harmony 鸿蒙ChildProcess
ChildProcess
Overview
The ChildProcess module provides APIs to manage child processes. You can call the APIs to create a native child process and establish an IPC channel between the parent and child processes to implement multi-process application development.
The created child process does not support the UI or the calling of context-related APIs. A maximum of 512 child processes can be started through this module and childProcessManager (non-SELF_FORK mode).
System capability: SystemCapability.Ability.AbilityRuntime.Core
Since: 12
Summary
Files
| Name | Description |
|---|---|
| native_child_process.h | Declares the APIs used to create a native child process and establish an IPC channel between the parent and child processes. File to include: Library: libchild_process.so |
Types
| Name | Description |
|---|---|
| typedef enum Ability_NativeChildProcess_ErrCode Ability_NativeChildProcess_ErrCode | Defines an enum for the error codes used by the native child process module. |
| typedef void(* OH_Ability_OnNativeChildProcessStarted) (int errCode, OHIPCRemoteProxy *remoteProxy) | Defines a callback function for notifying the child process startup result. |
| typedef struct NativeChildProcess_Fd | Defines a struct for the file descriptor of a child process. |
| typedef struct NativeChildProcess_FdList | Defines a struct for the linked list of file descriptors of a child process. |
| typedef struct NativeChildProcess_Args | Defines a struct for the arguments used for starting a child process. |
| typedef void(* OH_Ability_OnNativeChildProcessExit) (int32_t pid, int32_t signal) | Defines the callback function for detecting abnormal exit of a native child process. |
Enums
| Name | Description |
|---|---|
| Ability_NativeChildProcess_ErrCode { NCP_NO_ERROR = 0, NCP_ERR_INVALID_PARAM = 401, NCP_ERR_NOT_SUPPORTED = 801, NCP_ERR_INTERNAL = 16000050, NCP_ERR_BUSY = 16010001, NCP_ERR_TIMEOUT = 16010002, NCP_ERR_SERVICE_ERROR = 16010003, NCP_ERR_MULTI_PROCESS_DISABLED = 16010004, NCP_ERR_ALREADY_IN_CHILD = 16010005, NCP_ERR_MAX_CHILD_PROCESSES_REACHED = 16010006, NCP_ERR_LIB_LOADING_FAILED = 16010007, NCP_ERR_CONNECTION_FAILED = 16010008, NCP_ERR_CALLBACK_NOT_EXIST = 16010009 } |
Enumerates the error codes used by the native child process module. |
Functions
| Name | Description |
|---|---|
| int OH_Ability_CreateNativeChildProcess (const char *libName, OH_Ability_OnNativeChildProcessStarted onProcessStarted) | Creates a child process, loads the specified dynamic library file, and returns the startup result asynchronously through a callback parameter. The callback notification is an independent thread. When implementing the callback function, pay attention to thread synchronization and do not perform time-consuming operations to avoid long-time blocking. |
NOTE
This function is valid only for 2-in-1 devices. Since API version 15, a single process supports a maximum of 50 native child processes. In API version 14 and earlier versions, a single process supports only one native child process.
Type Description
OH_Ability_OnNativeChildProcessStarted
typedef void (*OH_Ability_OnNativeChildProcessStarted)(int errCode, OHIPCRemoteProxy *remoteProxy)
Description
Defines a callback function for notifying the child process startup result.
Since: 12
Parameters
| Name | Description |
|---|---|
| errCode | NCP_NO_ERROR - The child process is created successfully. NCP_ERR_LIB_LOADING_FAILED - Loading the dynamic library file fails or the necessary export function is not implemented in the dynamic library. NCP_ERR_CONNECTION_FAILED - The OnConnect method implemented in the dynamic library does not return a valid IPC stub pointer. For details, see Ability_NativeChildProcess_ErrCode. |
| remoteProxy | Pointer to the IPC object of the child process. If an exception occurs, the value may be nullptr. The pointer must be released by calling OH_IPCRemoteProxy_Destroy when it is no longer needed. |
See
OH_Ability_CreateNativeChildProcess
OH_Ability_OnNativeChildProcessExit
typedef void (*OH_Ability_OnNativeChildProcessExit)(int32_t pid, int32_t signal)
Description
Defines the callback function for detecting abnormal exit of a native child process.
Since: 20
Parameters
| Name | Description |
|---|---|
| pid | PID of the child process. |
| signal | Signal for abnormal exit of the child process. |
See
OH_Ability_RegisterNativeChildProcessExitCallback
OH_Ability_UnregisterNativeChildProcessExitCallback
NativeChildProcess_Fd
typedef struct NativeChildProcess_Fd {
char* fdName;
int32_t fd;
struct NativeChildProcess_Fd* next;
} NativeChildProcess_Fd;
Description
Defines a struct for the file descriptor of a child process.
