| 1 | // Package pathidentity separates paths used for filesystem access from keys |
| 2 | // used to compare filesystem identity. |
| 3 | package pathidentity |
| 4 | |
| 5 | import ( |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "os" |
| 9 | "path/filepath" |
| 10 | "runtime" |
| 11 | "slices" |
| 12 | "strings" |
| 13 | "syscall" |
| 14 | ) |
| 15 | |
| 16 | const Version = 3 |
| 17 | |
| 18 | type ErrorKind string |
| 19 | |
| 20 | const ( |
| 21 | ErrorInvalid ErrorKind = "invalid" |
| 22 | ErrorPermission ErrorKind = "permission" |
| 23 | ErrorLinkLoop ErrorKind = "link_loop" |
| 24 | ErrorUnavailable ErrorKind = "unavailable" |
| 25 | ErrorUnknown ErrorKind = "unknown" |
| 26 | ) |
| 27 | |
| 28 | type Error struct { |
| 29 | Kind ErrorKind |
| 30 | Stage string |
| 31 | Path string |
| 32 | Err error |
| 33 | } |
| 34 | |
| 35 | func (e *Error) Error() string { |
| 36 | if e == nil { |
| 37 | return "<nil>" |
| 38 | } |
| 39 | return fmt.Sprintf("resolve path identity (%s, %s): %v", e.Stage, e.Kind, e.Err) |
| 40 | } |
| 41 | |
| 42 | func (e *Error) Unwrap() error { return e.Err } |
| 43 | |
| 44 | type Options struct { |
| 45 | // BaseDir is required when path is relative. It must itself be absolute. |
| 46 | BaseDir string |
| 47 | // FollowLeaf resolves the final directory entry. Leave it false for |
| 48 | // rename/delete operations that act on the entry rather than its target. |
| 49 | FollowLeaf bool |
| 50 | } |
| 51 | |
| 52 | type Identity struct { |
| 53 | AccessPath string |
| 54 | PhysicalPath string |
| 55 | Key string |
| 56 | } |
| 57 | |
| 58 | func Resolve(path string, options Options) (Identity, error) { |
| 59 | access, err := absoluteAccessPath(path, options.BaseDir) |
| 60 | if err != nil { |
| 61 | return Identity{}, err |
| 62 | } |
| 63 | physical, err := resolvePhysicalPath(access, options.FollowLeaf) |
| 64 | if err != nil { |
| 65 | return Identity{}, err |
| 66 | } |
| 67 | key, err := platformIdentityKey(physical) |
| 68 | if err != nil { |
| 69 | return Identity{}, classify("compare", physical, err) |
| 70 | } |
| 71 | return Identity{AccessPath: access, PhysicalPath: physical, Key: filepath.Clean(key)}, nil |
| 72 | } |
| 73 | |
| 74 | func Same(a, b string, options Options) (bool, error) { |
| 75 | return NewMatcher(options, nil).Same(a, b) |
| 76 | } |
| 77 | |
| 78 | func statForMode(path string, followLeaf bool) (os.FileInfo, error) { |
| 79 | if followLeaf { |
| 80 | return os.Stat(path) |
| 81 | } |
| 82 | return os.Lstat(path) |
| 83 | } |
| 84 | |
| 85 | func absoluteAccessPath(path, baseDir string) (string, error) { |
| 86 | path = strings.TrimSpace(path) |
| 87 | if path == "" { |
| 88 | return "", &Error{Kind: ErrorInvalid, Stage: "input", Path: path, Err: errors.New("path is empty")} |
| 89 | } |
| 90 | path = filepath.Clean(path) |
| 91 | if !filepath.IsAbs(path) { |
| 92 | baseDir = strings.TrimSpace(baseDir) |
| 93 | if baseDir == "" || !filepath.IsAbs(baseDir) { |
| 94 | return "", &Error{Kind: ErrorInvalid, Stage: "input", Path: path, Err: errors.New("relative path requires an absolute base directory")} |
| 95 | } |
| 96 | path = filepath.Join(filepath.Clean(baseDir), path) |
| 97 | } |
| 98 | return filepath.Clean(path), nil |
| 99 | } |
| 100 | |
| 101 | func resolvePhysicalPath(access string, followLeaf bool) (string, error) { |
| 102 | target, leaf := access, "" |
| 103 | if !followLeaf { |
| 104 | parent := filepath.Dir(access) |
| 105 | if parent != access { |
| 106 | target, leaf = parent, filepath.Base(access) |
| 107 | } |
| 108 | } |
