heaptracker.c

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            /* Create single array of pointers to TraceInfo's, sort, and
             *   print top gdata->maxDump top space users.
             */
            list = (TraceInfo**)calloc(gdata->traceInfoCount, 
                                              sizeof(TraceInfo*));
            if ( list == NULL ) {
                fatal_error("ERROR: Ran out of malloc() space\n");
            }
            count = 0;
            for ( i = 0 ; i < HASH_BUCKET_COUNT ; i++ ) {
                TraceInfo *tinfo;

                tinfo = gdata->hashBuckets[i];
                while ( tinfo != NULL ) {
                    if ( count < gdata->traceInfoCount ) {
                        list[count++] = tinfo;
                    }
                    tinfo = tinfo->next;
                }
            }
            if ( count != gdata->traceInfoCount ) {
                fatal_error("ERROR: Count found by iterate doesn't match ours:"
                        " count=%d != traceInfoCount==%d\n",
                        count, gdata->traceInfoCount);
            }
            qsort(list, count, sizeof(TraceInfo*), &compareInfo);
            for ( i = 0 ; i < count ; i++ ) {
                if ( i >= gdata->maxDump ) {
                    break;
                }
                printTraceInfo(jvmti, i+1, list[i]);
            }
            (void)free(list);
        }

    } exitCriticalSection(jvmti);
        
}  

/* Callback for JVMTI_EVENT_VM_OBJECT_ALLOC */
static void JNICALL
cbVMObjectAlloc(jvmtiEnv *jvmti, JNIEnv *env, jthread thread, 
                jobject object, jclass object_klass, jlong size)
{
    TraceInfo *tinfo;
    
    if ( gdata->vmDead ) {
        return;
    }
    tinfo = findTraceInfo(jvmti, thread, TRACE_VM_OBJECT);
    tagObjectWithTraceInfo(jvmti, object, tinfo);
}

/* Callback for JVMTI_EVENT_OBJECT_FREE */
static void JNICALL
cbObjectFree(jvmtiEnv *jvmti, jlong tag)
{
    TraceInfo *tinfo;
  
    if ( gdata->vmDead ) {
        return;
    }
    
    /* The object tag is actually a pointer to a TraceInfo structure */
    tinfo = (TraceInfo*)(void*)(ptrdiff_t)tag;
    
    /* Decrement the use count */
    tinfo->useCount--;
}

/* Callback for JVMTI_EVENT_CLASS_FILE_LOAD_HOOK */
static void JNICALL
cbClassFileLoadHook(jvmtiEnv *jvmti, JNIEnv* env,
                jclass class_being_redefined, jobject loader,
                const char* name, jobject protection_domain,
                jint class_data_len, const unsigned char* class_data,
                jint* new_class_data_len, unsigned char** new_class_data)
{
    enterCriticalSection(jvmti); {
        /* It's possible we get here right after VmDeath event, be careful */
        if ( !gdata->vmDead ) {

            const char * classname;

            /* Name can be NULL, make sure we avoid SEGV's */
            if ( name == NULL ) {
                classname = java_crw_demo_classname(class_data, class_data_len,
                                NULL);
                if ( classname == NULL ) {
                    fatal_error("ERROR: No classname in classfile\n");
                }
            } else {
                classname = strdup(name);
                if ( classname == NULL ) {
                    fatal_error("ERROR: Ran out of malloc() space\n");
                }
            }

            *new_class_data_len = 0;
            *new_class_data     = NULL;

            /* The tracker class itself? */
            if ( strcmp(classname, STRING(HEAP_TRACKER_class)) != 0 ) {
                jint           cnum;
                int            systemClass;
                unsigned char *newImage;
                long           newLength;

                /* Get number for every class file image loaded */
                cnum = gdata->ccount++;

                /* Is it a system class? If the class load is before VmStart
                 *   then we will consider it a system class that should
                 *   be treated carefully. (See java_crw_demo)
                 */
                systemClass = 0;
                if ( !gdata->vmStarted ) {
                    systemClass = 1;
                }

                newImage = NULL;
                newLength = 0;

