/*
 * Copyright (c) 2017, Google and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "jvmti.h"

#ifdef __cplusplus
extern "C" {
#endif

#ifndef JNI_ENV_ARG

#ifdef __cplusplus
#define JNI_ENV_ARG(x, y) y
#define JNI_ENV_PTR(x) x
#else
#define JNI_ENV_ARG(x,y) x, y
#define JNI_ENV_PTR(x) (*x)
#endif

#endif

#define TRUE 1
#define FALSE 0
#define PRINT_OUT 1
#define MAX_TRACES 400

static const char *EXC_CNAME = "java/lang/Exception";
static jvmtiEnv *jvmti = NULL;

static int check_error(jvmtiError err, const char *s) {
  if (err != JVMTI_ERROR_NONE) {
    printf("  ## %s error: %d\n", s, err);
    return 1;
  }
  return 0;
}

static int check_capability_error(jvmtiError err, const char *s) {
  if (err != JVMTI_ERROR_NONE) {
    if (err == JVMTI_ERROR_MUST_POSSESS_CAPABILITY) {
      return 0;
    }
    printf("  ## %s error: %d\n", s, err);
    return 1;
  }
  return 1;
}

static
jint throw_exc(JNIEnv *env, char *msg) {
  jclass exc_class = JNI_ENV_PTR(env)->FindClass(JNI_ENV_ARG(env, EXC_CNAME));

  if (exc_class == NULL) {
    printf("throw_exc: Error in FindClass(env, %s)\n", EXC_CNAME);
    return -1;
  }
  return JNI_ENV_PTR(env)->ThrowNew(JNI_ENV_ARG(env, exc_class), msg);
}

static jint Agent_Initialize(JavaVM *jvm, char *options, void *reserved);

JNIEXPORT
jint JNICALL Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) {
  return Agent_Initialize(jvm, options, reserved);
}

JNIEXPORT
jint JNICALL Agent_OnAttach(JavaVM *jvm, char *options, void *reserved) {
  return Agent_Initialize(jvm, options, reserved);
}

JNIEXPORT
jint JNICALL JNI_OnLoad(JavaVM *jvm, void *reserved) {
  return JNI_VERSION_1_8;
}

static
jint Agent_Initialize(JavaVM *jvm, char *options, void *reserved) {
  jint res;

  res = JNI_ENV_PTR(jvm)->GetEnv(JNI_ENV_ARG(jvm, (void **) &jvmti),
                                 JVMTI_VERSION_9);
  if (res != JNI_OK || jvmti == NULL) {
    printf("    Error: wrong result of a valid call to GetEnv!\n");
    return JNI_ERR;
  }

  jvmtiEventCallbacks callbacks;
  memset(&callbacks, 0, sizeof(callbacks));

  jvmtiCapabilities caps;
  memset(&caps, 0, sizeof(caps));
  // Get line numbers, sample heap, and filename for the test.
  caps.can_get_line_numbers = 1;
  caps.can_sample_heap = 1;
  caps.can_get_source_file_name = 1;
  if (check_error((*jvmti)->AddCapabilities(jvmti, &caps),
                  "Add capabilities\n")){
    return JNI_ERR;
  }
  if (check_error((*jvmti)->SetEventCallbacks(jvmti, &callbacks,
                                              sizeof(jvmtiEventCallbacks)),
                  " Set Event Callbacks")) {
    return JNI_ERR;
  }
  return JNI_OK;
}

// Given a method and a location, this method gets the line number.
static
jint get_line_number(jvmtiEnv *jvmti, jmethodID method,
                     jlocation location) {
  // Read the line number table.
  jvmtiLineNumberEntry *table_ptr = 0;
  jint line_number_table_entries;
  int jvmti_error = (*jvmti)->GetLineNumberTable(jvmti, method,
                                                 &line_number_table_entries,
                                                 &table_ptr);

  if (JVMTI_ERROR_NONE != jvmti_error) {
    return -1;
  }
  if (line_number_table_entries <= 0) {
    return -1;
  }
  if (line_number_table_entries == 1) {
    return table_ptr[0].line_number;
  }

