1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
/*-------------------------------------------------------------------------
*
* pread.c
* Implementation of pread(2) for platforms that lack one.
*
* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/port/pread.c
*
* Note that this implementation changes the current file position, unlike
* the POSIX function, so we use the name pg_pread().
*
*-------------------------------------------------------------------------
*/
#include "c.h"
#ifdef WIN32
#include <windows.h>
#else
#include <unistd.h>
#endif
ssize_t
pg_pread(int fd, void *buf, size_t size, off_t offset)
{
#ifdef WIN32
OVERLAPPED overlapped = {0};
HANDLE handle;
DWORD result;
handle = (HANDLE) _get_osfhandle(fd);
if (handle == INVALID_HANDLE_VALUE)
{
errno = EBADF;
return -1;
}
overlapped.Offset = offset;
if (!ReadFile(handle, buf, size, &result, &overlapped))
{
if (GetLastError() == ERROR_HANDLE_EOF)
return 0;
_dosmaperr(GetLastError());
return -1;
}
return result;
#else
if (lseek(fd, offset, SEEK_SET) < 0)
return -1;
return read(fd, buf, size);
#endif
}
|
