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|
package snap
import (
"time"
"path/filepath"
"os"
"sort"
"io"
)
type Snapshot struct {
Name string
ModTime time.Time
Reference string
}
func getZFSRoot(reference string) string {
cursor := filepath.Dir(reference)
zfsNotFound := false
for !zfsNotFound {
zfsDir := filepath.Join(cursor, ".zfs")
if _, err := os.Stat(zfsDir); !os.IsNotExist(err) {
break
}
cursor = filepath.Join(cursor, "..")
zfsNotFound = filepath.ToSlash(cursor) == "/"
}
if(zfsNotFound) {
die.Fatal("Could not find a .zfs directory. Are you within a zfs dataset?")
}
return cursor
}
func (snap * Snapshot) tryReference(reference string) {
if _, err := os.Stat(reference); err != nil {
if !os.IsNotExist(err) {
die.Fatalf("Error encountered while attempting to read reference file in snapshot:\n%v", err)
}
snap.Reference = ""
} else {
snap.Reference = reference
}
}
func getSnapshots(reference string) []*Snapshot {
zfsRoot := getZFSRoot(reference)
snapshotDir := filepath.Join(zfsRoot, ".zfs", "snapshot");
files, err := os.ReadDir(snapshotDir)
if err != nil {
die.Fatalf("Could not find the snapshots directory inside \"%s\"", snapshotDir);
}
relPath, err := filepath.Rel(zfsRoot, reference)
if err != nil {
die.Fatalf("Could not find relative path to reference file: %v", err)
}
n_snaps := len(files) + 1
snaps := make([]*Snapshot, n_snaps)
for i, file := range files {
info, err := file.Info()
if(err != nil) {
die.Fatalf("Could not read file %v", err)
}
name := file.Name()
snaps[i] = &Snapshot{
Name: name,
ModTime: info.ModTime(),
}
pathInSnap := filepath.Join(snapshotDir, name, relPath)
snaps[i].tryReference(pathInSnap)
}
snaps[n_snaps - 1] = &Snapshot {
ModTime: time.Now(),
Name: "@",
}
snaps[n_snaps - 1].tryReference(reference)
return snaps
}
func GetTimeseries(reference string) []*Snapshot {
reference, err := filepath.Abs(reference)
if err != nil {
die.Fatal(err)
}
snaps := getSnapshots(reference)
sort.Slice(snaps, func(i, j int) bool {
return snaps[i].ModTime.Before(snaps[j].ModTime)
})
return snaps
}
func referenceMap(snapTs []*Snapshot) []int {
var trimmed []int
for i, snap := range snapTs {
if snap.Reference != "" {
trimmed = append(trimmed, i)
}
}
return trimmed
}
func buildNameMap(snapTs []*Snapshot) map[string] int {
namemap := make(map[string] int)
for i, snap := range snapTs {
namemap[snap.Name] = i
}
return namemap
}
type SnapshotOracle struct {
timeseries []*Snapshot
namemap map[string] int
};
func GetOracle(reference string) *SnapshotOracle {
timeseries := GetTimeseries(reference)
namemap := buildNameMap(timeseries)
return &SnapshotOracle {
timeseries,
namemap,
}
}
func (oracle *SnapshotOracle) PathTo(ref *Relative) string {
n_ts := len(oracle.timeseries)
nthRef := referenceMap(oracle.timeseries)
if len(nthRef) == 0 {
die.Fatalf("The reference file is not contained in any snapshot.")
}
var wanted int
switch (ref.snapshot) {
case "@":
wanted = nthRef[len(nthRef) - 1]
case "%":
wanted = nthRef[0]
default:
id, ok := oracle.namemap[ref.snapshot]
if !ok {
die.Fatalf("Could not find the snapshot \"%s\"", ref.snapshot)
}
wanted = id
}
wanted += ref.offset
if wanted < 0 || wanted >= n_ts {
die.Fatal("The snapshot you requested is out of range.")
}
return oracle.timeseries[wanted].Reference
}
func (oracle *SnapshotOracle) ReadAll(ref *Relative) string {
path := oracle.PathTo(ref)
file, err := os.Open(path)
data, err := io.ReadAll(file)
if err != nil {
die.Fatalf("Can't read snapshot.\n%v", err)
}
return string(data)
}
|
