gopkg.in/ubuntu-core/snappy.v0@v0.0.0-20210902073436-25a8614f10a6/overlord/snapstate/aux_store_info.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2018 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package snapstate
    21  
    22  import (
    23  	"encoding/json"
    24  	"fmt"
    25  	"os"
    26  	"path/filepath"
    27  
    28  	"github.com/snapcore/snapd/dirs"
    29  	"github.com/snapcore/snapd/osutil"
    30  	"github.com/snapcore/snapd/snap"
    31  )
    32  
    33  // auxStoreInfo is information about a snap (*not* a snap revision), not
    34  // needed in the state, that may be stored to augment the information
    35  // returned for locally-installed snaps
    36  type auxStoreInfo struct {
    37  	Media    snap.MediaInfos `json:"media,omitempty"`
    38  	Website  string          `json:"website,omitempty"`
    39  	StoreURL string          `json:"store-url,omitempty"`
    40  }
    41  
    42  func auxStoreInfoFilename(snapID string) string {
    43  	return filepath.Join(dirs.SnapAuxStoreInfoDir, snapID) + ".json"
    44  }
    45  
    46  // retrieveAuxStoreInfo loads the stored per-snap auxiliary store info into the given *snap.Info
    47  func retrieveAuxStoreInfo(info *snap.Info) error {
    48  	if info.SnapID == "" {
    49  		return nil
    50  	}
    51  	f, err := os.Open(auxStoreInfoFilename(info.SnapID))
    52  	if err != nil {
    53  		if os.IsNotExist(err) {
    54  			return nil
    55  		}
    56  		return err
    57  	}
    58  	defer f.Close()
    59  
    60  	var aux auxStoreInfo
    61  	dec := json.NewDecoder(f)
    62  	if err := dec.Decode(&aux); err != nil {
    63  		return fmt.Errorf("cannot decode auxiliary store info for snap %q: %v", info.InstanceName(), err)
    64  	}
    65  	if dec.More() {
    66  		return fmt.Errorf("cannot decode auxiliary store info for snap %q: spurious content after document body", info.InstanceName())
    67  	}
    68  
    69  	info.Media = aux.Media
    70  	info.Website = aux.Website
    71  	info.StoreURL = aux.StoreURL
    72  
    73  	return nil
    74  }
    75  
    76  // keepAuxStoreInfo saves the given auxiliary store info to disk.
    77  func keepAuxStoreInfo(snapID string, aux *auxStoreInfo) error {
    78  	if snapID == "" {
    79  		return nil
    80  	}
    81  	if err := os.MkdirAll(dirs.SnapAuxStoreInfoDir, 0755); err != nil {
    82  		return fmt.Errorf("cannot create directory for auxiliary store info: %v", err)
    83  	}
    84  
    85  	af, err := osutil.NewAtomicFile(auxStoreInfoFilename(snapID), 0644, 0, osutil.NoChown, osutil.NoChown)
    86  	if err != nil {
    87  		return fmt.Errorf("cannot create file for auxiliary store info for snap %s: %v", snapID, err)
    88  	}
    89  	// on success, Cancel becomes a nop
    90  	defer af.Cancel()
    91  
    92  	if err := json.NewEncoder(af).Encode(aux); err != nil {
    93  		return fmt.Errorf("cannot encode auxiliary store info for snap %s: %v", snapID, err)
    94  	}
    95  
    96  	if err := af.Commit(); err != nil {
    97  		return fmt.Errorf("cannot commit auxiliary store info file for snap %s: %v", snapID, err)
    98  	}
    99  	return nil
   100  }
   101  
   102  // discardAuxStoreInfo removes the auxiliary store info for the given snap from disk.
   103  func discardAuxStoreInfo(snapID string) error {
   104  	if snapID == "" {
   105  		return nil
   106  	}
   107  	if err := os.Remove(auxStoreInfoFilename(snapID)); err != nil && !os.IsNotExist(err) {
   108  		return fmt.Errorf("cannot remove auxiliary store info file for snap %s: %v", snapID, err)
   109  	}
   110  	return nil
   111  }