subr_sbuf.c

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/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2000-2008 Poul-Henning Kamp
 * Copyright (c) 2000-2008 Dag-Erling Coïdan Smørgrav
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include <sys/param.h>
 
#ifdef _KERNEL
#include <sys/ctype.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <machine/stdarg.h>
#else /* _KERNEL */
#include <ctype.h>
#include <errno.h>
#include <limits.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#endif /* _KERNEL */
 
#include <sys/sbuf.h>
 
#ifdef _KERNEL
static MALLOC_DEFINE(M_SBUF, "sbuf", "string buffers");
#define SBMALLOC(size, flags)   malloc(size, M_SBUF, (flags) | M_ZERO)
#define SBFREE(buf)             free(buf, M_SBUF)
#else /* _KERNEL */
#define KASSERT(e, m)
#define SBMALLOC(size, flags)   calloc(1, size)
#define SBFREE(buf)             free(buf)
#endif /* _KERNEL */
 
/*
 * Predicates
 */
#define SBUF_ISDYNAMIC(s)       ((s)->s_flags & SBUF_DYNAMIC)
#define SBUF_ISDYNSTRUCT(s)     ((s)->s_flags & SBUF_DYNSTRUCT)
#define SBUF_ISFINISHED(s)      ((s)->s_flags & SBUF_FINISHED)
#define SBUF_ISDRAINATEOL(s)    ((s)->s_flags & SBUF_DRAINATEOL)
#define SBUF_HASROOM(s)         ((s)->s_len < (s)->s_size - 1)
#define SBUF_FREESPACE(s)       ((s)->s_size - ((s)->s_len + 1))
#define SBUF_CANEXTEND(s)       ((s)->s_flags & SBUF_AUTOEXTEND)
#define SBUF_ISSECTION(s)       ((s)->s_flags & SBUF_INSECTION)
#define SBUF_NULINCLUDED(s)     ((s)->s_flags & SBUF_INCLUDENUL)
#define SBUF_ISDRAINTOEOR(s)    ((s)->s_flags & SBUF_DRAINTOEOR)
#define SBUF_DODRAINTOEOR(s)    (SBUF_ISSECTION(s) && SBUF_ISDRAINTOEOR(s))
#define SBUF_MALLOCFLAG(s)      \
        (((s)->s_flags & SBUF_NOWAIT) ? M_NOWAIT : M_WAITOK)
 
/*
 * Set / clear flags
 */
#define SBUF_SETFLAG(s, f)      do { (s)->s_flags |= (f); } while (0)
#define SBUF_CLEARFLAG(s, f)    do { (s)->s_flags &= ~(f); } while (0)
 
#define SBUF_MINSIZE             2              /* Min is 1 byte + nulterm. */
#define SBUF_MINEXTENDSIZE      16              /* Should be power of 2. */
 
#ifdef PAGE_SIZE
#define SBUF_MAXEXTENDSIZE      PAGE_SIZE
#define SBUF_MAXEXTENDINCR      PAGE_SIZE
#else
#define SBUF_MAXEXTENDSIZE      4096
#define SBUF_MAXEXTENDINCR      4096
#endif
 
/*
 * Debugging support
 */
#if defined(_KERNEL) && defined(INVARIANTS)
 
static void
_assert_sbuf_integrity(const char *fun, struct sbuf *s)
{
 
        KASSERT(s != NULL,
            ("%s called with a NULL sbuf pointer", fun));
        KASSERT(s->s_buf != NULL,
            ("%s called with uninitialized or corrupt sbuf", fun));
        if (SBUF_ISFINISHED(s) && SBUF_NULINCLUDED(s)) {
                KASSERT(s->s_len <= s->s_size,
                    ("wrote past end of sbuf (%jd >= %jd)",
                    (intmax_t)s->s_len, (intmax_t)s->s_size));
        } else {
                KASSERT(s->s_len < s->s_size,
                    ("wrote past end of sbuf (%jd >= %jd)",
                    (intmax_t)s->s_len, (intmax_t)s->s_size));
        }
}
 
static void
_assert_sbuf_state(const char *fun, struct sbuf *s, int state)
{
 
        KASSERT((s->s_flags & SBUF_FINISHED) == state,
            ("%s called with %sfinished or corrupt sbuf", fun,
            (state ? "un" : "")));
}
 
