118 lines
2.4 KiB
C
118 lines
2.4 KiB
C
/*-------------------------------------------------------------------------
|
|
*
|
|
* pg_iovec.h
|
|
* Header for vectored I/O functions, to use in place of <sys/uio.h>.
|
|
*
|
|
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
|
|
* Portions Copyright (c) 1994, Regents of the University of California
|
|
*
|
|
* src/include/port/pg_iovec.h
|
|
*
|
|
*-------------------------------------------------------------------------
|
|
*/
|
|
#ifndef PG_IOVEC_H
|
|
#define PG_IOVEC_H
|
|
|
|
#ifndef WIN32
|
|
|
|
#include <limits.h>
|
|
#include <sys/uio.h>
|
|
#include <unistd.h>
|
|
|
|
#else
|
|
|
|
/* POSIX requires at least 16 as a maximum iovcnt. */
|
|
#define IOV_MAX 16
|
|
|
|
/* Define our own POSIX-compatible iovec struct. */
|
|
struct iovec
|
|
{
|
|
void *iov_base;
|
|
size_t iov_len;
|
|
};
|
|
|
|
#endif
|
|
|
|
/* Define a reasonable maximum that is safe to use on the stack. */
|
|
#define PG_IOV_MAX Min(IOV_MAX, 32)
|
|
|
|
/*
|
|
* Like preadv(), but with a prefix to remind us of a side-effect: on Windows
|
|
* this changes the current file position.
|
|
*/
|
|
static inline ssize_t
|
|
pg_preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset)
|
|
{
|
|
#if HAVE_DECL_PREADV
|
|
/*
|
|
* Avoid a small amount of argument copying overhead in the kernel if
|
|
* there is only one iovec.
|
|
*/
|
|
if (iovcnt == 1)
|
|
return pread(fd, iov[0].iov_base, iov[0].iov_len, offset);
|
|
else
|
|
return preadv(fd, iov, iovcnt, offset);
|
|
#else
|
|
ssize_t sum = 0;
|
|
ssize_t part;
|
|
|
|
for (int i = 0; i < iovcnt; ++i)
|
|
{
|
|
part = pg_pread(fd, iov[i].iov_base, iov[i].iov_len, offset);
|
|
if (part < 0)
|
|
{
|
|
if (i == 0)
|
|
return -1;
|
|
else
|
|
return sum;
|
|
}
|
|
sum += part;
|
|
offset += part;
|
|
if (part < iov[i].iov_len)
|
|
return sum;
|
|
}
|
|
return sum;
|
|
#endif
|
|
}
|
|
|
|
/*
|
|
* Like pwritev(), but with a prefix to remind us of a side-effect: on Windows
|
|
* this changes the current file position.
|
|
*/
|
|
static inline ssize_t
|
|
pg_pwritev(int fd, const struct iovec *iov, int iovcnt, off_t offset)
|
|
{
|
|
#if HAVE_DECL_PWRITEV
|
|
/*
|
|
* Avoid a small amount of argument copying overhead in the kernel if
|
|
* there is only one iovec.
|
|
*/
|
|
if (iovcnt == 1)
|
|
return pwrite(fd, iov[0].iov_base, iov[0].iov_len, offset);
|
|
else
|
|
return pwritev(fd, iov, iovcnt, offset);
|
|
#else
|
|
ssize_t sum = 0;
|
|
ssize_t part;
|
|
|
|
for (int i = 0; i < iovcnt; ++i)
|
|
{
|
|
part = pg_pwrite(fd, iov[i].iov_base, iov[i].iov_len, offset);
|
|
if (part < 0)
|
|
{
|
|
if (i == 0)
|
|
return -1;
|
|
else
|
|
return sum;
|
|
}
|
|
sum += part;
|
|
offset += part;
|
|
if (part < iov[i].iov_len)
|
|
return sum;
|
|
}
|
|
return sum;
|
|
#endif
|
|
}
|
|
|
|
#endif /* PG_IOVEC_H */
|