
+void ExpandableStringInitialize(struct ExpandableString* s);
+
+// Release memory associated with ExpandableString.
+void ExpandableStringRelease(struct ExpandableString* s);
+
+// Append null-terminated string |text| to ExpandableString, expanding the storage if required.
+// Returns true on success, false othewise.
+bool ExpandableStringAppend(struct ExpandableString* s, const char* text);
+
+// Assign null-terminate string |text| to ExpandableString, expanding the storage if required.
+// Returns true on success, false othewise.
+bool ExpandableStringAssign(struct ExpandableString*s, const char* text);
+
+__END_DECLS