                /* Call the class file reader/write demo code */
                java_crw_demo(cnum,
                    classname,
                    class_data,
                    class_data_len,
                    systemClass,
                    STRING(HEAP_TRACKER_class),
                    "L" STRING(HEAP_TRACKER_class) ";",
                    NULL, NULL,
                    NULL, NULL,
                    STRING(HEAP_TRACKER_newobj), "(Ljava/lang/Object;)V",
                    STRING(HEAP_TRACKER_newarr), "(Ljava/lang/Object;)V",
                    &newImage,
                    &newLength,
                    NULL,
                    NULL);

                /* If we got back a new class image, return it back as "the"
                 *   new class image. This must be JVMTI Allocate space.
                 */
                if ( newLength > 0 ) {
                    unsigned char *jvmti_space;

                    jvmti_space = (unsigned char *)allocate(jvmti, (jint)newLength);
                    (void)memcpy((void*)jvmti_space, (void*)newImage, (int)newLength);
                    *new_class_data_len = (jint)newLength;
                    *new_class_data     = jvmti_space; /* VM will deallocate */
                }

                /* Always free up the space we get from java_crw_demo() */
                if ( newImage != NULL ) {
                    (void)free((void*)newImage); /* Free malloc() space with free() */
                }
            }
        
            (void)free((void*)classname);
        }
    } exitCriticalSection(jvmti);
}

/* Parse the options for this heapTracker agent */
static void
parse_agent_options(char *options)
{
    #define MAX_TOKEN_LENGTH        16
    char  token[MAX_TOKEN_LENGTH];
    char *next;

    /* Defaults */
    gdata->maxDump = 20;

    /* Parse options and set flags in gdata */
    if ( options==NULL ) {
        return;
    }
   
    /* Get the first token from the options string. */
    next = get_token(options, ",=", token, (int)sizeof(token));

    /* While not at the end of the options string, process this option. */
    while ( next != NULL ) {
        if ( strcmp(token,"help")==0 ) {
            stdout_message("The heapTracker JVMTI demo agent\n");
            stdout_message("\n");
            stdout_message(" java -agent:heapTracker[=options] ...\n");
            stdout_message("\n");
            stdout_message("The options are comma separated:\n");
            stdout_message("\t help\t\t\t Print help information\n");
            stdout_message("\t maxDump=n\t\t\t How many TraceInfo's to dump\n");
            stdout_message("\n");
            exit(0);
        } else if ( strcmp(token,"maxDump")==0 ) {
            char  number[MAX_TOKEN_LENGTH];
            
            next = get_token(next, ",=", number, (int)sizeof(number));
            if ( next == NULL ) {
                fatal_error("ERROR: Cannot parse maxDump=number: %s\n", options);
            }
            gdata->maxDump = atoi(number);
        } else if ( token[0]!=0 ) {
            /* We got a non-empty token and we don't know what it is. */
            fatal_error("ERROR: Unknown option: %s\n", token);
        }
        /* Get the next token (returns NULL if there are no more) */
        next = get_token(next, ",=", token, (int)sizeof(token));
    }
}

/* Agent_OnLoad: This is called immediately after the shared library is 
 *   loaded. This is the first code executed.
 */
JNIEXPORT jint JNICALL 
Agent_OnLoad(JavaVM *vm, char *options, void *reserved)
{
    static GlobalAgentData data;
    jvmtiEnv              *jvmti;
    jvmtiError             error;
    jint                   res;
    TraceFlavor            flavor;
    jvmtiCapabilities      capabilities;
    jvmtiEventCallbacks    callbacks;
    static Trace           empty;
    
    /* Setup initial global agent data area 
     *   Use of static/extern data should be handled carefully here.
     *   We need to make sure that we are able to cleanup after ourselves
     *     so anything allocated in this library needs to be freed in
     *     the Agent_OnUnload() function.
     */
    (void)memset((void*)&data, 0, sizeof(data));
    gdata = &data;
   
    /* First thing we need to do is get the jvmtiEnv* or JVMTI environment */
    res = (*vm)->GetEnv(vm, (void **)&jvmti, JVMTI_VERSION_1);
    if (res != JNI_OK) {
        /* This means that the VM was unable to obtain this version of the
         *   JVMTI interface, this is a fatal error.
         */
        fatal_error("ERROR: Unable to access JVMTI Version 1 (0x%x),"
                " is your JDK a 5.0 or newer version?"
                " JNIEnv's GetEnv() returned %d\n",
               JVMTI_VERSION_1, res);
    }

