libfoundation: Re-use iconv file descriptors

peter-b · peter-b · commit cc02b0441274 · 2017-03-06T14:40:02.000Z
Creating a new `iconv_t` file descriptor is an expensive operation.
For UTF-16 encoding/decoding, `iconv_open()` requires at least one
`open()` system call (and additional work) to load its UTF-16 support
shared library.

`iconv_t` file descriptors can be reused safely if they're reset to
their original state by calling `iconv()` with null input and output
pointers.

This patch eliminates about two thirds of the `open()` syscalls that
occur during IDE startup on Linux.
diff --git a/libfoundation/src/foundation-string.cpp b/libfoundation/src/foundation-string.cpp
@@ -6239,6 +6239,65 @@ bool MCStringIsGraphemeClusterBoundary(MCStringRef self, uindex_t p_index)
 
 ////////////////////////////////////////////////////////////////////////////////
 
+#if defined(__LINUX__)
+static const iconv_t k_invalid_iconv_fd = reinterpret_cast<iconv_t>(-1);
+
+static bool is_valid_iconv_fd(iconv_t p_fd)
+{
+    return p_fd != k_invalid_iconv_fd;
+}
+
+static iconv_t s_iconv_unicode_from_sys_fd = k_invalid_iconv_fd;
+static iconv_t s_iconv_unicode_to_sys_fd   = k_invalid_iconv_fd;
+static iconv_t s_iconv_native_to_sys_fd    = k_invalid_iconv_fd;
+
+static bool
+__MCStringInitializeIconv()
+{
+    const char *k_internal_iconv_charset =
+        (kMCByteOrderHost == kMCByteOrderLittleEndian ? "UTF-16LE" : "UTF-16BE");
+
+    // What is the system character encoding?
+    //
+    // Doing this here is unpleasant but the MCString*SysString functions are
+    // needed before the libfoundation initialise call completes
+    if (__MCSysCharset == nil)
+    {
+        setlocale(LC_CTYPE, "");
+        __MCSysCharset = nl_langinfo(CODESET);
+    }
+
+    s_iconv_unicode_from_sys_fd = iconv_open(k_internal_iconv_charset, __MCSysCharset);
+    if (!is_valid_iconv_fd(s_iconv_unicode_from_sys_fd))
+        return false;
+    s_iconv_unicode_to_sys_fd = iconv_open(__MCSysCharset, k_internal_iconv_charset);
+    if (!is_valid_iconv_fd(s_iconv_unicode_to_sys_fd))
+        return false;
+    s_iconv_native_to_sys_fd = iconv_open(__MCSysCharset, "ISO-8859-1");
+    if (!is_valid_iconv_fd(s_iconv_native_to_sys_fd))
+        return false;
+
+    return true;
+}
+
+static void
+__MCStringFinalizeIconv()
+{
+    auto t_iconv_cleanup = [](iconv_t& p_fd) {
+        if (is_valid_iconv_fd(p_fd))
+        {
+            iconv_close(p_fd);
+            p_fd = k_invalid_iconv_fd;
+        }
+    };
+
+    t_iconv_cleanup(s_iconv_unicode_from_sys_fd);
+    t_iconv_cleanup(s_iconv_unicode_to_sys_fd);
+    t_iconv_cleanup(s_iconv_native_to_sys_fd);
+}
+
+#endif /* __LINUX__ */
+
 MC_DLLEXPORT_DEF MCStringRef kMCEmptyString;
 MC_DLLEXPORT_DEF MCStringRef kMCTrueString;
 MC_DLLEXPORT_DEF MCStringRef kMCFalseString;
@@ -6249,6 +6308,11 @@ MC_DLLEXPORT_DEF MCStringRef kMCTabString;
 
 bool __MCStringInitialize(void)
 {
+#if defined(__LINUX__)
+    if (!__MCStringInitializeIconv())
+        return false;
+#endif
+
 	if (!MCStringCreateWithNativeChars((const char_t *)"", 0, kMCEmptyString))
 		return false;
     