| 109 | resolved, err := resolveThroughExistingAncestor(target) |
| 110 | if err != nil { |
| 111 | return "", err |
| 112 | } |
| 113 | if leaf != "" { |
| 114 | resolved = filepath.Join(resolved, leaf) |
| 115 | } |
| 116 | return filepath.Clean(resolved), nil |
| 117 | } |
| 118 | |
| 119 | func resolveThroughExistingAncestor(path string) (string, error) { |
| 120 | return resolveThroughExistingAncestorWith(path, resolveExistingPath) |
| 121 | } |
| 122 | |
| 123 | func resolveThroughExistingAncestorWith(path string, evalSymlinks func(string) (string, error)) (string, error) { |
| 124 | current := filepath.Clean(path) |
| 125 | missing := make([]string, 0, 4) |
| 126 | for { |
| 127 | // Inspect existence before resolving links. A missing entry may be |
| 128 | // created by another lock contender; that is not a dangling link. |
| 129 | _, err := os.Lstat(current) |
| 130 | if err == nil { |
| 131 | resolved, resolveErr := evalSymlinks(current) |
| 132 | if resolveErr != nil { |
| 133 | return "", classify("physical", current, resolveErr) |
| 134 | } |
| 135 | for _, part := range slices.Backward(missing) { |
| 136 | resolved = filepath.Join(resolved, part) |
| 137 | } |
| 138 | return filepath.Clean(resolved), nil |
| 139 | } |
| 140 | if !os.IsNotExist(err) { |
| 141 | return "", classify("physical", current, err) |
| 142 | } |
| 143 | parent := filepath.Dir(current) |
| 144 | if parent == current { |
| 145 | return "", &Error{Kind: ErrorUnavailable, Stage: "physical", Path: path, Err: err} |
| 146 | } |
| 147 | missing = append(missing, filepath.Base(current)) |
| 148 | current = parent |
| 149 | } |
| 150 | } |
| 151 | |
| 152 | func classify(stage, path string, err error) error { |
| 153 | kind := ErrorUnknown |
| 154 | switch { |
| 155 | case errors.Is(err, os.ErrPermission): |
| 156 | kind = ErrorPermission |
| 157 | case errors.Is(err, syscall.ELOOP) || platformLinkLoop(err) || strings.Contains(strings.ToLower(err.Error()), "too many links"): |
| 158 | kind = ErrorLinkLoop |
| 159 | case errors.Is(err, os.ErrNotExist): |
| 160 | kind = ErrorUnavailable |
| 161 | } |
| 162 | return &Error{Kind: kind, Stage: stage, Path: path, Err: err} |
| 163 | } |
| 164 | |
| 165 | // Canonical is the frozen v1 compatibility key used by historical locks. |
| 166 | // New identity-sensitive code must use Resolve so errors are not discarded. |
| 167 | func Canonical(path string) string { |
| 168 | key := filepath.Clean(strings.TrimSpace(path)) |
| 169 | if abs, err := filepath.Abs(key); err == nil { |
| 170 | key = abs |
| 171 | } |
| 172 | key = legacyResolvePathThroughExistingAncestor(key) |
| 173 | if runtime.GOOS == "windows" { |
| 174 | if strings.HasPrefix(strings.ToUpper(key), `\\?\UNC\`) { |
| 175 | key = `\\` + key[len(`\\?\UNC\`):] |
| 176 | } else { |
| 177 | key = strings.TrimPrefix(key, `\\?\`) |
| 178 | } |
| 179 | key = strings.ToLower(key) |
| 180 | } |
| 181 | return key |
| 182 | } |
| 183 | |
| 184 | func legacyResolvePathThroughExistingAncestor(path string) string { |
| 185 | current := filepath.Clean(path) |
| 186 | missing := make([]string, 0, 4) |
| 187 | for { |
| 188 | if resolved, err := filepath.EvalSymlinks(current); err == nil { |
| 189 | for _, part := range slices.Backward(missing) { |
| 190 | resolved = filepath.Join(resolved, part) |
| 191 | } |
| 192 | return resolved |
| 193 | } |
| 194 | parent := filepath.Dir(current) |
| 195 | if parent == current { |
| 196 | return path |
| 197 | } |
| 198 | missing = append(missing, filepath.Base(current)) |
| 199 | current = parent |
| 200 | } |
| 201 | } |
| 202 |