Add support for arbitrary decompression tools

This allows users to use non-unzip decompression tools such as
libarchive's `bsdtar`.

2 files changed, 25 insertions, 9 deletions

diff --git a/README.md b/README.md
index 52f7eea..f643795 100644
--- a/README.md
+++ b/README.md
@@ -29,11 +29,17 @@ and install with `M-x package-install RET nov RET`.
 
 ## Setup
 
-Make sure you have an `unzip` executable on `PATH`, otherwise the
-extraction of EPUB files will fail.  If you for some reason have
-`unzip` in a non-standard location, customize `nov-unzip-program` to
-its path.  You'll also need an Emacs compiled with `libxml2` support,
-otherwise rendering will fail.
+By default, `nov.el` uses `unzip` on `PATH` to extract EPUB files. You
+can customize `nov-unzip-program` if it is located elsewhere. You can
+also customize `nov-unzip-args` if you use a different decompression
+tool like `bsdtar`. It must accept a target `directory` where nov
+unzips the EPUB `filename`.
+
+    (setq nov-unzip-program (executable-find "bsdtar")
+          nov-unzip-args '("-xC" directory "-f" filename))
+
+You'll also need an Emacs compiled with `libxml2` support, otherwise
+rendering will fail.
 
 Put the following in your init file:
 
diff --git a/nov.el b/nov.el
index 73e8591..d53e5d0 100644
--- a/nov.el
+++ b/nov.el
@@ -69,10 +69,18 @@
   :group 'multimedia)
 
 (defcustom nov-unzip-program (executable-find "unzip")
-  "Path to `unzip` executable."
+  "Path to decompression executable."
   :type '(file :must-match t)
   :group 'nov)
 
+(defcustom nov-unzip-args '("-o" directory filename)
+  "Arguments to decompression executable.
+This variable expects a list of strings, except for `directory'
+and `filename' symbols, which will be replaced accordingly when
+opening an EPUB file."
+  :type 'list
+  :group 'nov)
+
 (defcustom nov-variable-pitch t
   "Non-nil if a variable pitch face should be used.
 Otherwise the default face is used."
@@ -186,9 +194,11 @@ Each element of the stack is a list (NODEINDEX BUFFERPOS).")
 (defun nov-unzip-epub (directory filename)
   "Extract FILENAME into DIRECTORY.
 Unnecessary nesting is removed with `nov-unnest-directory'."
-  (let ((status (call-process nov-unzip-program nil "*nov unzip*" t
-                              "-od" directory filename))
-        child)
+  (let* ((status (apply #'call-process nov-unzip-program nil "*nov unzip*" t
+                        (mapcar (lambda (e) (cond ((eq e 'directory) directory)
+                                                  ((eq e 'filename) filename)
+                                                  (t e))) nov-unzip-args)))
+         child)
     (while (setq child (nov-contains-nested-directory-p directory))
       (nov-unnest-directory directory child))
     ;; HACK: unzip preserves file permissions, no matter how silly they