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package monitor
//
// A min heap of chunks, ordered on each chunk's start index. This makes it
// easy to order the downloaded leaves when using multiple parallell fetchers.
//
// Credit: inspiration to use a heap from Aaron Gable, see
// https://github.com/aarongable/ctaudit
//
import (
"container/heap"
"crypto/sha256"
)
type chunk struct {
startIndex uint64 // Index of the first leaf
leafHashes [][sha256.Size]byte // List of consecutive leaf hashes
matches []LogEntry // Leaves that match some criteria
errors []error // Errors that ocurred while matching on the leaves
}
type chunks []*chunk
func newChunks() *chunks {
var h chunks
heap.Init((*internal)(&h))
return &h
}
func (h *chunks) push(c *chunk) {
heap.Push((*internal)(h), c)
}
func (h *chunks) pop() *chunk {
x := heap.Pop((*internal)(h))
return x.(*chunk)
}
// gap returns true if there's a gap between the provided start index and the
// top most chunk. If the top most chunk is in sequence, it is merged with
// any following chunks that are also in sequence to form one larger chunk.
func (h *chunks) gap(start uint64) bool {
if len(*h) == 0 {
return true
}
top := h.pop()
if start != top.startIndex {
h.push(top)
return true
}
for len(*h) > 0 {
c := h.pop()
if c.startIndex != top.startIndex+uint64(len(top.leafHashes)) {
h.push(c)
break
}
top.leafHashes = append(top.leafHashes, c.leafHashes...)
top.matches = append(top.matches, c.matches...)
top.errors = append(top.errors, c.errors...)
}
h.push(top)
return false
}
// internal implements the heap interface, see example:
// https://cs.opensource.google/go/go/+/refs/tags/go1.21.5:src/container/heap/example_intheap_test.go
type internal chunks
func (h internal) Len() int { return len(h) }
func (h internal) Less(i, j int) bool { return h[i].startIndex < h[j].startIndex }
func (h internal) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
func (h *internal) Push(x any) {
*h = append(*h, x.(*chunk))
}
func (h *internal) Pop() any {
old := *h
n := len(old)
x := old[n-1]
old[n-1] = nil // avoid memory leak
*h = old[:n-1]
return x
}
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