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// Copyright (C) 2022-2023 Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later
package btrfsvol
import (
"fmt"
"sort"
"git.lukeshu.com/btrfs-progs-ng/lib/containers"
"git.lukeshu.com/btrfs-progs-ng/lib/maps"
"git.lukeshu.com/btrfs-progs-ng/lib/slices"
)
// logical => []physical
type chunkMapping struct {
LAddr LogicalAddr
PAddrs []QualifiedPhysicalAddr
Size AddrDelta
SizeLocked bool
Flags containers.Optional[BlockGroupFlags]
}
// Compare implements containers.Ordered.
func (a chunkMapping) Compare(b chunkMapping) int {
return containers.NativeCompare(a.LAddr, b.LAddr)
}
// return -1 if 'a' is wholly to the left of 'b'
// return 0 if there is some overlap between 'a' and 'b'
// return 1 if 'a is wholly to the right of 'b'
func (a chunkMapping) compareRange(b chunkMapping) int {
switch {
case a.LAddr.Add(a.Size) <= b.LAddr:
// 'a' is wholly to the left of 'b'.
return -1
case b.LAddr.Add(b.Size) <= a.LAddr:
// 'a' is wholly to the right of 'b'.
return 1
default:
// There is some overlap.
return 0
}
}
func (a chunkMapping) union(rest ...chunkMapping) (chunkMapping, error) {
// sanity check
for _, chunk := range rest {
if a.compareRange(chunk) != 0 {
return chunkMapping{}, fmt.Errorf("chunks don't overlap")
}
}
chunks := append([]chunkMapping{a}, rest...)
// figure out the logical range (.LAddr and .Size)
beg := chunks[0].LAddr
end := chunks[0].LAddr.Add(chunks[0].Size)
for _, chunk := range chunks {
beg = slices.Min(beg, chunk.LAddr)
end = slices.Max(end, chunk.LAddr.Add(chunk.Size))
}
ret := chunkMapping{
LAddr: beg,
Size: end.Sub(beg),
}
for _, chunk := range chunks {
if chunk.SizeLocked {
ret.SizeLocked = true
if ret.Size != chunk.Size {
return chunkMapping{}, fmt.Errorf("member chunk has locked size=%v, but union would have size=%v",
chunk.Size, ret.Size)
}
}
}
// figure out the physical stripes (.PAddrs)
paddrs := make(containers.Set[QualifiedPhysicalAddr])
for _, chunk := range chunks {
offsetWithinRet := chunk.LAddr.Sub(ret.LAddr)
for _, stripe := range chunk.PAddrs {
paddrs.Insert(stripe.Add(-offsetWithinRet))
}
}
ret.PAddrs = maps.Keys(paddrs)
sort.Slice(ret.PAddrs, func(i, j int) bool {
return ret.PAddrs[i].Compare(ret.PAddrs[j]) < 0
})
// figure out the flags (.Flags)
for _, chunk := range chunks {
if !chunk.Flags.OK {
continue
}
if !ret.Flags.OK {
ret.Flags = chunk.Flags
}
if ret.Flags != chunk.Flags {
return ret, fmt.Errorf("mismatch flags: %v != %v", ret.Flags.Val, chunk.Flags.Val)
}
}
// done
return ret, nil
}
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