forked from snapcore/snapd
/
fsbackstore.go
160 lines (142 loc) · 4.57 KB
/
fsbackstore.go
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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2015-2016 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package asserts
import (
"fmt"
"net/url"
"os"
"path/filepath"
"sync"
)
// the default filesystem based backstore for assertions
const (
assertionsLayoutVersion = "v0"
assertionsRoot = "asserts-" + assertionsLayoutVersion
activeFname = "active"
)
type filesystemBackstore struct {
top string
mu sync.RWMutex
}
// OpenFSBackstore opens a filesystem backed assertions backstore under path.
func OpenFSBackstore(path string) (Backstore, error) {
top := filepath.Join(path, assertionsRoot)
err := ensureTop(top)
if err != nil {
return nil, err
}
return &filesystemBackstore{top: top}, nil
}
// guarantees that result assertion is of the expected type (both in the AssertionType and go type sense)
func (fsbs *filesystemBackstore) readAssertion(assertType *AssertionType, diskPrimaryPath string) (Assertion, error) {
encoded, err := readEntry(fsbs.top, assertType.Name, diskPrimaryPath)
if os.IsNotExist(err) {
return nil, ErrNotFound
}
if err != nil {
return nil, fmt.Errorf("broken assertion storage, cannot read assertion: %v", err)
}
assert, err := Decode(encoded)
if err != nil {
return nil, fmt.Errorf("broken assertion storage, cannot decode assertion: %v", err)
}
if assert.Type() != assertType {
return nil, fmt.Errorf("assertion that is not of type %q under their storage tree", assertType.Name)
}
// because of Decode() construction assert has also the expected go type
return assert, nil
}
func buildDiskPrimaryPath(primaryPath []string) string {
n := len(primaryPath)
comps := make([]string, n+1)
// safety against '/' etc
for i, comp := range primaryPath {
comps[i] = url.QueryEscape(comp)
}
comps[n] = activeFname
return filepath.Join(comps...)
}
func (fsbs *filesystemBackstore) Put(assertType *AssertionType, assert Assertion) error {
fsbs.mu.Lock()
defer fsbs.mu.Unlock()
primaryPath := make([]string, len(assertType.PrimaryKey))
for i, k := range assertType.PrimaryKey {
primaryPath[i] = assert.Header(k)
}
diskPrimaryPath := buildDiskPrimaryPath(primaryPath)
curAssert, err := fsbs.readAssertion(assertType, diskPrimaryPath)
if err == nil {
curRev := curAssert.Revision()
rev := assert.Revision()
if curRev >= rev {
return &RevisionError{Current: curRev, Used: rev}
}
} else if err != ErrNotFound {
return err
}
err = atomicWriteEntry(Encode(assert), false, fsbs.top, assertType.Name, diskPrimaryPath)
if err != nil {
return fmt.Errorf("broken assertion storage, cannot write assertion: %v", err)
}
return nil
}
func (fsbs *filesystemBackstore) Get(assertType *AssertionType, key []string) (Assertion, error) {
fsbs.mu.RLock()
defer fsbs.mu.RUnlock()
return fsbs.readAssertion(assertType, buildDiskPrimaryPath(key))
}
func (fsbs *filesystemBackstore) search(assertType *AssertionType, diskPattern []string, foundCb func(Assertion)) error {
assertTypeTop := filepath.Join(fsbs.top, assertType.Name)
candCb := func(diskPrimaryPath string) error {
a, err := fsbs.readAssertion(assertType, diskPrimaryPath)
if err == ErrNotFound {
return fmt.Errorf("broken assertion storage, disappearing entry: %s/%s", assertType.Name, diskPrimaryPath)
}
if err != nil {
return err
}
foundCb(a)
return nil
}
err := findWildcard(assertTypeTop, diskPattern, candCb)
if err != nil {
return fmt.Errorf("broken assertion storage, searching for %s: %v", assertType.Name, err)
}
return nil
}
func (fsbs *filesystemBackstore) Search(assertType *AssertionType, headers map[string]string, foundCb func(Assertion)) error {
fsbs.mu.RLock()
defer fsbs.mu.RUnlock()
n := len(assertType.PrimaryKey)
diskPattern := make([]string, n+1)
for i, k := range assertType.PrimaryKey {
keyVal := headers[k]
if keyVal == "" {
diskPattern[i] = "*"
} else {
diskPattern[i] = url.QueryEscape(keyVal)
}
}
diskPattern[n] = activeFname
candCb := func(a Assertion) {
if searchMatch(a, headers) {
foundCb(a)
}
}
return fsbs.search(assertType, diskPattern, candCb)
}