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trie: make stacktrie not mutate input values (#22673)

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The stacktrie is a bit un-untuitive, API-wise: since it mutates input values.
Such behaviour is dangerous, and easy to get wrong if the calling code 'forgets' this quirk. The behaviour is fixed by this PR, so that the input values are not modified by the stacktrie. 

Note: just as with the Trie, the stacktrie still references the live input objects, so it's still _not_ safe to mutate the values form the callsite.
This commit is contained in:
Martin Holst Swende
2021-04-16 14:21:01 +02:00
committed by GitHub
parent 65689e7fce
commit 4f3ba6742f
2 changed files with 56 additions and 11 deletions
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16
trie/stacktrie.go
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@ -346,8 +346,7 @@ func (st *StackTrie) hash() {
panic(err)
}
case emptyNode:
st.val = st.val[:0]
st.val = append(st.val, emptyRoot[:]...)
st.val = emptyRoot.Bytes()
st.key = st.key[:0]
st.nodeType = hashedNode
return
@ -357,17 +356,12 @@ func (st *StackTrie) hash() {
st.key = st.key[:0]
st.nodeType = hashedNode
if len(h.tmp) < 32 {
st.val = st.val[:0]
st.val = append(st.val, h.tmp...)
st.val = common.CopyBytes(h.tmp)
return
}
// Going to write the hash to the 'val'. Need to ensure it's properly sized first
// Typically, 'branchNode's will have no 'val', and require this allocation
if required := 32 - len(st.val); required > 0 {
buf := make([]byte, required)
st.val = append(st.val, buf...)
}
st.val = st.val[:32]
// Write the hash to the 'val'. We allocate a new val here to not mutate
// input values
st.val = make([]byte, 32)
h.sha.Reset()
h.sha.Write(h.tmp)
h.sha.Read(st.val)