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unmarshal.go
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unmarshal.go
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package codec
import (
"fmt"
"math"
"github.com/polydawn/refmt/shared"
"github.com/polydawn/refmt/tok"
ipld "github.com/ipld/go-ipld-prime"
)
// wishlist: if we could reconstruct the ipld.Path of an error while
// *unwinding* from that error... that'd be nice.
// (trying to build it proactively would waste tons of allocs on the happy path.)
// we can do this; it just requires well-typed errors and a bunch of work.
// Tests for all this are in the ipld.Node impl tests!
// They're effectively doing double duty: testing the builders, too.
// (Is that sensible? Should it be refactored? Not sure; maybe!)
// Unmarshal provides a very general tokens-to-node unmarshalling feature.
// It can handle either cbor or json by being combined with a refmt TokenSink.
//
// The unmarshalled data is fed to the given NodeAssembler, which accumulates it;
// at the end, any error is returned from the Unmarshal method,
// and the user can pick up the finished Node from wherever their assembler has it.
// Typical usage might look like the following:
//
// nb := basicnode.Prototype__Any{}.NewBuilder()
// err := codec.Unmarshal(nb, json.Decoder(reader))
// n := nb.Build()
//
// It is valid for all the data model types except links, which are only
// supported if the nodes are typed and provide additional information
// to clarify how links should be decoded through their type info.
// (The dag-cbor and dag-json formats can be used if links are of CID
// implementation and need to be decoded in a schemafree way.)
func Unmarshal(na ipld.NodeAssembler, tokSrc shared.TokenSource) error {
var tk tok.Token
done, err := tokSrc.Step(&tk)
if err != nil {
return err
}
if done && !tk.Type.IsValue() {
return fmt.Errorf("unexpected eof")
}
return unmarshal(na, tokSrc, &tk)
}
// starts with the first token already primed. Necessary to get recursion
// to flow right without a peek+unpeek system.
func unmarshal(na ipld.NodeAssembler, tokSrc shared.TokenSource, tk *tok.Token) error {
// FUTURE: check for schema.TypedNodeBuilder that's going to parse a Link (they can slurp any token kind they want).
switch tk.Type {
case tok.TMapOpen:
expectLen := tk.Length
allocLen := tk.Length
if tk.Length == -1 {
expectLen = math.MaxInt32
allocLen = 0
}
ma, err := na.BeginMap(int64(allocLen))
if err != nil {
return err
}
observedLen := 0
for {
_, err := tokSrc.Step(tk)
if err != nil {
return err
}
switch tk.Type {
case tok.TMapClose:
if expectLen != math.MaxInt32 && observedLen != expectLen {
return fmt.Errorf("unexpected mapClose before declared length")
}
return ma.Finish()
case tok.TString:
// continue
default:
return fmt.Errorf("unexpected %s token while expecting map key", tk.Type)
}
observedLen++
if observedLen > expectLen {
return fmt.Errorf("unexpected continuation of map elements beyond declared length")
}
mva, err := ma.AssembleEntry(tk.Str)
if err != nil { // return in error if the key was rejected
return err
}
err = Unmarshal(mva, tokSrc)
if err != nil { // return in error if some part of the recursion errored
return err
}
}
case tok.TMapClose:
return fmt.Errorf("unexpected mapClose token")
case tok.TArrOpen:
expectLen := tk.Length
allocLen := tk.Length
if tk.Length == -1 {
expectLen = math.MaxInt32
allocLen = 0
}
la, err := na.BeginList(int64(allocLen))
if err != nil {
return err
}
observedLen := 0
for {
_, err := tokSrc.Step(tk)
if err != nil {
return err
}
switch tk.Type {
case tok.TArrClose:
if expectLen != math.MaxInt32 && observedLen != expectLen {
return fmt.Errorf("unexpected arrClose before declared length")
}
return la.Finish()
default:
observedLen++
if observedLen > expectLen {
return fmt.Errorf("unexpected continuation of array elements beyond declared length")
}
err := unmarshal(la.AssembleValue(), tokSrc, tk)
if err != nil { // return in error if some part of the recursion errored
return err
}
}
}
case tok.TArrClose:
return fmt.Errorf("unexpected arrClose token")
case tok.TNull:
return na.AssignNull()
case tok.TString:
return na.AssignString(tk.Str)
case tok.TBytes:
return na.AssignBytes(tk.Bytes)
case tok.TBool:
return na.AssignBool(tk.Bool)
case tok.TInt:
return na.AssignInt(tk.Int)
case tok.TUint:
return na.AssignInt(int64(tk.Uint)) // FIXME overflow check
case tok.TFloat64:
return na.AssignFloat(tk.Float64)
default:
panic("unreachable")
}
}