path: root/swarm/api/manifest.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package api

import (
    "bytes"
    "encoding/json"
    "errors"
    "fmt"
    "io"
    "sync"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/log"
    "github.com/ethereum/go-ethereum/swarm/storage"
)

const (
    ManifestType = "application/bzz-manifest+json"
)

// Manifest represents a swarm manifest
type Manifest struct {
    Entries []ManifestEntry `json:"entries,omitempty"`
}

// ManifestEntry represents an entry in a swarm manifest
type ManifestEntry struct {
    Hash        string    `json:"hash,omitempty"`
    Path        string    `json:"path,omitempty"`
    ContentType string    `json:"contentType,omitempty"`
    Mode        int64     `json:"mode,omitempty"`
    Size        int64     `json:"size,omitempty"`
    ModTime     time.Time `json:"mod_time,omitempty"`
    Status      int       `json:"status,omitempty"`
}

// ManifestList represents the result of listing files in a manifest
type ManifestList struct {
    CommonPrefixes []string         `json:"common_prefixes,omitempty"`
    Entries        []*ManifestEntry `json:"entries,omitempty"`
}

// NewManifest creates and stores a new, empty manifest
func (a *Api) NewManifest() (storage.Key, error) {
    var manifest Manifest
    data, err := json.Marshal(&manifest)
    if err != nil {
        return nil, err
    }
    return a.Store(bytes.NewReader(data), int64(len(data)), nil)
}

// ManifestWriter is used to add and remove entries from an underlying manifest
type ManifestWriter struct {
    api   *Api
    trie  *manifestTrie
    quitC chan bool
}

func (a *Api) NewManifestWriter(key storage.Key, quitC chan bool) (*ManifestWriter, error) {
    trie, err := loadManifest(a.dpa, key, quitC)
    if err != nil {
        return nil, fmt.Errorf("error loading manifest %s: %s", key, err)
    }
    return &ManifestWriter{a, trie, quitC}, nil
}

// AddEntry stores the given data and adds the resulting key to the manifest
func (m *ManifestWriter) AddEntry(data io.Reader, e *ManifestEntry) (storage.Key, error) {
    key, err := m.api.Store(data, e.Size, nil)
    if err != nil {
        return nil, err
    }
    entry := newManifestTrieEntry(e, nil)
    entry.Hash = key.String()
    m.trie.addEntry(entry, m.quitC)
    return key, nil
}

// RemoveEntry removes the given path from the manifest
func (m *ManifestWriter) RemoveEntry(path string) error {
    m.trie.deleteEntry(path, m.quitC)
    return nil
}

// Store stores the manifest, returning the resulting storage key
func (m *ManifestWriter) Store() (storage.Key, error) {
    return m.trie.hash, m.trie.recalcAndStore()
}

// ManifestWalker is used to recursively walk the entries in the manifest and
// all of its submanifests
type ManifestWalker struct {
    api   *Api
    trie  *manifestTrie
    quitC chan bool
}

func (a *Api) NewManifestWalker(key storage.Key, quitC chan bool) (*ManifestWalker, error) {
    trie, err := loadManifest(a.dpa, key, quitC)
    if err != nil {
        return nil, fmt.Errorf("error loading manifest %s: %s", key, err)
    }
    return &ManifestWalker{a, trie, quitC}, nil
}

// SkipManifest is used as a return value from WalkFn to indicate that the
// manifest should be skipped
var SkipManifest = errors.New("skip this manifest")

// WalkFn is the type of function called for each entry visited by a recursive
// manifest walk
type WalkFn func(entry *ManifestEntry) error

// Walk recursively walks the manifest calling walkFn for each entry in the
// manifest, including submanifests
func (m *ManifestWalker) Walk(walkFn WalkFn) error {
    return m.walk(m.trie, "", walkFn)
}

func (m *ManifestWalker) walk(trie *manifestTrie, prefix string, walkFn WalkFn) error {
    for _, entry := range trie.entries {
        if entry == nil {
            continue
        }
        entry.Path = prefix + entry.Path
        err := walkFn(&entry.ManifestEntry)
        if err != nil {
            if entry.ContentType == ManifestType && err == SkipManifest {
                continue
            }
            return err
        }
        if entry.ContentType != ManifestType {
            continue
        }
        if err := trie.loadSubTrie(entry, nil); err != nil {
            return err
        }
        if err := m.walk(entry.subtrie, entry.Path, walkFn); err != nil {
            return err
        }
    }
    return nil
}

type manifestTrie struct {
    dpa     *storage.DPA
    entries [257]*manifestTrieEntry // indexed by first character of basePath, entries[256] is the empty basePath entry
    hash    storage.Key             // if hash != nil, it is stored
}

