Piotr Krysik | 9e2e835 | 2018-02-27 12:16:25 +0100 | [diff] [blame] | 1 | /* |
| 2 | * (C) 2011 by Harald Welte <laforge@gnumonks.org> |
| 3 | * (C) 2011 by Sylvain Munaut <tnt@246tNt.com> |
| 4 | * |
| 5 | * All Rights Reserved |
| 6 | * |
| 7 | * SPDX-License-Identifier: GPL-2.0+ |
| 8 | * |
| 9 | * This program is free software; you can redistribute it and/or modify |
| 10 | * it under the terms of the GNU General Public License as published by |
| 11 | * the Free Software Foundation; either version 2 of the License, or |
| 12 | * (at your option) any later version. |
| 13 | * |
| 14 | * This program is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 17 | * GNU General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU General Public License along |
| 20 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 21 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| 22 | * |
| 23 | */ |
| 24 | |
| 25 | #include <stdint.h> |
| 26 | |
| 27 | #include <osmocom/core/bits.h> |
| 28 | |
| 29 | /*! \addtogroup bits |
| 30 | * @{ |
| 31 | * Osmocom bit level support code. |
| 32 | * |
| 33 | * This module implements the notion of different bit-fields, such as |
| 34 | * - unpacked bits (\ref ubit_t), i.e. 1 bit per byte |
| 35 | * - packed bits (\ref pbit_t), i.e. 8 bits per byte |
| 36 | * - soft bits (\ref sbit_t), 1 bit per byte from -127 to 127 |
| 37 | * |
| 38 | * \file bits.c */ |
| 39 | |
| 40 | /*! convert unpacked bits to packed bits, return length in bytes |
| 41 | * \param[out] out output buffer of packed bits |
| 42 | * \param[in] in input buffer of unpacked bits |
| 43 | * \param[in] num_bits number of bits |
| 44 | */ |
| 45 | int osmo_ubit2pbit(pbit_t *out, const ubit_t *in, unsigned int num_bits) |
| 46 | { |
| 47 | unsigned int i; |
| 48 | uint8_t curbyte = 0; |
| 49 | pbit_t *outptr = out; |
| 50 | |
| 51 | for (i = 0; i < num_bits; i++) { |
| 52 | uint8_t bitnum = 7 - (i % 8); |
| 53 | |
| 54 | curbyte |= (in[i] << bitnum); |
| 55 | |
| 56 | if(i % 8 == 7){ |
| 57 | *outptr++ = curbyte; |
| 58 | curbyte = 0; |
| 59 | } |
| 60 | } |
| 61 | /* we have a non-modulo-8 bitcount */ |
| 62 | if (i % 8) |
| 63 | *outptr++ = curbyte; |
| 64 | |
| 65 | return outptr - out; |
| 66 | } |
| 67 | |
| 68 | /*! Shift unaligned input to octet-aligned output |
| 69 | * \param[out] out output buffer, unaligned |
| 70 | * \param[in] in input buffer, octet-aligned |
| 71 | * \param[in] num_nibbles number of nibbles |
| 72 | */ |
| 73 | void osmo_nibble_shift_right(uint8_t *out, const uint8_t *in, |
| 74 | unsigned int num_nibbles) |
| 75 | { |
| 76 | unsigned int i, num_whole_bytes = num_nibbles / 2; |
| 77 | if (!num_whole_bytes) |
| 78 | return; |
| 79 | |
| 80 | /* first byte: upper nibble empty, lower nibble from src */ |
| 81 | out[0] = (in[0] >> 4); |
| 82 | |
| 83 | /* bytes 1.. */ |
| 84 | for (i = 1; i < num_whole_bytes; i++) |
| 85 | out[i] = ((in[i - 1] & 0xF) << 4) | (in[i] >> 4); |
