Android: Add API for getting native histograms.

webrtc/api/java/jni/androidmetrics_jni.cc

+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <map>
+#include <memory>
+
+#include "webrtc/api/java/jni/classreferenceholder.h"
+#include "webrtc/api/java/jni/jni_helpers.h"
+#include "webrtc/api/java/jni/native_handle_impl.h"
+#include "webrtc/system_wrappers/include/metrics_default.h"
+
+// Enables collection of native histograms.
+namespace webrtc_jni {
+JOW(void, Metrics_nativeEnable)(JNIEnv* jni, jclass) {
+  webrtc::metrics::Enable();
+}
+
+// Gets and clears native histograms.
+JOW(jobject, Metrics_nativeGetAndReset)(JNIEnv* jni, jclass) {
+  jclass j_metrics_class = FindClass(jni, "org/webrtc/Metrics");
+  jmethodID j_add =
+      GetMethodID(jni, j_metrics_class, "add",
+                  "(Ljava/lang/String;Lorg/webrtc/Metrics$HistogramInfo;)V");
+  jclass j_info_class = FindClass(jni, "org/webrtc/Metrics$HistogramInfo");
+  jmethodID j_add_sample = GetMethodID(jni, j_info_class, "addSample", "(II)V");
+
+  // Create |Metrics|.
+  jobject j_metrics = jni->NewObject(
+      j_metrics_class, GetMethodID(jni, j_metrics_class, "<init>", "()V"));
+
+  std::map<std::string, std::unique_ptr<webrtc::metrics::SampleInfo>>
+      histograms;
+  webrtc::metrics::GetAndReset(&histograms);
+  for (const auto& kv : histograms) {
+    // Create and add samples to |HistogramInfo|.
+    jobject j_info = jni->NewObject(
+        j_info_class, GetMethodID(jni, j_info_class, "<init>", "(III)V"),
+        kv.second->min, kv.second->max,
+        static_cast<int>(kv.second->bucket_count));
+    for (const auto& sample : kv.second->samples) {
+      jni->CallVoidMethod(j_info, j_add_sample, sample.first, sample.second);
+    }
+    // Add |HistogramInfo| to |Metrics|.
+    jstring j_name = jni->NewStringUTF(kv.first.c_str());
+    jni->CallVoidMethod(j_metrics, j_add, j_name, j_info);
+    jni->DeleteLocalRef(j_name);
+    jni->DeleteLocalRef(j_info);
+  }
+  CHECK_EXCEPTION(jni);
+  return j_metrics;
+}
+}  // namespace webrtc_jni