Modernize codebase and add Rock Ridge extension support

- Add go.mod with Go 1.21 requirement
- Replace deprecated io/ioutil with io and os equivalents
- Fix WriteTo signature to implement io.WriterTo properly
- Remove unused volumeDescriptorBodySize constant
- Fix filename parsing for files without dot (upstream bugfix)
- Add Label() method to get volume label
- Add AddLocalDirectory() for recursive directory addition
- Add Rock Ridge extension support for reader:
  - SUSP (System Use Sharing Protocol) parsing
  - Rock Ridge PX (POSIX attributes) and NM (alternate names)
  - Long filenames, symlink detection, POSIX permissions
- Add comprehensive tests for SUSP and Rock Ridge
- Rename fixtures/ to testdata/ (goproxy exclusion)
- Update README with new features and examples

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: MagicalTux

README.md

@@ -1,11 +1,25 @@
 ## iso9660
+
 [![GoDoc](https://godoc.org/github.com/KarpelesLab/iso9660?status.svg)](https://godoc.org/github.com/KarpelesLab/iso9660)
 
-A package for reading and creating ISO9660, forked from https://github.com/kdomanski/iso9660.
+A Go package for reading and creating ISO9660 images, forked from https://github.com/kdomanski/iso9660.
+
+Requires Go 1.21 or newer.
+
+## Features
 
-Requires Go 1.13 or newer.
+### Reading
+- Basic ISO9660 support
+- Rock Ridge extensions (long filenames, POSIX permissions, symlinks)
+- SUSP (System Use Sharing Protocol)
 
-Joliet and Rock Ridge extensions are not supported.
+### Writing
+- Basic ISO9660 support
+- El Torito boot support
+- Hard links (same file added multiple times is written once)
+- Streaming writes (no temp files needed)
+
+Joliet extensions are not supported.
 
 ## Examples
 
@@ -16,6 +30,7 @@ package main
 
 import (
   "log"
+  "os"
 
   "github.com/KarpelesLab/iso9660/isoutil"
 )
@@ -33,6 +48,53 @@ func main() {
 }
 ```
 
+### Reading an ISO with Rock Ridge
+
+```go
+package main
+
+import (
+  "fmt"
+  "log"
+  "os"
+
+  "github.com/KarpelesLab/iso9660"
+)
+
+func main() {
+  f, err := os.Open("/home/user/myImage.iso")
+  if err != nil {
+    log.Fatalf("failed to open file: %s", err)
+  }
+  defer f.Close()
+
+  img, err := iso9660.OpenImage(f)
+  if err != nil {
+    log.Fatalf("failed to open image: %s", err)
+  }
+
+  // Get the volume label
+  label, _ := img.Label()
+  fmt.Printf("Volume: %s\n", label)
+
+  root, err := img.RootDir()
+  if err != nil {
+    log.Fatalf("failed to get root dir: %s", err)
+  }
+
+  children, err := root.GetChildren()
+  if err != nil {
+    log.Fatalf("failed to get children: %s", err)
+  }
+
+  for _, child := range children {
+    // With Rock Ridge, Name() returns the full filename
+    // Mode() returns POSIX permissions
+    fmt.Printf("%s %s (%d bytes)\n", child.Mode(), child.Name(), child.Size())
+  }
+}
+```
+
 ### Creating an ISO
 
 ```go
@@ -51,20 +113,27 @@ func main() {
     log.Fatalf("failed to create writer: %s", err)
   }
 
-  // set volume name
+  // Set volume name
   writer.Primary.VolumeIdentifier = "testvol"
 
+  // Add a single file
   err = writer.AddLocalFile("/home/user/myFile.txt", "folder/MYFILE.TXT")
   if err != nil {
     log.Fatalf("failed to add file: %s", err)
   }
 
-  outputFile, err := os.OpenFile("/home/user/output.iso", os.O_WRONLY | os.O_TRUNC | os.O_CREATE, 0644)
+  // Or add an entire directory recursively
+  err = writer.AddLocalDirectory("/home/user/myFolder", "folder")
+  if err != nil {
+    log.Fatalf("failed to add directory: %s", err)
+  }
+
+  outputFile, err := os.OpenFile("/home/user/output.iso", os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
   if err != nil {
     log.Fatalf("failed to create file: %s", err)
   }
 
-  err = writer.WriteTo(outputFile)
+  _, err = writer.WriteTo(outputFile)
   if err != nil {
     log.Fatalf("failed to write ISO image: %s", err)
   }
@@ -76,39 +145,113 @@ func main() {
 }
 ```
 
-### Streaming an ISO via HTTP
-
-It is possible to stream a dynamically generated file on request via HTTP in order to include files or customize configuration files:
+### Creating a Bootable ISO
 
 ```go
+package main
+
 import (
-  "http"
   "log"
+  "os"
 
   "github.com/KarpelesLab/iso9660"
 )
 
-func ServeHTTP(rw http.RequestWriter, req *http.Request) {
+func main() {
   writer, err := iso9660.NewWriter()
   if err != nil {
     log.Fatalf("failed to create writer: %s", err)
   }
 
