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author | Christopher Speller <crspeller@gmail.com> | 2018-04-16 05:37:14 -0700 |
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committer | Joram Wilander <jwawilander@gmail.com> | 2018-04-16 08:37:14 -0400 |
commit | 6e2cb00008cbf09e556b00f87603797fcaa47e09 (patch) | |
tree | 3c0eb55ff4226a3f024aad373140d1fb860a6404 /vendor/github.com/davecgh/go-spew/spew/bypass.go | |
parent | bf24f51c4e1cc6286885460672f7f449e8c6f5ef (diff) | |
download | chat-6e2cb00008cbf09e556b00f87603797fcaa47e09.tar.gz chat-6e2cb00008cbf09e556b00f87603797fcaa47e09.tar.bz2 chat-6e2cb00008cbf09e556b00f87603797fcaa47e09.zip |
Depenancy upgrades and movign to dep. (#8630)
Diffstat (limited to 'vendor/github.com/davecgh/go-spew/spew/bypass.go')
-rw-r--r-- | vendor/github.com/davecgh/go-spew/spew/bypass.go | 187 |
1 files changed, 97 insertions, 90 deletions
diff --git a/vendor/github.com/davecgh/go-spew/spew/bypass.go b/vendor/github.com/davecgh/go-spew/spew/bypass.go index 792994785..8a4a6589a 100644 --- a/vendor/github.com/davecgh/go-spew/spew/bypass.go +++ b/vendor/github.com/davecgh/go-spew/spew/bypass.go @@ -16,9 +16,7 @@ // 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. -// Go versions prior to 1.4 are disabled because they use a different layout -// for interfaces which make the implementation of unsafeReflectValue more complex. -// +build !js,!appengine,!safe,!disableunsafe,go1.4 +// +build !js,!appengine,!safe,!disableunsafe package spew @@ -36,49 +34,80 @@ const ( ptrSize = unsafe.Sizeof((*byte)(nil)) ) -type flag uintptr - var ( - // flagRO indicates whether the value field of a reflect.Value - // is read-only. - flagRO flag - - // flagAddr indicates whether the address of the reflect.Value's - // value may be taken. - flagAddr flag + // 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) ) -// flagKindMask holds the bits that make up the kind -// part of the flags field. In all the supported versions, -// it is in the lower 5 bits. -const flagKindMask = flag(0x1f) - -// Different versions of Go have used different -// bit layouts for the flags type. This table -// records the known combinations. -var okFlags = []struct { - ro, addr flag -}{{ - // From Go 1.4 to 1.5 - ro: 1 << 5, - addr: 1 << 7, -}, { - // Up to Go tip. - ro: 1<<5 | 1<<6, - addr: 1 << 8, -}} - -var flagValOffset = func() uintptr { - field, ok := reflect.TypeOf(reflect.Value{}).FieldByName("flag") - if !ok { - panic("reflect.Value has no flag field") +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 } - return field.Offset -}() -// flagField returns a pointer to the flag field of a reflect.Value. -func flagField(v *reflect.Value) *flag { - return (*flag)(unsafe.Pointer(uintptr(unsafe.Pointer(v)) + flagValOffset)) + // 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 @@ -90,56 +119,34 @@ func flagField(v *reflect.Value) *flag { // 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) reflect.Value { - if !v.IsValid() || (v.CanInterface() && v.CanAddr()) { - return v - } - flagFieldPtr := flagField(&v) - *flagFieldPtr &^= flagRO - *flagFieldPtr |= flagAddr - return v -} - -// Sanity checks against future reflect package changes -// to the type or semantics of the Value.flag field. -func init() { - field, ok := reflect.TypeOf(reflect.Value{}).FieldByName("flag") - if !ok { - panic("reflect.Value has no flag field") - } - if field.Type.Kind() != reflect.TypeOf(flag(0)).Kind() { - panic("reflect.Value flag field has changed kind") - } - type t0 int - var t struct { - A t0 - // t0 will have flagEmbedRO set. - t0 - // a will have flagStickyRO set - a t0 +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) + } } - vA := reflect.ValueOf(t).FieldByName("A") - va := reflect.ValueOf(t).FieldByName("a") - vt0 := reflect.ValueOf(t).FieldByName("t0") - - // Infer flagRO from the difference between the flags - // for the (otherwise identical) fields in t. - flagPublic := *flagField(&vA) - flagWithRO := *flagField(&va) | *flagField(&vt0) - flagRO = flagPublic ^ flagWithRO - // Infer flagAddr from the difference between a value - // taken from a pointer and not. - vPtrA := reflect.ValueOf(&t).Elem().FieldByName("A") - flagNoPtr := *flagField(&vA) - flagPtr := *flagField(&vPtrA) - flagAddr = flagNoPtr ^ flagPtr - - // Check that the inferred flags tally with one of the known versions. - for _, f := range okFlags { - if flagRO == f.ro && flagAddr == f.addr { - return - } + pv := reflect.NewAt(vt, upv) + rv = pv + for i := 0; i < indirects; i++ { + rv = rv.Elem() } - panic("reflect.Value read-only flag has changed semantics") + return rv } |