Make encoding conversions thread safe

This is the result of the discussion on the list "2.1.0 Blocker". Thanks to
all contributors!
The main idea is to use thread-local storage for all static variables.
This solution does not need any mutex. For more details, see the comment in
unicode.h.
This commit is contained in:
Georg Baum 2013-10-10 21:20:44 +02:00
parent 009809b41d
commit 6a30211fef
3 changed files with 87 additions and 28 deletions

View File

@ -69,14 +69,6 @@ string const to_ascii(docstring const & ucs4)
}
IconvProcessor & utf8ToUcs4()
{
static IconvProcessor iconv(ucs4_codeset, "UTF-8");
return iconv;
}
void utf8_to_ucs4(string const & utf8, docstring & ucs4)
{
size_t n = utf8.size();

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@ -14,7 +14,8 @@
#include "support/unicode.h"
#include "support/debug.h"
#include "support/mutex.h"
#include <QThreadStorage>
#include <iconv.h>
@ -66,8 +67,6 @@ struct IconvProcessor::Impl
iconv_t cd;
string tocode_;
string fromcode_;
Mutex mutex_; // iconv() is not thread save, see #7240
};
@ -124,8 +123,6 @@ bool IconvProcessor::init()
int IconvProcessor::convert(char const * buf, size_t buflen,
char * outbuf, size_t maxoutsize)
{
Mutex::Locker lock(&pimpl_->mutex_);
if (buflen == 0)
return 0;
@ -228,7 +225,10 @@ iconv_convert(IconvProcessor & processor, InType const * buf, size_t buflen)
char const * inbuf = reinterpret_cast<char const *>(buf);
size_t inbytesleft = buflen * sizeof(InType);
static std::vector<char> outbuf(32768);
static QThreadStorage<std::vector<char> *> static_outbuf;
if (!static_outbuf.hasLocalData())
static_outbuf.setLocalData(new std::vector<char>(32768));
std::vector<char> & outbuf = *static_outbuf.localData();
// The number of UCS4 code points in buf is at most inbytesleft.
// The output encoding will use at most
// max_encoded_bytes(pimpl_->tocode_) per UCS4 code point.
@ -249,6 +249,15 @@ iconv_convert(IconvProcessor & processor, InType const * buf, size_t buflen)
} // anon namespace
IconvProcessor & utf8ToUcs4()
{
static QThreadStorage<IconvProcessor *> processor;
if (!processor.hasLocalData())
processor.setLocalData(new IconvProcessor(ucs4_codeset, "UTF-8"));
return *processor.localData();
}
vector<char_type> utf8_to_ucs4(vector<char> const & utf8str)
{
if (utf8str.empty())
@ -261,32 +270,43 @@ vector<char_type> utf8_to_ucs4(vector<char> const & utf8str)
vector<char_type>
utf8_to_ucs4(char const * utf8str, size_t ls)
{
static IconvProcessor processor(ucs4_codeset, "UTF-8");
return iconv_convert<char_type>(processor, utf8str, ls);
return iconv_convert<char_type>(utf8ToUcs4(), utf8str, ls);
}
vector<char_type>
utf16_to_ucs4(unsigned short const * s, size_t ls)
{
static IconvProcessor processor(ucs4_codeset, utf16_codeset);
return iconv_convert<char_type>(processor, s, ls);
static QThreadStorage<IconvProcessor *> processor;
if (!processor.hasLocalData())
processor.setLocalData(new IconvProcessor(ucs4_codeset, utf16_codeset));
return iconv_convert<char_type>(*processor.localData(), s, ls);
}
vector<unsigned short>
ucs4_to_utf16(char_type const * s, size_t ls)
{
static IconvProcessor processor(utf16_codeset, ucs4_codeset);
return iconv_convert<unsigned short>(processor, s, ls);
static QThreadStorage<IconvProcessor *> processor;
if (!processor.hasLocalData())
processor.setLocalData(new IconvProcessor(utf16_codeset, ucs4_codeset));
return iconv_convert<unsigned short>(*processor.localData(), s, ls);
}
IconvProcessor & ucs4ToUtf8()
{
static QThreadStorage<IconvProcessor *> processor;
if (!processor.hasLocalData())
processor.setLocalData(new IconvProcessor("UTF-8", ucs4_codeset));
return *processor.localData();
}
vector<char>
ucs4_to_utf8(char_type c)
{
static IconvProcessor processor("UTF-8", ucs4_codeset);
return iconv_convert<char>(processor, &c, 1);
return iconv_convert<char>(ucs4ToUtf8(), &c, 1);
}
@ -303,15 +323,17 @@ ucs4_to_utf8(vector<char_type> const & ucs4str)
vector<char>
ucs4_to_utf8(char_type const * ucs4str, size_t ls)
{
static IconvProcessor processor("UTF-8", ucs4_codeset);
return iconv_convert<char>(processor, ucs4str, ls);
return iconv_convert<char>(ucs4ToUtf8(), ucs4str, ls);
}
vector<char_type>
eightbit_to_ucs4(char const * s, size_t ls, string const & encoding)
{
static map<string, IconvProcessor> processors;
static QThreadStorage<map<string, IconvProcessor> *> static_processors;
if (!static_processors.hasLocalData())
static_processors.setLocalData(new map<string, IconvProcessor>);
map<string, IconvProcessor> & processors = *static_processors.localData();
if (processors.find(encoding) == processors.end()) {
IconvProcessor processor(ucs4_codeset, encoding.c_str());
processors.insert(make_pair(encoding, processor));
@ -320,10 +342,23 @@ eightbit_to_ucs4(char const * s, size_t ls, string const & encoding)
}
namespace {
map<string, IconvProcessor> & ucs4To8bitProcessors()
{
static QThreadStorage<map<string, IconvProcessor> *> processors;
if (!processors.hasLocalData())
processors.setLocalData(new map<string, IconvProcessor>);
return *processors.localData();
}
}
vector<char>
ucs4_to_eightbit(char_type const * ucs4str, size_t ls, string const & encoding)
{
static map<string, IconvProcessor> processors;
map<string, IconvProcessor> & processors(ucs4To8bitProcessors());
if (processors.find(encoding) == processors.end()) {
IconvProcessor processor(encoding.c_str(), ucs4_codeset);
processors.insert(make_pair(encoding, processor));
@ -334,7 +369,7 @@ ucs4_to_eightbit(char_type const * ucs4str, size_t ls, string const & encoding)
char ucs4_to_eightbit(char_type ucs4, string const & encoding)
{
static map<string, IconvProcessor> processors;
map<string, IconvProcessor> & processors(ucs4To8bitProcessors());
map<string, IconvProcessor>::iterator it = processors.find(encoding);
if (it == processors.end()) {
IconvProcessor processor(encoding.c_str(), ucs4_codeset);
@ -352,7 +387,10 @@ char ucs4_to_eightbit(char_type ucs4, string const & encoding)
void ucs4_to_multibytes(char_type ucs4, vector<char> & out,
string const & encoding)
{
static map<string, IconvProcessor> processors;
static QThreadStorage<map<string, IconvProcessor> *> static_processors;
if (!static_processors.hasLocalData())
static_processors.setLocalData(new map<string, IconvProcessor>);
map<string, IconvProcessor> & processors = *static_processors.localData();
map<string, IconvProcessor>::iterator it = processors.find(encoding);
if (it == processors.end()) {
IconvProcessor processor(encoding.c_str(), ucs4_codeset);

View File

@ -21,6 +21,27 @@
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
{
public:
@ -51,6 +72,10 @@ private:
Impl * pimpl_;
};
/// 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 +91,10 @@ 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);