243 lines
6.5 KiB
C
243 lines
6.5 KiB
C
/*
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* Copyright (c) 2003 Ian Dowse. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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/*
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* Generic message buffer support routines.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/msgbuf.h>
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/* Read/write sequence numbers are modulo a multiple of the buffer size. */
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#define SEQMOD(size) ((size) * 16)
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static u_int msgbuf_cksum(struct msgbuf *mbp);
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/*
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* Initialize a message buffer of the specified size at the specified
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* location. This also zeros the buffer area.
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*/
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void
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msgbuf_init(struct msgbuf *mbp, void *ptr, int size)
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{
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mbp->msg_ptr = ptr;
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mbp->msg_size = size;
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mbp->msg_seqmod = SEQMOD(size);
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msgbuf_clear(mbp);
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mbp->msg_magic = MSG_MAGIC;
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}
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/*
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* Reinitialize a message buffer, retaining its previous contents if
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* the size and checksum are correct. If the old contents cannot be
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* recovered, the message buffer is cleared.
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*/
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void
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msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size)
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{
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u_int cksum;
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if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) {
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msgbuf_init(mbp, ptr, size);
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return;
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}
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mbp->msg_seqmod = SEQMOD(size);
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mbp->msg_wseq = MSGBUF_SEQNORM(mbp, mbp->msg_wseq);
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq);
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mbp->msg_ptr = ptr;
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cksum = msgbuf_cksum(mbp);
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if (cksum != mbp->msg_cksum) {
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if (bootverbose) {
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printf("msgbuf cksum mismatch (read %x, calc %x)\n",
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mbp->msg_cksum, cksum);
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printf("Old msgbuf not recovered\n");
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}
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msgbuf_clear(mbp);
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}
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}
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/*
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* Clear the message buffer.
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*/
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void
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msgbuf_clear(struct msgbuf *mbp)
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{
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bzero(mbp->msg_ptr, mbp->msg_size);
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mbp->msg_wseq = 0;
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mbp->msg_rseq = 0;
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mbp->msg_cksum = 0;
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}
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/*
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* Get a count of the number of unread characters in the message buffer.
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*/
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int
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msgbuf_getcount(struct msgbuf *mbp)
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{
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u_int len;
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len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq);
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if (len > mbp->msg_size)
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len = mbp->msg_size;
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return (len);
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}
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/*
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* Append a character to a message buffer. This function can be
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* considered fully reentrant so long as the number of concurrent
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* callers is less than the number of characters in the buffer.
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* However, the message buffer is only guaranteed to be consistent
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* for reading when there are no callers in this function.
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*/
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void
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msgbuf_addchar(struct msgbuf *mbp, int c)
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{
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u_int new_seq, pos, seq;
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do {
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seq = mbp->msg_wseq;
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new_seq = MSGBUF_SEQNORM(mbp, seq + 1);
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} while (atomic_cmpset_rel_int(&mbp->msg_wseq, seq, new_seq) == 0);
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pos = MSGBUF_SEQ_TO_POS(mbp, seq);
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atomic_add_int(&mbp->msg_cksum, (u_int)(u_char)c -
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(u_int)(u_char)mbp->msg_ptr[pos]);
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mbp->msg_ptr[pos] = c;
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}
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/*
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* Read and mark as read a character from a message buffer.
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* Returns the character, or -1 if no characters are available.
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*/
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int
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msgbuf_getchar(struct msgbuf *mbp)
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{
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u_int len, wseq;
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int c;
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wseq = mbp->msg_wseq;
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len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
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if (len == 0)
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return (-1);
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if (len > mbp->msg_size)
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)];
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1);
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return (c);
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}
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/*
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* Read and mark as read a number of characters from a message buffer.
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* Returns the number of characters that were placed in `buf'.
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*/
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int
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msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
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{
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u_int len, pos, wseq;
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wseq = mbp->msg_wseq;
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len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
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if (len == 0)
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return (0);
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if (len > mbp->msg_size) {
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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len = mbp->msg_size;
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}
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pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq);
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len = min(len, mbp->msg_size - pos);
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len = min(len, (u_int)buflen);
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bcopy(&mbp->msg_ptr[pos], buf, len);
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mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len);
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return (len);
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}
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/*
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* Peek at the full contents of a message buffer without marking any
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* data as read. `seqp' should point to an unsigned integer that
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* msgbuf_peekbytes() can use to retain state between calls so that
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* the whole message buffer can be read in multiple short reads.
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* To initialise this variable to the start of the message buffer,
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* call msgbuf_peekbytes() with a NULL `buf' parameter.
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*
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* Returns the number of characters that were placed in `buf'.
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*/
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int
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msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
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{
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u_int len, pos, wseq;
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if (buf == NULL) {
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/* Just initialise *seqp. */
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*seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size);
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return (0);
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}
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wseq = mbp->msg_wseq;
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len = MSGBUF_SEQSUB(mbp, wseq, *seqp);
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if (len == 0)
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return (0);
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if (len > mbp->msg_size) {
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*seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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len = mbp->msg_size;
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}
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pos = MSGBUF_SEQ_TO_POS(mbp, *seqp);
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len = min(len, mbp->msg_size - pos);
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len = min(len, (u_int)buflen);
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bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len);
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*seqp = MSGBUF_SEQNORM(mbp, *seqp + len);
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return (len);
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}
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/*
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* Compute the checksum for the complete message buffer contents.
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*/
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static u_int
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msgbuf_cksum(struct msgbuf *mbp)
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{
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u_int i, sum;
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sum = 0;
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for (i = 0; i < mbp->msg_size; i++)
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sum += (u_char)mbp->msg_ptr[i];
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return (sum);
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}
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/*
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* Copy from one message buffer to another.
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*/
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void
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msgbuf_copy(struct msgbuf *src, struct msgbuf *dst)
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{
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int c;
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while ((c = msgbuf_getchar(src)) >= 0)
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msgbuf_addchar(dst, c);
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}
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