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sfile.c (2823B)

      1 /*
      2  * Copyright (c) 2003 Gunnar Ritter
      3  *
      4  * This software is provided 'as-is', without any express or implied
      5  * warranty. In no event will the authors be held liable for any damages
      6  * arising from the use of this software.
      7  *
      8  * Permission is granted to anyone to use this software for any purpose,
      9  * including commercial applications, and to alter it and redistribute
     10  * it freely, subject to the following restrictions:
     11  *
     12  * 1. The origin of this software must not be misrepresented; you must not
     13  *    claim that you wrote the original software. If you use this software
     14  *    in a product, an acknowledgment in the product documentation would be
     15  *    appreciated but is not required.
     16  *
     17  * 2. Altered source versions must be plainly marked as such, and must not be
     18  *    misrepresented as being the original software.
     19  *
     20  * 3. This notice may not be removed or altered from any source distribution.
     21  */
     22 /*	Sccsid @(#)sfile.c	1.9 (gritter) 6/7/04	*/
     23 
     24 #ifdef	__linux__
     25 #undef	_FILE_OFFSET_BITS
     26 
     27 #include	<sys/types.h>
     28 #include	<sys/sendfile.h>
     29 #include	<sys/stat.h>
     30 #include	<unistd.h>
     31 #include	<limits.h>
     32 #include	<errno.h>
     33 #include	"sfile.h"
     34 
     35 long long
     36 sfile(int dfd, int sfd, mode_t mode, long long count)
     37 {
     38 	static int	enosys, einval, success;
     39 	off_t	offset;
     40 	ssize_t	sent, total;
     41 	extern void	writerr(void *, int, int);
     42 	/*
     43 	 * A process is not interruptible while executing a sendfile()
     44 	 * system call. So it is not advisable to to send an entire
     45 	 * file with one call; it is sent in parts so signals can
     46 	 * be delivered in between.
     47 	 */
     48 	const ssize_t	chunk = 196608;
     49 
     50 	/*
     51 	 * If a previous call returned ENOSYS, the operating system does
     52 	 * not support sendfile() at all and it makes no sense to try it
     53 	 * again.
     54 	 *
     55 	 * If a previous call returned EINVAL and there was no successful
     56 	 * call yet, it is very likely that this is a permanent error
     57 	 * condition (on Linux 2.6.0-test4, sendfile() may be used for
     58 	 * socket targets only; older versions don't support tmpfs as
     59 	 * source file system etc.).
     60 	 */
     61 	if (enosys || !success && einval ||
     62 			(mode&S_IFMT) != S_IFREG || count > SSIZE_MAX)
     63 		return 0;
     64 	offset = lseek(sfd, 0, SEEK_CUR);
     65 	sent = 0, total = 0;
     66 	while (count > 0 && (sent = sendfile(dfd, sfd, &offset,
     67 					count > chunk ? chunk : count)) > 0) {
     68 		count -= sent, total += sent;
     69 	}
     70 	if (total && lseek(sfd, offset, SEEK_SET) == (off_t)-1)
     71 		return -1;
     72 	if (count == 0 || sent == 0) {
     73 		success = 1;
     74 		return total;
     75 	}
     76 	switch (errno) {
     77 	case ENOSYS:
     78 		enosys = 1;
     79 		return 0;
     80 	case EINVAL:
     81 		einval = 1;
     82 		return 0;
     83 	case ENOMEM:
     84 		return 0;
     85 	default:
     86 		writerr(NULL, count > chunk ? chunk : count, 0);
     87 		return -1;
     88 	}
     89 }
     90 #else	/* !__linux__ */
     91 #include	<sys/types.h>
     92 
     93 /*ARGSUSED*/
     94 long long
     95 sfile(int dfd, int sfd, mode_t mode, long long count)
     96 {
     97 	return 0;
     98 }
     99 #endif	/* __linux__ */