Status.h revision 337c3ae7f5ce6e94d6ccaaa7fb4ac92c4069b2dd 
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_HARDWARE_BINDER_STATUS_H
18#define ANDROID_HARDWARE_BINDER_STATUS_H
19
20#include <cstdint>
21#include <sstream>
22
23#include <android-base/macros.h>
24#include <hidl/HidlInternal.h>
25#include <utils/String8.h>
26
27namespace android {
28namespace hardware {
29
30// An object similar in function to a status_t except that it understands
31// how exceptions are encoded in the prefix of a Parcel. Used like:
32//
33//     Parcel data;
34//     Parcel reply;
35//     status_t status;
36//     binder::Status remote_exception;
37//     if ((status = data.writeInterfaceToken(interface_descriptor)) != OK ||
38//         (status = data.writeInt32(function_input)) != OK) {
39//         // We failed to write into the memory of our local parcel?
40//     }
41//     if ((status = remote()->transact(transaction, data, &reply)) != OK) {
42//        // Something has gone wrong in the binder driver or libbinder.
43//     }
44//     if ((status = remote_exception.readFromParcel(reply)) != OK) {
45//         // The remote didn't correctly write the exception header to the
46//         // reply.
47//     }
48//     if (!remote_exception.isOk()) {
49//         // The transaction went through correctly, but the remote reported an
50//         // exception during handling.
51//     }
52//
53class Status final {
54public:
55    // Keep the exception codes in sync with android/os/Parcel.java.
56    enum Exception {
57        EX_NONE = 0,
58        EX_SECURITY = -1,
59        EX_BAD_PARCELABLE = -2,
60        EX_ILLEGAL_ARGUMENT = -3,
61        EX_NULL_POINTER = -4,
62        EX_ILLEGAL_STATE = -5,
63        EX_NETWORK_MAIN_THREAD = -6,
64        EX_UNSUPPORTED_OPERATION = -7,
65        EX_SERVICE_SPECIFIC = -8,
66
67        // This is special and Java specific; see Parcel.java.
68        EX_HAS_REPLY_HEADER = -128,
69        // This is special, and indicates to C++ binder proxies that the
70        // transaction has failed at a low level.
71        EX_TRANSACTION_FAILED = -129,
72    };
73
74    // A more readable alias for the default constructor.
75    static Status ok();
76    // Authors should explicitly pick whether their integer is:
77    //  - an exception code (EX_* above)
78    //  - service specific error code
79    //  - status_t
80    //
81    //  Prefer a generic exception code when possible, then a service specific
82    //  code, and finally a status_t for low level failures or legacy support.
83    //  Exception codes and service specific errors map to nicer exceptions for
84    //  Java clients.
85    static Status fromExceptionCode(int32_t exceptionCode);
86    static Status fromExceptionCode(int32_t exceptionCode,
87                                    const String8& message);
88    static Status fromServiceSpecificError(int32_t serviceSpecificErrorCode);
89    static Status fromServiceSpecificError(int32_t serviceSpecificErrorCode,
90                                           const String8& message);
91    static Status fromStatusT(status_t status);
92
93    Status() = default;
94    ~Status() = default;
95
96    // Status objects are copyable and contain just simple data.
97    Status(const Status& status) = default;
98    Status(Status&& status) = default;
99    Status& operator=(const Status& status) = default;
100
101    // Set one of the pre-defined exception types defined above.
102    void setException(int32_t ex, const String8& message);
103    // Set a service specific exception with error code.
104    void setServiceSpecificError(int32_t errorCode, const String8& message);
105    // Setting a |status| != OK causes generated code to return |status|
106    // from Binder transactions, rather than writing an exception into the
107    // reply Parcel.  This is the least preferable way of reporting errors.
108    void setFromStatusT(status_t status);
109
110    // Get information about an exception.
111    int32_t exceptionCode() const  { return mException; }
112    const String8& exceptionMessage() const { return mMessage; }
113    status_t transactionError() const {
114        return mException == EX_TRANSACTION_FAILED ? mErrorCode : OK;
115    }
116    int32_t serviceSpecificErrorCode() const {
117        return mException == EX_SERVICE_SPECIFIC ? mErrorCode : 0;
118    }
119
120    bool isOk() const { return mException == EX_NONE; }
121
122    // For logging.
123    String8 toString8() const;
124
125private:
126    Status(int32_t exceptionCode, int32_t errorCode);
127    Status(int32_t exceptionCode, int32_t errorCode, const String8& message);
128
129    // If |mException| == EX_TRANSACTION_FAILED, generated code will return
130    // |mErrorCode| as the result of the transaction rather than write an
131    // exception to the reply parcel.
132    //
133    // Otherwise, we always write |mException| to the parcel.
134    // If |mException| !=  EX_NONE, we write |mMessage| as well.
135    // If |mException| == EX_SERVICE_SPECIFIC we write |mErrorCode| as well.
136    int32_t mException = EX_NONE;
137    int32_t mErrorCode = 0;
138    String8 mMessage;
139};  // class Status
140
141// For gtest output logging
142std::stringstream& operator<< (std::stringstream& stream, const Status& s);
143
144template<typename T> class Return : private details::hidl_log_base {
145private:
146    T mVal {};
147    Status mStatus {};
148public:
149    Return(T v) : mVal{v} {}
150    Return(Status s) : mStatus(s) {}
151
152    T get() const {
153        if (!mStatus.isOk()) {
154            logAlwaysFatal("Attempted to retrieve value from hidl service, "
155                           "but there was a transport error.");
156        }
157        return mVal;
158    }
159    bool isOk() const {
160        return mStatus.isOk();
161    }
162
163    // TODO(b/31348667) deprecate, remove all usage, remove function
164    // Can't mark as deprecated yet because of all the projects built with -Werror.
165    // [[deprecated("Replaced by get()")]]
166    operator T() const { return mVal; }
167
168    const Status& getStatus() const {
169        return mStatus;
170    }
171};
172
173template<> class Return<void> {
174private:
175    Status mStatus {};
176public:
177    Return() = default;
178    Return(Status s) : mStatus(s) {}
179
180    bool isOk() const {
181        return mStatus.isOk();
182    }
183
184    const Status& getStatus() const {
185        return mStatus;
186    }
187};
188
189static inline Return<void> Void() {
190    return Return<void>();
191}
192
193}  // namespace hardware
194}  // namespace android
195
196#endif // ANDROID_HARDWARE_BINDER_STATUS_H
197