Drover's back, baby!

go/src/infra/libs/git/tree.go

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package git
+
+import (
+        "bytes"
+        "fmt"
+        "sort"
+        "strconv"
+        "strings"
+
+        "infra/libs/infra_util"
+)
+
+// Contstants //////////////////////////////////////////////////////////////////
+
+const EmptyTreeHash = "4b825dc642cb6eb9a060e54bf8d69288fbee4904"
+
+// Types ///////////////////////////////////////////////////////////////////////
+
+// Tree is a true tree which represents a git 'tree' of objects, and can
+// represent those objects recursively (unlike a true git 'tree').
+//
+// Trees are also mutable, so you can manipulate them with impunity. Note that
+// ID() is not continuously updated, and you must call Rehash in order to
+// recalculate the correct ID() after manipulating the Tree.
+type Tree struct {
+        id              *ObjectID
+        cachedRawString *string
+
+        children map[string]*Child
+}
+
+// Constructors  ///////////////////////////////////////////////////////////////
+
+// NewEmptyTree creates a new Tree with the given |id|, but no children (e.g.
+// it is !Complete()). You only want to use this if you know that you're going
+// to be adding children to the Tree, otherwise use EmptyObject(TreeType, id).
+func NewEmptyTree(id Identifiable, childrenHint int) *Tree {
+        return &Tree{
+                id:       id.ID(),
+                children: make(map[string]*Child, childrenHint),
+        }
+}
+
+func BlankTreeChild(childrenHint int) *Child {
+        return &Child{NewEmptyTree(&NoID, childrenHint), 040000}
+}
+
+// TreeFromText returns a Complete() Tree for a `git ls-tree`-formatted
+// tree string.
+func NewTreeFromText(data []byte) (ret *Tree, err error) {
+        lines := strings.Split(strings.TrimSpace(string(data)), "\n")
+        retPtr := NewEmptyTree(&NoID, len(lines))
+        for _, line := range lines {
+                infoPath := strings.SplitN(line, "\t", 2)
+                if len(infoPath) != 2 {
+                        return nil, fmt.Errorf("NewTreeFromText: unparsable line %#v", line)
+                }
+                var path string
+                if infoPath[1][0] == '"' {
+                        path, err = strconv.Unquote(infoPath[1])
+                        if err != nil {
+                                return
+                        }
+                } else {
+                        path = infoPath[1]
+                }
+
+                modeTypeID := strings.Fields(infoPath[0])
+                if len(modeTypeID) != 3 {
+                        return nil, fmt.Errorf("NewTreeFromText: unparsable line %#v", line)
+                }
+                var mode uint64
+                mode, err = strconv.ParseUint(modeTypeID[0], 8, 32)
+                if err != nil {
+                        return
+                }
+
+                id, err := MakeObjectIDErr(modeTypeID[2])
+                if err != nil {
+                        return nil, err
+                }
+                c, err := NewEmptyChild(Mode(mode), id)
+                if err != nil {
+                        return nil, err
+                }
+                retPtr.SetChild(path, c)
+        }
+        retPtr.RawString()
+        ret = retPtr
+        return
+}
+
+func NewTreeFromRaw(data []byte) (ret *Tree, err error) {
+        return NewTreeFromRawWithID(MakeObjectIDForData(TreeType, data), data)
+}
+
+// TreeFromRawWithID trusts id, and will return a Complete() *Tree. Data is
+// formatted the same as RawString (i.e. in the raw git tree format).
