85fee3197a
this case, ugly macros, but the data tables can be reused: Put one copy of the software HDLC tables in its own file.
300 lines
8.4 KiB
C
300 lines
8.4 KiB
C
/*
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* Copyright (c) 2000 Hans Petter Selasky. 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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*---------------------------------------------------------------------------
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*
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* i4b_hdlc.h - software-HDLC header file
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* --------------------------------------
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*
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* $Id: i4b_hdlc.h,v 1.5 2000/08/28 07:41:19 hm Exp $
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*
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* $FreeBSD$
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*
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* last edit-date: [Wed Jul 19 09:41:13 2000]
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*
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*---------------------------------------------------------------------------*/
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#ifndef _I4B_HDLC_H_
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#define _I4B_HDLC_H_
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extern const u_short HDLC_FCS_TAB[256];
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extern const u_short HDLC_BIT_TAB[256];
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/*---------------------------------------------------------------------------*
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* HDLC_DECODE
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* ===========
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*
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* u_char: flag, blevel
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* u_short: crc, ib, tmp, tmp2, len
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*
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* next: 'continue' or 'goto xxx'
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*
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* cfr: complete frame
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* nfr: new frame
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* NOTE: must setup 'len' and 'dst', so that 'dst' may be written
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* at most 'len' times.
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*
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* rab: abort
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* rdd: read data (read byte is stored in 'tmp2')
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* rdo: overflow
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*
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* d: dummy
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*
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* NOTE: setting flag to '0' and len to '0' => recover from rdu
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* NOTE: bits[8 .. ] of tmp2 may be used to store custom data/flags
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* NOTE: these variables have to be 'suspended' / 'resumed' somehow:
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* flag, blevel, crc, ib, tmp, len
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* NOTE: zero is default value for all variables.
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* NOTE: each time 'dst' is written, 'len' is decreased by one.
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*---------------------------------------------------------------------------*/
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#define HDLC_DECODE(dst, len, tmp, tmp2, blevel, ib, crc, flag, rddcmd, nfrcmd, \
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cfrcmd, rabcmd, rdocmd, nextcmd, d) \
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\
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rddcmd; \
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\
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ib += HDLC_BIT_TAB[(u_char)tmp2]; \
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\
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if ((u_char)ib >= 5) \
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{ \
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if (ib & 0x20) /* de-stuff (msb) */ \
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{ \
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if ((u_char)tmp2 == 0x7e) goto j0##d; \
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tmp2 += tmp2 & 0x7f; \
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blevel--; \
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\
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if ((ib += 0x100) & 0xc) tmp2 |= 1; /* */ \
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} \
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\
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ib &= ~0xe0; \
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\
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if ((u_char)ib == 6) /* flag seq (lsb) */ \
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{ \
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j0##d: if (flag >= 2) \
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{ \
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len += (4 - flag) & 3; /* remove CRC bytes */ \
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crc ^= 0xf0b8; \
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cfrcmd; \
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len = 0; \
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} \
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\
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flag = 1; \
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\
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blevel = (ib >> 8) & 0xf; \
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tmp = ((u_char)tmp2) >> blevel; \
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blevel = 8 - blevel; \
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\
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ib >>= 12; \
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\
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nextcmd; \
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} \
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if ((u_char)ib >= 7) /* abort (msb & lsb) */ \
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{ \
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if (flag >= 2) \
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{ \
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rabcmd; \
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len = 0; \
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} \
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\
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flag = 0; \
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\
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ib >>= 12; \
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\
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nextcmd; \
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} \
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if ((u_char)ib == 5) /* de-stuff (lsb) */ \
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{ \
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tmp2 = (tmp2 | (tmp2 + 1)) & ~0x1; \
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blevel--; \
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} \
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if (blevel > 7) /* EO - bits */ \
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{ \
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tmp |= (u_char)tmp2 >> (8 - (blevel &= 7)); \
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\
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ib >>= 12; \
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\
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nextcmd; \
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} \
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} \
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\
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tmp |= (u_char)tmp2 << blevel; \
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\
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if (!len--) \
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{ \
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len++; \
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\
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if (!flag++) { flag--; goto j5##d;} /* hunt mode */ \
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\
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switch (flag) \
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{ case 2: /* new frame */ \
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nfrcmd; \
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crc = -1; \
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if (!len--) { len++; flag++; goto j4##d; } \
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goto j3##d; \
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case 3: /* CRC (lsb's) */ \
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case 4: /* CRC (msb's) */ \
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goto j4##d; \
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case 5: /* RDO */ \
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rdocmd; \
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flag = 0; \
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break; \
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} \
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} \
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else \
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{ \
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j3##d: dst = (u_char)tmp; \
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j4##d: crc = (HDLC_FCS_TAB[(u_char)(tmp ^ crc)] ^ (u_char)(crc >> 8)); \
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} \
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\
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j5##d: ib >>= 12; \
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tmp >>= 8; \
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/*------ end of HDLC_DECODE -------------------------------------------------*/
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/*---------------------------------------------------------------------------*
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* HDLC_ENCODE
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* ===========
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*
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* u_char: flag, src
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* u_short: tmp2, blevel, ib, crc, len
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* u_int: tmp
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*
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* gfr: This is the place where you free the last [mbuf] chain, and get
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* the next one. If a mbuf is available the code should setup 'len'
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* and 'src' so that 'src' may be read 'len' times. If no mbuf is
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* available leave 'len' and 'src' untouched.
