github.com/luchsh/agentlib.go@v0.0.0-20221115155834-ffd0caec4d72/jgo/callbacks.go (about)

     1  //
     2  // Copyright 2020 chuanshenglu@gmail.com
     3  //
     4  // Licensed under the Apache License, Version 2.0 (the "License");
     5  // you may not use this file except in compliance with the License.
     6  // You may obtain a copy of the License at
     7  //
     8  // http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  //
    16  package jgo
    17  
    18  //#include "wrapper.h"
    19  import "C"
    20  
    21  import (
    22  	"fmt"
    23  	"unsafe"
    24  )
    25  
    26  // JVMTI event ID definitions
    27  // TODO: need shorter GO name
    28  const (
    29  	// Fake events
    30  	JVMTI_MIN_FAKE_EVENT_TYPE_VAL = 100
    31  	JVMTI_EVENT_AGENT_UNLOAD      = 100
    32  	JVMTI_MAX_FAKE_EVENT_TYPE_VAL = 100
    33  	JVMTI_EVENT_TYPE_LIMIT        = 100
    34  )
    35  
    36  // JvmtiCallbacks holds the JVMTI event callbacks
    37  type JvmtiCallbacks struct {
    38  	// to hold callbacks
    39  	cbs []func(jvmtiEnv, ...JvmtiArg)
    40  }
    41  
    42  func (callbacks *JvmtiCallbacks) init() {
    43  	callbacks.cbs = make([]func(jvmtiEnv, ...JvmtiArg), JVMTI_EVENT_TYPE_LIMIT-JVMTI_MIN_EVENT_TYPE_VAL+1)
    44  }
    45  
    46  type JvmtiArg uintptr
    47  
    48  // SetCallback links a go method to process a specific JVMTI event
    49  func (callbacks *JvmtiCallbacks) SetCallback(eventId int, fn func(jvmtiEnv, ...JvmtiArg)) {
    50  	if eventId <= JVMTI_MAX_EVENT_TYPE_VAL && eventId >= JVMTI_MIN_EVENT_TYPE_VAL {
    51  		callbacks.cbs[eventId-JVMTI_MIN_EVENT_TYPE_VAL] = fn
    52  		C.EnableJvmtiCallback(unsafe.Pointer(_lib.jvmti), C.int(eventId))
    53  	} else if eventId <= JVMTI_MAX_FAKE_EVENT_TYPE_VAL && eventId >= JVMTI_MIN_FAKE_EVENT_TYPE_VAL {
    54  		C.EnableJvmtiCallback(unsafe.Pointer(_lib.jvmti), C.int(eventId))
    55  	} else {
    56  		fmt.Println("GO: Bad event id ", eventId)
    57  	}
    58  }
    59  
    60  func (callbacks *JvmtiCallbacks) dispatch(eventId int, jvmti jvmtiEnv, args ...JvmtiArg) {
    61  	fn := callbacks.cbs[eventId-JVMTI_MIN_EVENT_TYPE_VAL]
    62  	if fn != nil {
    63  		fn(jvmti, args...)
    64  	}
    65  }
    66  
    67  type rawArray struct {
    68  	base  uintptr
    69  	len   int
    70  	eSize int
    71  	idx   int
    72  }
    73  
    74  func newRawArray(b uintptr, l int) *rawArray {
    75  	ar := new(rawArray)
    76  	ar.base = b
    77  	ar.len = l
    78  	ar.eSize = int(unsafe.Sizeof(ar.base))
    79  	return ar
    80  }
    81  
    82  func (arr *rawArray) ptrAt(idx int) uintptr {
    83  	p := arr.base + uintptr(arr.eSize*idx)
    84  	return *(*uintptr)(unsafe.Pointer(p))
    85  }
    86  
    87  func (arr *rawArray) next() uintptr {
    88  	if arr.idx >= arr.len {
    89  		return uintptr(0)
    90  	}
    91  	p := arr.base + uintptr(arr.eSize*arr.idx)
    92  	return *(*uintptr)(unsafe.Pointer(p))
    93  }
    94  
    95  // OnJvmtiEvent dispatches all the event to corresponding Go handlers
    96  // runs on a JavaThread
    97  //export OnJvmtiEvent
    98  func OnJvmtiEvent(eventId int, jvmti, params uintptr, paramsLen int) {
    99  	if _lib == nil {
   100  		return
   101  	}
   102  	callbacks := _lib.GetCallbacks()
   103  	jvmtiEnv := jvmtiEnv(jvmti)
   104  	ra := newRawArray(params, paramsLen)
   105  
   106  	args := make([]JvmtiArg, paramsLen)
   107  	for i := 0; i < paramsLen; i++ {
   108  		args[i] = JvmtiArg(ra.ptrAt(i))
   109  	}
   110  
   111  	callbacks.dispatch(eventId, jvmtiEnv, args...)
   112  }