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7aebfb3c71
Implement foundational types and algorithms for the NOMT storage engine: - node.go: Node/KeyPath/ValueHash types with MSB-based kind discrimination - hasher.go: Keccak256 hashing with leaf/internal MSB labeling - page.go: 4096-byte RawPage layout (126 nodes + elided children + pageID) - pageid.go: PageID encode/decode with shift-then-add encoding - triepos.go: TriePosition navigation (Down/Up/Sibling/PageID/NodeIndex) - pagediff.go: 128-bit PageDiff bitfield for tracking changed nodes - update.go: BuildTrie 3-pointer left-frontier algorithm, LeafOpsSpliced Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
71 lines
2.1 KiB
Go
71 lines
2.1 KiB
Go
package core
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import "encoding/binary"
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// Page layout constants.
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const (
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// PageDepth is the depth of the rootless sub-binary tree stored in a page.
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PageDepth = 6
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// NodesPerPage is the total number of nodes in one page: (2^(depth+1)) - 2 = 126.
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NodesPerPage = (1 << (PageDepth + 1)) - 2
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// NumChildren is the number of child pages each page can have: 2^depth = 64.
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NumChildren = 1 << PageDepth
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// PageSize is the size of a raw page in bytes, aligned to SSD page size.
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PageSize = 4096
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// elidedChildrenOffset stores the 8-byte elided children bitfield.
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// Layout: [nodes 4032] [padding 24] [elided 8] [pageID 32] = 4096
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elidedChildrenOffset = PageSize - 32 - 8 // 4056
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// pageIDOffset stores the 32-byte encoded PageID.
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pageIDOffset = PageSize - 32 // 4064
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)
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// RawPage is a 4096-byte page storing a rootless sub-tree of depth 6.
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//
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// Layout:
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//
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// [0..4032) 126 nodes × 32 bytes each, in level-order
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// [4032..4056) 24 bytes padding
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// [4056..4064) ElidedChildren bitfield (8 bytes, little-endian uint64)
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// [4064..4096) PageID encoded (32 bytes)
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type RawPage [PageSize]byte
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// NodeAt reads the 32-byte node at the given index (0-based level-order).
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func (p *RawPage) NodeAt(index int) Node {
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var n Node
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off := index * 32
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copy(n[:], p[off:off+32])
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return n
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}
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// SetNodeAt writes a 32-byte node at the given index.
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func (p *RawPage) SetNodeAt(index int, n Node) {
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off := index * 32
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copy(p[off:off+32], n[:])
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}
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// ElidedChildren reads the 8-byte elided children bitfield.
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func (p *RawPage) ElidedChildren() uint64 {
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return binary.LittleEndian.Uint64(p[elidedChildrenOffset:])
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}
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// SetElidedChildren writes the 8-byte elided children bitfield.
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func (p *RawPage) SetElidedChildren(ec uint64) {
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binary.LittleEndian.PutUint64(p[elidedChildrenOffset:], ec)
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}
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// PageIDBytes reads the 32-byte encoded PageID from the page.
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func (p *RawPage) PageIDBytes() [32]byte {
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var id [32]byte
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copy(id[:], p[pageIDOffset:pageIDOffset+32])
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return id
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}
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// SetPageIDBytes writes the 32-byte encoded PageID into the page.
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func (p *RawPage) SetPageIDBytes(id [32]byte) {
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copy(p[pageIDOffset:pageIDOffset+32], id[:])
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}
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