#define assert_sbuf_integrity(s) _assert_sbuf_integrity(__func__, (s))
#define assert_sbuf_state(s, i)  _assert_sbuf_state(__func__, (s), (i))
 
#else /* _KERNEL && INVARIANTS */
 
#define assert_sbuf_integrity(s) do { } while (0)
#define assert_sbuf_state(s, i)  do { } while (0)
 
#endif /* _KERNEL && INVARIANTS */
 
#ifdef CTASSERT
CTASSERT(powerof2(SBUF_MAXEXTENDSIZE));
CTASSERT(powerof2(SBUF_MAXEXTENDINCR));
#endif
 
static int
sbuf_extendsize(int size)
{
        int newsize;
 
        if (size < (int)SBUF_MAXEXTENDSIZE) {
                newsize = SBUF_MINEXTENDSIZE;
                while (newsize < size)
                        newsize *= 2;
        } else {
                newsize = roundup2(size, SBUF_MAXEXTENDINCR);
        }
        KASSERT(newsize >= size, ("%s: %d < %d\n", __func__, newsize, size));
        return (newsize);
}
 
/*
 * Extend an sbuf.
 */
static int
sbuf_extend(struct sbuf *s, int addlen)
{
        char *newbuf;
        int newsize;
 
        if (!SBUF_CANEXTEND(s))
                return (-1);
        newsize = sbuf_extendsize(s->s_size + addlen);
        newbuf = SBMALLOC(newsize, SBUF_MALLOCFLAG(s));
        if (newbuf == NULL)
                return (-1);
        memcpy(newbuf, s->s_buf, s->s_size);
        if (SBUF_ISDYNAMIC(s))
                SBFREE(s->s_buf);
        else
                SBUF_SETFLAG(s, SBUF_DYNAMIC);
        s->s_buf = newbuf;
        s->s_size = newsize;
        return (0);
}
 
/*
 * Initialize an sbuf.
 * If buf is non-NULL, it points to a static or already-allocated string
 * big enough to hold at least length characters.
 */
struct sbuf *
sbuf_new(struct sbuf *s, char *buf, int length, int flags)
{
 
        KASSERT(length >= 0,
            ("attempt to create an sbuf of negative length (%d)", length));
        KASSERT((flags & ~SBUF_USRFLAGMSK) == 0,
            ("%s called with invalid flags", __func__));
        KASSERT((flags & SBUF_AUTOEXTEND) || length >= SBUF_MINSIZE,
            ("sbuf buffer %d smaller than minimum %d bytes", length,
            SBUF_MINSIZE));
 
        flags &= SBUF_USRFLAGMSK;
 
        /*
         * Allocate 'DYNSTRUCT' sbuf from the heap, if NULL 's' was provided.
         */
        if (s == NULL) {
                s = SBMALLOC(sizeof(*s),
                    (flags & SBUF_NOWAIT) ?  M_NOWAIT : M_WAITOK);
                if (s == NULL)
                        goto out;
                SBUF_SETFLAG(s, SBUF_DYNSTRUCT);
        } else {
                /*
                 * DYNSTRUCT SBMALLOC sbufs are allocated with M_ZERO, but
                 * user-provided sbuf objects must be initialized.
                 */
                memset(s, 0, sizeof(*s));
        }
 
        s->s_flags |= flags;
        s->s_size = length;
        s->s_buf = buf;
        /*
         * Never-written sbufs do not need \n termination.
         */
        SBUF_SETFLAG(s, SBUF_DRAINATEOL);
 
