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authorPřemysl Eric Janouch <p@janouch.name>2021-12-09 14:06:48 +0100
committerPřemysl Eric Janouch <p@janouch.name>2021-12-09 15:24:25 +0100
commitb358467791bb1e277edcc997c31098f5d7a052f5 (patch)
treed379b1891f69f576bc425d1f792c3fd901359fc0
parentd0f80aa6ae5d02a2e55850c58b2871c1662cb7e1 (diff)
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Add an external VFS for Midnight Commander
-rw-r--r--cmd/extfs-pdf/main.go132
1 files changed, 132 insertions, 0 deletions
diff --git a/cmd/extfs-pdf/main.go b/cmd/extfs-pdf/main.go
new file mode 100644
index 0000000..74f8433
--- /dev/null
+++ b/cmd/extfs-pdf/main.go
@@ -0,0 +1,132 @@
+//
+// Copyright (c) 2021, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+// extfs-pdf is an external VFS plugin for Midnight Commander.
+// More serious image extractors should rewrite this to use pdfimages(1).
+package main
+
+import (
+ "flag"
+ "fmt"
+ "os"
+
+ "janouch.name/pdf-simple-sign/pdf"
+)
+
+func die(status int, format string, args ...interface{}) {
+ os.Stderr.WriteString(fmt.Sprintf(format+"\n", args...))
+ os.Exit(status)
+}
+
+func usage() {
+ die(1, "Usage: %s [-h] COMMAND DOCUMENT [ARG...]", os.Args[0])
+}
+
+func streamSuffix(o *pdf.Object) string {
+ if filter, _ := o.Dict["Filter"]; filter.Kind == pdf.Name {
+ switch filter.String {
+ case "JBIG2Decode":
+ // This is the file extension used by pdfimages(1).
+ // This is not a complete JBIG2 standalone file.
+ return "jb2e"
+ case "JPXDecode":
+ return "jp2"
+ case "DCTDecode":
+ return "jpg"
+ default:
+ return filter.String
+ }
+ }
+ return "stream"
+}
+
+func list(updater *pdf.Updater) {
+ for _, o := range updater.ListIndirect() {
+ object, err := updater.Get(o.N, o.Generation)
+ size := 0
+ if err != nil {
+ fmt.Fprintf(os.Stderr, "%s\n", err)
+ } else {
+ // Accidental transformation, retrieving original data is more work.
+ size = len(object.Serialize())
+ }
+ fmt.Printf("-r--r--r-- 1 0 0 %d 01-01-1970 00:00 %d-%d\n",
+ size, o.N, o.Generation)
+ if object.Kind == pdf.Stream {
+ fmt.Printf("-r--r--r-- 1 0 0 %d 01-01-1970 00:00 %d-%d.%s\n",
+ len(object.Stream), o.N, o.Generation, streamSuffix(&object))
+ }
+ }
+}
+
+func copyout(updater *pdf.Updater, storedFilename, extractTo string) {
+ var (
+ n, generation uint
+ suffix string
+ )
+ m, err := fmt.Sscanf(storedFilename, "%d-%d%s", &n, &generation, &suffix)
+ if m < 2 {
+ die(3, "%s: %s", storedFilename, err)
+ }
+
+ object, err := updater.Get(n, generation)
+ if err != nil {
+ die(3, "%s: %s", storedFilename, err)
+ }
+
+ content := []byte(object.Serialize())
+ if suffix != "" {
+ content = object.Stream
+ }
+ if err = os.WriteFile(extractTo, content, 0666); err != nil {
+ die(3, "%s", err)
+ }
+}
+
+func main() {
+ flag.Usage = usage
+ flag.Parse()
+ if flag.NArg() < 2 {
+ usage()
+ }
+
+ command, documentPath := flag.Arg(0), flag.Arg(1)
+ doc, err := os.ReadFile(documentPath)
+ if err != nil {
+ die(1, "%s", err)
+ }
+
+ updater, err := pdf.NewUpdater(doc)
+ if err != nil {
+ die(2, "%s", err)
+ }
+
+ switch command {
+ default:
+ die(1, "unsupported command: %s", command)
+ case "list":
+ if flag.NArg() != 2 {
+ usage()
+ } else {
+ list(updater)
+ }
+ case "copyout":
+ if flag.NArg() != 4 {
+ usage()
+ } else {
+ copyout(updater, flag.Arg(2), flag.Arg(3))
+ }
+ }
+}