libbinder_ndk: add read/write string methods.

utf16 is left on the wire, but utf8 is exposed in the NDK.

Bug: 111445392
Test: atest android.binder.cts
Change-Id: Ie4f19ba52dc2323b1c6cf0c4b5e60c7bf2802cf8

4 files changed, 175 insertions, 0 deletions

diff --git a/libs/binder/ndk/include_ndk/android/binder_parcel.h b/libs/binder/ndk/include_ndk/android/binder_parcel.h
index a3800da160..0e97b507c5 100644
--- a/libs/binder/ndk/include_ndk/android/binder_parcel.h
+++ b/libs/binder/ndk/include_ndk/android/binder_parcel.h
@@ -88,6 +88,43 @@ binder_status_t AParcel_writeStatusHeader(AParcel* parcel, const AStatus* status
 binder_status_t AParcel_readStatusHeader(const AParcel* parcel, AStatus** status)
         __INTRODUCED_IN(29);
 
+/**
+ * Writes string value to the next location in a non-null parcel.
+ */
+binder_status_t AParcel_writeString(AParcel* parcel, const char* string, size_t length)
+        __INTRODUCED_IN(29);
+
+/**
+ * This is called to allocate a buffer
+ *
+ * The length here includes the space required to insert a '\0' for a properly formed c-str. If the
+ * buffer returned from this function is retStr, it will be filled by AParcel_readString with the
+ * data from the remote process, and it will be filled such that retStr[length] == '\0'.
+ *
+ * If allocation fails, null should be returned.
+ */
+typedef void* (*AParcel_string_reallocator)(void* stringData, size_t length);
+
+/**
+ * This is called to get the buffer from a stringData object.
+ */
+typedef char* (*AParcel_string_getter)(void* stringData);
+
+/**
+ * Reads and allocates string value from the next location in a non-null parcel.
+ *
+ * Data is passed to the string allocator once the string size is known. This data should be used to
+ * point to some kind of string data. For instance, it could be a char*, and the string allocator
+ * could be realloc. Then the getter would simply be a cast to char*. In more complicated cases,
+ * stringData could be a structure containing additional string data.
+ *
+ * If this function returns a success, the buffer returned by allocator when passed stringData will
+ * contain a null-terminated c-str read from the binder.
+ */
+binder_status_t AParcel_readString(const AParcel* parcel, AParcel_string_reallocator reallocator,
+                                   AParcel_string_getter getter, void** stringData)
+        __INTRODUCED_IN(29);
+
 // @START
 /**
  * Writes int32_t value to the next location in a non-null parcel.
diff --git a/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h b/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h
new file mode 100644
index 0000000000..7b261d6f98
--- /dev/null
+++ b/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h
@@ -0,0 +1,71 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+/**
+ * @addtogroup NdkBinder
+ * @{
+ */
+
+/**
+ * @file binder_parcel_utils.h
+ * @brief A collection of helper wrappers for AParcel.
+ */
+
+#pragma once
+
+#include <android/binder_parcel.h>
+
+#ifdef __cplusplus
+
+#include <string>
+
+/**
+ * Takes a std::string and reallocates it to the specified length. For use with AParcel_readString.
+ * See use below in AParcel_readString.
+ */
+static inline void* AParcel_std_string_reallocator(void* stringData, size_t length) {
+    std::string* str = static_cast<std::string*>(stringData);
+    str->resize(length - 1);
+    return stringData;
+}
+
+/**
+ * Takes a std::string and returns the inner char*.
+ */
+static inline char* AParcel_std_string_getter(void* stringData) {
+    std::string* str = static_cast<std::string*>(stringData);
+    return &(*str)[0];
+}
+
+/**
+ * Convenience API for writing a std::string.
+ */
+static inline binder_status_t AParcel_writeString(AParcel* parcel, const std::string& str) {
+    return AParcel_writeString(parcel, str.c_str(), str.size());
+}
+
+/**
+ * Convenience API for reading a std::string.
+ */
+static inline binder_status_t AParcel_readString(const AParcel* parcel, std::string* str) {
+    void* stringData = static_cast<void*>(str);
+    return AParcel_readString(parcel, AParcel_std_string_reallocator, AParcel_std_string_getter,
+                              &stringData);
+}
+
+#endif // __cplusplus
+
+/** @} */
diff --git a/libs/binder/ndk/libbinder_ndk.map.txt b/libs/binder/ndk/libbinder_ndk.map.txt
index 4f486c99ba..2a1bff131c 100644
--- a/libs/binder/ndk/libbinder_ndk.map.txt
+++ b/libs/binder/ndk/libbinder_ndk.map.txt
@@ -32,6 +32,7 @@ LIBBINDER_NDK { # introduced=29
     AParcel_readInt64;
     AParcel_readNullableStrongBinder;
     AParcel_readStatusHeader;
+    AParcel_readString;
     AParcel_readStrongBinder;
     AParcel_readUint32;
     AParcel_readUint64;
@@ -43,6 +44,7 @@ LIBBINDER_NDK { # introduced=29
     AParcel_writeInt32;
     AParcel_writeInt64;
     AParcel_writeStatusHeader;
+    AParcel_writeString;
     AParcel_writeStrongBinder;
     AParcel_writeUint32;
     AParcel_writeUint64;
diff --git a/libs/binder/ndk/parcel.cpp b/libs/binder/ndk/parcel.cpp
index 385e898aeb..3e03e907bb 100644
--- a/libs/binder/ndk/parcel.cpp
+++ b/libs/binder/ndk/parcel.cpp
@@ -20,7 +20,11 @@
 #include "ibinder_internal.h"
 #include "status_internal.h"
 
