+++ /dev/null
-// Copyright (c) 2015 Dave Collins <dave@davec.name>
-//
-// Permission to use, copy, modify, and distribute this software for any
-// purpose with or without fee is hereby granted, provided that the above
-// copyright notice and this permission notice appear in all copies.
-//
-// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
-// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
-// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
-// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
-// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
-// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
-// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-
-// NOTE: Due to the following build constraints, this file will only be compiled
-// when the code is not running on Google App Engine, compiled by GopherJS, and
-// "-tags safe" is not added to the go build command line. The "disableunsafe"
-// tag is deprecated and thus should not be used.
-// +build !js,!appengine,!safe,!disableunsafe
-
-package spew
-
-import (
- "reflect"
- "unsafe"
-)
-
-const (
- // UnsafeDisabled is a build-time constant which specifies whether or
- // not access to the unsafe package is available.
- UnsafeDisabled = false
-
- // ptrSize is the size of a pointer on the current arch.
- ptrSize = unsafe.Sizeof((*byte)(nil))
-)
-
-var (
- // offsetPtr, offsetScalar, and offsetFlag are the offsets for the
- // internal reflect.Value fields. These values are valid before golang
- // commit ecccf07e7f9d which changed the format. The are also valid
- // after commit 82f48826c6c7 which changed the format again to mirror
- // the original format. Code in the init function updates these offsets
- // as necessary.
- offsetPtr = uintptr(ptrSize)
- offsetScalar = uintptr(0)
- offsetFlag = uintptr(ptrSize * 2)
-
- // flagKindWidth and flagKindShift indicate various bits that the
- // reflect package uses internally to track kind information.
- //
- // flagRO indicates whether or not the value field of a reflect.Value is
- // read-only.
- //
- // flagIndir indicates whether the value field of a reflect.Value is
- // the actual data or a pointer to the data.
- //
- // These values are valid before golang commit 90a7c3c86944 which
- // changed their positions. Code in the init function updates these
- // flags as necessary.
- flagKindWidth = uintptr(5)
- flagKindShift = uintptr(flagKindWidth - 1)
- flagRO = uintptr(1 << 0)
- flagIndir = uintptr(1 << 1)
-)
-
-func init() {
- // Older versions of reflect.Value stored small integers directly in the
- // ptr field (which is named val in the older versions). Versions
- // between commits ecccf07e7f9d and 82f48826c6c7 added a new field named
- // scalar for this purpose which unfortunately came before the flag
- // field, so the offset of the flag field is different for those
- // versions.
- //
- // This code constructs a new reflect.Value from a known small integer
- // and checks if the size of the reflect.Value struct indicates it has
- // the scalar field. When it does, the offsets are updated accordingly.
- vv := reflect.ValueOf(0xf00)
- if unsafe.Sizeof(vv) == (ptrSize * 4) {
- offsetScalar = ptrSize * 2
- offsetFlag = ptrSize * 3
- }
-
- // Commit 90a7c3c86944 changed the flag positions such that the low
- // order bits are the kind. This code extracts the kind from the flags
- // field and ensures it's the correct type. When it's not, the flag
- // order has been changed to the newer format, so the flags are updated
- // accordingly.
- upf := unsafe.Pointer(uintptr(unsafe.Pointer(&vv)) + offsetFlag)
- upfv := *(*uintptr)(upf)
- flagKindMask := uintptr((1<<flagKindWidth - 1) << flagKindShift)
- if (upfv&flagKindMask)>>flagKindShift != uintptr(reflect.Int) {
- flagKindShift = 0
- flagRO = 1 << 5
- flagIndir = 1 << 6
-
- // Commit adf9b30e5594 modified the flags to separate the
- // flagRO flag into two bits which specifies whether or not the
- // field is embedded. This causes flagIndir to move over a bit
- // and means that flagRO is the combination of either of the
- // original flagRO bit and the new bit.
- //
- // This code detects the change by extracting what used to be
- // the indirect bit to ensure it's set. When it's not, the flag
- // order has been changed to the newer format, so the flags are
- // updated accordingly.
- if upfv&flagIndir == 0 {
- flagRO = 3 << 5
- flagIndir = 1 << 7
- }
- }
-}
-
-// unsafeReflectValue converts the passed reflect.Value into a one that bypasses
-// the typical safety restrictions preventing access to unaddressable and
-// unexported data. It works by digging the raw pointer to the underlying
-// value out of the protected value and generating a new unprotected (unsafe)
-// reflect.Value to it.
-//
-// This allows us to check for implementations of the Stringer and error
-// interfaces to be used for pretty printing ordinarily unaddressable and
-// inaccessible values such as unexported struct fields.
-func unsafeReflectValue(v reflect.Value) (rv reflect.Value) {
- indirects := 1
- vt := v.Type()
- upv := unsafe.Pointer(uintptr(unsafe.Pointer(&v)) + offsetPtr)
- rvf := *(*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(&v)) + offsetFlag))
- if rvf&flagIndir != 0 {
- vt = reflect.PtrTo(v.Type())
- indirects++
- } else if offsetScalar != 0 {
- // The value is in the scalar field when it's not one of the
- // reference types.
- switch vt.Kind() {
- case reflect.Uintptr:
- case reflect.Chan:
- case reflect.Func:
- case reflect.Map:
- case reflect.Ptr:
- case reflect.UnsafePointer:
- default:
- upv = unsafe.Pointer(uintptr(unsafe.Pointer(&v)) +
- offsetScalar)
- }
- }
-
- pv := reflect.NewAt(vt, upv)
- rv = pv
- for i := 0; i < indirects; i++ {
- rv = rv.Elem()
- }
- return rv
-}
OSDN Git Service
