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

/*
 * This file is part of libtrace
 *
 * Copyright (c) 2007,2008,2009,2010 The University of Waikato, Hamilton, 
 * New Zealand.
 *
 * Authors: Daniel Lawson 
 *          Perry Lorier
 *          Shane Alcock 
 *          
 * All rights reserved.
 *
 * This code has been developed by the University of Waikato WAND 
 * research group. For further information please see http://www.wand.net.nz/
 *
 * libtrace is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * libtrace is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with libtrace; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id$
 *
 */


#define _GNU_SOURCE 1
#include "wandio.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>

/* Libtrace IO module implementing a standard IO writer, i.e. no decompression
 */

enum { MIN_WRITE_SIZE = 4096 };

struct stdiow_t {
        char buffer[MIN_WRITE_SIZE];
        int offset;
        int fd;
};

extern iow_source_t stdio_wsource;

#define DATA(iow) ((struct stdiow_t *)((iow)->data))

static int safe_open(const char *filename)
{
        int fd;
/* Try opening with O_DIRECT */
#ifdef O_DIRECT
        fd = open(filename,
                O_WRONLY
                |O_CREAT
                |O_TRUNC
                |(force_directio_write?O_DIRECT:0),
                0666);
        if (fd != -1)
                return fd;
#endif
/* If that failed (or we don't support O_DIRECT) try opening without */
        fd = open(filename,
                O_WRONLY
                |O_CREAT
                |O_TRUNC,
                0666);
        if (fd != -1)
                return fd;
        return fd;
}

iow_t *stdio_wopen(const char *filename)
{
        iow_t *iow = malloc(sizeof(iow_t));
        iow->source = &stdio_wsource;
        iow->data = malloc(sizeof(struct stdiow_t));

        if (strcmp(filename,"-") == 0) 
                DATA(iow)->fd = 1; /* STDOUT */
        else {
                DATA(iow)->fd = safe_open(filename);
        }

        if (DATA(iow)->fd == -1) {
                free(iow);
                return NULL;
        }

        DATA(iow)->offset = 0;

        return iow;
}

#define min(a,b) ((a)<(b) ? (a) : (b))
#define max(a,b) ((a)>(b) ? (a) : (b))
/* Round A Down to the nearest multiple of B */
#define rounddown(a,b) ((a)-((a)%b)

/* When doing directio (O_DIRECT) we need to make sure that we write multiples of MIN_WRITE_SIZE.
 * So we accumulate data into DATA(iow)->buffer, and write it out when we get at least MIN_WRITE_SIZE.
 *
 * Since most writes are likely to be larger than MIN_WRITE_SIZE optimise for that case.
 */
static off_t stdio_wwrite(iow_t *iow, const char *buffer, off_t len)
{
        struct iovec iov[2];
        int err;
        /* Round down size to the nearest multiple of MIN_WRITE_SIZE */

        assert(len >= 0);
        
        if (DATA(iow)->offset + len >= MIN_WRITE_SIZE) {
                int amount;
                iov[0].iov_base = DATA(iow)->buffer;
                iov[0].iov_len = DATA(iow)->offset;
                iov[1].iov_base = (void*)buffer; /* cast away constness, which is safe here */
                iov[1].iov_len = len - (DATA(iow)->offset+len) % MIN_WRITE_SIZE;
                err=writev(DATA(iow)->fd, iov, 2);
                if (err==-1)
                        return -1;
                /* Drop off "err" bytes from the beginning of the buffers */
                amount = min(DATA(iow)->offset, err);
                DATA(iow)->offset -= amount;
                err -= amount;
                buffer += err;
                len -= err;
        }

        /* Make sure we're not going to overflow the buffer.  The above writev should assure
         * that this is true
         */
        assert(DATA(iow)->offset + len <= MIN_WRITE_SIZE);
        assert(len >= 0);

        /* Copy the remainder into the buffer to write next time. */
        memcpy(DATA(iow)->buffer + DATA(iow)->offset, buffer, len);
        DATA(iow)->offset += len;

        return len;
}

static void stdio_wclose(iow_t *iow)
{
        long err;
        /* Now, there might be some non multiple of the direct filesize left over, if so turn off
         * O_DIRECT and write the final chunk.
         */
#ifdef O_DIRECT
        err=fcntl(DATA(iow)->fd, F_GETFL);
        if (err != -1 && (err & O_DIRECT) != 0) {
                fcntl(DATA(iow)->fd,F_SETFL, err & ~O_DIRECT);
        }
        write(DATA(iow)->fd, DATA(iow)->buffer, DATA(iow)->offset);
        DATA(iow)->offset = 0;
#endif
        close(DATA(iow)->fd);
        free(iow->data);
        free(iow);
}

iow_source_t stdio_wsource = {
        "stdiow",
        stdio_wwrite,
        stdio_wclose
};