source: lib/iow-stdio.c @ 026eb88

4.0.1-hotfixescachetimestampsdevelopdpdk-ndagetsilivegetfragoffhelplibtrace4ndag_formatpfringrc-4.0.1rc-4.0.2rc-4.0.3rc-4.0.4ringdecrementfixringperformanceringtimestampfixes
Last change on this file since 026eb88 was 026eb88, checked in by Perry Lorier <perry@…>, 12 years ago

Make sure we write in multiples of 4k to keep O_DIRECT happy

  • Property mode set to 100644
File size: 4.4 KB
Line 
1/*
2 * This file is part of libtrace
3 *
4 * Copyright (c) 2007,2008,2009,2010 The University of Waikato, Hamilton,
5 * New Zealand.
6 *
7 * Authors: Daniel Lawson
8 *          Perry Lorier
9 *          Shane Alcock
10 *         
11 * All rights reserved.
12 *
13 * This code has been developed by the University of Waikato WAND
14 * research group. For further information please see http://www.wand.net.nz/
15 *
16 * libtrace is free software; you can redistribute it and/or modify
17 * it under the terms of the GNU General Public License as published by
18 * the Free Software Foundation; either version 2 of the License, or
19 * (at your option) any later version.
20 *
21 * libtrace is distributed in the hope that it will be useful,
22 * but WITHOUT ANY WARRANTY; without even the implied warranty of
23 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
24 * GNU General Public License for more details.
25 *
26 * You should have received a copy of the GNU General Public License
27 * along with libtrace; if not, write to the Free Software
28 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
29 *
30 * $Id$
31 *
32 */
33
34
35#define _GNU_SOURCE 1
36#include "wandio.h"
37#include <sys/types.h>
38#include <sys/stat.h>
39#include <sys/uio.h>
40#include <fcntl.h>
41#include <stdlib.h>
42#include <unistd.h>
43#include <string.h>
44#include <assert.h>
45
46/* Libtrace IO module implementing a standard IO writer, i.e. no decompression
47 */
48
49enum { MIN_WRITE_SIZE = 4096 };
50
51struct stdiow_t {
52        char buffer[MIN_WRITE_SIZE];
53        int offset;
54        int fd;
55};
56
57extern iow_source_t stdio_wsource;
58
59#define DATA(iow) ((struct stdiow_t *)((iow)->data))
60
61static int safe_open(const char *filename)
62{
63        int fd;
64/* Try opening with O_DIRECT */
65#ifdef O_DIRECT
66        fd = open(filename,
67                O_WRONLY
68                |O_CREAT
69                |O_TRUNC
70                |(force_directio_write?O_DIRECT:0),
71                0666);
72        if (fd != -1)
73                return fd;
74#endif
75/* If that failed (or we don't support O_DIRECT) try opening without */
76        fd = open(filename,
77                O_WRONLY
78                |O_CREAT
79                |O_TRUNC,
80                0666);
81        if (fd != -1)
82                return fd;
83        return fd;
84}
85
86iow_t *stdio_wopen(const char *filename)
87{
88        iow_t *iow = malloc(sizeof(iow_t));
89        iow->source = &stdio_wsource;
90        iow->data = malloc(sizeof(struct stdiow_t));
91
92        if (strcmp(filename,"-") == 0) 
93                DATA(iow)->fd = 1; /* STDOUT */
94        else {
95                DATA(iow)->fd = safe_open(filename);
96        }
97
98        if (DATA(iow)->fd == -1) {
99                free(iow);
100                return NULL;
101        }
102
103        DATA(iow)->offset = 0;
104
105        return iow;
106}
107
108#define min(a,b) ((a)<(b) ? (a) : (b))
109#define max(a,b) ((a)>(b) ? (a) : (b))
110/* Round A Down to the nearest multiple of B */
111#define rounddown(a,b) ((a)-((a)%b)
112
113/* When doing directio (O_DIRECT) we need to make sure that we write multiples of MIN_WRITE_SIZE.
114 * So we accumulate data into DATA(iow)->buffer, and write it out when we get at least MIN_WRITE_SIZE.
115 *
116 * Since most writes are likely to be larger than MIN_WRITE_SIZE optimise for that case.
117 */
118static off_t stdio_wwrite(iow_t *iow, const char *buffer, off_t len)
119{
120        struct iovec iov[2];
121        int err;
122        /* Round down size to the nearest multiple of MIN_WRITE_SIZE */
123
124        assert(len >= 0);
125       
126        if (DATA(iow)->offset + len >= MIN_WRITE_SIZE) {
127                int amount;
128                iov[0].iov_base = DATA(iow)->buffer;
129                iov[0].iov_len = DATA(iow)->offset;
130                iov[1].iov_base = (void*)buffer; /* cast away constness, which is safe here */
131                iov[1].iov_len = len - (DATA(iow)->offset+len) % MIN_WRITE_SIZE;
132                err=writev(DATA(iow)->fd, iov, 2);
133                if (err==-1)
134                        return -1;
135                /* Drop off "err" bytes from the beginning of the buffers */
136                amount = min(DATA(iow)->offset, err);
137                DATA(iow)->offset -= amount;
138                err -= amount;
139                buffer += err;
140                len -= err;
141        }
142
143        /* Make sure we're not going to overflow the buffer.  The above writev should assure
144         * that this is true
145         */
146        assert(DATA(iow)->offset + len <= MIN_WRITE_SIZE);
147        assert(len >= 0);
148
149        /* Copy the remainder into the buffer to write next time. */
150        memcpy(DATA(iow)->buffer + DATA(iow)->offset, buffer, len);
151        DATA(iow)->offset += len;
152
153        return len;
154}
155
156static void stdio_wclose(iow_t *iow)
157{
158        long err;
159        /* Now, there might be some non multiple of the direct filesize left over, if so turn off
160         * O_DIRECT and write the final chunk.
161         */
162#ifdef O_DIRECT
163        err=fcntl(DATA(iow)->fd, F_GETFL);
164        if (err != -1 && (err & O_DIRECT) != 0) {
165                fcntl(DATA(iow)->fd,F_SETFL, err & ~O_DIRECT);
166        }
167        write(DATA(iow)->fd, DATA(iow)->buffer, DATA(iow)->offset);
168        DATA(iow)->offset = 0;
169#endif
170        close(DATA(iow)->fd);
171        free(iow->data);
172        free(iow);
173}
174
175iow_source_t stdio_wsource = {
176        "stdiow",
177        stdio_wwrite,
178        stdio_wclose
179};
Note: See TracBrowser for help on using the repository browser.