        /*
         * Allocate DYNAMIC, i.e., heap data buffer backing the sbuf, if no
         * buffer was provided.
         */
        if (s->s_buf == NULL) {
                if (SBUF_CANEXTEND(s))
                        s->s_size = sbuf_extendsize(s->s_size);
                s->s_buf = SBMALLOC(s->s_size, SBUF_MALLOCFLAG(s));
                if (s->s_buf == NULL)
                        goto out;
                SBUF_SETFLAG(s, SBUF_DYNAMIC);
        }
 
out:
        if (s != NULL && s->s_buf == NULL) {
                if (SBUF_ISDYNSTRUCT(s))
                        SBFREE(s);
                s = NULL;
        }
        return (s);
}
 
#ifdef _KERNEL
/*
 * Create an sbuf with uio data
 */
struct sbuf *
sbuf_uionew(struct sbuf *s, struct uio *uio, int *error)
{
 
        KASSERT(uio != NULL,
            ("%s called with NULL uio pointer", __func__));
        KASSERT(error != NULL,
            ("%s called with NULL error pointer", __func__));
 
        if (uio->uio_resid >= INT_MAX || uio->uio_resid < SBUF_MINSIZE - 1) {
                *error = EINVAL;
                return (NULL);
        }
        s = sbuf_new(s, NULL, uio->uio_resid + 1, 0);
        if (s == NULL) {
                *error = ENOMEM;
                return (NULL);
        }
        *error = uiomove(s->s_buf, uio->uio_resid, uio);
        if (*error != 0) {
                sbuf_delete(s);
                return (NULL);
        }
        s->s_len = s->s_size - 1;
        if (SBUF_ISSECTION(s))
                s->s_sect_len = s->s_size - 1;
        *error = 0;
        return (s);
}
#endif
 
int
sbuf_get_flags(struct sbuf *s)
{
 
        return (s->s_flags & SBUF_USRFLAGMSK);
}
 
void
sbuf_clear_flags(struct sbuf *s, int flags)
{
 
        s->s_flags &= ~(flags & SBUF_USRFLAGMSK);
}
 
void
sbuf_set_flags(struct sbuf *s, int flags)
{
 
        s->s_flags |= (flags & SBUF_USRFLAGMSK);
}
 
/*
 * Clear an sbuf and reset its position.
 */
void
sbuf_clear(struct sbuf *s)
{
 
        assert_sbuf_integrity(s);
        /* don't care if it's finished or not */
        KASSERT(s->s_drain_func == NULL,
            ("%s makes no sense on sbuf %p with drain", __func__, s));
 
        SBUF_CLEARFLAG(s, SBUF_FINISHED);
        s->s_error = 0;
        s->s_len = 0;
        s->s_rec_off = 0;
        s->s_sect_len = 0;
}
 
/*
 * Set the sbuf's end position to an arbitrary value.
 * Effectively truncates the sbuf at the new position.
 */
int
sbuf_setpos(struct sbuf *s, ssize_t pos)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        KASSERT(pos >= 0,
            ("attempt to seek to a negative position (%jd)", (intmax_t)pos));
        KASSERT(pos < s->s_size,
            ("attempt to seek past end of sbuf (%jd >= %jd)",
            (intmax_t)pos, (intmax_t)s->s_size));
        KASSERT(!SBUF_ISSECTION(s),
            ("attempt to seek when in a section"));
 
        if (pos < 0 || pos > s->s_len)
                return (-1);
        s->s_len = pos;
        return (0);
}
 
