mirror of
https://github.com/golang/go.git
synced 2025-12-08 06:10:04 +00:00
reflect: implement StructOf
This change exposes a facility to create new struct types from a slice of
reflect.StructFields.
- reflect: first stab at implementing StructOf
- reflect: tests for StructOf
StructOf creates new struct types in the form of structTypeWithMethods
to accomodate the GC (especially the uncommonType.methods slice field.)
Creating struct types with embedded interfaces with unexported methods
is not supported yet and will panic.
Creating struct types with non-ASCII field names or types is not yet
supported (see #15064.)
Binaries' sizes for linux_amd64:
old=tip (0104a31)
old bytes new bytes delta
bin/go 9911336 9915456 +0.04%
reflect 781704 830048 +6.18%
Updates #5748.
Updates #15064.
Change-Id: I3b8fd4fadd6ce3b1b922e284f0ae72a3a8e3ce44
Reviewed-on: https://go-review.googlesource.com/9251
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: David Crawshaw <crawshaw@golang.org>
This commit is contained in:
Sebastien Binet
David Crawshaw
parent
014f3e1e09
commit
633ab7426a
3 changed files with 1043 additions and 7 deletions
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@ -484,6 +484,46 @@ func round(n, a uintptr) uintptr {
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return (n + a - 1) &^ (a - 1)
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}
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func newName(n, tag, pkgPath string, exported bool) name {
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if len(n) > 1<<16-1 {
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panic("reflect.nameFrom: name too long: " + n)
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}
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if len(tag) > 1<<16-1 {
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panic("reflect.nameFrom: tag too long: " + tag)
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}
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var bits byte
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l := 1 + 2 + len(n)
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if exported {
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bits |= 1 << 0
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}
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if len(tag) > 0 {
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l += 2 + len(tag)
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bits |= 1 << 1
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}
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if pkgPath != "" {
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bits |= 1 << 2
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}
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b := make([]byte, l)
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b[0] = bits
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b[1] = uint8(len(n) >> 8)
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b[2] = uint8(len(n))
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copy(b[3:], n)
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if len(tag) > 0 {
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tb := b[3+len(n):]
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tb[0] = uint8(len(tag) >> 8)
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tb[1] = uint8(len(tag))
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copy(tb[2:], tag)
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}
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if pkgPath != "" {
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panic("reflect: creating a name with a package path is not supported")
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}
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return name{bytes: &b[0]}
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}
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/*
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* The compiler knows the exact layout of all the data structures above.
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* The compiler does not know about the data structures and methods below.
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@ -562,11 +602,7 @@ func (t *rtype) uncommon() *uncommonType {
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}
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switch t.Kind() {
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case Struct:
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type u struct {
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structType
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u uncommonType
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}
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return &(*u)(unsafe.Pointer(t)).u
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return &(*structTypeWithMethods)(unsafe.Pointer(t)).u
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case Ptr:
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type u struct {
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ptrType
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@ -1572,7 +1608,7 @@ func typesByString(s string) []*rtype {
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return ret
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}
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// The lookupCache caches ChanOf, MapOf, and SliceOf lookups.
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// The lookupCache caches ArrayOf, ChanOf, MapOf and SliceOf lookups.
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var lookupCache struct {
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sync.RWMutex
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m map[cacheKey]*rtype
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@ -2112,6 +2148,431 @@ func SliceOf(t Type) Type {
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return cachePut(ckey, &slice.rtype)
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}
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// structTypeWithMethods is a structType created at runtime with StructOf.
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// It is needed to pin the []method slice from its associated uncommonType struct.
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// Keep in sync with the memory layout of structType.
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type structTypeWithMethods struct {
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structType
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u uncommonType
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}
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// The structLookupCache caches StructOf lookups.
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// StructOf does not share the common lookupCache since we need to pin
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// the *structType and its associated *uncommonType (especially the
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// []method slice field of that uncommonType.)
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var structLookupCache struct {
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sync.RWMutex
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m map[uint32][]*structTypeWithMethods // keyed by hash calculated in StructOf
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}
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// StructOf returns the struct type containing fields.
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// The Offset and Index fields are ignored and computed as they would be
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// by the compiler.
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//
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// StructOf does not support creating structs with UTF-8 field names or
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// UTF-8 (embedded) type names.
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// This limitation may be lifted eventually.
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func StructOf(fields []StructField) Type {
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var (
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hash = fnv1(0, []byte("struct {")...)
