harmony 鸿蒙HiLog_Lite Development

2022-08-09
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HiLog_Lite Development

Overview

HiLog_Lite is the HiLog framework for Mini-System Devices (reference memory ≥ 128 KiB) and Small-System Devices (reference memory ≥ 1 MiB). It implements functions such as log printing, log output, and flow control.

Available APIs

HiLog_lite provides the following C APIs:

HILOG_DEBUG(mod, fmt, ...)
HILOG_INFO/HILOG_WARN/HILOG_ERROR/HILOG_FATAL

Table 1 Parameters of C APIs

Parameter	Mandatory?	Data Type	Description
mod	Yes	uint8	Indicates the module or service ID. IDs are planned and assigned in a unified manner. A maximum of 64 IDs are supported. Third-party applications use HILOG_MODULE_APP as their module ID.
fmt	Yes	char *	Indicates the format specifier for output. A maximum of six variable parameters are supported. %s is not supported. The maximum length of a formatted log record is 128 bytes. If the maximum length is exceeded, the log cannot be printed.
Variable parameters	No	int32	Only numeric types are supported. A maximum of six variable parameters are allowed.

Parameter

Mandatory?

Data Type

Description

mod

Yes

uint8

Indicates the module or service ID.

IDs are planned and assigned in a unified manner. A maximum of 64 IDs are supported. Third-party applications use HILOG_MODULE_APP as their module ID.

fmt

Yes

char *

Indicates the format specifier for output.

A maximum of six variable parameters are supported. %s is not supported.
The maximum length of a formatted log record is 128 bytes. If the maximum length is exceeded, the log cannot be printed.

Variable parameters

int32

Only numeric types are supported. A maximum of six variable parameters are allowed.

How to Develop

The following provides an example of how the Samgr_Lite module uses the HiLog_Lite framework.

Add the module ID, and define HILOG_MODULE_SAMGR in the HiLogModuleType structure in base/hiviewdfx/hilog_lite/interfaces/native/kits/hilog_lite/hiview_log.h.
```
typedef enum {
    ...
    HILOG_MODULE_SAMGR,
    ...
} HiLogModuleType;
```
Register the module. Specifically, add the registration code to the HiLogInit function in base/hiviewdfx/hilog_lite/frameworks/mini/hiview_log.c.
```
HiLogRegisterModule(HILOG_MODULE_SAMGR, "SAMGR");
```
Add the header file dependencies to the foundation/systemabilitymgr/samgr_lite/samgr/BUILD.gn file.
```
 include_dirs = [
      "//base/hiviewdfx/hilog_lite/interfaces/native/kits/hilog_lite",
 ]
```

Reference the header file in the foundation/systemabilitymgr/samgr_lite/samgr/source/message.c file and call the related APIs.

#include <log.h>
uint32 *SAMGR_SendSharedRequest(const Identity *identity, const Request *request, uint32 *token, Handler handler)
{
    ...
    if (err != EC_SUCCESS) {
        HILOG_ERROR(HILOG_MODULE_SAMGR, "SharedSend [%p] failed(%d)!", identity->queueId, err);
        (void)FreeReference(&exchange);
    }
    ...
}