/*
 * Drain into a counter.  Counts amount of data without producing output.
 * Useful for cases like sysctl, where user may first request only size.
 * This allows to avoid pointless allocation/freeing of large buffers.
 */
int
sbuf_count_drain(void *arg, const char *data __unused, int len)
{
        size_t *sizep;
 
        sizep = (size_t *)arg;
        *sizep += len;
        return (len);
}
 
/*
 * Set up a drain function and argument on an sbuf to flush data to
 * when the sbuf buffer overflows.
 */
void
sbuf_set_drain(struct sbuf *s, sbuf_drain_func *func, void *ctx)
{
 
        assert_sbuf_state(s, 0);
        assert_sbuf_integrity(s);
        KASSERT(func == s->s_drain_func || s->s_len == 0,
            ("Cannot change drain to %p on non-empty sbuf %p", func, s));
        s->s_drain_func = func;
        s->s_drain_arg = ctx;
}
 
/*
 * Call the drain and process the return.
 */
int
sbuf_drain(struct sbuf *s)
{
        int len;
 
        /*
         * Immediately return when no work to do,
         * or an error has already been accumulated.
         */
        if ((s->s_len == 0) || (s->s_error != 0))
                return(s->s_error);
 
        if (SBUF_DODRAINTOEOR(s) && s->s_rec_off == 0)
                return (s->s_error = EDEADLK);
        len = s->s_drain_func(s->s_drain_arg, s->s_buf,
            SBUF_DODRAINTOEOR(s) ? s->s_rec_off : s->s_len);
        if (len <= 0) {
                s->s_error = len ? -len : EDEADLK;
                return (s->s_error);
        }
        KASSERT(len > 0 && len <= s->s_len,
            ("Bad drain amount %d for sbuf %p", len, s));
        s->s_len -= len;
        s->s_rec_off -= len;
        /*
         * Fast path for the expected case where all the data was
         * drained.
         */
        if (s->s_len == 0) {
                /*
                 * When the s_buf is entirely drained, we need to remember if
                 * the last character was a '\n' or not for
                 * sbuf_nl_terminate().
                 */
                if (s->s_buf[len - 1] == '\n')
                        SBUF_SETFLAG(s, SBUF_DRAINATEOL);
                else
                        SBUF_CLEARFLAG(s, SBUF_DRAINATEOL);
                return (0);
        }
        /*
         * Move the remaining characters to the beginning of the
         * string.
         */
        memmove(s->s_buf, s->s_buf + len, s->s_len);
        return (0);
}
 
/*
 * Append bytes to an sbuf.  This is the core function for appending
 * to an sbuf and is the main place that deals with extending the
 * buffer and marking overflow.
 */
static void
sbuf_put_bytes(struct sbuf *s, const char *buf, size_t len)
{
        size_t n;
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        if (s->s_error != 0)
                return;
        while (len > 0) {
                if (SBUF_FREESPACE(s) <= 0) {
                        /*
                         * If there is a drain, use it, otherwise extend the
                         * buffer.
                         */
                        if (s->s_drain_func != NULL)
                                (void)sbuf_drain(s);
                        else if (sbuf_extend(s, len > INT_MAX ? INT_MAX : len)
                            < 0)
                                s->s_error = ENOMEM;
                        if (s->s_error != 0)
                                return;
                }
                n = SBUF_FREESPACE(s);
                if (len < n)
                        n = len;
                memcpy(&s->s_buf[s->s_len], buf, n);
                s->s_len += n;
                if (SBUF_ISSECTION(s))
                        s->s_sect_len += n;
                len -= n;
                buf += n;
        }
}
 
static void
sbuf_put_byte(struct sbuf *s, char c)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        if (__predict_false(s->s_error != 0))
                return;
        if (__predict_false(SBUF_FREESPACE(s) <= 0)) {
                /*
                 * If there is a drain, use it, otherwise extend the
                 * buffer.
                 */
                if (s->s_drain_func != NULL)
                        (void)sbuf_drain(s);
                else if (sbuf_extend(s, 1) < 0)
                        s->s_error = ENOMEM;
                if (s->s_error != 0)
                        return;
        }
        s->s_buf[s->s_len++] = c;
        if (SBUF_ISSECTION(s))
                s->s_sect_len++;
}
 