+func NewTreeFromRawWithID(id Identifiable, data []byte) (ret *Tree, err error) {
+        defer func() {
+                if r := recover(); r != nil {
+                        err = r.(error)
+                }
+        }()
+
+        retPtr := NewEmptyTree(id, 16)
+        // <mode> SP <name> NUL [20]byte
+        buf := bytes.NewBuffer(data)
+        nom := infra_util.Nom(buf)
+        yoink := infra_util.Yoink(buf)
+        for buf.Len() != 0 {
+                var mode uint64
+                mode, err = strconv.ParseUint(nom(' '), 8, 64)
+                if err != nil {
+                        return
+                }
+                name := nom('\x00')
+
+                id := ObjectID{}
+                copy(id.raw[:], yoink(20))
+                c, err := NewEmptyChild(Mode(int(mode)), &id)
+                if err != nil {
+                        return nil, err
+                }
+
+                retPtr.SetChild(name, c)
+        }
+        s := string(data)
+        retPtr.cachedRawString = &s
+        ret = retPtr
+        return
+}
+
+// Factories ///////////////////////////////////////////////////////////////////
+
+// LoadFullTree gets a recursively-enumerated Tree (or an EmptyObject)
+//
+// withBlobs:
+//   true  - Load blobs from Repo
+//   false - Blobs will be EmptyObject
+//
+// missingErr:
+//   true  - All entries in tree must load
+//   false - Missing entries will remain EmptyObject (or an !Complete() Tree)
+func LoadFullTree(s GitService, id Identifiable, withBlobs, missingErr bool) (Object, error) {
+        obj, err := s.GetObjectID(id)
+        if err != nil {
+                return nil, err
+        }
+        if obj == nil {
+                if !missingErr {
+                        return NewEmptyObjectErr(TreeType, id)
+                }
+                return nil, fmt.Errorf("object %s missing", id)
+        }
+
+        switch x := obj.(type) {
+        case *Tree:
+        case *Commit:
+                info := s.ObjectInfo(x.ID().String() + ":")
+                if info == nil {
+                        return nil, fmt.Errorf("object %s: missing", x.ID())
+                }
+                return LoadFullTree(s, info.ID, withBlobs, missingErr)
+        default:
+                return nil, fmt.Errorf("object %v is not a Tree!", x)
+        }
+        base := obj.(*Tree)
+
+        type change struct {
+                path  string
+                child *Child
+        }
+        changes := make(chan change, len(base.children))
+        allErrs := infra_util.FanOutIn(len(base.children), func(ch chan<- func() error) {
+                for p, c := range base.children {
+                        p, c := p, c
+                        ch <- func() (err error) {
+                                var rslt Object
+
+                                switch c.Mode.Type() {
+                                case TreeType:
+                                        rslt, err = LoadFullTree(s, c.Object.ID(), withBlobs, missingErr)
+
+                                case BlobType:
+                                        rslt = c.Object
+                                        if withBlobs {
+                                                rslt, err = s.GetObjectID(c.Object)
+                                        }
+                                }
+
+                                if err == nil {
+                                        if rslt != nil {
+                                                changes <- change{p, &Child{rslt, c.Mode}}
+                                        } else if missingErr {
+                                                err = fmt.Errorf("object %s missing", c.Object.ID())
+                                        }
+                                }
+                                return
+                        }
+                }
+        })
+        close(changes)
+        for c := range changes {
+                base.children[c.path] = c.child
+        }
+
+        return base, allErrs
+}
+
+// Member functions ////////////////////////////////////////////////////////////
+
+func (t *Tree) String() string {
+        return fmt.Sprintf("Tree(%s, %v)", t.id, t.children)
+}
+
+// ID returns the last-calculated ObjectId of this tree. Note that this ID()
+// may be out-of-date if you have modified this Tree with {Set,Del}Child().
+func (t *Tree) ID() *ObjectID { return t.id }
+
+// Type returns TreeType to satisfy the Object interface
+func (t *Tree) Type() ObjectType { return TreeType }
+
+// Complete indicates that this tree's ID() matches its contents. It can
+// become false if you call DelChild or SetChild on this Tree.
+func (t *Tree) Complete() bool { return t.cachedRawString != nil }
+
+// NumChildren returns the number of immediate children this tree has.
+func (t *Tree) NumChildren() int { return len(t.children) }
+
+// Intern recursively interns this tree into the given repo.
+//
+// If the tree contains a missing object which is internable (i.g. not
+// EmptyObject), it will also be interned.
+//
+// If the tree contains an object with an ID of NoID, this method will panic.
+//
+// If the tree contains a missing object which is not internable, this method
+// will panic (see InternAllowMissing to negate this condition).
+//
+// This method has the side effect of causing all internable but !Complete()
+// objects to become Complete(). In particular, this means that the value of
+// t.ID() will be correct after calling this.
+func (t *Tree) Intern(s GitService, allowMissing bool) (*ObjectID, error) {
+        err := infra_util.FanOutIn(len(t.children), func(ch chan<- func() error) {
+                for _, c := range t.children {
+                        c := c
+                        ch <- func() (err error) {
+                                switch x := c.Object.(type) {
+                                case *Tree:
+                                        _, err = x.Intern(s, allowMissing)
+                                case InternableObject:
+                                        s.Intern(x)
+                                case Object:
+                                        if !s.HasObjectID(x) && !allowMissing {
+                                                return fmt.Errorf("missing non-internable object: %v", x)
+                                        }
+                                        if *x.ID() == NoID {
+                                                return fmt.Errorf("object has an ID of <NoID>")
+                                        }
+                                }
+                                return err
+                        }
+                }
+        })
+
+        if err != nil {
+                return nil, err
+        }
+
+        return s.Intern(t)
+}
+
+// GetChild returns the Child at the slash-delemited |path| relative to this
+// Tree, or nil (if the child was not found).