    /* Here we save the jvmtiEnv* for Agent_OnUnload(). */
    gdata->jvmti = jvmti;
   
    /* Parse any options supplied on java command line */
    parse_agent_options(options);
   
    /* Immediately after getting the jvmtiEnv* we need to ask for the
     *   capabilities this agent will need. 
     */
    (void)memset(&capabilities,0, sizeof(capabilities));
    capabilities.can_generate_all_class_hook_events = 1;
    capabilities.can_tag_objects  = 1;
    capabilities.can_generate_object_free_events  = 1;
    capabilities.can_get_source_file_name  = 1;
    capabilities.can_get_line_numbers  = 1;
    capabilities.can_generate_vm_object_alloc_events  = 1;
    error = (*jvmti)->AddCapabilities(jvmti, &capabilities);
    check_jvmti_error(jvmti, error, "Unable to get necessary JVMTI capabilities.");
    
    /* Next we need to provide the pointers to the callback functions to
     *   to this jvmtiEnv*
     */
    (void)memset(&callbacks,0, sizeof(callbacks));
    /* JVMTI_EVENT_VM_START */
    callbacks.VMStart           = &cbVMStart;      
    /* JVMTI_EVENT_VM_INIT */
    callbacks.VMInit            = &cbVMInit;      
    /* JVMTI_EVENT_VM_DEATH */
    callbacks.VMDeath           = &cbVMDeath;     
    /* JVMTI_EVENT_OBJECT_FREE */
    callbacks.ObjectFree        = &cbObjectFree;     
    /* JVMTI_EVENT_VM_OBJECT_ALLOC */
    callbacks.VMObjectAlloc     = &cbVMObjectAlloc;     
    /* JVMTI_EVENT_CLASS_FILE_LOAD_HOOK */
    callbacks.ClassFileLoadHook = &cbClassFileLoadHook; 
    error = (*jvmti)->SetEventCallbacks(jvmti, &callbacks, (jint)sizeof(callbacks));
    check_jvmti_error(jvmti, error, "Cannot set jvmti callbacks");
   
    /* At first the only initial events we are interested in are VM
     *   initialization, VM death, and Class File Loads. 
     *   Once the VM is initialized we will request more events.
     */
    error = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, 
                          JVMTI_EVENT_VM_START, (jthread)NULL);
    check_jvmti_error(jvmti, error, "Cannot set event notification");
    error = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, 
                          JVMTI_EVENT_VM_INIT, (jthread)NULL);
    check_jvmti_error(jvmti, error, "Cannot set event notification");
    error = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, 
                          JVMTI_EVENT_VM_DEATH, (jthread)NULL);
    check_jvmti_error(jvmti, error, "Cannot set event notification");
    error = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, 
                          JVMTI_EVENT_OBJECT_FREE, (jthread)NULL);
    check_jvmti_error(jvmti, error, "Cannot set event notification");
    error = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, 
                          JVMTI_EVENT_VM_OBJECT_ALLOC, (jthread)NULL);
    check_jvmti_error(jvmti, error, "Cannot set event notification");
    error = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE, 
                          JVMTI_EVENT_CLASS_FILE_LOAD_HOOK, (jthread)NULL);
    check_jvmti_error(jvmti, error, "Cannot set event notification");
   
    /* Here we create a raw monitor for our use in this agent to
     *   protect critical sections of code.
     */
    error = (*jvmti)->CreateRawMonitor(jvmti, "agent data", &(gdata->lock));
    check_jvmti_error(jvmti, error, "Cannot create raw monitor");

    /* Create the TraceInfo for various flavors of empty traces */
    for ( flavor = TRACE_FIRST ; flavor <= TRACE_LAST ; flavor++ ) {
        gdata->emptyTrace[flavor] = 
               newTraceInfo(&empty, hashTrace(&empty), flavor);
    }

    /* Add jar file to boot classpath */
    add_demo_jar_to_bootclasspath(jvmti, "heapTracker");

    /* We return JNI_OK to signify success */
    return JNI_OK;
}

/* Agent_OnUnload: This is called immediately before the shared library is 
 *   unloaded. This is the last code executed.
 */
JNIEXPORT void JNICALL 
Agent_OnUnload(JavaVM *vm)
{
    /* Skip any cleanup, VM is about to die anyway */
}