src/port/pwrite.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * pwrite.c
   4  *        Implementation of pwrite(2) for platforms that lack one.
   5  *
   6  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *        src/port/pwrite.c
  10  *
  11  * Note that this implementation changes the current file position, unlike
  12  * the POSIX function, so we use the name pg_pwrite().
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17
  18 #include "postgres.h"
  19
  20 #ifdef WIN32
  21 #include <windows.h>
  22 #else
  23 #include <unistd.h>
  24 #endif
  25
  26 ssize_t
  27 pg_pwrite(int fd, const void *buf, size_t size, off_t offset)
  28 {
  29 #ifdef WIN32
  30         OVERLAPPED      overlapped = {0};
  31         HANDLE          handle;
  32         DWORD           result;
  33
  34         handle = (HANDLE) _get_osfhandle(fd);
  35         if (handle == INVALID_HANDLE_VALUE)
  36         {
  37                 errno = EBADF;
  38                 return -1;
  39         }
  40
  41         overlapped.Offset = offset;
  42         if (!WriteFile(handle, buf, size, &result, &overlapped))
  43         {
  44                 _dosmaperr(GetLastError());
  45                 return -1;
  46         }
  47
  48         return result;
  49 #else
  50         if (lseek(fd, offset, SEEK_SET) < 0)
  51                 return -1;
  52
  53         return write(fd, buf, size);
  54 #endif
  55 }