©2004 by Marc J. Rochkind. All rights reserved. Portions marked "Open Source" may be copied under license.

 

                 

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c2/bufio.c

Go to the documentation of this file.

/*
    Functions for User Buffering
    AUP2, Sec. 2.12.2

    Copyright 2003 by Marc J. Rochkind. All rights reserved.
    May be copied only for purposes and under conditions described
    on the Web page www.basepath.com/aup/copyright.htm.

    The Example Files are provided "as is," without any warranty;
    without even the implied warranty of merchantability or fitness
    for a particular purpose. The author and his publisher are not
    responsible for any damages, direct or incidental, resulting
    from the use or non-use of these Example Files.

    The Example Files may contain defects, and some contain deliberate
    coding mistakes that were included for educational reasons.
    You are responsible for determining if and how the Example Files
    are to be used.
*/
#include "defs.h"
#include "bufio.h"

static BUFIO *Bopen_internal(int fd, const char *path, const char *dir)
{
    BUFIO *b = NULL;
    int flags;

    switch (dir[0]) {
    case 'r':
        flags = O_RDONLY;
        break;
    case 'w':
        flags = O_WRONLY | O_CREAT | O_TRUNC;
        break;
    default:
        errno = EINVAL;
        EC_FAIL
    }
    ec_null( b = calloc(1, sizeof(BUFIO)) )
    b->fdopen = path == NULL;
    if (b->fdopen)
        b->fd = fd;
    else
        b->fd = open(path, flags, PERM_FILE);
    ec_neg1( b->fd )
    b->dir = dir[0];
    return b;

EC_CLEANUP_BGN
    free(b);
    return NULL;
EC_CLEANUP_END
}

BUFIO *Bfdopen(int fd, const char *dir)
{
    return Bopen_internal(fd, NULL, dir);
}

/*[bufio.c]*/
#if 0 /* non-Bfdopen version, as appeared in Chap. 2 of book */
BUFIO *Bopen(const char *path, const char *dir)
{
    BUFIO *b = NULL;
    int flags;

    switch (dir[0]) {
    case 'r':
        flags = O_RDONLY;
        break;
    case 'w':
        flags = O_WRONLY | O_CREAT | O_TRUNC;
        break;
    default:
        errno = EINVAL;
        EC_FAIL
    }
    ec_null( b = calloc(1, sizeof(BUFIO)) )
    ec_neg1( b->fd = open(path, flags, PERM_FILE) )
    b->dir = dir[0];
    return b;

EC_CLEANUP_BGN
    free(b);
    return NULL;
EC_CLEANUP_END
}
#else
BUFIO *Bopen(const char *path, const char *dir)
{
    return Bopen_internal(-1, path, dir);
}
#endif

static bool readbuf(BUFIO *b)
{
    if (b->timeout.tv_sec != 0 || b->timeout.tv_usec != 0) {
        fd_set set;

        FD_ZERO(&set);
        FD_SET(b->fd, &set);
        ec_neg1( select(b->fd + 1, &set, NULL, NULL, &b->timeout) )
        if (!FD_ISSET(b->fd, &set)) {
            errno = ETIMEDOUT;
            return false;
        }
    }
    ec_neg1( b->total = read(b->fd, b->buf, sizeof(b->buf)) )
    if (b->total == 0) {
        errno = 0;
        return false;
    }
    b->next = 0;
    return true;

EC_CLEANUP_BGN
    return false;
EC_CLEANUP_END
}

static bool writebuf(BUFIO *b)  /* flush buffer */
{
    ssize_t n, total;

    total = 0;
    while (total < b->next) {
        ec_neg1( n = write(b->fd, &b->buf[total], b->next - total) )
        total += n;
    }
    b->next = 0;
    return true;

EC_CLEANUP_BGN
    return false;
EC_CLEANUP_END
}

int Bgetc(BUFIO *b)
{
    if (b->next >= b->total)
        if (!readbuf(b)) {
            if (errno == 0)
                return -1;
            EC_FAIL
        }
    return b->buf[b->next++];

EC_CLEANUP_BGN
    return -1;
EC_CLEANUP_END
}

bool Bputc(BUFIO *b, int c)
{
    b->buf[b->next++] = c;
    if (b->next >= sizeof(b->buf))
        ec_false( writebuf(b) )
    return true;

EC_CLEANUP_BGN
    return false;
EC_CLEANUP_END
}

bool Bclose(BUFIO *b)
{
    if (b != NULL) {
        if (b->dir == 'w')
            ec_false( writebuf(b) )
        if (!b->fdopen) /* this line not in book */
            ec_neg1( close(b->fd) )
        free(b);
    }
    return true;

EC_CLEANUP_BGN
    return false;
EC_CLEANUP_END
}
/*[]*/

/*
    Rest of functions not in book.
*/
bool Bgets(BUFIO *b, char *s, size_t smax)
{
    int c, i;
    bool ok = true;

    for (i = 0; i < smax - 1; i++) {
        switch (c = Bgetc(b)) {
        case '\n':
            break;
        case -1:
            ok = i > 0;
            break;
        default:
            s[i] = (char)c;
            continue;
        }
        break;
    }
    s[i] = '\0';
    return ok;
}

void Bsettimeout(BUFIO *b, struct timeval *timeout)
{
    b->timeout = *timeout;
}

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