  // Go through all the line numbers...
  jint last_location = table_ptr[0].start_location;
  int l;
  for (l = 1; l < line_number_table_entries; l++) {
    // ... and if you see one that is in the right place for your
    // location, you've found the line number!
    if ((location < table_ptr[l].start_location) &&
        (location >= last_location)) {
      return table_ptr[l - 1].line_number;
    }
    last_location = table_ptr[l].start_location;
  }

  if (location >= last_location) {
    return table_ptr[line_number_table_entries - 1].line_number;
  } else {
    return -1;
  }
}

typedef struct _ExpectedContentFrame {
  const char *name;
  const char *signature;
  const char *file_name;
  int line_number;
} ExpectedContentFrame;

static jboolean check_sample_content(JNIEnv *env,
                                     jvmtiStackTrace *trace,
                                     ExpectedContentFrame *expected,
                                     int expected_count,
                                     int print_out_comparisons) {
  int i;

  if (expected_count > trace->frame_count) {
    return FALSE;
  }

  for (i = 0; i < expected_count; i++) {
    // Get basic information out of the trace.
    int bci = trace->frames[i].location;
    jmethodID methodid = trace->frames[i].method;
    char *name = NULL, *signature = NULL, *file_name = NULL;

    if (bci < 0) {
      return FALSE;
    }

    // Transform into usable information.
    int line_number = get_line_number(jvmti, methodid, bci);
    (*jvmti)->GetMethodName(jvmti, methodid, &name, &signature, 0);

    jclass declaring_class;
    if (JVMTI_ERROR_NONE !=
        (*jvmti)->GetMethodDeclaringClass(jvmti, methodid, &declaring_class)) {
      return FALSE;
    }

    jvmtiError err = (*jvmti)->GetSourceFileName(jvmti, declaring_class,
                                                 &file_name);
    if (err != JVMTI_ERROR_NONE) {
      return FALSE;
    }

    // Compare now, none should be NULL.
    if (name == NULL) {
      return FALSE;
    }

    if (file_name == NULL) {
      return FALSE;
    }

    if (signature == NULL) {
      return FALSE;
    }

    if (print_out_comparisons) {
      fprintf(stderr, "Comparing:\n");
      fprintf(stderr, "\tNames: %s and %s\n", name, expected[i].name);
      fprintf(stderr, "\tSignatures: %s and %s\n", signature, expected[i].signature);
      fprintf(stderr, "\tFile name: %s and %s\n", file_name, expected[i].file_name);
      fprintf(stderr, "\tLines: %d and %d\n", line_number, expected[i].line_number);
      fprintf(stderr, "\tResult is %d\n",
              (strcmp(name, expected[i].name) ||
               strcmp(signature, expected[i].signature) ||
               strcmp(file_name, expected[i].file_name) ||
               line_number != expected[i].line_number));
    }

    if (strcmp(name, expected[i].name) ||
        strcmp(signature, expected[i].signature) ||
        strcmp(file_name, expected[i].file_name) ||
        line_number != expected[i].line_number) {
      return FALSE;
    }
  }

  return TRUE;
}

static jboolean compare_samples(JNIEnv* env, jvmtiStackTrace* traces,
                                int trace_count,
                                ExpectedContentFrame* expected_content,
                                size_t size,
                                int print_out_comparisons) {
  // We expect the code to record correctly the bci, retrieve the line
  // number, have the right method and the class name of the first frames.
  int i;
  for (i = 0; i < trace_count; i++) {
    jvmtiStackTrace *trace = traces + i;
    if (check_sample_content(env, trace, expected_content, size,
                             print_out_comparisons)) {
      // At least one frame matched what we were looking for.
      return TRUE;
    }
  }

  return FALSE;
}

static jboolean
check_samples(JNIEnv* env,
              ExpectedContentFrame* expected,
              size_t size,
              jvmtiError (*const get_traces)(jvmtiEnv*, jvmtiStackTraces*),
              int print_out_comparisons) {
  jvmtiStackTraces traces;
  jvmtiError error = get_traces(jvmti, &traces);

  if (error != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  int result = compare_samples(env, traces.stack_traces, traces.trace_count,
                               expected, size, print_out_comparisons);
  (*jvmti)->ReleaseTraces(jvmti, &traces);
  return result;
}

static jboolean frames_exist_live(JNIEnv* env,
                                  ExpectedContentFrame* expected,
                                  size_t size,
                                  int print_out_comparisons) {
  return check_samples(env, expected, size, (*jvmti)->GetLiveTraces,
                       print_out_comparisons);
}

