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# dumpcoverage
libdumpcoverage.so is a JVMTI agent designed to dump coverage information for a process, where the binaries have been instrumented by JaCoCo. JaCoCo automatically starts recording data on process start, and we need a way to trigger the resetting or dumping of this data.
The JVMTI agent is used to make the calls to JaCoCo in its process.
# Usage
Note that these examples assume you have an instrumented build (userdebug_coverage). Here is, for example, how to dump coverage information regarding the default clock app. First some setup is necessary:
```
adb root # necessary to copy files in/out of the /data/data/{package} folder
adb shell 'mkdir /data/data/com.android.deskclock/folder-to-use'
```
Then we can run the command to dump the data:
```
adb shell 'am attach-agent com.android.deskclock /system/lib/libdumpcoverage.so=dump:/data/data/com.android.deskclock/folder-to-use/coverage-file.ec'
```
We can also reset the coverage information with
```
adb shell 'am attach-agent com.android.deskclock /system/lib/libdumpcoverage.so=reset'
```
then perform more actions, then dump the data again. To get the files, we can get
```
adb pull /data/data/com.android.deskclock/folder-to-use/coverage-file.ec ~/path-on-your-computer
```
And you should have `coverage-file.ec` on your machine under the folder `~/path-on-your-computer`
# Details
In dump mode, the agent makes JNI calls equivalent to
```
Agent.getInstance().getExecutionData(/*reset = */ false);
```
and then saves the result to a file specified by the passed in directory
In reset mode, it makes a JNI call equivalent to
```
Agent.getInstance().reset();
```
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