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*
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* wrd: write data (output = (u_char)tmp)
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*
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* d: dummy
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*
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* NOTE: setting flag to '-2' and len to '0' => abort bytes will be sent
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* NOTE: these variables have to be 'suspended' / 'resumed' somehow:
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* flag, blevel, crc, ib, tmp, len
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* NOTE: zero is default value for all variables.
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* NOTE: each time 'src' is read, 'len' is decreased by one.
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* NOTE: neither cmd's should exit through 'goto' or 'break' statements.
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*---------------------------------------------------------------------------*/
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#define HDLC_ENCODE(src, len, tmp, tmp2, blevel, ib, crc, flag, gfrcmd, wrdcmd, d) \
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\
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if (blevel >= 0x800) { blevel -= 0x800; goto j4##d; } \
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\
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if (!len--) \
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{ \
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len++; \
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\
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switch(++flag) \
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{ default: /* abort */ \
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tmp = blevel = 0; /* zero is default */ \
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tmp2 = 0xff; \
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goto j3##d; \
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case 1: /* 1st time FS */ \
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case 2: /* 2nd time FS */ \
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tmp2 = 0x7e; \
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goto j3##d; \
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case 3: \
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gfrcmd; /* get new frame */ \
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if (!len--) \
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{ \
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len++; \
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flag--; /* don't proceed */ \
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tmp2 = 0x7e; \
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goto j3##d; /* final FS */ \
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} \
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else \
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{ \
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crc = -1; \
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ib = 0; \
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goto j1##d; /* first byte */ \
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} \
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case 4: \
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crc ^= -1; \
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tmp2 = (u_char)crc; \
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goto j2##d; /* CRC (lsb's) */ \
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case 5: \
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tmp2 = (u_char)(crc >> 8); \
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flag = 1; \
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goto j2##d; /* CRC (msb's) */ \
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} \
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} \
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else \
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{ j1##d : \
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tmp2 = (u_char)src; \
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crc =(HDLC_FCS_TAB[(u_char)(crc ^ tmp2)] ^ (u_char)(crc >> 8)); \
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j2##d: \
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\
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ib >>= 12; \
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ib += HDLC_BIT_TAB[(u_char)tmp2]; \
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\
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if ((u_char)ib >= 5) /* stuffing */ \
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{ \
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blevel &= ~0xff; \
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\
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if (ib & 0xc0) /* bit stuff (msb) */ \
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{ \
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tmp2 += tmp2 & (0xff * (ib & 0xc0)); \
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ib %= 0x5000; \
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blevel++; \
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} \
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\
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ib &= ~0xf0; \
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\
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if ((u_char)ib >= 5) /* bit stuff (lsb) */ \
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{ \
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tmp2 += tmp2 & ~0x1f >> ((ib - (ib >> 8) + 1) \
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& 7); \
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blevel++; \
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\
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if ((u_char)ib >= 10) /* bit stuff (msb) */ \
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{ \
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tmp2 += tmp2 & ~0x7ff >> ((ib - \
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(ib >> 8) + 1) & 7); \
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blevel++; \
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} \
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if (ib & 0x8000) /* bit walk */ \
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{ \
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ib = ((u_char)ib % 5) << 12; \
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} \
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} \
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\
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tmp |= tmp2 << (u_char)(blevel >> 8); \
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blevel += (u_char)blevel << 8; \
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} \
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else /* no stuffing */ \
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{ \
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j3##d:tmp |= tmp2 << (u_char)(blevel >> 8); \
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} \
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} \
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\
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j4##d: wrdcmd; \
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tmp >>= 8; \
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/*------ end of HDLC_ENCODE -------------------------------------------------*/
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#endif /* _I4B_HDLC_H_ */
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