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size uintptr
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typalign uint8
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comparable = true
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hashable = true
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typ = new(structTypeWithMethods)
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fs = make([]structField, len(fields))
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repr = make([]byte, 0, 64)
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fset = map[string]struct{}{} // fields' names
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hasPtr = false // records whether at least one struct-field is a pointer
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hasGCProg = false // records whether a struct-field type has a GCProg
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)
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repr = append(repr, "struct {"...)
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for i, field := range fields {
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if field.Type == nil {
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panic("reflect.StructOf: field " + strconv.Itoa(i) + " has no type")
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}
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f := runtimeStructField(field)
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ft := f.typ
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if ft.kind&kindGCProg != 0 {
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hasGCProg = true
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}
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if ft.pointers() {
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hasPtr = true
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}
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name := ""
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// Update string and hash
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if f.name.nameLen() > 0 {
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hash = fnv1(hash, []byte(f.name.name())...)
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repr = append(repr, (" " + f.name.name())...)
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name = f.name.name()
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} else {
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// Embedded field
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if f.typ.Kind() == Ptr {
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// Embedded ** and *interface{} are illegal
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elem := ft.Elem()
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if k := elem.Kind(); k == Ptr || k == Interface {
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panic("reflect.StructOf: illegal anonymous field type " + ft.string)
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}
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name = elem.String()
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} else {
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name = ft.string
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}
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// TODO(sbinet) check for syntactically impossible type names?
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switch f.typ.Kind() {
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case Interface:
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ift := (*interfaceType)(unsafe.Pointer(ft))
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for im, m := range ift.methods {
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if m.name.pkgPath() != nil {
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// TODO(sbinet)
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panic("reflect: embedded interface with unexported method(s) not implemented")
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}
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var (
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ifield = i
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imethod = im
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ifn Value
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tfn Value
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)
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if ft.kind&kindDirectIface != 0 {
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tfn = MakeFunc(m.typ, func(in []Value) []Value {
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var args []Value
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var recv = in[0]
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if len(in) > 1 {
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args = in[1:]
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}
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return recv.Field(ifield).Method(imethod).Call(args)
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})
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ifn = MakeFunc(m.typ, func(in []Value) []Value {
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var args []Value
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var recv = in[0]
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if len(in) > 1 {
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args = in[1:]
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}
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return recv.Field(ifield).Method(imethod).Call(args)
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})
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} else {
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tfn = MakeFunc(m.typ, func(in []Value) []Value {
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var args []Value
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var recv = in[0]
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if len(in) > 1 {
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args = in[1:]
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}
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return recv.Field(ifield).Method(imethod).Call(args)
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})
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ifn = MakeFunc(m.typ, func(in []Value) []Value {
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var args []Value
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var recv = Indirect(in[0])
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if len(in) > 1 {
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args = in[1:]
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}
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return recv.Field(ifield).Method(imethod).Call(args)
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})
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}
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typ.u.methods = append(
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typ.u.methods,
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method{
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name: m.name,
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mtyp: m.typ,
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ifn: unsafe.Pointer(&ifn),
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tfn: unsafe.Pointer(&tfn),
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},
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)
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}
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case Ptr:
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ptr := (*ptrType)(unsafe.Pointer(ft))
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if unt := ptr.uncommon(); unt != nil {
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for _, m := range unt.methods {
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if m.name.pkgPath() != nil {
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// TODO(sbinet)
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panic("reflect: embedded interface with unexported method(s) not implemented")
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}
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typ.u.methods = append(typ.u.methods, m)
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}
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}
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if unt := ptr.elem.uncommon(); unt != nil {
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for _, m := range unt.methods {
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if m.name.pkgPath() != nil {
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// TODO(sbinet)
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panic("reflect: embedded interface with unexported method(s) not implemented")
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}
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typ.u.methods = append(typ.u.methods, m)
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}
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}
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default:
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if unt := ft.uncommon(); unt != nil {
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for _, m := range unt.methods {
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if m.name.pkgPath() != nil {
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// TODO(sbinet)
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panic("reflect: embedded interface with unexported method(s) not implemented")
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}
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typ.u.methods = append(typ.u.methods, m)
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}
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}
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}
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}
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if _, dup := fset[name]; dup {
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panic("reflect.StructOf: duplicate field " + name)
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}
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fset[name] = struct{}{}
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hash = fnv1(hash, byte(ft.hash>>24), byte(ft.hash>>16), byte(ft.hash>>8), byte(ft.hash))
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repr = append(repr, (" " + ft.string)...)
