github.com/Lephar/snapd@v0.0.0-20210825215435-c7fba9cef4d2/snap/snapfile/snapfile.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2020 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 snapfile
    21  
    22  import (
    23  	"github.com/snapcore/snapd/snap"
    24  	"github.com/snapcore/snapd/snap/snapdir"
    25  	"github.com/snapcore/snapd/snap/squashfs"
    26  )
    27  
    28  // backend implements a specific snap format
    29  type snapFormat struct {
    30  	matches func(string) bool
    31  	open    func(string) (snap.Container, error)
    32  }
    33  
    34  // formatHandlers is the registry of known formats that work with Open
    35  var formatHandlers = []snapFormat{
    36  	// standard squashfs snap file format
    37  	{
    38  		squashfs.FileHasSquashfsHeader,
    39  		func(p string) (snap.Container, error) { return squashfs.New(p), nil },
    40  	},
    41  	// snap directory format, i.e. snap try <dir>
    42  	{
    43  		snapdir.IsSnapDir,
    44  		func(p string) (snap.Container, error) { return snapdir.New(p), nil },
    45  	},
    46  }
    47  
    48  // Open opens a given snap file with the right backend.
    49  func Open(path string) (snap.Container, error) {
    50  	for _, h := range formatHandlers {
    51  		if h.matches(path) {
    52  			return h.open(path)
    53  		}
    54  	}
    55  
    56  	return nil, snap.NotSnapError{Path: path}
    57  }