Change coverage dump to specify the output file instead of directory. am: 3f81e072

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'

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

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 ~/path-on-your-computer

adb pull /data/data/com.android.deskclock/folder-to-use/coverage-file.ec ~/path-on-your-computer

```

And you should have timestamped `.exec` files on your machine under the folder `~/path-on-your-computer`

And you should have `coverage-file.ec` on your machine under the folder `~/path-on-your-computer`

# Details

#include <jvmti.h>

#include <string.h>

#include <atomic>

#include <ctime>

#include <fstream>

#include <iomanip>

#include <iostream>

#include <istream>

#include <memory>

#include <sstream>

#include <string>

#include <vector>

using std::get;

using std::tuple;

using std::chrono::system_clock;

namespace dump_coverage {

  return java_result_array;

}

// Gets the filename to write execution data to

//  dirname: the directory in which to place the file

//  outputs <dirname>/YYYY-MM-DD-HH-MM-SS.SSS.exec

static std::string GetFilename(const std::string& dirname) {

  system_clock::time_point time_point = system_clock::now();

  auto seconds = std::chrono::time_point_cast<std::chrono::seconds>(time_point);

  auto fractional_time = time_point - seconds;

  auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(fractional_time);

  std::time_t time = system_clock::to_time_t(time_point);

  auto tm = *std::gmtime(&time);

  std::ostringstream oss;

  oss

    << dirname

    << "/"

    << std::put_time(&tm, "%Y-%m-%d-%H-%M-%S.")

    << std::setfill('0') << std::setw(3) << millis.count()

    << ".ec";

  return oss.str();

}

// Writes the execution data to a file

//  data, length: represent the data, as a sequence of bytes

//  dirname: directory name to contain the file

// Writes the execution data to a file.

//  data, length: represent the data, as a sequence of bytes.

//  filename: file to write coverage data to.

//  returns JNI_ERR if there is an error in writing the file, otherwise JNI_OK.

static jint WriteFile(const char* data, int length, const std::string& dirname) {

  auto filename = GetFilename(dirname);

static jint WriteFile(const char* data, int length, const std::string& filename) {

  LOG(INFO) << "Writing file of length " << length << " to '" << filename

            << "'";

  std::ofstream file(filename, std::ios::binary);

  return JNI_OK;

}

// Grabs execution data and writes it to a file

//  dirname: directory name to contain the file

// Grabs execution data and writes it to a file.

//  filename: file to write coverage data to.

//  returns JNI_ERR if there is an error writing the file.

// Will crash if the Agent isn't found or if any Java Exception occurs.

static jint Dump(const std::string& dirname) {

static jint Dump(const std::string& filename) {

  LOG(INFO) << "Dumping file";

  JNIEnv* env = GetJNIEnv();

  int result_len = env->GetArrayLength(java_result_array);

  return WriteFile((const char*) result_ptr, result_len, dirname);

  return WriteFile((const char*) result_ptr, result_len, filename);

}

// Resets execution data, performing the equivalent of

//  Agent.getInstance().reset();

//  args: should be empty

//  args: should be empty.

//  returns JNI_ERR if the arguments are invalid.

// Will crash if the Agent isn't found or if any Java Exception occurs.

static jint Reset(const std::string& args) {