Since: 13
Parameters
| Name | Description |
|---|---|
| fdName | Pointer to the keyword of the file descriptor. A maximum of 20 characters are allowed. |
| fd | File descriptor handle. |
| next | Pointer to the next file descriptor. |
NativeChildProcess_FdList
typedef struct NativeChildProcess_FdList {
struct NativeChildProcess_Fd* head;
} NativeChildProcess_FdList;
Description
Defines a struct for the linked list of file descriptors of a child process. A maximum of 16 file descriptors are supported.
Since: 13
Parameters
| Name | Description |
|---|---|
| head | First file descriptor record in the linked list. For details, see NativeChildProcess_FdList. |
NativeChildProcess_Args
typedef struct NativeChildProcess_Args {
char* entryParams;
struct NativeChildProcess_FdList fdList;
} NativeChildProcess_Args;
Description
Defines a struct for the arguments used for starting a child process.
Since: 13
Parameters
| Name | Description |
|---|---|
| entryParams | Pointer to the entry parameters. The size cannot exceed 150 KB. |
| fdList | Linked list of File descriptors. For details, see NativeChildProcess_FdList. |
NativeChildProcess_Options
typedef struct NativeChildProcess_Options {
NativeChildProcess_IsolationMode isolationMode;
int64_t reserved;
} NativeChildProcess_Options;
Description
Defines a struct for the child process options.
Since: 13
Parameters
| Name | Description |
|---|---|
| isolationMode | Process isolation mode. For details, see NativeChildProcess_IsolationMode. |
| reserved | Reserved field. |
Enum Description
Ability_NativeChildProcess_ErrCode
enum Ability_NativeChildProcess_ErrCode
Description
Enumerates the error codes used by the native child process module.
Since: 12
| Value | Description |
|---|---|
| NCP_NO_ERROR | Operation successful. |
| NCP_ERR_INVALID_PARAM | Invalid parameter. |
| NCP_ERR_NOT_SUPPORTED | Creating a native child process is not supported. |
| NCP_ERR_INTERNAL | Internal error. |
| NCP_ERR_BUSY | A new child process cannot be created during the startup of another native child process. You can try again after the child process is started. This function is deprecated since API version 15. |
| NCP_ERR_TIMEOUT | Starting the native child process times out. |
| NCP_ERR_SERVICE_ERROR | Server error. |
| NCP_ERR_MULTI_PROCESS_DISABLED | The multi-process mode is disabled. A child process cannot be started. |
| NCP_ERR_ALREADY_IN_CHILD | A process cannot be created in a child process. |
| NCP_ERR_MAX_CHILD_PROCESSES_REACHED | The number of native child processes reaches the maximum. |
| NCP_ERR_LIB_LOADING_FAILED | The child process fails to load the dynamic library because the file does not exist or the corresponding method is not implemented or exported. |
| NCP_ERR_CONNECTION_FAILED | The child process fails to call the OnConnect method of the dynamic library. An invalid IPC object pointer may be returned. |
| NCP_ERR_CALLBACK_NOT_EXIST | The child process calls the OH_Ability_UnregisterNativeChildProcessExitCallback function to unregister a callback function, but the callback function is not found. |
NativeChildProcess_IsolationMode
enum NativeChildProcess_IsolationMode
Description
Enumerates the isolation modes of a child process.
Since: 13
| Value | Description |
|---|---|
| NCP_ISOLATION_MODE_NORMAL | Normal mode. The child process shares the data sandbox and network environment with the main process. |
| NCP_ISOLATION_MODE_ISOLATED | Isolated mode. The child process does not share the data sandbox and network environment with the main process. |
Function Description
OH_Ability_CreateNativeChildProcess
int OH_Ability_CreateNativeChildProcess (const char *libName, OH_Ability_OnNativeChildProcessStarted onProcessStarted)
Description
Creates a child process, loads the specified dynamic library file, and returns the startup result asynchronously through a callback parameter. The callback notification is an independent thread. When implementing the callback function, pay attention to thread synchronization and do not perform time-consuming operations to avoid long-time blocking.