static jboolean frames_exist_recent(JNIEnv* env,
                                    ExpectedContentFrame* expected,
                                    size_t size,
                                    int print_out_comparisons) {
  return check_samples(env, expected, size, (*jvmti)->GetGarbageTraces,
                       print_out_comparisons);
}

static jboolean frames_exist_frequent(JNIEnv* env,
                                      ExpectedContentFrame* expected,
                                      size_t size,
                                      int print_out_comparisons) {
  return check_samples(env, expected, size, (*jvmti)->GetFrequentGarbageTraces,
                       print_out_comparisons);
}

// Static native API for various tests.
static void fill_native_frames(JNIEnv* env, jobjectArray frames,
                               ExpectedContentFrame* native_frames, size_t size) {
  size_t i;
  for(i = 0; i < size; i++) {
    jobject obj = (*env)->GetObjectArrayElement(env, frames, i);
    jclass frame_class = (*env)->GetObjectClass(env, obj);
    jfieldID line_number_field_id = (*env)->GetFieldID(env, frame_class,
                                                       "lineNumber", "I");
    int line_number = (*env)->GetIntField(env, obj, line_number_field_id);

    jfieldID string_id = (*env)->GetFieldID(env, frame_class, "method",
                                            "Ljava/lang/String;");
    jstring string_object = (jstring) (*env)->GetObjectField(env, obj,
                                                             string_id);
    const char* method = (*env)->GetStringUTFChars(env, string_object, 0);

    string_id = (*env)->GetFieldID(env, frame_class, "fileName",
                                   "Ljava/lang/String;");
    string_object = (jstring) (*env)->GetObjectField(env, obj, string_id);
    const char* file_name = (*env)->GetStringUTFChars(env, string_object, 0);

    string_id = (*env)->GetFieldID(env, frame_class, "signature",
                                   "Ljava/lang/String;");
    string_object = (jstring) (*env)->GetObjectField(env, obj, string_id);
    const char* signature= (*env)->GetStringUTFChars(env, string_object, 0);

    native_frames[i].name = method;
    native_frames[i].file_name = file_name;
    native_frames[i].signature = signature;
    native_frames[i].line_number = line_number;
  }
}

static jboolean check_and(JNIEnv *env, jobjectArray frames, int live,
                          int recent, int frequent, int print_out) {
  jobject loader = NULL;

  if (frames == NULL) {
    return FALSE;
  }

  // Start by transforming the frames into a C-friendly structure.
  jsize size = (*env)->GetArrayLength(env, frames);
  ExpectedContentFrame native_frames[size];
  fill_native_frames(env, frames, native_frames, size);

  if (jvmti == NULL) {
    throw_exc(env, "JVMTI client was not properly loaded!\n");
    return FALSE;
  }

  int result = TRUE;

  if (live) {
    result = frames_exist_live(env, native_frames, size, print_out);
  }

  if (recent) {
    result = result &&
        frames_exist_recent(env, native_frames, size, print_out);
  }

  if (frequent) {
    result = result &&
        frames_exist_frequent(env, native_frames, size, print_out);
  }

  return result;
}

static jboolean check_or(JNIEnv *env, jobjectArray frames, int live, int recent,
                         int frequent, int print_out) {
  jobject loader = NULL;

  if (frames == NULL) {
    return FALSE;
  }

  // Start by transforming the frames into a C-friendly structure.
  jsize size = (*env)->GetArrayLength(env, frames);
  ExpectedContentFrame native_frames[size];
  fill_native_frames(env, frames, native_frames, size);

  if (jvmti == NULL) {
    throw_exc(env, "JVMTI client was not properly loaded!\n");
    return FALSE;
  }

  jboolean result = FALSE;

  if (live) {
    result = frames_exist_live(env, native_frames, size, print_out);
  }

  if (recent) {
    result = result ||
        frames_exist_recent(env, native_frames, size, print_out);
  }

  if (frequent) {
    result = result ||
        frames_exist_frequent(env, native_frames, size, print_out);
  }

  return result;
}

static jboolean checkAll(JNIEnv *env, jobjectArray frames, int print_out) {
  return check_and(env, frames, 1, 1, 1, print_out);
}

