[nongnu] elpa/annotate e53c0f5adf 296/372: - added checking encrypted (GPG) file format

[ELPA Syncer]

branch: elpa/annotate
commit e53c0f5adff8e8c0c6ef3f3ddca5706f974ccf70
Author: cage <cage-invalid@invalid>
Commit: cage <cage-invalid@invalid>

    - added checking encrypted (GPG) file format
    
    In  many parts  of  the code  we  use 'annotate-guess-file-format',  a
    function that  try to guess the  format of the file  that produced the
    contents of a  buffer. Sometimes (for example buffers  that shows info
    nodes)  this check  is very  expensive because  involves reading  (and
    possibly decompress or even decrypt) the file contents and check for a
    regular expression.
    
    If we could  know in advance that the file  is symmetrically encrypted
    with GPG we could skip other,  more expensive checks for guessing file
    format (like info files).
---
 annotate.el | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/annotate.el b/annotate.el
index db0fd1540f..59ceadfd99 100644
--- a/annotate.el
+++ b/annotate.el
@@ -2212,8 +2212,31 @@ sophisticated way than plain text"
                                          (and has-separator-p
                                               has-info-p))
                                      :info
-                                   nil))))))
-    (info-format-p)))
+                                   nil)))))
+              (gpg-format-p ()
+                            (with-temp-buffer
+                              (let* ((magic-0    #x8c)
+                                     (magic-1    #x0d)
+                                     (magic-4    #x03)
+                                     (magic-5    #x02)
+                                     (attributes (file-attributes filename))
+                                     (file-size  (file-attribute-size 
attributes)))
+                                (when (> file-size 6)
+                                  (let* ((bytes      
(insert-file-contents-literally filename
+                                                                               
      nil
+                                                                               
      0
+                                                                               
      7)))
+                                    (setf bytes
+                                          (cl-loop for i from 1 to 6 collect
+                                                   (elt 
(buffer-substring-no-properties i (1+ i))
+                                                        0)))
+                                    (when (and (= (logand (elt bytes 0) 
#x0000ff) magic-0)
+                                               (= (logand (elt bytes 1) 
#x0000ff) magic-1)
+                                               (= (logand (elt bytes 4) 
#x0000ff) magic-4)
+                                               (= (logand (elt bytes 5) 
#x0000ff) magic-5))
+                                      :encrypted-symmetric)))))))
+    (or (gpg-format-p)
+        (info-format-p)))) ;; keep this one for last as it is the slowest
 
 ;;;; summary window procedures