Backport Fix for Bug#24509 - 2048 file descriptor limit on windows needs increasing.

The patch replaces the use of the POSIX I/O interfaces in mysys on Windows with 
the Win32 API calls (CreateFile, WriteFile, etc). The Windows HANDLE for the open
 file is stored in the my_file_info struct, along with a flag for append mode 
(because the Windows API does not support opening files in append mode in all cases)
The default max open files has been increased to 16384 and can be increased further
by setting --max-open-files=<value> during the server start.

Noteworthy benefit of this patch is that it removes limits from the table_cache size - 
allowing for more simultaneus users

1 files changed, 25 insertions, 23 deletions

diff --git a/mysys/my_fopen.c b/mysys/my_fopen.c
index a4b0c9f895d..ae631a59353 100644
--- a/mysys/my_fopen.c
+++ b/mysys/my_fopen.c
@@ -46,24 +46,14 @@ FILE *my_fopen(const char *filename, int flags, myf MyFlags)
   DBUG_ENTER("my_fopen");
   DBUG_PRINT("my",("Name: '%s'  flags: %d  MyFlags: %d",
 		   filename, flags, MyFlags));
-  /* 
-    if we are not creating, then we need to use my_access to make sure  
-    the file exists since Windows doesn't handle files like "com1.sym" 
-    very  well 
-  */
-#ifdef __WIN__
-  if (check_if_legal_filename(filename))
-  {
-    errno= EACCES;
-    fd= 0;
-  }
-  else
+
+  make_ftype(type,flags);
+
+#ifdef _WIN32
+  fd= my_win_fopen(filename, type);
+#else
+  fd= fopen(filename, type);
 #endif
-  {
-    make_ftype(type,flags);
-    fd = fopen(filename, type);
-  }
-  
   if (fd != 0)
   {
     /*
@@ -71,18 +61,20 @@ FILE *my_fopen(const char *filename, int flags, myf MyFlags)
       on some OS (SUNOS). Actually the filename save isn't that important
       so we can ignore if this doesn't work.
     */
-    if ((uint) fileno(fd) >= my_file_limit)
+
+    int filedesc= my_fileno(fd);
+    if ((uint)filedesc >= my_file_limit)
     {
       thread_safe_increment(my_stream_opened,&THR_LOCK_open);
       DBUG_RETURN(fd);				/* safeguard */
     }
     pthread_mutex_lock(&THR_LOCK_open);
-    if ((my_file_info[fileno(fd)].name = (char*)
+    if ((my_file_info[filedesc].name= (char*)
 	 my_strdup(filename,MyFlags)))
     {
       my_stream_opened++;
       my_file_total_opened++;
-      my_file_info[fileno(fd)].type = STREAM_BY_FOPEN;
+      my_file_info[filedesc].type= STREAM_BY_FOPEN;
       pthread_mutex_unlock(&THR_LOCK_open);
       DBUG_PRINT("exit",("stream: 0x%lx", (long) fd));
       DBUG_RETURN(fd);
@@ -240,8 +232,13 @@ int my_fclose(FILE *fd, myf MyFlags)
   DBUG_PRINT("my",("stream: 0x%lx  MyFlags: %d", (long) fd, MyFlags));
 
   pthread_mutex_lock(&THR_LOCK_open);
-  file=fileno(fd);
-  if ((err = fclose(fd)) < 0)
+  file= my_fileno(fd);
+#ifndef _WIN32
+  err= fclose(fd);
+#else
+  err= my_win_fclose(fd);
+#endif
+  if(err < 0)
   {
     my_errno=errno;
     if (MyFlags & (MY_FAE | MY_WME))
@@ -272,7 +269,12 @@ FILE *my_fdopen(File Filedes, const char *name, int Flags, myf MyFlags)
 		   Filedes, Flags, MyFlags));
 
   make_ftype(type,Flags);
-  if ((fd = fdopen(Filedes, type)) == 0)
+#ifdef _WIN32
+  fd= my_win_fdopen(Filedes, type);
+#else
+  fd= fdopen(Filedes, type);
+#endif
+  if (!fd)
   {
     my_errno=errno;
     if (MyFlags & (MY_FAE | MY_WME))