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by brian
clean slate |
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/* Copyright (C) 2000 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#include "mysys_priv.h" |
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/*
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Seek to a position in a file.
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ARGUMENTS
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File fd The file descriptor
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my_off_t pos The expected position (absolute or relative)
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int whence A direction parameter and one of
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{SEEK_SET, SEEK_CUR, SEEK_END}
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myf MyFlags MY_THREADSAFE must be set in case my_seek may be mixed
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with my_pread/my_pwrite calls and fd is shared among
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threads.
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DESCRIPTION
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The my_seek function is a wrapper around the system call lseek and
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repositions the offset of the file descriptor fd to the argument
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offset according to the directive whence as follows:
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SEEK_SET The offset is set to offset bytes.
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SEEK_CUR The offset is set to its current location plus offset bytes
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SEEK_END The offset is set to the size of the file plus offset bytes
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RETURN VALUE
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my_off_t newpos The new position in the file.
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MY_FILEPOS_ERROR An error was encountered while performing
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the seek. my_errno is set to indicate the
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actual error.
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*/
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my_off_t my_seek(File fd, my_off_t pos, int whence, |
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myf MyFlags __attribute__((unused))) |
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{
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register os_off_t newpos= -1; |
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DBUG_ENTER("my_seek"); |
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DBUG_PRINT("my",("Fd: %d Hpos: %lu Pos: %lu Whence: %d MyFlags: %d", |
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fd, (ulong) (((ulonglong) pos) >> 32), (ulong) pos, |
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whence, MyFlags)); |
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DBUG_ASSERT(pos != MY_FILEPOS_ERROR); /* safety check */ |
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/*
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Make sure we are using a valid file descriptor!
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*/
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DBUG_ASSERT(fd != -1); |
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28.1.35
by Monty Taylor
Removed all references to THREAD. |
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#if !defined(HAVE_PREAD)
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1
by brian
clean slate |
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if (MyFlags & MY_THREADSAFE) |
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{
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pthread_mutex_lock(&my_file_info[fd].mutex); |
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newpos= lseek(fd, pos, whence); |
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pthread_mutex_unlock(&my_file_info[fd].mutex); |
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}
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else
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#endif
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newpos= lseek(fd, pos, whence); |
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if (newpos == (os_off_t) -1) |
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{
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my_errno=errno; |
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DBUG_PRINT("error",("lseek: %lu errno: %d", (ulong) newpos,errno)); |
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DBUG_RETURN(MY_FILEPOS_ERROR); |
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}
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if ((my_off_t) newpos != pos) |
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{
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DBUG_PRINT("exit",("pos: %lu", (ulong) newpos)); |
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}
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DBUG_RETURN((my_off_t) newpos); |
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} /* my_seek */ |
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/* Tell current position of file */
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/* ARGSUSED */
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my_off_t my_tell(File fd, myf MyFlags __attribute__((unused))) |
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{
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os_off_t pos; |
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DBUG_ENTER("my_tell"); |
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DBUG_PRINT("my",("Fd: %d MyFlags: %d",fd, MyFlags)); |
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DBUG_ASSERT(fd >= 0); |
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#ifdef HAVE_TELL
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pos=tell(fd); |
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#else
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pos=lseek(fd, 0L, MY_SEEK_CUR); |
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#endif
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if (pos == (os_off_t) -1) |
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my_errno=errno; |
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DBUG_PRINT("exit",("pos: %lu", (ulong) pos)); |
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DBUG_RETURN((my_off_t) pos); |
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} /* my_tell */ |