mirror of
https://github.com/Luzifer/ansible-role-version.git
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188 lines
4.8 KiB
Go
188 lines
4.8 KiB
Go
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package merkletrie
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import (
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"fmt"
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"io"
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"gopkg.in/src-d/go-git.v4/utils/merkletrie/noder"
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)
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// A doubleIter is a convenience type to keep track of the current
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// noders in two merkletries that are going to be iterated in parallel.
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// It has methods for:
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//
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// - iterating over the merkletries, both at the same time or
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// individually: nextFrom, nextTo, nextBoth, stepBoth
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//
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// - checking if there are noders left in one or both of them with the
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// remaining method and its associated returned type.
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//
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// - comparing the current noders of both merkletries in several ways,
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// with the compare method and its associated returned type.
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type doubleIter struct {
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from struct {
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iter *Iter
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current noder.Path // nil if no more nodes
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}
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to struct {
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iter *Iter
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current noder.Path // nil if no more nodes
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}
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hashEqual noder.Equal
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}
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// NewdoubleIter returns a new doubleIter for the merkletries "from" and
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// "to". The hashEqual callback function will be used by the doubleIter
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// to compare the hash of the noders in the merkletries. The doubleIter
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// will be initialized to the first elements in each merkletrie if any.
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func newDoubleIter(from, to noder.Noder, hashEqual noder.Equal) (
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*doubleIter, error) {
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var ii doubleIter
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var err error
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if ii.from.iter, err = NewIter(from); err != nil {
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return nil, fmt.Errorf("from: %s", err)
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}
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if ii.from.current, err = ii.from.iter.Next(); turnEOFIntoNil(err) != nil {
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return nil, fmt.Errorf("from: %s", err)
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}
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if ii.to.iter, err = NewIter(to); err != nil {
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return nil, fmt.Errorf("to: %s", err)
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}
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if ii.to.current, err = ii.to.iter.Next(); turnEOFIntoNil(err) != nil {
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return nil, fmt.Errorf("to: %s", err)
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}
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ii.hashEqual = hashEqual
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return &ii, nil
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}
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func turnEOFIntoNil(e error) error {
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if e != nil && e != io.EOF {
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return e
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}
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return nil
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}
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// NextBoth makes d advance to the next noder in both merkletries. If
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// any of them is a directory, it skips its contents.
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func (d *doubleIter) nextBoth() error {
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if err := d.nextFrom(); err != nil {
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return err
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}
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if err := d.nextTo(); err != nil {
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return err
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}
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return nil
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}
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// NextFrom makes d advance to the next noder in the "from" merkletrie,
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// skipping its contents if it is a directory.
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func (d *doubleIter) nextFrom() (err error) {
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d.from.current, err = d.from.iter.Next()
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return turnEOFIntoNil(err)
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}
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// NextTo makes d advance to the next noder in the "to" merkletrie,
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// skipping its contents if it is a directory.
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func (d *doubleIter) nextTo() (err error) {
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d.to.current, err = d.to.iter.Next()
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return turnEOFIntoNil(err)
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}
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// StepBoth makes d advance to the next noder in both merkletries,
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// getting deeper into directories if that is the case.
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func (d *doubleIter) stepBoth() (err error) {
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if d.from.current, err = d.from.iter.Step(); turnEOFIntoNil(err) != nil {
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return err
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}
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if d.to.current, err = d.to.iter.Step(); turnEOFIntoNil(err) != nil {
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return err
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}
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return nil
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}
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// Remaining returns if there are no more noders in the tree, if both
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// have noders or if one of them doesn't.
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func (d *doubleIter) remaining() remaining {
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if d.from.current == nil && d.to.current == nil {
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return noMoreNoders
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}
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if d.from.current == nil && d.to.current != nil {
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return onlyToRemains
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}
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if d.from.current != nil && d.to.current == nil {
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return onlyFromRemains
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}
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return bothHaveNodes
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}
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// Remaining values tells you whether both trees still have noders, or
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// only one of them or none of them.
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type remaining int
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const (
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noMoreNoders remaining = iota
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onlyToRemains
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onlyFromRemains
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bothHaveNodes
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)
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// Compare returns the comparison between the current elements in the
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// merkletries.
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func (d *doubleIter) compare() (s comparison, err error) {
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s.sameHash = d.hashEqual(d.from.current, d.to.current)
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fromIsDir := d.from.current.IsDir()
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toIsDir := d.to.current.IsDir()
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s.bothAreDirs = fromIsDir && toIsDir
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s.bothAreFiles = !fromIsDir && !toIsDir
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s.fileAndDir = !s.bothAreDirs && !s.bothAreFiles
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fromNumChildren, err := d.from.current.NumChildren()
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if err != nil {
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return comparison{}, fmt.Errorf("from: %s", err)
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}
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toNumChildren, err := d.to.current.NumChildren()
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if err != nil {
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return comparison{}, fmt.Errorf("to: %s", err)
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}
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s.fromIsEmptyDir = fromIsDir && fromNumChildren == 0
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s.toIsEmptyDir = toIsDir && toNumChildren == 0
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return
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}
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// Answers to a lot of questions you can ask about how to noders are
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// equal or different.
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type comparison struct {
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// the following are only valid if both nodes have the same name
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// (i.e. nameComparison == 0)
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// Do both nodes have the same hash?
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sameHash bool
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// Are both nodes files?
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bothAreFiles bool
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// the following are only valid if any of the noders are dirs,
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// this is, if !bothAreFiles
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// Is one a file and the other a dir?
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fileAndDir bool
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// Are both nodes dirs?
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bothAreDirs bool
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// Is the from node an empty dir?
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fromIsEmptyDir bool
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// Is the to Node an empty dir?
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toIsEmptyDir bool
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}
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