func newManifestTrieEntry(entry *ManifestEntry, subtrie *manifestTrie) *manifestTrieEntry {
    return &manifestTrieEntry{
        ManifestEntry: *entry,
        subtrie:       subtrie,
    }
}

type manifestTrieEntry struct {
    ManifestEntry

    subtrie *manifestTrie
}

func loadManifest(dpa *storage.DPA, hash storage.Key, quitC chan bool) (trie *manifestTrie, err error) { // non-recursive, subtrees are downloaded on-demand

    log.Trace(fmt.Sprintf("manifest lookup key: '%v'.", hash.Log()))
    // retrieve manifest via DPA
    manifestReader := dpa.Retrieve(hash)
    return readManifest(manifestReader, hash, dpa, quitC)
}

func readManifest(manifestReader storage.LazySectionReader, hash storage.Key, dpa *storage.DPA, quitC chan bool) (trie *manifestTrie, err error) { // non-recursive, subtrees are downloaded on-demand

    // TODO check size for oversized manifests
    size, err := manifestReader.Size(quitC)
    if err != nil { // size == 0
        // can't determine size means we don't have the root chunk
        err = fmt.Errorf("Manifest not Found")
        return
    }
    manifestData := make([]byte, size)
    read, err := manifestReader.Read(manifestData)
    if int64(read) < size {
        log.Trace(fmt.Sprintf("Manifest %v not found.", hash.Log()))
        if err == nil {
            err = fmt.Errorf("Manifest retrieval cut short: read %v, expect %v", read, size)
        }
        return
    }

    log.Trace(fmt.Sprintf("Manifest %v retrieved", hash.Log()))
    var man struct {
        Entries []*manifestTrieEntry `json:"entries"`
    }
    err = json.Unmarshal(manifestData, &man)
    if err != nil {
        err = fmt.Errorf("Manifest %v is malformed: %v", hash.Log(), err)
        log.Trace(fmt.Sprintf("%v", err))
        return
    }

    log.Trace(fmt.Sprintf("Manifest %v has %d entries.", hash.Log(), len(man.Entries)))

    trie = &manifestTrie{
        dpa: dpa,
    }
    for _, entry := range man.Entries {
        trie.addEntry(entry, quitC)
    }
    return
}

func (self *manifestTrie) addEntry(entry *manifestTrieEntry, quitC chan bool) {
    self.hash = nil // trie modified, hash needs to be re-calculated on demand

    if len(entry.Path) == 0 {
        self.entries[256] = entry
        return
    }

    b := byte(entry.Path[0])
    oldentry := self.entries[b]
    if (oldentry == nil) || (oldentry.Path == entry.Path && oldentry.ContentType != ManifestType) {
        self.entries[b] = entry
        return
    }

    cpl := 0
    for (len(entry.Path) > cpl) && (len(oldentry.Path) > cpl) && (entry.Path[cpl] == oldentry.Path[cpl]) {
        cpl++
    }

    if (oldentry.ContentType == ManifestType) && (cpl == len(oldentry.Path)) {
        if self.loadSubTrie(oldentry, quitC) != nil {
            return
        }
        entry.Path = entry.Path[cpl:]
        oldentry.subtrie.addEntry(entry, quitC)
        oldentry.Hash = ""
        return
    }

    commonPrefix := entry.Path[:cpl]

    subtrie := &manifestTrie{
        dpa: self.dpa,
    }
    entry.Path = entry.Path[cpl:]
    oldentry.Path = oldentry.Path[cpl:]
    subtrie.addEntry(entry, quitC)
    subtrie.addEntry(oldentry, quitC)

    self.entries[b] = newManifestTrieEntry(&ManifestEntry{
        Path:        commonPrefix,
        ContentType: ManifestType,
    }, subtrie)
}

func (self *manifestTrie) getCountLast() (cnt int, entry *manifestTrieEntry) {
    for _, e := range self.entries {
        if e != nil {
            cnt++
            entry = e
        }
    }
    return
}

func (self *manifestTrie) deleteEntry(path string, quitC chan bool) {
    self.hash = nil // trie modified, hash needs to be re-calculated on demand

    if len(path) == 0 {
        self.entries[256] = nil
        return
    }

    b := byte(path[0])
    entry := self.entries[b]
    if entry == nil {
        return
    }
    if entry.Path == path {
        self.entries[b] = nil
        return
    }

    epl := len(entry.Path)
    if (entry.ContentType == ManifestType) && (len(path) >= epl) && (path[:epl] == entry.Path) {
        if self.loadSubTrie(entry, quitC) != nil {
            return
        }
        entry.subtrie.deleteEntry(path[epl:], quitC)
        entry.Hash = ""
        // remove subtree if it has less than 2 elements
        cnt, lastentry := entry.subtrie.getCountLast()
        if cnt < 2 {
            if lastentry != nil {
                lastentry.Path = entry.Path + lastentry.Path
            }
            self.entries[b] = lastentry
        }
    }
}