/*
 * Append a byte string to an sbuf.
 */
int
sbuf_bcat(struct sbuf *s, const void *buf, size_t len)
{
 
        sbuf_put_bytes(s, buf, len);
        if (s->s_error != 0)
                return (-1);
        return (0);
}
 
#ifdef _KERNEL
/*
 * Copy a byte string from userland into an sbuf.
 */
int
sbuf_bcopyin(struct sbuf *s, const void *uaddr, size_t len)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
        KASSERT(s->s_drain_func == NULL,
            ("Nonsensical copyin to sbuf %p with a drain", s));
 
        if (s->s_error != 0)
                return (-1);
        if (len == 0)
                return (0);
        if (len > SBUF_FREESPACE(s)) {
                sbuf_extend(s, len - SBUF_FREESPACE(s));
                if (SBUF_FREESPACE(s) < len)
                        len = SBUF_FREESPACE(s);
        }
        if (copyin(uaddr, s->s_buf + s->s_len, len) != 0)
                return (-1);
        s->s_len += len;
 
        return (0);
}
#endif
 
/*
 * Copy a byte string into an sbuf.
 */
int
sbuf_bcpy(struct sbuf *s, const void *buf, size_t len)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        sbuf_clear(s);
        return (sbuf_bcat(s, buf, len));
}
 
/*
 * Append a string to an sbuf.
 */
int
sbuf_cat(struct sbuf *s, const char *str)
{
        size_t n;
 
        n = strlen(str);
        sbuf_put_bytes(s, str, n);
        if (s->s_error != 0)
                return (-1);
        return (0);
}
 
#ifdef _KERNEL
/*
 * Append a string from userland to an sbuf.
 */
int
sbuf_copyin(struct sbuf *s, const void *uaddr, size_t len)
{
        size_t done;
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
        KASSERT(s->s_drain_func == NULL,
            ("Nonsensical copyin to sbuf %p with a drain", s));
 
        if (s->s_error != 0)
                return (-1);
 
        if (len == 0)
                len = SBUF_FREESPACE(s);        /* XXX return 0? */
        if (len > SBUF_FREESPACE(s)) {
                sbuf_extend(s, len);
                if (SBUF_FREESPACE(s) < len)
                        len = SBUF_FREESPACE(s);
        }
        switch (copyinstr(uaddr, s->s_buf + s->s_len, len + 1, &done)) {
        case ENAMETOOLONG:
                s->s_error = ENOMEM;
                /* fall through */
        case 0:
                s->s_len += done - 1;
                if (SBUF_ISSECTION(s))
                        s->s_sect_len += done - 1;
                break;
        default:
                return (-1);    /* XXX */
        }
 
        return (done);
}
#endif
 
/*
 * Copy a string into an sbuf.
 */
int
sbuf_cpy(struct sbuf *s, const char *str)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        sbuf_clear(s);
        return (sbuf_cat(s, str));
}
 
/*
 * Format the given argument list and append the resulting string to an sbuf.
 */
#ifdef _KERNEL
 
/*
 * Append a non-NUL character to an sbuf.  This prototype signature is
 * suitable for use with kvprintf(9).
 */
static void
sbuf_putc_func(int c, void *arg)
{
 
        if (__predict_true(c != '\0'))
                sbuf_put_byte(arg, c);
}
 
int
sbuf_vprintf(struct sbuf *s, const char *fmt, va_list ap)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        KASSERT(fmt != NULL,
            ("%s called with a NULL format string", __func__));
 
        (void)kvprintf(fmt, sbuf_putc_func, s, 10, ap);
        if (s->s_error != 0)
                return (-1);
        return (0);
}
#else /* !_KERNEL */
int
sbuf_vprintf(struct sbuf *s, const char *fmt, va_list ap)
{
        va_list ap_copy;
        int error, len;
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        KASSERT(fmt != NULL,
            ("%s called with a NULL format string", __func__));
 
        if (s->s_error != 0)
                return (-1);
 
