1 /* $Id: tpam_crcpc.c,v 1.1.2.1 2001/11/20 14:19:37 kai Exp $
2 *
3 * Turbo PAM ISDN driver for Linux. (Kernel Driver - CRC encoding)
4 *
5 * Copyright 1998-2000 AUVERTECH T�l�com
6 * Copyright 2001 Stelian Pop <stelian.pop@fr.alcove.com>, Alc�ve
7 *
8 * This software may be used and distributed according to the terms
9 * of the GNU General Public License, incorporated herein by reference.
10 *
11 * For all support questions please contact: <support@auvertech.fr>
12 *
13 */
14
15 /*+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
16
17 Module Name:
18
19 crcpc.c
20
21 Abstract:
22
23 Modem HDLC coding
24 Software HDLC coding / decoding
25
26 Revision History:
27
28 ---------------------------------------------------------------------------*/
29
30 #include "tpam.h"
31
32 #define HDLC_CTRL_CHAR_CMPL_MASK 0x20 /* HDLC control character complement mask */
33 #define HDLC_FLAG 0x7E /* HDLC flag */
34 #define HDLC_CTRL_ESC 0x7D /* HDLC control escapr character */
35 #define HDLC_LIKE_FCS_INIT_VAL 0xFFFF /* FCS initial value (0xFFFF for new equipment or 0) */
36 #define HDLC_FCS_OK 0xF0B8 /* This value is the only valid value of FCS */
37
38 #define TRUE 1
39 #define FALSE 0
40
41 static u16 t_ap_hdlc_like_fcs [256] = {
42 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
43 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
44 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
45 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
46 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
47 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
48 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
49 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
50 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
51 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
52 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
53 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
54 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
55 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
56 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
57 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
58 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
59 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
60 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
61 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
62 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
63 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
64 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
65 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
66 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
67 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
68 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
69 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
70 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
71 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
72 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
73 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
74 };
75
76 static u8 ap_t_ctrl_char_complemented[256]; /* list of characters to complement */
77
ap_hdlc_like_ctrl_char_list(u32 ctrl_char)78 static void ap_hdlc_like_ctrl_char_list (u32 ctrl_char) {
79 int i;
80
81 for (i = 0; i < 256; ++i)
82 ap_t_ctrl_char_complemented[i] = FALSE;
83 for (i = 0; i < 32; ++i)
84 if ((ctrl_char >> i) & 0x0001)
85 ap_t_ctrl_char_complemented [i] = TRUE;
86 ap_t_ctrl_char_complemented[HDLC_FLAG] = TRUE;
87 ap_t_ctrl_char_complemented[HDLC_CTRL_ESC] = TRUE;
88
89 }
90
init_CRC()91 void init_CRC() {
92 ap_hdlc_like_ctrl_char_list(0xffffffff);
93 }
94
hdlc_encode_modem(u8 * buffer_in,u32 lng_in,u8 * buffer_out,u32 * lng_out)95 void hdlc_encode_modem(u8 *buffer_in, u32 lng_in,
96 u8 *buffer_out, u32 *lng_out) {
97 u16 fcs;
98 register u8 data;
99 register u8 *p_data_out = buffer_out;
100
101 fcs = HDLC_LIKE_FCS_INIT_VAL;
102
103 /*
104 * Insert HDLC flag at the beginning of the frame
105 */
106 *p_data_out++ = HDLC_FLAG;
107
108 #define ESCAPE_CHAR(data_out, data) \
109 if (ap_t_ctrl_char_complemented[data]) { \
110 *data_out++ = HDLC_CTRL_ESC; \
111 *data_out++ = data ^ 0x20; \
112 } \
113 else \
114 *data_out++ = data;
115
116 while (lng_in--) {
117 data = *buffer_in++;
118
119 /*
120 * FCS calculation
121 */
122 fcs = (fcs>>8) ^ t_ap_hdlc_like_fcs[((u8)(fcs^data)) & 0xff];
123
124 ESCAPE_CHAR(p_data_out, data);
125 }
126
127 /*
128 * Add FCS and closing flag
129 */
130 fcs ^= 0xFFFF; // Complement
131
132 data = (u8)(fcs & 0xff); /* LSB */
133 ESCAPE_CHAR(p_data_out, data);
134
135 data = (u8)((fcs >> 8)); /* MSB */
136 ESCAPE_CHAR(p_data_out, data);
137 #undef ESCAPE_CHAR
138
139 *p_data_out++ = HDLC_FLAG;
140
141 *lng_out = (u32)(p_data_out - buffer_out);
142 }
143
hdlc_no_accm_encode(u8 * buffer_in,u32 lng_in,u8 * buffer_out,u32 * lng_out)144 void hdlc_no_accm_encode(u8 *buffer_in, u32 lng_in,
145 u8 *buffer_out, u32 *lng_out) {
146 u16 fcs;
147 register u8 data;
148 register u8 *p_data_out = buffer_out;
149
150 /*
151 * Insert HDLC flag at the beginning of the frame
152 */
153 fcs = HDLC_LIKE_FCS_INIT_VAL;
154
155 while (lng_in--) {
156 data = *buffer_in++;
157 /* calculate FCS */
158 fcs = (fcs>>8) ^ t_ap_hdlc_like_fcs[((u8)(fcs^data)) & 0xff];
159 *p_data_out++ = data;
160 }
161
162 /*
163 * Add FCS and closing flag
164 */
165 fcs ^= 0xFFFF; // Complement
166 data = (u8)(fcs);
167 *p_data_out++ = data;
168
169 data =(u8)((fcs >> 8)); // revense MSB / LSB
170 *p_data_out++ = data;
171
172 *lng_out = (u32)(p_data_out - buffer_out);
173 }
174
hdlc_no_accm_decode(u8 * buffer_in,u32 lng_in)175 u32 hdlc_no_accm_decode(u8 *buffer_in, u32 lng_in) {
176 u16 fcs;
177 u32 lng = lng_in;
178 register u8 data;
179
180 /*
181 * Insert HDLC flag at the beginning of the frame
182 */
183 fcs = HDLC_LIKE_FCS_INIT_VAL;
184
185 while (lng_in--) {
186 data = *buffer_in++;
187 /* calculate FCS */
188 fcs = (fcs>>8) ^ t_ap_hdlc_like_fcs[((u8)(fcs^data)) & 0xff];
189 }
190
191 if (fcs == HDLC_FCS_OK)
192 return (lng-2);
193 else
194 return 0;
195 }
196
197