func (self *manifestTrie) recalcAndStore() error {
    if self.hash != nil {
        return nil
    }

    var buffer bytes.Buffer
    buffer.WriteString(`{"entries":[`)

    list := &Manifest{}
    for _, entry := range self.entries {
        if entry != nil {
            if entry.Hash == "" { // TODO: paralellize
                err := entry.subtrie.recalcAndStore()
                if err != nil {
                    return err
                }
                entry.Hash = entry.subtrie.hash.String()
            }
            list.Entries = append(list.Entries, entry.ManifestEntry)
        }

    }

    manifest, err := json.Marshal(list)
    if err != nil {
        return err
    }

    sr := bytes.NewReader(manifest)
    wg := &sync.WaitGroup{}
    key, err2 := self.dpa.Store(sr, int64(len(manifest)), wg, nil)
    wg.Wait()
    self.hash = key
    return err2
}

func (self *manifestTrie) loadSubTrie(entry *manifestTrieEntry, quitC chan bool) (err error) {
    if entry.subtrie == nil {
        hash := common.Hex2Bytes(entry.Hash)
        entry.subtrie, err = loadManifest(self.dpa, hash, quitC)
        entry.Hash = "" // might not match, should be recalculated
    }
    return
}

func (self *manifestTrie) listWithPrefixInt(prefix, rp string, quitC chan bool, cb func(entry *manifestTrieEntry, suffix string)) error {
    plen := len(prefix)
    var start, stop int
    if plen == 0 {
        start = 0
        stop = 256
    } else {
        start = int(prefix[0])
        stop = start
    }

    for i := start; i <= stop; i++ {
        select {
        case <-quitC:
            return fmt.Errorf("aborted")
        default:
        }
        entry := self.entries[i]
        if entry != nil {
            epl := len(entry.Path)
            if entry.ContentType == ManifestType {
                l := plen
                if epl < l {
                    l = epl
                }
                if prefix[:l] == entry.Path[:l] {
                    err := self.loadSubTrie(entry, quitC)
                    if err != nil {
                        return err
                    }
                    err = entry.subtrie.listWithPrefixInt(prefix[l:], rp+entry.Path[l:], quitC, cb)
                    if err != nil {
                        return err
                    }
                }
            } else {
                if (epl >= plen) && (prefix == entry.Path[:plen]) {
                    cb(entry, rp+entry.Path[plen:])
                }
            }
        }
    }
    return nil
}

func (self *manifestTrie) listWithPrefix(prefix string, quitC chan bool, cb func(entry *manifestTrieEntry, suffix string)) (err error) {
    return self.listWithPrefixInt(prefix, "", quitC, cb)
}

func (self *manifestTrie) findPrefixOf(path string, quitC chan bool) (entry *manifestTrieEntry, pos int) {

    log.Trace(fmt.Sprintf("findPrefixOf(%s)", path))

    if len(path) == 0 {
        return self.entries[256], 0
    }

    b := byte(path[0])
    entry = self.entries[b]
    if entry == nil {
        return self.entries[256], 0
    }
    epl := len(entry.Path)
    log.Trace(fmt.Sprintf("path = %v  entry.Path = %v  epl = %v", path, entry.Path, epl))
    if (len(path) >= epl) && (path[:epl] == entry.Path) {
        log.Trace(fmt.Sprintf("entry.ContentType = %v", entry.ContentType))
        if entry.ContentType == ManifestType {
            err := self.loadSubTrie(entry, quitC)
            if err != nil {
                return nil, 0
            }
            entry, pos = entry.subtrie.findPrefixOf(path[epl:], quitC)
            if entry != nil {
                pos += epl
            }
        } else {
            pos = epl
        }
    }
    return
}

// file system manifest always contains regularized paths
// no leading or trailing slashes, only single slashes inside
func RegularSlashes(path string) (res string) {
    for i := 0; i < len(path); i++ {
        if (path[i] != '/') || ((i > 0) && (path[i-1] != '/')) {
            res = res + path[i:i+1]
        }
    }
    if (len(res) > 0) && (res[len(res)-1] == '/') {
        res = res[:len(res)-1]
    }
    return
}

func (self *manifestTrie) getEntry(spath string) (entry *manifestTrieEntry, fullpath string) {
    path := RegularSlashes(spath)
    var pos int
    quitC := make(chan bool)
    entry, pos = self.findPrefixOf(path, quitC)
    return entry, path[:pos]
}