@@ -6290,6 +6354,10 @@ void __MCStringFinalize(void)
     kMCLineEndString = nil;
     MCValueRelease(kMCTabString);
     kMCTabString = nil;
+
+#if defined(__LINUX__)
+    __MCStringFinalizeIconv();
+#endif
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -6308,6 +6376,9 @@ static bool do_iconv(iconv_t fd, const char *in, size_t in_len, char * &out, siz
     char * t_out;
 	char * t_out_cursor;
 
+    /* Reset the iconv file descriptor */
+    iconv(fd, nullptr, nullptr, nullptr, nullptr);
+
     t_out = (char*)malloc(in_len);
     if (t_out == nil)
         return false;
@@ -6380,27 +6451,8 @@ bool MCStringCreateWithSysString(const char *p_system_string, MCStringRef &r_str
         return true;
     }
 
-
-    // What is the system character encoding?
-    //
-    // Doing this here is unpleasant but the MCString*SysString functions are
-    // needed before the libfoundation initialise call is made
-    if (__MCSysCharset == nil)
-    {
-        setlocale(LC_CTYPE, "");
-        __MCSysCharset = nl_langinfo(CODESET);
-    }
-
-    // Create the pseudo-FD that iconv uses for character conversion. The most
-	// convenient form is UTF-16 as StringRefs can be constructed directly from that.
-#ifdef __LITTLE_ENDIAN__
-    iconv_t t_fd = iconv_open("UTF-16LE", __MCSysCharset);
-#else
-    iconv_t t_fd = iconv_open("UTF-16BE", __MCSysCharset);
-#endif
-	
     // Was creation of the iconv FD successful?
-    if (t_fd == (iconv_t)-1)
+    if (!is_valid_iconv_fd(s_iconv_unicode_from_sys_fd))
         return false;
 
     // Measure the string
@@ -6411,8 +6463,8 @@ bool MCStringCreateWithSysString(const char *p_system_string, MCStringRef &r_str
 	char *t_utf16_bytes;
 	size_t t_utf16_byte_len;
 	bool t_success;
-    t_success = do_iconv(t_fd, p_system_string, t_len, t_utf16_bytes, t_utf16_byte_len);
-	iconv_close(t_fd);
+    t_success = do_iconv(s_iconv_unicode_from_sys_fd, p_system_string, t_len,
+                         t_utf16_bytes, t_utf16_byte_len);
 	
 	if (!t_success)
 		return false;
@@ -6450,31 +6502,26 @@ bool MCStringConvertToSysString(MCStringRef p_string, char *& r_system_string, s
 
 	if (MCStringIsNative(p_string) && MCStringGetNativeCharPtr(p_string) != nil)
     {
-        t_fd = iconv_open(__MCSysCharset, "ISO-8859-1");
+        t_fd = s_iconv_native_to_sys_fd;
 		t_mc_string = (const char *)MCStringGetNativeCharPtr(p_string);
 		t_mc_len = MCStringGetLength(p_string);
 	}
 	else
 	{
-#ifdef __LITTLE_ENDIAN__
-        t_fd = iconv_open(__MCSysCharset, "UTF-16LE");
-#else
-        t_fd = iconv_open(__MCSysCharset, "UTF-16BE");
-#endif
+        t_fd = s_iconv_unicode_to_sys_fd;
 		t_mc_string = (const char *)MCStringGetCharPtr(p_string);
 		t_mc_len = MCStringGetLength(p_string) * sizeof(unichar_t);
 	}
 
     // Was creation of the iconv FD successful?
-    if (t_fd == (iconv_t)-1)
+    if (!is_valid_iconv_fd(t_fd))
         return false;
 	
 	// Perform the conversion
 	bool t_success;
 	char *t_sys_string;
 	size_t t_sys_len;
 	t_success = do_iconv(t_fd, t_mc_string, t_mc_len, t_sys_string, t_sys_len);
-	iconv_close(t_fd);
 	
 	if (!t_success)
 		return false;