        /*
         * For the moment, there is no way to get vsnprintf(3) to hand
         * back a character at a time, to push everything into
         * sbuf_putc_func() as was done for the kernel.
         *
         * In userspace, while drains are useful, there's generally
         * not a problem attempting to malloc(3) on out of space.  So
         * expand a userland sbuf if there is not enough room for the
         * data produced by sbuf_[v]printf(3).
         */
 
        error = 0;
        do {
                va_copy(ap_copy, ap);
                len = vsnprintf(&s->s_buf[s->s_len], SBUF_FREESPACE(s) + 1,
                    fmt, ap_copy);
                if (len < 0) {
                        s->s_error = errno;
                        return (-1);
                }
                va_end(ap_copy);
 
                if (SBUF_FREESPACE(s) >= len)
                        break;
                /* Cannot print with the current available space. */
                if (s->s_drain_func != NULL && s->s_len > 0)
                        error = sbuf_drain(s); /* sbuf_drain() sets s_error. */
                else if (sbuf_extend(s, len - SBUF_FREESPACE(s)) != 0)
                        s->s_error = error = ENOMEM;
        } while (error == 0);
 
        /*
         * s->s_len is the length of the string, without the terminating nul.
         * When updating s->s_len, we must subtract 1 from the length that
         * we passed into vsnprintf() because that length includes the
         * terminating nul.
         *
         * vsnprintf() returns the amount that would have been copied,
         * given sufficient space, so don't over-increment s_len.
         */
        if (SBUF_FREESPACE(s) < len)
                len = SBUF_FREESPACE(s);
        s->s_len += len;
        if (SBUF_ISSECTION(s))
                s->s_sect_len += len;
 
        KASSERT(s->s_len < s->s_size,
            ("wrote past end of sbuf (%d >= %d)", s->s_len, s->s_size));
 
        if (s->s_error != 0)
                return (-1);
        return (0);
}
#endif /* _KERNEL */
 
/*
 * Format the given arguments and append the resulting string to an sbuf.
 */
int
sbuf_printf(struct sbuf *s, const char *fmt, ...)
{
        va_list ap;
        int result;
 
        va_start(ap, fmt);
        result = sbuf_vprintf(s, fmt, ap);
        va_end(ap);
        return (result);
}
 
/*
 * Append a character to an sbuf.
 */
int
sbuf_putc(struct sbuf *s, int c)
{
 
        sbuf_put_byte(s, c);
        if (s->s_error != 0)
                return (-1);
        return (0);
}
 
/*
 * Append a trailing newline to a non-empty sbuf, if one is not already
 * present.  Handles sbufs with drain functions correctly.
 */
int
sbuf_nl_terminate(struct sbuf *s)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        /*
         * If the s_buf isn't empty, the last byte is simply s_buf[s_len - 1].
         *
         * If the s_buf is empty because a drain function drained it, we
         * remember if the last byte was a \n with the SBUF_DRAINATEOL flag in
         * sbuf_drain().
         *
         * In either case, we only append a \n if the previous character was
         * something else.
         */
        if (s->s_len == 0) {
                if (!SBUF_ISDRAINATEOL(s))
                        sbuf_put_byte(s, '\n');
        } else if (s->s_buf[s->s_len - 1] != '\n')
                sbuf_put_byte(s, '\n');
 
        if (s->s_error != 0)
                return (-1);
        return (0);
}
 
/*
 * Trim whitespace characters from end of an sbuf.
 */
int
sbuf_trim(struct sbuf *s)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
        KASSERT(s->s_drain_func == NULL,
            ("%s makes no sense on sbuf %p with drain", __func__, s));
 
        if (s->s_error != 0)
                return (-1);
 
        while (s->s_len > 0 && isspace(s->s_buf[s->s_len-1])) {
                --s->s_len;
                if (SBUF_ISSECTION(s))
                        s->s_sect_len--;
        }
 
