github.com/bugraaydogar/snapd@v0.0.0-20210315170335-8c70bb858939/bootloader/assets/assets.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 assets
    21  
    22  import (
    23  	"fmt"
    24  	"sort"
    25  
    26  	"github.com/snapcore/snapd/osutil"
    27  )
    28  
    29  var registeredAssets = map[string][]byte{}
    30  
    31  // ForEditions wraps a snippet that is used in editions starting with
    32  // FirstEdition.
    33  type ForEditions struct {
    34  	// First edition this snippet is used in
    35  	FirstEdition uint
    36  	// Snippet data
    37  	Snippet []byte
    38  }
    39  
    40  var registeredEditionSnippets = map[string][]ForEditions{}
    41  
    42  // registerInternal registers an internal asset under the given name.
    43  func registerInternal(name string, data []byte) {
    44  	if _, ok := registeredAssets[name]; ok {
    45  		panic(fmt.Sprintf("asset %q is already registered", name))
    46  	}
    47  	registeredAssets[name] = data
    48  }
    49  
    50  // Internal returns the content of an internal asset registered under the given
    51  // name, or nil when none was found.
    52  func Internal(name string) []byte {
    53  	return registeredAssets[name]
    54  }
    55  
    56  type byFirstEdition []ForEditions
    57  
    58  func (b byFirstEdition) Len() int           { return len(b) }
    59  func (b byFirstEdition) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
    60  func (b byFirstEdition) Less(i, j int) bool { return b[i].FirstEdition < b[j].FirstEdition }
    61  
    62  func sanitizeSnippets(snippets []ForEditions) error {
    63  	if !sort.IsSorted(byFirstEdition(snippets)) {
    64  		return fmt.Errorf("snippets must be sorted in ascending edition number order")
    65  	}
    66  	for i := range snippets {
    67  		if i == 0 {
    68  			continue
    69  		}
    70  		if snippets[i-1].FirstEdition == snippets[i].FirstEdition {
    71  			return fmt.Errorf(`first edition %v repeated`, snippets[i].FirstEdition)
    72  		}
    73  	}
    74  	return nil
    75  }
    76  
    77  // registerSnippetForEditions register a set of snippets, each carrying the
    78  // first edition number it applies to, under a given key.
    79  func registerSnippetForEditions(name string, snippets []ForEditions) {
    80  	if _, ok := registeredEditionSnippets[name]; ok {
    81  		panic(fmt.Sprintf("edition snippets %q are already registered", name))
    82  	}
    83  
    84  	if err := sanitizeSnippets(snippets); err != nil {
    85  		panic(fmt.Errorf("cannot validate snippets %q: %v", name, err))
    86  	}
    87  	registeredEditionSnippets[name] = snippets
    88  }
    89  
    90  // SnippetForEdition returns a snippet registered under given name,
    91  // applicable for the provided edition number.
    92  func SnippetForEdition(name string, edition uint) []byte {
    93  	snippets := registeredEditionSnippets[name]
    94  	if snippets == nil {
    95  		return nil
    96  	}
    97  	var current []byte
    98  	// snippets are sorted by ascending edition number when adding
    99  	for _, snip := range snippets {
   100  		if edition >= snip.FirstEdition {
   101  			current = snip.Snippet
   102  		} else {
   103  			break
   104  		}
   105  	}
   106  	return current
   107  }
   108  
   109  // MockInternal mocks the contents of an internal asset for use in testing.
   110  func MockInternal(name string, data []byte) (restore func()) {
   111  	osutil.MustBeTestBinary("mocking can be done only in tests")
   112  
   113  	old, ok := registeredAssets[name]
   114  	registeredAssets[name] = data
   115  	return func() {
   116  		if ok {
   117  			registeredAssets[name] = old
   118  		} else {
   119  			delete(registeredAssets, name)
   120  		}
   121  	}
   122  }
   123  
   124  // MockSnippetsForEdition mocks the contents of per-edition snippets.
   125  func MockSnippetsForEdition(name string, snippets []ForEditions) (restore func()) {
   126  	osutil.MustBeTestBinary("mocking can be done only in tests")
   127  
   128  	old, ok := registeredEditionSnippets[name]
   129  	snippetsCopy := make([]ForEditions, len(snippets))
   130  	copy(snippetsCopy, snippets)
   131  	if ok {
   132  		delete(registeredEditionSnippets, name)
   133  	}
   134  	registerSnippetForEditions(name, snippetsCopy)
   135  
   136  	return func() {
   137  		if ok {
   138  			registeredEditionSnippets[name] = old
   139  		} else {
   140  			delete(registeredAssets, name)
   141  		}
   142  	}
   143  }