static jboolean checkNone(JNIEnv *env, jobjectArray frames,
                          int print_out) {
  jobject loader = NULL;

  if (frames == NULL) {
    return FALSE;
  }

  // Start by transforming the frames into a C-friendly structure.
  jsize size = (*env)->GetArrayLength(env, frames);
  ExpectedContentFrame native_frames[size];
  fill_native_frames(env, frames, native_frames, size);

  if (jvmti == NULL) {
    throw_exc(env, "JVMTI client was not properly loaded!\n");
    return FALSE ;
  }

  if ((!frames_exist_live(env, native_frames, size, print_out)) &&
      (!frames_exist_recent(env, native_frames, size, print_out)) &&
      (!frames_exist_frequent(env, native_frames, size, print_out))) {
    return TRUE;
  }
  return FALSE;
}

JNIEXPORT void JNICALL
Java_MyPackage_HeapMonitor_enableSampling(JNIEnv *env, jclass cls, int rate,
                                          int max_traces) {
  check_error((*jvmti)->StartHeapSampling(jvmti, rate, max_traces),
              "Start Heap Sampling");
}

JNIEXPORT void JNICALL
Java_MyPackage_HeapMonitor_disableSampling(JNIEnv *env, jclass cls) {
  check_error((*jvmti)->StopHeapSampling(jvmti), "Stop Heap Sampling");
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitor_areSamplingStatisticsZero(JNIEnv *env, jclass cls) {
  jvmtiHeapSamplingStats stats;
  check_error((*jvmti)->GetHeapSamplingStats(jvmti, &stats),
              "Heap Sampling Statistics");

  jvmtiHeapSamplingStats zero;
  memset(&zero, 0, sizeof(zero));
  return memcmp(&stats, &zero, sizeof(zero)) == 0;
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitor_framesExistEverywhere(JNIEnv *env, jclass cls,
                                                 jobjectArray frames) {
  // We want the frames in each part.
  return checkAll(env, frames, PRINT_OUT);
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitor_framesExistNowhere(JNIEnv *env, jclass cls,
                                              jobjectArray frames) {
  // We want the frames in none of the parts.
  return checkNone(env, frames, PRINT_OUT);
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorRecentTest_framesNotInLiveOrRecent(JNIEnv *env,
                                                             jclass cls,
                                                             jobjectArray frames) {
  return !check_or(env, frames, TRUE, TRUE, FALSE, PRINT_OUT);
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorRecentTest_framesExistInLiveAndRecent(JNIEnv *env,
                                                                jclass cls,
                                                                jobjectArray frames) {
  return check_and(env, frames, TRUE, TRUE, FALSE, PRINT_OUT);
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorFrequentTest_framesExistInFrequent(JNIEnv *env,
                                                             jclass cls,
                                                             jobjectArray frames) {
  return check_and(env, frames, FALSE, FALSE, TRUE, PRINT_OUT);
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorNoCapabilityTest_allSamplingMethodsFail(JNIEnv *env,
                                                                  jclass cls) {
  jvmtiCapabilities caps;
  memset(&caps, 0, sizeof(caps));
  caps.can_sample_heap= 1;
  if (check_error((*jvmti)->RelinquishCapabilities(jvmti, &caps),
                  "Add capabilities\n")){
    return FALSE;
  }

  if (check_capability_error((*jvmti)->StartHeapSampling(jvmti, 1<<19,
                                                         MAX_TRACES),
                             "Start Heap Sampling")) {
    return FALSE;
  }

  if (check_capability_error((*jvmti)->StopHeapSampling(jvmti),
                             "Stop Heap Sampling")) {
    return FALSE;
  }

  if (check_capability_error((*jvmti)->ReleaseTraces(jvmti, NULL),
                             "Release Traces")) {
    return FALSE;
  }

  if (check_capability_error((*jvmti)->GetHeapSamplingStats(jvmti, NULL),
                             "Get Heap Sampling Stats")) {
    return FALSE;
  }

  if (check_capability_error((*jvmti)->GetGarbageTraces(jvmti, NULL),
                             "Get Garbage Traces")) {
    return FALSE;
  }

  if (check_capability_error((*jvmti)->GetFrequentGarbageTraces(jvmti, NULL),
                             "Get Frequent Garbage Traces")) {
    return FALSE;
  }

