1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_BINDER_STATUS_H
18#define ANDROID_BINDER_STATUS_H
19
20#include <cstdint>
21
22#include <binder/Parcel.h>
23#include <utils/String8.h>
24
25namespace android {
26namespace binder {
27
28// An object similar in function to a status_t except that it understands
29// how exceptions are encoded in the prefix of a Parcel. Used like:
30//
31//     Parcel data;
32//     Parcel reply;
33//     status_t status;
34//     binder::Status remote_exception;
35//     if ((status = data.writeInterfaceToken(interface_descriptor)) != OK ||
36//         (status = data.writeInt32(function_input)) != OK) {
37//         // We failed to write into the memory of our local parcel?
38//     }
39//     if ((status = remote()->transact(transaction, data, &reply)) != OK) {
40//        // Something has gone wrong in the binder driver or libbinder.
41//     }
42//     if ((status = remote_exception.readFromParcel(reply)) != OK) {
43//         // The remote didn't correctly write the exception header to the
44//         // reply.
45//     }
46//     if (!remote_exception.isOk()) {
47//         // The transaction went through correctly, but the remote reported an
48//         // exception during handling.
49//     }
50//
51class Status final {
52public:
53    // Keep the exception codes in sync with android/os/Parcel.java.
54    enum Exception {
55        EX_NONE = 0,
56        EX_SECURITY = -1,
57        EX_BAD_PARCELABLE = -2,
58        EX_ILLEGAL_ARGUMENT = -3,
59        EX_NULL_POINTER = -4,
60        EX_ILLEGAL_STATE = -5,
61        EX_NETWORK_MAIN_THREAD = -6,
62        EX_UNSUPPORTED_OPERATION = -7,
63        EX_SERVICE_SPECIFIC = -8,
64
65        // This is special and Java specific; see Parcel.java.
66        EX_HAS_REPLY_HEADER = -128,
67        // This is special, and indicates to C++ binder proxies that the
68        // transaction has failed at a low level.
69        EX_TRANSACTION_FAILED = -129,
70    };
71
72    // A more readable alias for the default constructor.
73    static Status ok();
74    // Authors should explicitly pick whether their integer is:
75    //  - an exception code (EX_* above)
76    //  - service specific error code
77    //  - status_t
78    //
79    //  Prefer a generic exception code when possible, then a service specific
80    //  code, and finally a status_t for low level failures or legacy support.
81    //  Exception codes and service specific errors map to nicer exceptions for
82    //  Java clients.
83    static Status fromExceptionCode(int32_t exceptionCode);
84    static Status fromExceptionCode(int32_t exceptionCode,
85                                    const String8& message);
86    static Status fromServiceSpecificError(int32_t serviceSpecificErrorCode);
87    static Status fromServiceSpecificError(int32_t serviceSpecificErrorCode,
88                                           const String8& message);
89    static Status fromStatusT(status_t status);
90
91    Status() = default;
92    ~Status() = default;
93
94    // Status objects are copyable and contain just simple data.
95    Status(const Status& status) = default;
96    Status(Status&& status) = default;
97    Status& operator=(const Status& status) = default;
98
99    // Bear in mind that if the client or service is a Java endpoint, this
100    // is not the logic which will provide/interpret the data here.
101    status_t readFromParcel(const Parcel& parcel);
102    status_t writeToParcel(Parcel* parcel) const;
103
104    // Set one of the pre-defined exception types defined above.
105    void setException(int32_t ex, const String8& message);
106    // Set a service specific exception with error code.
107    void setServiceSpecificError(int32_t errorCode, const String8& message);
108    // Setting a |status| != OK causes generated code to return |status|
109    // from Binder transactions, rather than writing an exception into the
110    // reply Parcel.  This is the least preferable way of reporting errors.
111    void setFromStatusT(status_t status);
112
113    // Get information about an exception.
114    int32_t exceptionCode() const  { return mException; }
115    const String8& exceptionMessage() const { return mMessage; }
116    status_t transactionError() const {
117        return mException == EX_TRANSACTION_FAILED ? mErrorCode : OK;
118    }
119    int32_t serviceSpecificErrorCode() const {
120        return mException == EX_SERVICE_SPECIFIC ? mErrorCode : 0;
121    }
122
123    bool isOk() const { return mException == EX_NONE; }
124
125    // For logging.
126    String8 toString8() const;
127
128private:
129    Status(int32_t exceptionCode, int32_t errorCode);
130    Status(int32_t exceptionCode, int32_t errorCode, const String8& message);
131
132    // If |mException| == EX_TRANSACTION_FAILED, generated code will return
133    // |mErrorCode| as the result of the transaction rather than write an
134    // exception to the reply parcel.
135    //
136    // Otherwise, we always write |mException| to the parcel.
137    // If |mException| !=  EX_NONE, we write |mMessage| as well.
138    // If |mException| == EX_SERVICE_SPECIFIC we write |mErrorCode| as well.
139    int32_t mException = EX_NONE;
140    int32_t mErrorCode = 0;
141    String8 mMessage;
142};  // class Status
143
144// For gtest output logging
145template<typename T>
146T& operator<< (T& stream, const Status& s) {
147    stream << s.toString8().string();
148    return stream;
149}
150
151}  // namespace binder
152}  // namespace android
153
154#endif // ANDROID_BINDER_STATUS_H
155