amend 6144bbfb

[lyx.git] / src / support / unicode.h

diff --git a/src/support/unicode.h b/src/support/unicode.h
index 6e83180c10692edcbe03fcba4af10fb7a6d6c407..6373e470ba0e446a192f08ea18f07f241b582437 100644 (file)
--- a/src/support/unicode.h
+++ b/src/support/unicode.h
@@ -1,3 +1,4 @@
+// -*- C++ -*-
 /**
  * \file unicode.h
  * This file is part of LyX, the document processor.
@@ -14,43 +15,61 @@
 #define LYX_SUPPORT_UNICODE_H
 
 #include "support/strfwd.h"
+#include "support/unique_ptr.h"
 
 #include <cstddef>
+#include <string>
 #include <vector>
 
 
 namespace lyx {
 
+/**
+ * Wrapper for iconv(3).
+ *
+ * According to the POSIX standard, all specified functions are thread-safe,
+ * with some exceptions. The iconv() function is not listed as an exception:
+ * http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xsh_chap02.html#tag_22_02_09_09
+ * http://man7.org/linux/man-pages/man7/pthreads.7.html
+ *
+ * Therefore, you can use as many instances of this class in parallel as you
+ * like. However, you need to ensure that each instance is only used by one
+ * thread at any given time. If this condition is not met you get nasty
+ * mixtures of different thread data as in bug 7240.
+ *
+ * From a performance point of view it is best to use one static instance
+ * per thread for each in/out encoding pair. This can e.g. be achieved by
+ * using helpers for thread-local storage such as QThreadStorage or
+ * boost::thread_specific_ptr. A single static instance protected by a mutex
+ * would work as well, and might be preferrable for exotic encoding pairs.
+ * Creating local IconvProcessor instances should be avoided because of the
+ * overhead in iconv_open().
+ */
 class IconvProcessor
 {
+       /// open iconv.
+       /// \return true if the processor is ready to use.
+       bool init();
+       std::string const tocode_;
+       std::string const fromcode_;
+       struct Handler;
+       unique_ptr<Handler> h_;
 public:
-       IconvProcessor(char const * tocode = "", char const * fromcode = "");
-       /// copy constructor needed because of pimpl_
-       IconvProcessor(IconvProcessor const &);
-       /// assignment operator needed because of pimpl_
-       void operator=(IconvProcessor const &);
-       /// destructor
-       ~IconvProcessor();
-
+       IconvProcessor(std::string tocode, std::string fromcode);
        /// convert any data from \c fromcode to \c tocode unicode format.
        /// \return the number of bytes of the converted output buffer.
        int convert(char const * in_buffer, size_t in_size,
                char * out_buffer, size_t max_out_size);
-
-       /// source encoding
-       std::string from() const;
        /// target encoding
-       std::string to() const;
-
-private:
-       /// open iconv.
-       /// \return true if the processor is ready to use.
-       bool init();
-       /// hide internals
-       struct Impl;
-       Impl * pimpl_;
+       std::string to() const { return tocode_; }
+       // required by g++ 4.7
+       IconvProcessor(IconvProcessor &&) = default;
 };
 
+/// Get the global IconvProcessor instance of the current thread for
+/// utf8->ucs4 conversions
+IconvProcessor & utf8ToUcs4();
+
 // A single codepoint conversion for utf8_to_ucs4 does not make
 // sense, so that function is left out.
 
@@ -66,6 +85,10 @@ std::vector<char_type> utf16_to_ucs4(unsigned short const * s, size_t ls);
 
 std::vector<unsigned short> ucs4_to_utf16(char_type const * s, size_t ls);
 
+/// Get the global IconvProcessor instance of the current thread for
+/// ucs4->utf8 conversions
+IconvProcessor & ucs4ToUtf8();
+
 // ucs4_to_utf8
 
 std::vector<char> ucs4_to_utf8(char_type c);