Documentation
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Overview ¶
Legacy (v2) AMT support.
Filecoin's block message AMTs (MsgMeta.BlsMessages / SecpkMessages) and the per-tipset ParentMessageReceipts AMT are encoded with the ORIGINAL go-amt-ipld v2 format: a 3-field root [Height, Count, Node] with an implicit fixed width of 8 (bitWidth 3) that is NOT stored in the root.
FEVM contract-state AMTs and most modern actor sub-AMTs use the v4 format (4-field root [BitWidth, Height, Count, Node]). Loading a v2 root with the v4 loader fails with "cbor input had wrong number of fields" because the v4 internal.Root decoder expects 4 fields and the bytes carry 3.
This file provides v2-format Lookup / ForEach over the same path-recording store the rest of state/amt uses, so message-search (chain/msgsearch) can resolve receipts locally with zero external trust.
Package amt is Lantern's proof-recording AMT walker.
Filecoin uses Array-Mapped Tries (AMTs) for indexed arrays in actor state: message receipts, miner sectors, partition expirations, market deal proposals, etc. The on-disk encoding is documented in github.com/filecoin-project/go-amt-ipld/v4.
We delegate the actual node decoding and traversal to that library (pure Go, no CGo) and wrap it with a BlockGetter abstraction + proof-path recorder, mirroring the state/hamt design.
Index ¶
- Constants
- Variables
- func ForEachRaw(ctx context.Context, root cid.Cid, bg hamt.BlockGetter, opts *LookupOptions, ...) ([]cid.Cid, error)
- func ForEachV2CIDs(ctx context.Context, root cid.Cid, bg hamt.BlockGetter) ([]cid.Cid, error)
- func Lookup(ctx context.Context, root cid.Cid, i uint64, bg hamt.BlockGetter, ...) ([]byte, []cid.Cid, error)
- func LookupCBOR(ctx context.Context, root cid.Cid, i uint64, bg hamt.BlockGetter, ...) ([]cid.Cid, error)
- func LookupV2(ctx context.Context, root cid.Cid, i uint64, bg hamt.BlockGetter) ([]byte, []cid.Cid, error)
- func VerifyProof(ctx context.Context, root cid.Cid, i uint64, value []byte, proof []cid.Cid, ...) error
- type LookupOptions
Constants ¶
const FilBitWidth = 3
FilBitWidth is the default Filecoin AMT bit-width. Most actor sub-AMTs use width = 3 (8 entries per node); see go-amt-ipld/v4 docs.
Variables ¶
var ErrNotFound = fmt.Errorf("index not found in AMT")
ErrNotFound is returned by Lookup when the index is not in the AMT.
Functions ¶
func ForEachRaw ¶
func ForEachRaw(ctx context.Context, root cid.Cid, bg hamt.BlockGetter, opts *LookupOptions, fn func(i uint64, val []byte) error) ([]cid.Cid, error)
ForEachRaw walks a v4 AMT in index order, invoking fn with each entry's index and raw value bytes. Used to enumerate small per-receipt AMTs like the EventsRoot events AMT (lantern#73). Returns the proof path (node CIDs fetched). fn must not retain the value slice past the call.
func ForEachV2CIDs ¶
ForEachV2CIDs walks a legacy (v2) AMT-of-CIDs in index order, returning the CIDs. This is the canonical way to enumerate a block's message AMT (each leaf value is a CBOR-tagged CID).
func Lookup ¶
func Lookup(ctx context.Context, root cid.Cid, i uint64, bg hamt.BlockGetter, opts *LookupOptions) ([]byte, []cid.Cid, error)
Lookup walks the AMT rooted at `root`, fetching nodes via `bg`. It returns the raw value bytes at index `i`, the proof path (list of node CIDs in fetch order), and an error.
func LookupCBOR ¶
func LookupCBOR(ctx context.Context, root cid.Cid, i uint64, bg hamt.BlockGetter, out cbg.CBORUnmarshaler, opts *LookupOptions) ([]cid.Cid, error)
LookupCBOR is a convenience wrapper that decodes the leaf bytes via cbor-gen into `out`.
func LookupV2 ¶
func LookupV2(ctx context.Context, root cid.Cid, i uint64, bg hamt.BlockGetter) ([]byte, []cid.Cid, error)
LookupV2 reads the raw value bytes at index `i` from a legacy (v2) AMT rooted at `root`, returning the value bytes and the proof path (node CIDs fetched in order). Use this for block message AMTs and ParentMessageReceipts.
func VerifyProof ¶
func VerifyProof(ctx context.Context, root cid.Cid, i uint64, value []byte, proof []cid.Cid, bg hamt.BlockGetter, opts *LookupOptions) error
VerifyProof independently re-verifies an AMT lookup proof. See state/hamt.VerifyProof for the design rationale.
Types ¶
type LookupOptions ¶
type LookupOptions struct {
BitWidth uint // default FilBitWidth (3)
}
LookupOptions on a single Lookup call.
Source Files