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d216942b7c
Comparing against emptyRef (the single value makeRef(kindEmpty, 0)) only works because no other nodeRef with kindEmpty is ever constructed. That invariant is easy to break if future code ever produces a kindEmpty ref with nonzero index. Test the kind directly so any kindEmpty ref reads as empty regardless of index.
56 lines
1.9 KiB
Go
56 lines
1.9 KiB
Go
// Copyright 2026 go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package bintrie
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// nodeKind identifies the type of a trie node stored in a nodeRef.
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type nodeKind uint8
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const (
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kindEmpty nodeKind = iota
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kindInternal
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kindStem // up to 256 values per stem
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kindHashed
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)
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// nodeRef is a compact, GC-invisible reference to a node in a NodeStore.
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// It packs a 2-bit type tag (bits 31-30) and a 30-bit index (bits 29-0)
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// into a single uint32. Because nodeRef contains no Go pointers, slices
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// of structs containing nodeRef fields are allocated in noscan spans —
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// the garbage collector never examines them.
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type nodeRef uint32
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const (
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kindShift uint32 = 30
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indexMask uint32 = (1 << kindShift) - 1
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// emptyRef represents an empty node.
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emptyRef nodeRef = 0
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)
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func makeRef(kind nodeKind, idx uint32) nodeRef {
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if idx > indexMask {
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panic("nodeRef index overflow")
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}
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return nodeRef(uint32(kind)<<kindShift | idx)
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}
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func (r nodeRef) Kind() nodeKind { return nodeKind(uint32(r) >> kindShift) }
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// Index within the typed pool.
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func (r nodeRef) Index() uint32 { return uint32(r) & indexMask }
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func (r nodeRef) IsEmpty() bool { return r.Kind() == kindEmpty }
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