  if (check_capability_error((*jvmti)->GetLiveTraces(jvmti, NULL),
                             "Get Live Traces")) {
    return FALSE;
  }
  return TRUE;
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitor_statsHaveExpectedNumberSamples(JNIEnv *env,
                                                          jclass cls,
                                                          int expected,
                                                          int percent_error) {
  jvmtiHeapSamplingStats stats;
  check_error((*jvmti)->GetHeapSamplingStats(jvmti, &stats),
              "Heap Sampling Statistics");

  fprintf(stderr, "Sample data count %ld, rate %ld, rate count %ld\n",
          stats.sample_count, stats.sample_rate_accumulation, stats.sample_rate_count);
  double diff_ratio = (stats.sample_count - expected);
  diff_ratio = (diff_ratio < 0) ? -diff_ratio : diff_ratio;
  diff_ratio /= expected;

  return diff_ratio * 100 < percent_error;
}

JNIEXPORT jdouble JNICALL
Java_MyPackage_HeapMonitorStatRateTest_getAverageRate(JNIEnv *env, jclass cls) {
  jvmtiHeapSamplingStats stats;
  check_error((*jvmti)->GetHeapSamplingStats(jvmti, &stats),
              "Heap Sampling Statistics");
  return ((double) stats.sample_rate_accumulation) / stats.sample_rate_count;
}

JNIEXPORT jdouble JNICALL
Java_MyPackage_HeapMonitorStackDepthTest_getAverageStackDepth(JNIEnv *env,
                                                              jclass cls) {
  jvmtiStackTraces traces;
  jvmtiError error = (*jvmti)->GetLiveTraces(jvmti, &traces);;

  if (error != JVMTI_ERROR_NONE) {
    return 0;
  }

  int trace_count = traces.trace_count;

  if (trace_count == 0) {
    return 0;
  }

  int i;
  jvmtiStackTrace* stack_traces = traces.stack_traces;
  double sum = 0;
  for (i = 0; i < trace_count; i++) {
    jvmtiStackTrace *stack_trace = stack_traces + i;
    sum += stack_trace->frame_count;
  }

  return sum / i;
}

typedef struct sThreadsFound {
  jint *threads;
  int num_threads;
} ThreadsFound;

static void find_threads_in_traces(jvmtiStackTraces* traces,
                                   ThreadsFound* thread_data) {
  int i;
  jvmtiStackTrace* stack_traces = traces->stack_traces;
  int trace_count = traces->trace_count;

  jint *threads = thread_data->threads;
  int num_threads = thread_data->num_threads;

  // We are looking for at last expected_num_threads different traces.
  for (i = 0; i < trace_count; i++) {
    jvmtiStackTrace *stack_trace = stack_traces + i;
    jlong thread_id = stack_trace->thread_id;

    // Check it is the right frame: only accept helper top framed traces.
    jmethodID methodid = stack_trace->frames[0].method;
    char *name = NULL, *signature = NULL, *file_name = NULL;
    (*jvmti)->GetMethodName(jvmti, methodid, &name, &signature, 0);

    if (strcmp(name, "helper")) {
      continue;
    }

    // Really not efficient look-up but it's for a test...
    int found = 0;
    int j;
    for (j = 0; j < num_threads; j++) {
      if (thread_id == threads[j]) {
        found = 1;
        break;
      }
    }

    if (!found) {
      threads[num_threads] = thread_id;
      num_threads++;
    }
  }
  thread_data->num_threads = num_threads;
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorThreadTest_checkSamples(JNIEnv* env, jclass cls,
                                                  jintArray threads) {
  jvmtiStackTraces traces;
  ThreadsFound thread_data;
  thread_data.threads = (*env)->GetIntArrayElements(env, threads, 0);
  thread_data.num_threads = 0;

  // Get live and garbage traces to ensure we capture all the threads that have
  // been sampled.
  if ((*jvmti)->GetLiveTraces(jvmti, &traces) != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  find_threads_in_traces(&traces, &thread_data);

  if ((*jvmti)->ReleaseTraces(jvmti, &traces) != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  if ((*jvmti)->GetGarbageTraces(jvmti, &traces) != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  find_threads_in_traces(&traces, &thread_data);

  if ((*jvmti)->ReleaseTraces(jvmti, &traces) != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  (*env)->ReleaseIntArrayElements(env, threads, thread_data.threads, 0);
  return TRUE;
}