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if f.name.tagLen() > 0 {
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hash = fnv1(hash, []byte(f.name.tag())...)
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repr = append(repr, (" " + strconv.Quote(f.name.tag()))...)
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}
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if i < len(fields)-1 {
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repr = append(repr, ';')
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}
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comparable = comparable && (ft.alg.equal != nil)
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hashable = hashable && (ft.alg.hash != nil)
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f.offset = align(size, uintptr(ft.align))
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if ft.align > typalign {
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typalign = ft.align
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}
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size = f.offset + ft.size
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fs[i] = f
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}
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if len(fs) > 0 {
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repr = append(repr, ' ')
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}
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repr = append(repr, '}')
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hash = fnv1(hash, '}')
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str := string(repr)
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// Round the size up to be a multiple of the alignment.
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size = align(size, uintptr(typalign))
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// Make the struct type.
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var istruct interface{} = struct{}{}
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prototype := *(**structType)(unsafe.Pointer(&istruct))
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typ.structType = *prototype
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typ.structType.fields = fs
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// Look in cache
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structLookupCache.RLock()
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for _, t := range structLookupCache.m[hash] {
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if haveIdenticalUnderlyingType(&typ.rtype, &t.rtype) {
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structLookupCache.RUnlock()
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return &t.rtype
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}
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}
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structLookupCache.RUnlock()
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// not in cache, lock and retry
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structLookupCache.Lock()
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defer structLookupCache.Unlock()
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if structLookupCache.m == nil {
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structLookupCache.m = make(map[uint32][]*structTypeWithMethods)
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}
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for _, t := range structLookupCache.m[hash] {
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if haveIdenticalUnderlyingType(&typ.rtype, &t.rtype) {
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return &t.rtype
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}
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}
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// Look in known types.
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for _, t := range typesByString(str) {
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if haveIdenticalUnderlyingType(&typ.rtype, t) {
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// even if 't' wasn't a structType with methods, we should be ok
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// as the 'u uncommonType' field won't be accessed except when
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// tflag&tflagUncommon is set.
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tt := (*structTypeWithMethods)(unsafe.Pointer(t))
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structLookupCache.m[hash] = append(structLookupCache.m[hash], tt)
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return &tt.rtype
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}
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}
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typ.string = str
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typ.hash = hash
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typ.size = size
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typ.align = typalign
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typ.fieldAlign = typalign
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if len(typ.u.methods) > 0 {
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typ.tflag |= tflagUncommon
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}
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if !hasPtr {
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typ.kind |= kindNoPointers
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} else {
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typ.kind &^= kindNoPointers
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}
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if hasGCProg {
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lastPtrField := 0
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for i, ft := range fs {
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if ft.typ.pointers() {
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lastPtrField = i
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}
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}
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prog := []byte{0, 0, 0, 0} // will be length of prog
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for i, ft := range fs {
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if i > lastPtrField {
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// gcprog should not include anything for any field after
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// the last field that contains pointer data
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break
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}
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// FIXME(sbinet) handle padding, fields smaller than a word
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elemGC := (*[1 << 30]byte)(unsafe.Pointer(ft.typ.gcdata))[:]
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elemPtrs := ft.typ.ptrdata / ptrSize
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switch {
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case ft.typ.kind&kindGCProg == 0 && ft.typ.ptrdata != 0:
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// Element is small with pointer mask; use as literal bits.
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mask := elemGC
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// Emit 120-bit chunks of full bytes (max is 127 but we avoid using partial bytes).
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var n uintptr
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for n := elemPtrs; n > 120; n -= 120 {
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prog = append(prog, 120)
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prog = append(prog, mask[:15]...)
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mask = mask[15:]
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}
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prog = append(prog, byte(n))
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prog = append(prog, mask[:(n+7)/8]...)
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case ft.typ.kind&kindGCProg != 0:
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// Element has GC program; emit one element.
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elemProg := elemGC[4 : 4+*(*uint32)(unsafe.Pointer(&elemGC[0]))-1]
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prog = append(prog, elemProg...)
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}
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// Pad from ptrdata to size.
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elemWords := ft.typ.size / ptrSize
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if elemPtrs < elemWords {
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// Emit literal 0 bit, then repeat as needed.