-  // set volume name
-  writer.Primary.VolumeIdentifier = "LIVE IMAGE"
+  writer.Primary.VolumeIdentifier = "BOOTABLE"
+
+  // Add El Torito boot entry
+  isolinux, err := iso9660.NewItemFile("/usr/share/syslinux/isolinux.bin")
+  if err != nil {
+    log.Fatalf("failed to open isolinux.bin: %s", err)
+  }
+
+  err = writer.AddBootEntry(&iso9660.BootCatalogEntry{BootInfoTable: true}, isolinux, "isolinux/isolinux.bin")
+  if err != nil {
+    log.Fatalf("failed to add boot entry: %s", err)
+  }
+
+  // Add other boot files
+  writer.AddLocalFile("/usr/share/syslinux/ldlinux.c32", "isolinux/ldlinux.c32")
 
-  if syslinux, err := iso9660.NewItemFile("/pkg/main/sys-boot.syslinux.core/share/syslinux/isolinux.bin"); err == nil {
-    writer.AddBootEntry(&iso9660.BootCatalogEntry{BootInfoTable: true}, isolinux, "isolinux/isolinux.bin")
-    writer.AddLocalFile("/pkg/main/sys-boot.syslinux.core/share/syslinux/linux.c32", "isolinux/linux.c32")
-    writer.AddLocalFile("/pkg/main/sys-boot.syslinux.core/share/syslinux/ldlinux.c32", "isolinux/ldlinux.c32")
+  outputFile, err := os.Create("/home/user/bootable.iso")
+  if err != nil {
+    log.Fatalf("failed to create file: %s", err)
   }
 
-  writer.AddLocalFile("kernel.img", "isolinux/kernel.img")
-  writer.AddLocalFile("initrd.img", "isolinux/initrd.img")
-  writer.AddLocalFile("root.squashfs", "root.img")
-  writer.AddFile(getSyslinuxConfig(), "isolinux/isolinux.cfg")
+  _, err = writer.WriteTo(outputFile)
+  if err != nil {
+    log.Fatalf("failed to write ISO image: %s", err)
+  }
+
+  outputFile.Close()
+}
+```
+
+### Streaming an ISO via HTTP
+
+It is possible to stream a dynamically generated ISO via HTTP:
+
+```go
+package main
+
+import (
+  "net/http"
+  "log"
+
+  "github.com/KarpelesLab/iso9660"
+)
+
+func handler(rw http.ResponseWriter, req *http.Request) {
+  writer, err := iso9660.NewWriter()
+  if err != nil {
+    http.Error(rw, err.Error(), 500)
+    return
+  }
+
+  writer.Primary.VolumeIdentifier = "LIVE IMAGE"
+
+  // Add files dynamically
+  writer.AddLocalFile("kernel.img", "boot/kernel.img")
+  writer.AddLocalFile("initrd.img", "boot/initrd.img")
 
   rw.Header().Set("Content-Type", "application/x-iso9660-image")
+  rw.Header().Set("Content-Disposition", "attachment; filename=image.iso")
+
   writer.WriteTo(rw)
 }
+
+func main() {
+  http.HandleFunc("/image.iso", handler)
+  log.Fatal(http.ListenAndServe(":8080", nil))
+}
 ```
+
+## API
+
+### Reader
+
+- `OpenImage(ra io.ReaderAt) (*Image, error)` - Open an ISO image for reading
+- `(*Image) RootDir() (*File, error)` - Get the root directory
+- `(*Image) Label() (string, error)` - Get the volume label
+- `(*File) GetChildren() ([]*File, error)` - Get directory children (excludes `.` and `..`)
+- `(*File) GetAllChildren() ([]*File, error)` - Get all directory children (includes `.` and `..`)
+- `(*File) Reader() io.Reader` - Get a reader for file contents
+- `(*File) Name() string` - Get filename (Rock Ridge long name if available)
+- `(*File) Mode() os.FileMode` - Get file mode (Rock Ridge permissions if available)
+- `(*File) IsDir() bool` - Check if entry is a directory
+- `(*File) Size() int64` - Get file size
+
+### Writer
+
+- `NewWriter() (*ImageWriter, error)` - Create a new ISO writer
+- `(*ImageWriter) AddFile(data io.Reader, filePath string) error` - Add a file from a reader
+- `(*ImageWriter) AddLocalFile(localPath, filePath string) error` - Add a file from the filesystem
+- `(*ImageWriter) AddLocalDirectory(origin, target string) error` - Add a directory recursively
+- `(*ImageWriter) AddBootEntry(boot *BootCatalogEntry, data Item, filePath string) error` - Add El Torito boot entry
+- `(*ImageWriter) WriteTo(w io.Writer) (int64, error)` - Write the ISO image

go.mod

@@ -0,0 +1,11 @@
+module github.com/KarpelesLab/iso9660
+
+go 1.21
+
+require github.com/stretchr/testify v1.8.4
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=