trie: simplify StackTrie implementation (#23950)
Trim the search key from head as it's being pushed deeper into the trie. Previously the search key was never modified but each node kept information how to slice and compare it in keyOffset. Now the keyOffset is not needed as this information is included in the slice of the search key. This way the keyOffset can be removed and key manipulation simplified.
This commit is contained in:
Paweł Bylica
GitHub
parent
c10a0a62c3
commit
86fe359a56
@ -54,12 +54,11 @@ func returnToPool(st *StackTrie) {
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// in order. Once it determines that a subtree will no longer be inserted
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// into, it will hash it and free up the memory it uses.
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type StackTrie struct {
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nodeType uint8 // node type (as in branch, ext, leaf)
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val []byte // value contained by this node if it's a leaf
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key []byte // key chunk covered by this (full|ext) node
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keyOffset int // offset of the key chunk inside a full key
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children [16]*StackTrie // list of children (for fullnodes and exts)
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db ethdb.KeyValueWriter // Pointer to the commit db, can be nil
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nodeType uint8 // node type (as in branch, ext, leaf)
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val []byte // value contained by this node if it's a leaf
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key []byte // key chunk covered by this (leaf|ext) node
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children [16]*StackTrie // list of children (for branch and exts)
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db ethdb.KeyValueWriter // Pointer to the commit db, can be nil
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}
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// NewStackTrie allocates and initializes an empty trie.
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@ -90,15 +89,13 @@ func (st *StackTrie) MarshalBinary() (data []byte, err error) {
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w = bufio.NewWriter(&b)
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)
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if err := gob.NewEncoder(w).Encode(struct {
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Nodetype uint8
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Val []byte
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Key []byte
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KeyOffset uint8
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Nodetype uint8
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Val []byte
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Key []byte
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}{
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st.nodeType,
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st.val,
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st.key,
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uint8(st.keyOffset),
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}); err != nil {
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return nil, err
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}
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@ -126,16 +123,14 @@ func (st *StackTrie) UnmarshalBinary(data []byte) error {
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func (st *StackTrie) unmarshalBinary(r io.Reader) error {
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var dec struct {
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Nodetype uint8
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Val []byte
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Key []byte
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KeyOffset uint8
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Nodetype uint8
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Val []byte
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Key []byte
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}
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gob.NewDecoder(r).Decode(&dec)
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st.nodeType = dec.Nodetype
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st.val = dec.Val
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st.key = dec.Key
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st.keyOffset = int(dec.KeyOffset)
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var hasChild = make([]byte, 1)
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for i := range st.children {
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@ -160,20 +155,18 @@ func (st *StackTrie) setDb(db ethdb.KeyValueWriter) {
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}
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}
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func newLeaf(ko int, key, val []byte, db ethdb.KeyValueWriter) *StackTrie {
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func newLeaf(key, val []byte, db ethdb.KeyValueWriter) *StackTrie {
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st := stackTrieFromPool(db)
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st.nodeType = leafNode
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st.keyOffset = ko
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st.key = append(st.key, key[ko:]...)
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st.key = append(st.key, key...)
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st.val = val
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return st
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}
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func newExt(ko int, key []byte, child *StackTrie, db ethdb.KeyValueWriter) *StackTrie {
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func newExt(key []byte, child *StackTrie, db ethdb.KeyValueWriter) *StackTrie {
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st := stackTrieFromPool(db)
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st.nodeType = extNode
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st.keyOffset = ko
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st.key = append(st.key, key[ko:]...)
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st.key = append(st.key, key...)
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st.children[0] = child
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return st
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}
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@ -211,17 +204,18 @@ func (st *StackTrie) Reset() {
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st.children[i] = nil
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}
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st.nodeType = emptyNode
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st.keyOffset = 0
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}
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// Helper function that, given a full key, determines the index
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// at which the chunk pointed by st.keyOffset is different from
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// the same chunk in the full key.
