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Correct child and orphan block removal logic.

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It is not safe to remove elements from a slice while iterating them with
the range statement since it does not reevaluate the slice on each
iteration nor does it adjust the index for the modified slice.  This
commit modifies the code to use a for loop with an index (which does
reevaluate on every iteration) and manually adjusts the index when
elements are removed from the slice.
This commit is contained in:
Dave Collins 2013-08-17 14:05:36 -05:00
parent 10a62a37a3
commit 2835238287
1 changed files with 14 additions and 5 deletions
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19
chain.go
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@ -122,11 +122,16 @@ func removeChildNode(children []*blockNode, node *blockNode) []*blockNode {
if node == nil {
return children
}
for i, n := range children {
if n.hash.IsEqual(node.hash) {
// An indexing for loop is intentionally used over a range here as range
// does not reevaluate the slice on each iteration nor does it adjust
// the index for the modified slice.
for i := 0; i < len(children); i++ {
if children[i].hash.IsEqual(node.hash) {
copy(children[i:], children[i+1:])
children[len(children)-1] = nil
return children[:len(children)-1]
i--
}
}
return children
@ -186,15 +191,19 @@ func (b *BlockChain) removeOrphanBlock(orphan *orphanBlock) {
orphanHash, _ := orphan.block.Sha()
delete(b.orphans, *orphanHash)
// Remove the reference from the previous orphan index too.
// Remove the reference from the previous orphan index too. An indexing
// for loop is intentionally used over a range here as range does not
// reevaluate the slice on each iteration nor does it adjust the index
// for the modified slice.
prevHash := &orphan.block.MsgBlock().Header.PrevBlock
orphans := b.prevOrphans[*prevHash]
for i, ob := range orphans {
hash, _ := ob.block.Sha()
for i := 0; i < len(orphans); i++ {
hash, _ := orphans[i].block.Sha()
if hash.IsEqual(orphanHash) {
copy(orphans[i:], orphans[i+1:])
orphans[len(orphans)-1] = nil
orphans = orphans[:len(orphans)-1]
i--
}
}
b.prevOrphans[*prevHash] = orphans