+#include <limits>
+
+#include <android-base/logging.h>
 #include <binder/Parcel.h>
+#include <utils/Unicode.h>
 
 using ::android::IBinder;
 using ::android::Parcel;
@@ -69,6 +73,67 @@ binder_status_t AParcel_readStatusHeader(const AParcel* parcel, AStatus** status
     return ret;
 }
 
+binder_status_t AParcel_writeString(AParcel* parcel, const char* string, size_t length) {
+    const uint8_t* str8 = (uint8_t*)string;
+
+    const ssize_t len16 = utf8_to_utf16_length(str8, length);
+
+    if (len16 < 0 || len16 >= std::numeric_limits<int32_t>::max()) {
+        LOG(WARNING) << __func__ << ": Invalid string length: " << len16;
+        return STATUS_BAD_VALUE;
+    }
+
+    status_t err = parcel->get()->writeInt32(len16);
+    if (err) {
+        return PruneStatusT(err);
+    }
+
+    void* str16 = parcel->get()->writeInplace((len16 + 1) * sizeof(char16_t));
+    if (str16 == nullptr) {
+        return STATUS_NO_MEMORY;
+    }
+
+    utf8_to_utf16(str8, length, (char16_t*)str16, (size_t)len16 + 1);
+
+    return STATUS_OK;
+}
+
+binder_status_t AParcel_readString(const AParcel* parcel, AParcel_string_reallocator reallocator,
+                                   AParcel_string_getter getter, void** stringData) {
+    size_t len16;
+    const char16_t* str16 = parcel->get()->readString16Inplace(&len16);
+
+    if (str16 == nullptr) {
+        LOG(WARNING) << __func__ << ": Failed to read string in place.";
+        return STATUS_UNEXPECTED_NULL;
+    }
+
+    ssize_t len8;
+
+    if (len16 == 0) {
+        len8 = 1;
+    } else {
+        len8 = utf16_to_utf8_length(str16, len16) + 1;
+    }
+
+    if (len8 <= 0 || len8 >= std::numeric_limits<int32_t>::max()) {
+        LOG(WARNING) << __func__ << ": Invalid string length: " << len8;
+        return STATUS_BAD_VALUE;
+    }
+
+    *stringData = reallocator(*stringData, len8);
+    char* str8 = getter(*stringData);
+
+    if (str8 == nullptr) {
+        LOG(WARNING) << __func__ << ": AParcel_string_allocator failed to allocate.";
+        return STATUS_NO_MEMORY;
+    }
+
+    utf16_to_utf8(str16, len16, str8, len8);
+
+    return STATUS_OK;
+}
+
 // See gen_parcel_helper.py. These auto-generated read/write methods use the same types for
 // libbinder and this library.
 // @START