| /* |
| * |
| * AT chat library with GLib integration |
| * |
| * Copyright (C) 2011 Intel Corporation. All rights reserved. |
| * Copyright (C) 2009 Trolltech ASA. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| * |
| */ |
| |
| #ifdef HAVE_CONFIG_H |
| #include <config.h> |
| #endif |
| |
| #include <string.h> |
| |
| #include <glib.h> |
| |
| #include "gsm0710.h" |
| |
| static const unsigned char crc_table[256] = { |
| 0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75, |
| 0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B, |
| 0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69, |
| 0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67, |
| 0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D, |
| 0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43, |
| 0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51, |
| 0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F, |
| 0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05, |
| 0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B, |
| 0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19, |
| 0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17, |
| 0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D, |
| 0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33, |
| 0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21, |
| 0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F, |
| 0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95, |
| 0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B, |
| 0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89, |
| 0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87, |
| 0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD, |
| 0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3, |
| 0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1, |
| 0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF, |
| 0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5, |
| 0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB, |
| 0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9, |
| 0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7, |
| 0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD, |
| 0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3, |
| 0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1, |
| 0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF |
| }; |
| |
| static inline guint8 gsm0710_crc(const guint8 *data, int len) |
| { |
| guint8 crc = 0xFF; |
| int i; |
| |
| for (i = 0; i < len; i++) |
| crc = crc_table[crc ^ data[i]]; |
| |
| return crc; |
| } |
| |
| static inline guint8 gsm0710_fcs(const guint8 *data, int len) |
| { |
| return 0xff - gsm0710_crc(data, len); |
| } |
| |
| static inline gboolean gsm0710_check_fcs(const guint8 *data, int len, |
| guint8 cfcs) |
| { |
| guint8 fcs = gsm0710_crc(data, len); |
| |
| fcs = crc_table[fcs ^ cfcs]; |
| |
| if (fcs == 0xcf) |
| return TRUE; |
| |
| return FALSE; |
| } |
| |
| int gsm0710_advanced_extract_frame(guint8 *buf, int len, |
| guint8 *out_dlc, guint8 *out_control, |
| guint8 **out_frame, int *out_len) |
| { |
| int posn = 0; |
| int posn2; |
| int framelen; |
| guint8 dlc; |
| guint8 control; |
| |
| while (posn < len) { |
| if (buf[posn] != 0x7E) { |
| posn += 1; |
| continue; |
| } |
| |
| /* Skip additional 0x7E bytes between frames */ |
| while ((posn + 1) < len && buf[posn + 1] == 0x7E) |
| posn += 1; |
| |
| /* Search for the end of the packet (the next 0x7E byte) */ |
| framelen = posn + 1; |
| while (framelen < len && buf[framelen] != 0x7E) |
| framelen += 1; |
| |
| if (framelen >= len) |
| break; |
| |
| if (framelen < 4) { |
| posn = framelen; |
| continue; |
| } |
| |
| /* Undo control byte quoting in the packet */ |
| posn2 = 0; |
| ++posn; |
| while (posn < framelen) { |
| if (buf[posn] == 0x7D) { |
| ++posn; |
| |
| if (posn >= framelen) |
| break; |
| |
| buf[posn2++] = buf[posn++] ^ 0x20; |
| } else { |
| buf[posn2++] = buf[posn++]; |
| } |
| } |
| |
| /* Validate the checksum on the packet header */ |
| if (!gsm0710_check_fcs(buf, 2, buf[posn2 - 1])) |
| continue; |
| |
| /* Decode and dispatch the packet */ |
| dlc = (buf[0] >> 2) & 0x3F; |
| control = buf[1] & 0xEF; /* Strip "PF" bit */ |
| |
| if (out_frame) |
| *out_frame = buf + 2; |
| |
| if (out_len) |
| *out_len = posn2 - 3; |
| |
| if (out_dlc) |
| *out_dlc = dlc; |
| |
| if (out_control) |