The dynamic library specified must implement and export the following functions:
1. OHIPCRemoteStub* NativeChildProcess_OnConnect()
2. void NativeChildProcess_MainProc()
The processing logic sequence is shown in the following pseudocode:
Parent process:
1. OH_Ability_CreateNativeChildProcess(libName, onProcessStartedCallback)
Child process:
2. dlopen(libName)
3. dlsym("NativeChildProcess_OnConnect")
4. dlsym("NativeChildProcess_MainProc")
5. ipcRemote = NativeChildProcess_OnConnect()
6. NativeChildProcess_MainProc()
Parent process:
7. onProcessStartedCallback(ipcRemote, errCode)
Child process:
8. The child process exits after the NativeChildProcess_MainProc() function is returned.
NOTE
This function is valid only for 2-in-1 devices.
Since API version 15, a single process supports a maximum of 50 native child processes. In API version 14 and earlier versions, a single process supports only one native child process.
Since: 12
Parameters
| Name | Description |
|---|---|
| libName | Pointer to the name of the dynamic library file loaded in the child process. The value cannot be nullptr. |
| onProcessStartedCallback | Pointer to the callback function for notifying the child process startup result. The value cannot be nullptr. For details, see OH_Ability_OnNativeChildProcessStarted. |
Returns
Returns NCP_NO_ERROR if the operation is successful; returns an error code defined in Ability_NativeChildProcess_ErrCode otherwise.
OH_Ability_StartNativeChildProcess
Ability_NativeChildProcess_ErrCode OH_Ability_StartNativeChildProcess(
const char* entry, NativeChildProcess_Args args,
NativeChildProcess_Options options, int32_t *pid)
Description
Starts a native child process, loads the specified dynamic library file, and calls the entry function. Arguments can be passed to the child process. The ArkTS basic runtime environment cannot be created in the child process.
The specified dynamic library must implement and export the entry parameters of NativeChildProcess_Args. For details, see Native Child Process Development (C/C++) - Creating a Child Process That Supports Pass-by-Parameter.
NOTE
This function is valid only for 2-in-1 devices and tablets.
Since: 13
Parameters
| Name | Description |
|---|---|
| entry | The symbol and entry function of the dynamic library called in the child process are separated by a colon (:), for example, libentry.so:Main. The value cannot be a null pointer. |
| args | Arguments passed to the child process. For details, see NativeChildProcess_Args. |
| options | Startup configuration options of the child process. For details, see NativeChildProcess_Options. |
| pid | ID of the child process to start. |
Returns
Returns NCP_NO_ERROR if the operation is successful; returns an error code defined in Ability_NativeChildProcess_ErrCode otherwise.
OH_Ability_GetCurrentChildProcessArgs
NativeChildProcess_Args* OH_Ability_GetCurrentChildProcessArgs();
Description
Used by a child process, after being started by calling OH_Ability_StartNativeChildProcess, to obtain the startup parameter NativeChildProcess_Args from any .so file or child thread.
NOTE
This function is valid only for 2-in-1 devices and tablets.
Since: 17
Returns
Returns the pointer to a NativeChildProcess_Args object if the operation is successful; returns a null pointer otherwise.
OH_Ability_RegisterNativeChildProcessExitCallback
Ability_NativeChildProcess_ErrCode OH_Ability_RegisterNativeChildProcessExitCallback(
OH_Ability_OnNativeChildProcessExit onProcessExit)
Description
Registers a callback function for detecting abnormal exit of a native child process. When a child process started by calling OH_Ability_StartNativeChildProcess or startNativeChildProcess in @ohos.app.ability.childProcessManager exits abnormally, the callback function is invoked. If the same callback function is registered multiple times, the callback function is executed only once when the child process exits.
The parameter must implement the entry function OH_Ability_OnNativeChildProcessExit. For details, see Registering the Native Child Process Exit Callback Function.
Since: 20
Parameters
| Name | Description |
|---|---|
| onProcessExit | Address of the callback function to be called when the child process exits. The value cannot be a null pointer. |
Returns
Returns NCP_NO_ERROR if the operation is successful; returns an error code defined in Ability_NativeChildProcess_ErrCode otherwise.
OH_Ability_UnregisterNativeChildProcessExitCallback
Ability_NativeChildProcess_ErrCode OH_Ability_UnregisterNativeChildProcessExitCallback(
OH_Ability_OnNativeChildProcessExit onProcessExit)
Description
Unregisters the callback function used for detecting abnormal exit of a native child process.
The parameter must implement the entry function OH_Ability_OnNativeChildProcessExit. For details, see Registering the Native Child Process Exit Callback Function.
Since: 20
Parameters
| Name | Description |
|---|---|
| onProcessExit | Address of the callback function to be called when the child process exits. The value cannot be a null pointer. |
Returns
Returns NCP_NO_ERROR if the operation is successful; returns an error code defined in Ability_NativeChildProcess_ErrCode otherwise.
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