JNIEXPORT void JNICALL
Java_MyPackage_HeapMonitorCachedTest_getLiveTracesToForceGc(JNIEnv *env,
                                                            jclass cls) {
  jvmtiStackTraces live_traces;
  jvmtiError error = (*jvmti)->GetLiveTraces(jvmti, &live_traces);

  if (error != JVMTI_ERROR_NONE) {
    return;
  }

  (*jvmti)->ReleaseTraces(jvmti, &live_traces);
}

static jboolean compare_traces(jvmtiStackTraces* traces,
                               jvmtiStackTraces* other_traces,
                               int print_out_comparisons) {
  int trace_count = traces->trace_count;
  if (trace_count != other_traces->trace_count) {
    return FALSE;
  }

  int i;
  for (i = 0; i < trace_count; i++) {
    jvmtiStackTrace* trace = traces->stack_traces + i;
    jvmtiStackTrace* other_trace = other_traces->stack_traces + i;

    if (trace->frame_count != other_trace->frame_count) {
      return FALSE;
    }

    if (trace->size != other_trace->size) {
      return FALSE;
    }

    if (trace->thread_id != other_trace->thread_id) {
      return FALSE;
    }

    jvmtiFrameInfo* frames = trace->frames;
    jvmtiFrameInfo* other_frames = other_trace->frames;
    if (memcmp(frames, other_frames, sizeof(*frames) * trace->frame_count)) {
      return FALSE;
    }
  }

  return TRUE;
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorCachedTest_cachedAndLiveAreSame(JNIEnv *env,
                                                          jclass cls) {
  // Get cached first, then get live (since live performs a GC).
  jvmtiStackTraces cached_traces;
  jvmtiError error = (*jvmti)->GetCachedTraces(jvmti, &cached_traces);

  if (error != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  jvmtiStackTraces live_traces;
  error = (*jvmti)->GetLiveTraces(jvmti, &live_traces);

  if (error != JVMTI_ERROR_NONE) {
    return FALSE;
  }

  int result = compare_traces(&cached_traces, &live_traces, PRINT_OUT);

  (*jvmti)->ReleaseTraces(jvmti, &cached_traces);
  (*jvmti)->ReleaseTraces(jvmti, &live_traces);
  return result;
}

static long hash(long hash_code, long value) {
  return hash_code * 31 + value;
}

static long get_hash_code(jvmtiStackTraces* traces) {
  int trace_count = traces->trace_count;
  int hash_code = 17;

  int i;
  hash_code = hash(hash_code, trace_count);
  for (i = 0; i < trace_count; i++) {
    jvmtiStackTrace* trace = traces->stack_traces + i;
    hash_code = hash(hash_code, trace->frame_count);
    hash_code = hash(hash_code, trace->size);
    hash_code = hash(hash_code, trace->thread_id);

    int j;
    int frame_count = trace->frame_count;
    jvmtiFrameInfo* frames = trace->frames;
    hash_code = hash(hash_code, frame_count);
    for (j = 0; j < frame_count; j++) {
      hash_code = hash(hash_code, (long) frames[i].method);
      hash_code = hash(hash_code, frames[i].location);
    }
  }

  return TRUE;
}

JNIEXPORT jlong JNICALL
Java_MyPackage_HeapMonitorCachedTest_getCachedHashCode(JNIEnv *env,
                                                       jclass cls) {
  // Get cached first, then get live.
  jvmtiStackTraces cached_traces;
  jvmtiError error = (*jvmti)->GetCachedTraces(jvmti, &cached_traces);

  if (error != JVMTI_ERROR_NONE) {
    return 0;
  }

  long hash_code = get_hash_code(&cached_traces);
  (*jvmti)->ReleaseTraces(jvmti, &cached_traces);

  return hash_code;
}

JNIEXPORT jboolean JNICALL
Java_MyPackage_HeapMonitorTest_framesAreNotLive(JNIEnv *env,
                                                jclass cls,
                                                jobjectArray frames) {
  return !check_and(env, frames, FALSE, FALSE, TRUE, PRINT_OUT);
}

#ifdef __cplusplus
}
#endif