cloudflared-mirror/vendor/zombiezen.com/go/capnproto2/capn.go

428 lines
11 KiB
Go

package capnp
import (
"encoding/binary"
"errors"
)
// A SegmentID is a numeric identifier for a Segment.
type SegmentID uint32
// A Segment is an allocation arena for Cap'n Proto objects.
// It is part of a Message, which can contain other segments that
// reference each other.
type Segment struct {
msg *Message
id SegmentID
data []byte
}
// Message returns the message that contains s.
func (s *Segment) Message() *Message {
return s.msg
}
// ID returns the segment's ID.
func (s *Segment) ID() SegmentID {
return s.id
}
// Data returns the raw byte slice for the segment.
func (s *Segment) Data() []byte {
return s.data
}
func (s *Segment) inBounds(addr Address) bool {
return addr < Address(len(s.data))
}
func (s *Segment) regionInBounds(base Address, sz Size) bool {
end, ok := base.addSize(sz)
if !ok {
return false
}
return end <= Address(len(s.data))
}
// slice returns the segment of data from base to base+sz.
func (s *Segment) slice(base Address, sz Size) []byte {
// Bounds check should have happened before calling slice.
return s.data[base : base+Address(sz)]
}
func (s *Segment) readUint8(addr Address) uint8 {
return s.slice(addr, 1)[0]
}
func (s *Segment) readUint16(addr Address) uint16 {
return binary.LittleEndian.Uint16(s.slice(addr, 2))
}
func (s *Segment) readUint32(addr Address) uint32 {
return binary.LittleEndian.Uint32(s.slice(addr, 4))
}
func (s *Segment) readUint64(addr Address) uint64 {
return binary.LittleEndian.Uint64(s.slice(addr, 8))
}
func (s *Segment) readRawPointer(addr Address) rawPointer {
return rawPointer(s.readUint64(addr))
}
func (s *Segment) writeUint8(addr Address, val uint8) {
s.slice(addr, 1)[0] = val
}
func (s *Segment) writeUint16(addr Address, val uint16) {
binary.LittleEndian.PutUint16(s.slice(addr, 2), val)
}
func (s *Segment) writeUint32(addr Address, val uint32) {
binary.LittleEndian.PutUint32(s.slice(addr, 4), val)
}
func (s *Segment) writeUint64(addr Address, val uint64) {
binary.LittleEndian.PutUint64(s.slice(addr, 8), val)
}
func (s *Segment) writeRawPointer(addr Address, val rawPointer) {
s.writeUint64(addr, uint64(val))
}
// root returns a 1-element pointer list that references the first word
// in the segment. This only makes sense to call on the first segment
// in a message.
func (s *Segment) root() PointerList {
sz := ObjectSize{PointerCount: 1}
if !s.regionInBounds(0, sz.totalSize()) {
return PointerList{}
}
return PointerList{List{
seg: s,
length: 1,
size: sz,
depthLimit: s.msg.depthLimit(),
}}
}
func (s *Segment) lookupSegment(id SegmentID) (*Segment, error) {
if s.id == id {
return s, nil
}
return s.msg.Segment(id)
}
func (s *Segment) readPtr(paddr Address, depthLimit uint) (ptr Ptr, err error) {
s, base, val, err := s.resolveFarPointer(paddr)
if err != nil {
return Ptr{}, err
}
if val == 0 {
return Ptr{}, nil
}
if depthLimit == 0 {
return Ptr{}, errDepthLimit
}
switch val.pointerType() {
case structPointer:
sp, err := s.readStructPtr(base, val)
if err != nil {
return Ptr{}, err
}
if !s.msg.ReadLimiter().canRead(sp.readSize()) {
return Ptr{}, errReadLimit
}
sp.depthLimit = depthLimit - 1
return sp.ToPtr(), nil
case listPointer:
lp, err := s.readListPtr(base, val)
if err != nil {
return Ptr{}, err
}
if !s.msg.ReadLimiter().canRead(lp.readSize()) {
return Ptr{}, errReadLimit
}
lp.depthLimit = depthLimit - 1
return lp.ToPtr(), nil
case otherPointer:
if val.otherPointerType() != 0 {
return Ptr{}, errOtherPointer
}
return Interface{
seg: s,
cap: val.capabilityIndex(),
}.ToPtr(), nil
default:
// Only other types are far pointers.
return Ptr{}, errBadLandingPad
}
}
func (s *Segment) readStructPtr(base Address, val rawPointer) (Struct, error) {
addr, ok := val.offset().resolve(base)
if !ok {
return Struct{}, errPointerAddress
}
sz := val.structSize()
if !s.regionInBounds(addr, sz.totalSize()) {
return Struct{}, errPointerAddress
}
return Struct{
seg: s,
off: addr,
size: sz,
}, nil
}
func (s *Segment) readListPtr(base Address, val rawPointer) (List, error) {
addr, ok := val.offset().resolve(base)
if !ok {
return List{}, errPointerAddress
}
lsize, ok := val.totalListSize()
if !ok {
return List{}, errOverflow
}
if !s.regionInBounds(addr, lsize) {
return List{}, errPointerAddress
}
lt := val.listType()
if lt == compositeList {
hdr := s.readRawPointer(addr)
var ok bool
addr, ok = addr.addSize(wordSize)
if !ok {
return List{}, errOverflow
}
if hdr.pointerType() != structPointer {
return List{}, errBadTag
}
sz := hdr.structSize()
n := int32(hdr.offset())
// TODO(light): check that this has the same end address
if tsize, ok := sz.totalSize().times(n); !ok {
return List{}, errOverflow
} else if !s.regionInBounds(addr, tsize) {
return List{}, errPointerAddress
}
return List{
seg: s,
size: sz,
off: addr,
length: n,
flags: isCompositeList,
}, nil
}
if lt == bit1List {
return List{
seg: s,
off: addr,
length: val.numListElements(),
flags: isBitList,
}, nil
}
return List{
seg: s,
size: val.elementSize(),
off: addr,
length: val.numListElements(),
}, nil
}
func (s *Segment) resolveFarPointer(paddr Address) (dst *Segment, base Address, resolved rawPointer, err error) {
// Encoding details at https://capnproto.org/encoding.html#inter-segment-pointers
val := s.readRawPointer(paddr)
switch val.pointerType() {
case doubleFarPointer:
padSeg, err := s.lookupSegment(val.farSegment())
if err != nil {
return nil, 0, 0, err
}
padAddr := val.farAddress()
if !padSeg.regionInBounds(padAddr, wordSize*2) {
return nil, 0, 0, errPointerAddress
}
far := padSeg.readRawPointer(padAddr)
if far.pointerType() != farPointer {
return nil, 0, 0, errBadLandingPad
}
tagAddr, ok := padAddr.addSize(wordSize)
if !ok {
return nil, 0, 0, errOverflow
}
tag := padSeg.readRawPointer(tagAddr)
if pt := tag.pointerType(); (pt != structPointer && pt != listPointer) || tag.offset() != 0 {
return nil, 0, 0, errBadLandingPad
}
if dst, err = s.lookupSegment(far.farSegment()); err != nil {
return nil, 0, 0, err
}
return dst, 0, landingPadNearPointer(far, tag), nil
case farPointer:
var err error
dst, err = s.lookupSegment(val.farSegment())
if err != nil {
return nil, 0, 0, err
}
padAddr := val.farAddress()
if !dst.regionInBounds(padAddr, wordSize) {
return nil, 0, 0, errPointerAddress
}
var ok bool
base, ok = padAddr.addSize(wordSize)
if !ok {
return nil, 0, 0, errOverflow
}
return dst, base, dst.readRawPointer(padAddr), nil
default:
var ok bool
base, ok = paddr.addSize(wordSize)
if !ok {
return nil, 0, 0, errOverflow
}
return s, base, val, nil
}
}
func (s *Segment) writePtr(off Address, src Ptr, forceCopy bool) error {
if !src.IsValid() {
s.writeRawPointer(off, 0)
return nil
}
// Copy src, if needed, and process pointers where placement is
// irrelevant (capabilities and zero-sized structs).
var srcAddr Address
var srcRaw rawPointer
switch src.flags.ptrType() {
case structPtrType:
st := src.Struct()
if st.size.isZero() {
// Zero-sized structs should always be encoded with offset -1 in
// order to avoid conflating with null. No allocation needed.
s.writeRawPointer(off, rawStructPointer(-1, ObjectSize{}))
return nil
}
if forceCopy || src.seg.msg != s.msg || st.flags&isListMember != 0 {
newSeg, newAddr, err := alloc(s, st.size.totalSize())
if err != nil {
return err
}
dst := Struct{
seg: newSeg,
off: newAddr,
size: st.size,
depthLimit: maxDepth,
// clear flags
}
if err := copyStruct(dst, st); err != nil {
return err
}
st = dst
src = dst.ToPtr()
}
srcAddr = st.off
srcRaw = rawStructPointer(0, st.size)
case listPtrType:
l := src.List()
if forceCopy || src.seg.msg != s.msg {
sz := l.allocSize()
newSeg, newAddr, err := alloc(s, sz)
if err != nil {
return err
}
dst := List{
seg: newSeg,
off: newAddr,
length: l.length,
size: l.size,
flags: l.flags,
depthLimit: maxDepth,
}
if dst.flags&isCompositeList != 0 {
// Copy tag word
newSeg.writeRawPointer(newAddr, l.seg.readRawPointer(l.off-Address(wordSize)))
var ok bool
dst.off, ok = dst.off.addSize(wordSize)
if !ok {
return errOverflow
}
sz -= wordSize
}
if dst.flags&isBitList != 0 || dst.size.PointerCount == 0 {
end, _ := l.off.addSize(sz) // list was already validated
copy(newSeg.data[dst.off:], l.seg.data[l.off:end])
} else {
for i := 0; i < l.Len(); i++ {
err := copyStruct(dst.Struct(i), l.Struct(i))
if err != nil {
return err
}
}
}
l = dst
src = dst.ToPtr()
}
srcAddr = l.off
if l.flags&isCompositeList != 0 {
srcAddr -= Address(wordSize)
}
srcRaw = l.raw()
case interfacePtrType:
i := src.Interface()
if src.seg.msg != s.msg {
c := s.msg.AddCap(i.Client())
i = NewInterface(s, c)
}
s.writeRawPointer(off, i.value(off))
return nil
default:
panic("unreachable")
}
switch {
case src.seg == s:
// Common case: src is in same segment as pointer.
// Use a near pointer.
s.writeRawPointer(off, srcRaw.withOffset(nearPointerOffset(off, srcAddr)))
return nil
case hasCapacity(src.seg.data, wordSize):
// Enough room adjacent to src to write a far pointer landing pad.
_, padAddr, _ := alloc(src.seg, wordSize)
src.seg.writeRawPointer(padAddr, srcRaw.withOffset(nearPointerOffset(padAddr, srcAddr)))
s.writeRawPointer(off, rawFarPointer(src.seg.id, padAddr))
return nil
default:
// Not enough room for a landing pad, need to use a double-far pointer.
padSeg, padAddr, err := alloc(s, wordSize*2)
if err != nil {
return err
}
padSeg.writeRawPointer(padAddr, rawFarPointer(src.seg.id, srcAddr))
padSeg.writeRawPointer(padAddr+Address(wordSize), srcRaw)
s.writeRawPointer(off, rawDoubleFarPointer(padSeg.id, padAddr))
return nil
}
}
var (
errPointerAddress = errors.New("capnp: invalid pointer address")
errBadLandingPad = errors.New("capnp: invalid far pointer landing pad")
errBadTag = errors.New("capnp: invalid tag word")
errOtherPointer = errors.New("capnp: unknown pointer type")
errObjectSize = errors.New("capnp: invalid object size")
errElementSize = errors.New("capnp: mismatched list element size")
errReadLimit = errors.New("capnp: read traversal limit reached")
errDepthLimit = errors.New("capnp: depth limit reached")
)
var (
errOverflow = errors.New("capnp: address or size overflow")
errOutOfBounds = errors.New("capnp: address out of bounds")
errCopyDepth = errors.New("capnp: copy depth too large")
errOverlap = errors.New("capnp: overlapping data on copy")
errListSize = errors.New("capnp: invalid list size")
)