commit 4c6a341ab592b2389083579dba08d1961a0380b7
Author: Jean-Marc Lasgouttes <[email protected]>
Date:   Tue Jul 3 11:36:12 2018 +0200

    Encapsulate libmagic support in a class
    
    This makes the code much easier to read and, additionally, allows to
    parse the magic file with magic_load() only once per session.
    
    As a result, getFormatFromFile is slightly faster.
---
 src/Format.cpp          |   76 +++++++++++++++++----------------------------
 src/support/Magic.h     |   77 +++++++++++++++++++++++++++++++++++++++++++++++
 src/support/Makefile.am |    1 +
 3 files changed, 107 insertions(+), 47 deletions(-)

diff --git a/src/Format.cpp b/src/Format.cpp
index 3b3a10d..feefd1e 100644
--- a/src/Format.cpp
+++ b/src/Format.cpp
@@ -19,11 +19,12 @@
 #include "frontends/alert.h" //to be removed?
 
 #include "support/debug.h"
+#include "support/docstream.h"
 #include "support/filetools.h"
 #include "support/gettext.h"
 #include "support/lstrings.h"
+#include "support/Magic.h"
 #include "support/mutex.h"
-#include "support/docstream.h"
 #include "support/os.h"
 #include "support/PathChanger.h"
 #include "support/Systemcall.h"
@@ -39,10 +40,6 @@
 #include "support/linkback/LinkBackProxy.h"
 #endif
 
-#ifdef HAVE_MAGIC_H
-#include <magic.h>
-#endif
-
 using namespace std;
 using namespace lyx::support;
 
@@ -407,52 +404,37 @@ string Formats::getFormatFromFile(FileName const & 
filename) const
 
        string psformat;
        string format;
-#ifdef HAVE_MAGIC_H
        if (filename.exists()) {
-               magic_t magic_cookie = magic_open(MAGIC_MIME);
-               if (magic_cookie) {
-                       if (magic_load(magic_cookie, NULL) != 0) {
-                               LYXERR(Debug::GRAPHICS, 
"Formats::getFormatFromFile\n"
-                                       << "\tCouldn't load magic database - "
-                                       << magic_error(magic_cookie));
-                       } else {
-                               char const * result = magic_file(magic_cookie,
-                                       
filename.toFilesystemEncoding().c_str());
-                               string mime;
-                               if (result)
-                                       mime = token(result, ';', 0);
-                               else {
-                                       LYXERR(Debug::GRAPHICS, 
"Formats::getFormatFromFile\n"
-                                               << "\tCouldn't query magic 
database - "
-                                               << magic_error(magic_cookie));
-                               }
-                               // our own detection is better for binary files 
(can be anything)
-                               // and different plain text formats
-                               if (!mime.empty() && mime != 
"application/octet-stream" &&
-                                   mime != "text/plain") {
-                                       Formats::const_iterator cit =
-                                               find_if(formatlist_.begin(), 
formatlist_.end(),
-                                                       FormatMimeEqual(mime));
-                                       if (cit != formatlist_.end()) {
-                                               LYXERR(Debug::GRAPHICS, "\tgot 
format from MIME type: "
-                                                       << mime << " -> " << 
cit->name());
-                                               // See special eps/ps handling 
below
-                                               if (mime == 
"application/postscript")
-                                                       psformat = cit->name();
-                                               else
-                                                       format = cit->name();
-                                       }
-                               }
+               // one instance of Magic that will be reused for next calls
+               // This avoids to read the magic file everytime
+               // If libmagic is not available, Magic::file returns an empty 
string.
+               static Magic magic;
+               string const result = 
magic.file(filename.toFilesystemEncoding());
+               string const mime = token(result, ';', 0);
+               // our own detection is better for binary files (can be 
anything)
+               // and different plain text formats
+               if (!mime.empty() && mime != "application/octet-stream" &&
+                       mime != "text/plain") {
+                       Formats::const_iterator cit =
+                               find_if(formatlist_.begin(), formatlist_.end(),
+                                               FormatMimeEqual(mime));
+                       if (cit != formatlist_.end()) {
+                               LYXERR(Debug::GRAPHICS, "\tgot format from MIME 
type: "
+                                          << mime << " -> " << cit->name());
+                               // See special eps/ps handling below
+                               if (mime == "application/postscript")
+                                       psformat = cit->name();
+                               else
+                                       format = cit->name();
                        }
-                       magic_close(magic_cookie);
-                       // libmagic recognizes as latex also some formats of 
ours
-                       // such as pstex and pdftex. Therefore we have to 
perform
-                       // additional checks in this case (bug 9244).
-                       if (!format.empty() && format != "latex")
-                               return format;
                }
+
+               // libmagic recognizes as latex also some formats of ours
+               // such as pstex and pdftex. Therefore we have to perform
+               // additional checks in this case (bug 9244).
+               if (!format.empty() && format != "latex")
+                       return format;
        }
-#endif
 
        string const ext = getExtension(filename.absFileName());
        if (format.empty()) {
diff --git a/src/support/Magic.h b/src/support/Magic.h
new file mode 100644
index 0000000..ca87f0c
--- /dev/null
+++ b/src/support/Magic.h
@@ -0,0 +1,77 @@
+// -*- C++ -*-
+/**
+ * \file Magic.h
+ * This file is part of LyX, the document processor.
+ * Licence details can be found in the file COPYING.
+ *
+ * \author Jean-Marc Lasgouttes
+ *
+ * Full author contact details are available in file CREDITS.
+ */
+
+#ifndef LYX_MAGIC_H
+#define LYX_MAGIC_H
+
+namespace lyx {
+
+#ifdef HAVE_MAGIC_H
+
+#include "support/debug.h"
+
+#include <magic.h>
+
+class Magic {
+public:
+       Magic() : ok_(false) {
+               cookie_ = magic_open(MAGIC_MIME);
+               if (cookie_) {
+                       if (magic_load(cookie_, NULL) != 0)
+                               LYXERR(Debug::GRAPHICS, "Magic: couldn't load 
magic database - "
+                                       << magic_error(cookie_));
+                       else
+                               ok_ = true;
+               }
+       }
+
+       ~Magic() {
+               if(cookie_)
+                       magic_close(cookie_);
+       }
+
+       // returns a string of the form "mime-type;encoding", or an empty 
string on error.
+       std::string file(std::string const & name) const {
+               if (!ok_)
+                       return std::string();
+
+               char const * result = magic_file(cookie_, name.c_str());
+               if (result)
+                       return result;
+               else
+                       LYXERR(Debug::GRAPHICS, "Magic: couldn't query magic 
database - "
+                                  << magic_error(cookie_));
+
+               return std::string();
+       }
+
+private:
+       magic_t cookie_;
+       bool ok_;
+};
+
+#else // !HAVE_MAGIC_T
+
+// A dummy Magic class that always returns an empty result
+class Magic {
+public:
+       Magic() {
+               LYXERR(Debug::GRAPHICS, "Magic: libmagic support not 
configured");
+       }
+
+       std::string file(std::string const & name) const { return empty_string; 
}
+};
+
+#endif // HAVE_MAGIC_T
+
+}
+
+#endif // LYX_MAGIC_H
diff --git a/src/support/Makefile.am b/src/support/Makefile.am
index d3c902c..c86cd48 100644
--- a/src/support/Makefile.am
+++ b/src/support/Makefile.am
@@ -76,6 +76,7 @@ liblyxsupport_a_SOURCES = \
        lyxlib.h \
        lyxtime.cpp \
        lyxtime.h \
+       Magic.h \
        mutex.h \
        mutex.cpp \
        Messages.cpp \

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