+func (t *Tree) GetChild(path string) *Child {
+        pathParts := strings.SplitN(path, "/", 2)
+        if len(pathParts) == 1 {
+                return t.children[path]
+        }
+
+        dir, rest := pathParts[0], pathParts[1]
+        intermediate, exists := t.children[dir]
+        if !exists {
+                return nil
+        }
+
+        if childTree, ok := intermediate.Object.(*Tree); !ok {
+                panic(fmt.Errorf("entry path is not a tree: %s", dir))
+        } else {
+                return childTree.GetChild(rest)
+        }
+}
+
+// SetChild adds |child| to this Tree at the given slash-delimited |path|. It
+// will create intermediate empty Trees if necessary, but will panic() if you
+// attempt to set the child under something which is not a tree.
+func (t *Tree) SetChild(path string, child *Child) {
+        t.cachedRawString = nil
+        pathParts := strings.SplitN(path, "/", 2)
+        if len(pathParts) == 1 {
+                if len(path) == 0 {
+                        panic(fmt.Errorf("attempting to SetChild with an empty path"))
+                }
+                t.children[path] = child
+        } else {
+                dir, rest := pathParts[0], pathParts[1]
+                intermediate, exists := t.children[dir]
+                if !exists {
+                        intermediate = BlankTreeChild(1)
+                        t.children[dir] = intermediate
+                }
+
+                switch x := intermediate.Object.(type) {
+                case *Tree:
+                        x.SetChild(rest, child)
+                        return
+                case *EmptyObject:
+                        if x.Type() == TreeType {
+                                if *x.ID() == NoID || x.ID().String() == EmptyTreeHash {
+                                        intermediate := BlankTreeChild(1)
+                                        t.children[dir] = intermediate
+                                        intermediate.Object.(*Tree).SetChild(rest, child)
+                                } else {
+                                        panic(fmt.Errorf("entry path was a placeholder tree with an id: %v", x))
+                                }
+                                return
+                        }
+                }
+                panic(fmt.Errorf("entry path is not a tree: %s", dir))
+        }
+}
+
+// DelChild removes the child at the slash-delimited |path|. Will panic if
+// |path| does not exist, or if one of the intermediate paths is not a Tree.
+func (t *Tree) DelChild(path string) bool {
+        t.cachedRawString = nil
+        pathParts := strings.SplitN(path, "/", 2)
+        if len(pathParts) == 1 {
+                var ret bool
+                _, ret = t.children[path]
+                delete(t.children, path)
+                return ret
+        } else {
+                dir, rest := pathParts[0], pathParts[1]
+                child, exists := t.children[dir]
+                if !exists {
+                        return false
+                }
+
+                if childTree, ok := child.Object.(*Tree); !ok {
+                        panic(fmt.Errorf("entry path is not a tree: %s", dir))
+                } else {
+                        ret := childTree.DelChild(rest)
+                        if childTree.NumChildren() == 0 {
+                                delete(t.children, dir)
+                        }
+                        return ret
+                }
+        }
+}
+
+// RawString returns a git hash-object compatible representation of this Tree,
+// according to the currently-set children (e.g. it may return something which
+// does not match ID).
+func (t *Tree) RawString() string {
+        if t.cachedRawString == nil {
+                buf := &bytes.Buffer{}
+
+                entries := make(treeEntries, 0, len(t.children))
+                for path, child := range t.children {
+                        switch x := child.Object.(type) {
+                        case *Tree:
+                                x.RawString()
+                        }
+
+                        entries = append(entries, treeEntry{
+                                id:   child.Object.ID(),
+                                mode: child.Mode,
+                                name: path,
+                        })
+                }
+
+                sort.Sort(entries)
+
+                for _, ent := range entries {
+                        fmt.Fprintf(buf, "%o %s\x00%s", ent.mode, ent.name, ent.id.RawString())
+                }
+                s := buf.String()
+                t.id = MakeObjectIDForData(TreeType, buf.Bytes())
+                t.cachedRawString = &s
+        }
+        return *t.cachedRawString
+}
+
+/// Private ///////////////////////////////////////////////////////////////////
+
+type treeEntry struct {
+        id   *ObjectID
+        mode Mode
+        name string
+}
+type treeEntries []treeEntry
+
+func (s treeEntries) Len() int { return len(s) }
+
+// Extra trailing slash is how git sorts the tree objects too.
+func (s treeEntries) Less(i, j int) bool {
+        a, b := s[i].name, s[j].name
+
+        if s[i].mode.Type() == TreeType {
+                a += "/"
+        }
+        if s[j].mode.Type() == TreeType {
+                b += "/"
+        }
+
+        return a < b
+}
+func (s treeEntries) Swap(i, j int) { s[i], s[j] = s[j], s[i] }