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func (st *StackTrie) getDiffIndex(key []byte) int {
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diffindex := 0
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for ; diffindex < len(st.key) && st.key[diffindex] == key[st.keyOffset+diffindex]; diffindex++ {
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for idx, nibble := range st.key {
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if nibble != key[idx] {
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return idx
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}
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}
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return diffindex
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return len(st.key)
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}
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// Helper function to that inserts a (key, value) pair into
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@ -229,7 +223,7 @@ func (st *StackTrie) getDiffIndex(key []byte) int {
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func (st *StackTrie) insert(key, value []byte) {
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switch st.nodeType {
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case branchNode: /* Branch */
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idx := int(key[st.keyOffset])
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idx := int(key[0])
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// Unresolve elder siblings
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for i := idx - 1; i >= 0; i-- {
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if st.children[i] != nil {
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@ -241,10 +235,10 @@ func (st *StackTrie) insert(key, value []byte) {
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}
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// Add new child
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if st.children[idx] == nil {
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st.children[idx] = stackTrieFromPool(st.db)
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st.children[idx].keyOffset = st.keyOffset + 1
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st.children[idx] = newLeaf(key[1:], value, st.db)
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} else {
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st.children[idx].insert(key[1:], value)
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}
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st.children[idx].insert(key, value)
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case extNode: /* Ext */
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// Compare both key chunks and see where they differ
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diffidx := st.getDiffIndex(key)
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@ -257,7 +251,7 @@ func (st *StackTrie) insert(key, value []byte) {
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if diffidx == len(st.key) {
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// Ext key and key segment are identical, recurse into
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// the child node.
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st.children[0].insert(key, value)
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st.children[0].insert(key[diffidx:], value)
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return
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}
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// Save the original part. Depending if the break is
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@ -266,7 +260,7 @@ func (st *StackTrie) insert(key, value []byte) {
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// node directly.
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var n *StackTrie
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if diffidx < len(st.key)-1 {
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n = newExt(diffidx+1, st.key, st.children[0], st.db)
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n = newExt(st.key[diffidx+1:], st.children[0], st.db)
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} else {
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// Break on the last byte, no need to insert
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// an extension node: reuse the current node
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@ -288,15 +282,14 @@ func (st *StackTrie) insert(key, value []byte) {
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// node.
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st.children[0] = stackTrieFromPool(st.db)
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st.children[0].nodeType = branchNode
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st.children[0].keyOffset = st.keyOffset + diffidx
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p = st.children[0]
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}
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// Create a leaf for the inserted part
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o := newLeaf(st.keyOffset+diffidx+1, key, value, st.db)
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o := newLeaf(key[diffidx+1:], value, st.db)
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// Insert both child leaves where they belong:
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origIdx := st.key[diffidx]
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newIdx := key[diffidx+st.keyOffset]
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newIdx := key[diffidx]
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p.children[origIdx] = n
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p.children[newIdx] = o
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st.key = st.key[:diffidx]
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@ -330,7 +323,6 @@ func (st *StackTrie) insert(key, value []byte) {
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st.nodeType = extNode
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st.children[0] = NewStackTrie(st.db)
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st.children[0].nodeType = branchNode
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st.children[0].keyOffset = st.keyOffset + diffidx
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p = st.children[0]
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}
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@ -339,11 +331,11 @@ func (st *StackTrie) insert(key, value []byte) {
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// The child leave will be hashed directly in order to
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// free up some memory.
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origIdx := st.key[diffidx]
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p.children[origIdx] = newLeaf(diffidx+1, st.key, st.val, st.db)
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p.children[origIdx] = newLeaf(st.key[diffidx+1:], st.val, st.db)
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p.children[origIdx].hash()
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newIdx := key[diffidx+st.keyOffset]
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p.children[newIdx] = newLeaf(p.keyOffset+1, key, value, st.db)
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newIdx := key[diffidx]
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p.children[newIdx] = newLeaf(key[diffidx+1:], value, st.db)
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// Finally, cut off the key part that has been passed
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// over to the children.
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@ -351,7 +343,7 @@ func (st *StackTrie) insert(key, value []byte) {
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st.val = nil
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case emptyNode: /* Empty */
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st.nodeType = leafNode
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st.key = key[st.keyOffset:]
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st.key = key
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st.val = value
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case hashedNode:
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panic("trying to insert into hash")
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