This is the downport of

Bug#24509 - 2048 file descriptor limit on windows needs increasing, also 
WL#3049 - improved Windows I/O
                        
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.
                              
Another major change in this patch that almost all Windows specific file IO code
has been moved to a new file my_winfile.c, greatly reducing the amount of code 
in #ifdef blocks within mysys, thus improving readability.
                               
                                    
Minor enhancements:
- my_(f)stat() is changed to use __stati64 structure with  64 file size
and timestamps. It will return correct file size now (C runtime implementation
used to report outdated information)
- my_lock on Windows is prepared to handle additional timeout parameter
- after review : changed __WIN__ to _WIN32 in the new and changed code.

1 files changed, 37 insertions, 4 deletions

diff --git a/include/my_global.h b/include/my_global.h
index 4ad851e9e5d..f7e65d80dbb 100644
--- a/include/my_global.h
+++ b/include/my_global.h
@@ -736,7 +736,41 @@ typedef SOCKET_SIZE_TYPE size_socket;
 #define FN_LIBCHAR	'/'
 #define FN_ROOTDIR	"/"
 #endif
-#define MY_NFILE	64	/* This is only used to save filenames */
+
+/* 
+  MY_FILE_MIN is  Windows speciality and is used to quickly detect
+  the mismatch of CRT and mysys file IO usage on Windows at runtime.
+  CRT file descriptors can be in the range 0-2047, whereas descriptors returned
+  by my_open() will start with 2048. If a file descriptor with value less then
+  MY_FILE_MIN is passed to mysys IO function, chances are it stemms from
+  open()/fileno() and not my_open()/my_fileno.
+
+  For Posix,  mysys functions are light wrappers around libc, and MY_FILE_MIN
+  is logically 0.
+*/
+
+#ifdef _WIN32
+#define MY_FILE_MIN  2048
+#else
+#define MY_FILE_MIN  0
+#endif
+
+/* 
+  MY_NFILE is the default size of my_file_info array.
+
+  It is larger on Windows, because it all file handles are stored in my_file_info
+  Default size is 16384 and this should be enough for most cases.If it is not 
+  enough, --max-open-files with larger value can be used.
+
+  For Posix , my_file_info array is only used to store filenames for
+  error reporting and its size is not a limitation for number of open files.
+*/ 
+#ifdef _WIN32
+#define MY_NFILE (16384 + MY_FILE_MIN)
+#else
+#define MY_NFILE 64
+#endif
+
 #ifndef OS_FILE_LIMIT
 #define OS_FILE_LIMIT	65535
 #endif
@@ -773,9 +807,8 @@ typedef SOCKET_SIZE_TYPE size_socket;
 	/* Some things that this system doesn't have */
 
 #define NO_HASH			/* Not needed anymore */
-#ifdef __WIN__
-#define NO_DIR_LIBRARY		/* Not standar dir-library */
-#define USE_MY_STAT_STRUCT	/* For my_lib */
+#ifdef _WIN32
+#define NO_DIR_LIBRARY		/* Not standard dir-library */
 #endif
 
 /* Some defines of functions for portability */