goid_go1.4.go 1.2 KB

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  1. // Copyright 2015 Peter Mattis.
  2. //
  3. // Licensed under the Apache License, Version 2.0 (the "License");
  4. // you may not use this file except in compliance with the License.
  5. // You may obtain a copy of the License at
  6. //
  7. // http://www.apache.org/licenses/LICENSE-2.0
  8. //
  9. // Unless required by applicable law or agreed to in writing, software
  10. // distributed under the License is distributed on an "AS IS" BASIS,
  11. // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
  12. // implied. See the License for the specific language governing
  13. // permissions and limitations under the License. See the AUTHORS file
  14. // for names of contributors.
  15. //go:build go1.4 && !go1.5
  16. // +build go1.4,!go1.5
  17. package goid
  18. import "unsafe"
  19. var pointerSize = unsafe.Sizeof(uintptr(0))
  20. // Backdoor access to runtime·getg().
  21. func getg() uintptr // in goid_go1.4.s
  22. // Get returns the id of the current goroutine.
  23. func Get() int64 {
  24. // The goid is the 16th field in the G struct where each field is a
  25. // pointer, uintptr or padded to that size. See runtime.h from the
  26. // Go sources. I'm not aware of a cleaner way to determine the
  27. // offset.
  28. return *(*int64)(unsafe.Pointer(getg() + 16*pointerSize))
  29. }