Closes #1321

pread/pwrite now threadsafe and do not modify file pointer

git-svn-id: file:///svn/toku/tokudb.1032b@8369 c7de825b-a66e-492c-adef-691d508d4ae1

windows/files.c

@@ -4,27 +4,36 @@
 #include <unistd.h>
 #include <windows.h>
 
-// Note: pread and pwrite are not thread safe on the same fildes as they
-// rely on the file offset
-
 int64_t
 pread(int fildes, void *buf, size_t nbyte, int64_t offset) {
-    int64_t r = _lseeki64(fildes, offset, SEEK_SET);
-    if (r>=0) {
-        assert(r==offset);
-        r = read(fildes, buf, nbyte);
-    }
+    HANDLE     handle;
+    OVERLAPPED offset = {0}; 
+    handle =  _get_osfhandle(fildes);
+    offset.Offset     = offset % (1LL<<32LL);
+    offset.OffsetHigh = offset / (1LL<<32LL);
+
+    size_t bytes_read;
+    int64_t r = ReadFile(handle, buf, nbyte, &bytes_read, &offset);
+    if (!r) r = GetLastError();
+    else    r = bytes_read;
+
     // printf("%s: %d %p %u %I64d %I64d\n", __FUNCTION__, fildes, buf, nbyte, offset, r); fflush(stdout);
     return r;
 }
 
 int64_t
 pwrite(int fildes, const void *buf, size_t nbyte, int64_t offset) {
-    int64_t r = _lseeki64(fildes, offset, SEEK_SET);
-    if (r>=0) {
-        assert(r==offset);
-        r = write(fildes, buf, nbyte);
-    }
+    HANDLE     handle;
+    OVERLAPPED offset = {0}; 
+    handle =  _get_osfhandle(fildes);
+    offset.Offset     = offset % (1LL<<32LL);
+    offset.OffsetHigh = offset / (1LL<<32LL);
+
+    size_t bytes_written;
+    int64_t r = ReadFile(handle, buf, nbyte, &bytes_written, &offset);
+    if (!r) r = GetLastError();
+    else    r = bytes_written;
+
     // printf("%s: %d %p %u %I64d %I64d\n", __FUNCTION__, fildes, buf, nbyte, offset, r); fflush(stdout);
     return r;
 }