        return (0);
}
 
/*
 * Check if an sbuf has an error.
 */
int
sbuf_error(const struct sbuf *s)
{
 
        return (s->s_error);
}
 
/*
 * Finish off an sbuf.
 */
int
sbuf_finish(struct sbuf *s)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        s->s_buf[s->s_len] = '\0';
        if (SBUF_NULINCLUDED(s))
                s->s_len++;
        if (s->s_drain_func != NULL) {
                while (s->s_len > 0 && s->s_error == 0)
                        s->s_error = sbuf_drain(s);
        }
        SBUF_SETFLAG(s, SBUF_FINISHED);
#ifdef _KERNEL
        return (s->s_error);
#else
        if (s->s_error != 0) {
                errno = s->s_error;
                return (-1);
        }
        return (0);
#endif
}
 
/*
 * Return a pointer to the sbuf data.
 */
char *
sbuf_data(struct sbuf *s)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, SBUF_FINISHED);
        KASSERT(s->s_drain_func == NULL,
            ("%s makes no sense on sbuf %p with drain", __func__, s));
 
        return (s->s_buf);
}
 
/*
 * Return the length of the sbuf data.
 */
ssize_t
sbuf_len(struct sbuf *s)
{
 
        assert_sbuf_integrity(s);
        /* don't care if it's finished or not */
        KASSERT(s->s_drain_func == NULL,
            ("%s makes no sense on sbuf %p with drain", __func__, s));
 
        if (s->s_error != 0)
                return (-1);
 
        /* If finished, nulterm is already in len, else add one. */
        if (SBUF_NULINCLUDED(s) && !SBUF_ISFINISHED(s))
                return (s->s_len + 1);
        return (s->s_len);
}
 
/*
 * Clear an sbuf, free its buffer if necessary.
 */
void
sbuf_delete(struct sbuf *s)
{
        int isdyn;
 
        assert_sbuf_integrity(s);
        /* don't care if it's finished or not */
 
        if (SBUF_ISDYNAMIC(s))
                SBFREE(s->s_buf);
        isdyn = SBUF_ISDYNSTRUCT(s);
        memset(s, 0, sizeof(*s));
        if (isdyn)
                SBFREE(s);
}
 
/*
 * Check if an sbuf has been finished.
 */
int
sbuf_done(const struct sbuf *s)
{
 
        return (SBUF_ISFINISHED(s));
}
 
/*
 * Start a section.
 */
void
sbuf_start_section(struct sbuf *s, ssize_t *old_lenp)
{
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
 
        if (!SBUF_ISSECTION(s)) {
                KASSERT(s->s_sect_len == 0,
                    ("s_sect_len != 0 when starting a section"));
                if (old_lenp != NULL)
                        *old_lenp = -1;
                s->s_rec_off = s->s_len;
                SBUF_SETFLAG(s, SBUF_INSECTION);
        } else {
                KASSERT(old_lenp != NULL,
                    ("s_sect_len should be saved when starting a subsection"));
                *old_lenp = s->s_sect_len;
                s->s_sect_len = 0;
        }
}
 
/*
 * End the section padding to the specified length with the specified
 * character.
 */
ssize_t
sbuf_end_section(struct sbuf *s, ssize_t old_len, size_t pad, int c)
{
        ssize_t len;
 
        assert_sbuf_integrity(s);
        assert_sbuf_state(s, 0);
        KASSERT(SBUF_ISSECTION(s),
            ("attempt to end a section when not in a section"));
 
        if (pad > 1) {
                len = roundup(s->s_sect_len, pad) - s->s_sect_len;
                for (; s->s_error == 0 && len > 0; len--)
                        sbuf_put_byte(s, c);
        }
        len = s->s_sect_len;
        if (old_len == -1) {
                s->s_rec_off = s->s_sect_len = 0;
                SBUF_CLEARFLAG(s, SBUF_INSECTION);
        } else {
                s->s_sect_len += old_len;
        }
        if (s->s_error != 0)
                return (-1);
        return (len);
}