| *out_control = control; |
| |
| break; |
| } |
| |
| return posn; |
| } |
| |
| int gsm0710_advanced_fill_frame(guint8 *frame, guint8 dlc, guint8 type, |
| const guint8 *data, int len) |
| { |
| int temp, crc; |
| int size; |
| |
| frame[0] = 0x7E; |
| frame[1] = ((dlc << 2) | 0x03); |
| frame[2] = type; |
| |
| crc = gsm0710_fcs(frame + 1, 2); |
| |
| /* The Address field might need to be escaped if this is a response |
| * frame |
| */ |
| |
| /* Need to quote the type field now that crc has been computed */ |
| if (type == 0x7E || type == 0x7D) { |
| frame[2] = 0x7D; |
| frame[3] = (type ^ 0x20); |
| size = 4; |
| } else { |
| size = 3; |
| } |
| |
| while (len > 0) { |
| temp = *data++ & 0xFF; |
| --len; |
| |
| if (temp != 0x7E && temp != 0x7D) { |
| frame[size++] = temp; |
| } else { |
| frame[size++] = 0x7D; |
| frame[size++] = (temp ^ 0x20); |
| } |
| } |
| |
| if (crc != 0x7E && crc != 0x7D) { |
| frame[size++] = crc; |
| } else { |
| frame[size++] = 0x7D; |
| frame[size++] = (crc ^ 0x20); |
| } |
| |
| frame[size++] = 0x7E; |
| |
| return size; |
| } |
| |
| int gsm0710_basic_extract_frame(guint8 *buf, int len, |
| guint8 *out_dlc, guint8 *out_control, |
| guint8 **out_frame, int *out_len) |
| { |
| int posn = 0; |
| int framelen; |
| int header_size; |
| guint8 fcs; |
| guint8 dlc; |
| guint8 type; |
| |
| while (posn < len) { |
| if (buf[posn] != 0xF9) { |
| posn += 1; |
| continue; |
| } |
| |
| /* Skip additional 0xF9 bytes between frames */ |
| while ((posn + 1) < len && buf[posn + 1] == 0xF9) |
| posn += 1; |
| |
| /* We need at least 4 bytes for the flag + header */ |
| if ((posn + 4) > len) |
| break; |
| |
| /* The low bit of the second byte should be 1, |
| which indicates a short channel number. According to |
| 27.010 Section 5.2.3, if this is not true, then |
| the frame is invalid and should be discarded |
| */ |
| if ((buf[posn + 1] & 0x01) == 0) { |
| ++posn; |
| continue; |
| } |
| |
| /* Get the packet length and validate it */ |
| framelen = buf[posn + 3] >> 1; |
| |
| if ((buf[posn + 3] & 0x01) != 0) { |
| /* Single-byte length indication */ |
| header_size = 3; |
| } else { |
| /* Double-byte length indication */ |
| if ((posn + 5) > len) |
| break; |
| |
| framelen |= buf[posn + 4] << 7; |
| header_size = 4; |
| } |
| |
| /* Total size of the packet is the flag + 3 or 4 byte header |
| * Address Control Length followed by Information and FCS. |
| * However, we must check the presence of the end flag |
| * according to 27.010 Section 5.2.3 |
| */ |
| if ((posn + header_size + 3 + framelen) > len) |
| break; |
| |
| fcs = buf[posn + 1 + header_size + framelen]; |
| |
| /* |
| * The end flag is not guaranteed to be only ours |
| * according to 27.010 Section 5.2.6.1: |
| * "The closing flag may also be the opening flag of the |
| * following frame", thus we do not consume it in the following |
| * stages |
| */ |
| |
| /* |
| * If FCS is invalid, discard the packet in accordance to |
| * Section 5.2.3 of 27.010 |
| */ |
| if (!gsm0710_check_fcs(buf + posn + 1, header_size, fcs)) { |
| posn += header_size + framelen + 2; |
| continue; |
| } |
| |
| if (buf[posn + header_size + framelen + 2] != 0xF9) { |
| posn += header_size + framelen + 2; |
| continue; |
| } |
| |
| /* Get the channel number and packet type from the header */ |
| dlc = buf[posn + 1] >> 2; |
| type = buf[posn + 2] & 0xEF; /* Strip "PF" bit */ |
| |
| if (out_frame) |
| *out_frame = buf + posn + 1 + header_size; |
| |
| if (out_len) |
| *out_len = framelen; |
| |
| if (out_dlc) |
| *out_dlc = dlc; |
| |
| if (out_control) |
| *out_control = type; |
| |
| posn += header_size + framelen + 2; |
| |
| break; |
| } |
| |
| return posn; |
| } |
| |
| int gsm0710_basic_fill_frame(guint8 *frame, guint8 dlc, guint8 type, |
| const guint8 *data, int len) |
| { |
| int size; |
| int header_size; |
| |
| frame[0] = 0xF9; |
| frame[1] = ((dlc << 2) | 0x03); |
| frame[2] = type; |
| |
| if (len <= 127) { |
| frame[3] = ((len << 1) | 0x01); |
| header_size = 4; |
| } else { |
| frame[3] = (len << 1); |
| frame[4] = (len >> 7); |
| header_size = 5; |
| } |
| |
| size = header_size; |
| |
| if (len > 0) { |
| memcpy(frame + header_size, data, len); |
| size += len; |
| } |
| |
| /* Note: GSM 07.10 says that the CRC is only computed over the header */ |
| frame[size++] = gsm0710_fcs(frame + 1, header_size - 1); |
| frame[size++] = 0xF9; |
| |
| return size; |
| } |