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prog = append(prog, 0x01, 0x00)
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if elemPtrs+1 < elemWords {
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prog = append(prog, 0x81)
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prog = appendVarint(prog, elemWords-elemPtrs-1)
|
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}
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}
|
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}
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*(*uint32)(unsafe.Pointer(&prog[0])) = uint32(len(prog) - 4)
|
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typ.kind |= kindGCProg
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typ.gcdata = &prog[0]
|
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} else {
|
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typ.kind &^= kindGCProg
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bv := new(bitVector)
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addTypeBits(bv, 0, typ.common())
|
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if len(bv.data) > 0 {
|
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typ.gcdata = &bv.data[0]
|
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}
|
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}
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typ.ptrdata = typeptrdata(typ.common())
|
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typ.alg = new(typeAlg)
|
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if hashable {
|
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typ.alg.hash = func(p unsafe.Pointer, seed uintptr) uintptr {
|
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o := seed
|
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for _, ft := range typ.fields {
|
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pi := unsafe.Pointer(uintptr(p) + ft.offset)
|
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o = ft.typ.alg.hash(pi, o)
|
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}
|
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return o
|
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}
|
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}
|
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|
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if comparable {
|
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typ.alg.equal = func(p, q unsafe.Pointer) bool {
|
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for _, ft := range typ.fields {
|
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pi := unsafe.Pointer(uintptr(p) + ft.offset)
|
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qi := unsafe.Pointer(uintptr(q) + ft.offset)
|
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if !ft.typ.alg.equal(pi, qi) {
|
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return false
|
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}
|
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}
|
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return true
|
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}
|
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}
|
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|
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switch {
|
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case len(fs) == 1 && !ifaceIndir(fs[0].typ):
|
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// structs of 1 direct iface type can be direct
|
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typ.kind |= kindDirectIface
|
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default:
|
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typ.kind &^= kindDirectIface
|
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}
|
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|
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structLookupCache.m[hash] = append(structLookupCache.m[hash], typ)
|
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return &typ.rtype
|
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}
|
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|
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func runtimeStructField(field StructField) structField {
|
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exported := field.PkgPath == ""
|
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if field.Name == "" {
|
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t := field.Type
|
||||
if t.Kind() == Ptr {
|
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t = t.Elem()
|
||||
}
|
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exported = isExported(t.Name())
|
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} else if exported {
|
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b0 := field.Name[0]
|
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if ('a' <= b0 && b0 <= 'z') || b0 == '_' {
|
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panic("reflect.StructOf: field \"" + field.Name + "\" is unexported but has no PkgPath")
|
||||
}
|
||||
}
|
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|
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return structField{
|
||||
name: newName(field.Name, string(field.Tag), field.PkgPath, exported),
|
||||
typ: field.Type.common(),
|
||||
offset: 0,
|
||||
}
|
||||
}
|
||||
|
||||
func isExported(s string) bool {
|
||||
if s == "" {
|
||||
return false
|
||||
}
|
||||
// FIXME(sbinet): handle utf8/runes (see https://golang.org/issue/15064)
|
||||
// TODO: turn rtype.string into a reflect.name type, and put the exported
|
||||
// bit on there which can be checked here with field.Type.(*rtype).string.isExported()
|
||||
// When done, remove the documented limitation of StructOf.
|
||||
r := s[0]
|
||||
switch {
|
||||
case 'A' <= r && r <= 'Z':
|
||||
return true
|
||||
case r == '_' || 'a' <= r && r <= 'z':
|
||||
return false
|
||||
default:
|
||||
panic("reflect.StructOf: creating a struct with UTF-8 fields is not supported yet")
|
||||
}
|
||||
}
|
||||
|
||||
// typeptrdata returns the length in bytes of the prefix of t
|
||||
// containing pointer data. Anything after this offset is scalar data.
|
||||
// keep in sync with ../cmd/compile/internal/gc/reflect.go
|
||||
func typeptrdata(t *rtype) uintptr {
|
||||
if !t.pointers() {
|
||||
return 0
|
||||
}
|
||||
switch t.Kind() {
|
||||
case Struct:
|
||||
st := (*structType)(unsafe.Pointer(t))
|
||||
// find the last field that has pointers.
|
||||
field := 0
|
||||
for i := range st.fields {
|
||||
ft := st.fields[i].typ
|
||||
if ft.pointers() {
|
||||
field = i
|
||||
}
|
||||
}
|
||||
f := st.fields[field]
|
||||
return f.offset + f.typ.ptrdata
|
||||
|
||||
default:
|
||||
panic("reflect.typeptrdata: unexpected type, " + t.String())
|
||||
}
|
||||
return 0
|
||||
}
|
||||
|
||||
// See cmd/compile/internal/gc/reflect.go for derivation of constant.
|
||||
const maxPtrmaskBytes = 2048
|
||||
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue