/
vm_serialization.go
262 lines (224 loc) · 6.88 KB
/
vm_serialization.go
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/******************************************************************************\
* The Romualdo Language *
* *
* Copyright 2020-2023 Leandro Motta Barros *
* Licensed under the MIT license (see LICENSE.txt for details) *
\******************************************************************************/
package vm
import (
"hash/crc32"
"io"
"github.com/stackedboxes/romualdo/pkg/errs"
"github.com/stackedboxes/romualdo/pkg/romutil"
)
const (
// savedStateVersion is the current version of a Romualdo saved state.
savedStateVersion uint32 = 0
)
// savedStateMagic is the "magic number" identifying a Romualdo VM saved state.
// It is comprised of the "RmldSav" string followed by a SUB character (which in
// times long gone used to represent a "soft end-of-file").
var savedStateMagic = []byte{0x52, 0x6D, 0x6C, 0x64, 0x53, 0x61, 0x76, 0x1A}
// Serialize serializes the VM state to the given io.Writer.
func (vm *VM) Serialize(w io.Writer) errs.Error {
err := vm.serializeHeader(w)
if err != nil {
return err
}
crc32, err := vm.serializePayload(w)
if err != nil {
return err
}
err = vm.serializeFooter(w, crc32)
return err
}
// serializedHeader writes the header of a VM saved state to the given
// io.Writer.
func (vm *VM) serializeHeader(w io.Writer) errs.Error {
_, plainErr := w.Write(savedStateMagic)
if plainErr != nil {
return errs.NewRomualdoTool("serializing VM state magic: %v", plainErr)
}
err := romutil.SerializeU32(w, savedStateVersion)
return err
}
// serializePayload writes the payload of a VM saved state to the given
// io.Writer. In other words, this the function doing the actual serialization.
// Returns the CRC32 of the data written to w, and an error.
func (vm *VM) serializePayload(w io.Writer) (uint32, errs.Error) {
crc := crc32.NewIEEE()
mw := io.MultiWriter(w, crc)
// Swid and swov
err := romutil.SerializeString(mw, vm.Swid)
if err != nil {
return 0, err
}
err = romutil.SerializeI32(mw, vm.Swov)
if err != nil {
return 0, err
}
// VM State
err = romutil.SerializeU32(mw, uint32(vm.State))
if err != nil {
return 0, err
}
// Options
err = romutil.SerializeString(mw, vm.Options)
if err != nil {
return 0, err
}
// Stack
err = vm.stack.Serialize(mw)
if err != nil {
return 0, err
}
// Frames
err = romutil.SerializeU32(mw, uint32(len(vm.frames)))
if err != nil {
return 0, err
}
for _, f := range vm.frames {
err = f.Serialize(mw)
if err != nil {
return 0, err
}
}
// Voilà!
return crc.Sum32(), nil
}
// serializeFooter writes the footer of a VM saved state to the given io.Writer.
func (vm *VM) serializeFooter(w io.Writer, crc32 uint32) errs.Error {
err := romutil.SerializeU32(w, crc32)
return err
}
// Deserialize deserializes a VM state from the given io.Reader.
func (vm *VM) Deserialize(r io.Reader) errs.Error {
err := vm.deserializeHeader(r)
if err != nil {
return err
}
crc32, err := vm.deserializePayload(r)
if err != nil {
return err
}
err = vm.deserializeFooter(r, crc32)
if err != nil {
return err
}
// Post-deserialization adjustments
vm.frame = nil
if len(vm.frames) > 0 {
vm.frame = vm.frames[len(vm.frames)-1]
}
vm.outBuffer.Reset()
return nil
}
// deserializeHeader reads and checks the header of a VM saved state from the
// given io.Reader. If everything is OK, it returns nil, otherwise it returns an
// error.
func (vm *VM) deserializeHeader(r io.Reader) errs.Error {
// Magic
readMagic := make([]byte, len(savedStateMagic))
_, err := io.ReadFull(r, readMagic)
if err != nil {
// TODO: This isn't really a Romualdo tool error. But also not really a
// Runtime error. And I am not sure I want to create a brand new error
// type just for this. Think about it. And the same for other cases in
// this file. *And*, all generic serialization stuff in romutil that
// gets used here indirectly! (Maybe those should return normal Go
// errors? So that callers need to add more context in an errs.Error?)
return errs.NewRomualdoTool("deserializing VM state header magic: %v", err)
}
for i, b := range readMagic {
if b != savedStateMagic[i] {
// TODO: Could be friendlier here, by comparing readMagic with other
// Romualdo magic numbers and reporting a more meaningful error.
return errs.NewRomualdoTool("invalid VM state magic number")
}
}
// Version
readVersion, err := romutil.DeserializeU32(r)
if err != nil {
return errs.NewRomualdoTool("deserializing VM state header version: %v", err)
}
if readVersion != savedStateVersion {
return errs.NewRomualdoTool("unsupported VM state version: %v", readVersion)
}
// Header is OK
return nil
}
// deserializePayload reads the payload of a VM saved state from the given
// io.Reader. In other words, this the function doing the actual
// deserialization. Returns the CRC32 of the data read from r, and an error. It
// updates the VM saved state with the deserialized data as it goes.
func (vm *VM) deserializePayload(r io.Reader) (uint32, errs.Error) {
crcSummer := crc32.NewIEEE()
tr := io.TeeReader(r, crcSummer)
// Swid and swov
swid, err := romutil.DeserializeString(tr)
if err != nil {
return 0, err
}
if swid != vm.Swid {
return 0, errs.NewRomualdoTool("saved state swid '%v' mismatches VM swid '%v'", swid, vm.Swid)
}
vm.Swid = swid
swov, err := romutil.DeserializeI32(tr)
if err != nil {
return 0, err
}
// TODO: Actually... negative versions are not guaranteed to be compatible
// with themselves. They are dev versions, the code is changing all the
// time.
if romutil.Abs(swov) > romutil.Abs(vm.Swov) {
return 0, errs.NewRomualdoTool("saved state swov %v is greater than VM swov %v", swov, vm.Swov)
}
vm.Swov = swov
// VM State
vmState, err := romutil.DeserializeU32(tr)
if err != nil {
return 0, err
}
vm.State = State(vmState)
// Options
options, err := romutil.DeserializeString(tr)
if err != nil {
return 0, err
}
vm.Options = options
// Stack
stack, err := DeserializeStack(tr)
if err != nil {
return 0, err
}
vm.stack = stack
// Frames
frameCount, err := romutil.DeserializeU32(tr)
if err != nil {
return 0, err
}
frames := make([]*callFrame, frameCount)
for i := 0; i < int(frameCount); i++ {
frame, err := DeserializeCallFrame(tr, vm.stack)
if err != nil {
return 0, err
}
frames = append(frames, frame)
}
vm.frames = frames
// Voilà!
return crcSummer.Sum32(), nil
}
// deserializeFooter reads and checks the footer of a CompiledStoryworld from
// the given io.Reader. You must pass the CRC32 of the payload previously read
// from r.
func (vm *VM) deserializeFooter(r io.Reader, crc32 uint32) errs.Error {
readCRC32, err := romutil.DeserializeU32(r)
if err != nil {
return err
}
if readCRC32 != crc32 {
return errs.NewRomualdoTool("compiled storyworld CRC32 mismatch")
}
return nil
}