| 86 | |
| 87 | /* shift the last nibble, in case there's an odd count */ |
| 88 | i = num_whole_bytes; |
| 89 | if (num_nibbles & 1) |
| 90 | out[i] = ((in[i - 1] & 0xF) << 4) | (in[i] >> 4); |
| 91 | else |
| 92 | out[i] = (in[i - 1] & 0xF) << 4; |
| 93 | } |
| 94 | |
| 95 | /*! Shift unaligned input to octet-aligned output |
| 96 | * \param[out] out output buffer, octet-aligned |
| 97 | * \param[in] in input buffer, unaligned |
| 98 | * \param[in] num_nibbles number of nibbles |
| 99 | */ |
| 100 | void osmo_nibble_shift_left_unal(uint8_t *out, const uint8_t *in, |
| 101 | unsigned int num_nibbles) |
| 102 | { |
| 103 | unsigned int i, num_whole_bytes = num_nibbles / 2; |
| 104 | if (!num_whole_bytes) |
| 105 | return; |
| 106 | |
| 107 | for (i = 0; i < num_whole_bytes; i++) |
| 108 | out[i] = ((in[i] & 0xF) << 4) | (in[i + 1] >> 4); |
| 109 | |
| 110 | /* shift the last nibble, in case there's an odd count */ |
| 111 | i = num_whole_bytes; |
| 112 | if (num_nibbles & 1) |
| 113 | out[i] = (in[i] & 0xF) << 4; |
| 114 | } |
| 115 | |
| 116 | /*! convert unpacked bits to soft bits |
| 117 | * \param[out] out output buffer of soft bits |
| 118 | * \param[in] in input buffer of unpacked bits |
| 119 | * \param[in] num_bits number of bits |
| 120 | */ |
| 121 | void osmo_ubit2sbit(sbit_t *out, const ubit_t *in, unsigned int num_bits) |
| 122 | { |
| 123 | unsigned int i; |
| 124 | for (i = 0; i < num_bits; i++) |
| 125 | out[i] = in[i] ? -127 : 127; |
| 126 | } |
| 127 | |
| 128 | /*! convert soft bits to unpacked bits |
| 129 | * \param[out] out output buffer of unpacked bits |
| 130 | * \param[in] in input buffer of soft bits |
| 131 | * \param[in] num_bits number of bits |
| 132 | */ |
| 133 | void osmo_sbit2ubit(ubit_t *out, const sbit_t *in, unsigned int num_bits) |
| 134 | { |
| 135 | unsigned int i; |
| 136 | for (i = 0; i < num_bits; i++) |
| 137 | out[i] = in[i] < 0; |
| 138 | } |
| 139 | |
| 140 | /*! convert packed bits to unpacked bits, return length in bytes |
| 141 | * \param[out] out output buffer of unpacked bits |
| 142 | * \param[in] in input buffer of packed bits |
| 143 | * \param[in] num_bits number of bits |
| 144 | * \return number of bytes used in \ref out |
| 145 | */ |
| 146 | int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits) |
| 147 | { |
| 148 | unsigned int i; |
| 149 | ubit_t *cur = out; |
| 150 | ubit_t *limit = out + num_bits; |
| 151 | |
| 152 | for (i = 0; i < (num_bits/8)+1; i++) { |
| 153 | pbit_t byte = in[i]; |
| 154 | *cur++ = (byte >> 7) & 1; |
| 155 | if (cur >= limit) |
| 156 | break; |
| 157 | *cur++ = (byte >> 6) & 1; |
| 158 | if (cur >= limit) |
| 159 | break; |
| 160 | *cur++ = (byte >> 5) & 1; |
| 161 | if (cur >= limit) |
| 162 | break; |
| 163 | *cur++ = (byte >> 4) & 1; |
| 164 | if (cur >= limit) |
| 165 | break; |
| 166 | *cur++ = (byte >> 3) & 1; |
| 167 | if (cur >= limit) |
| 168 | break; |
| 169 | *cur++ = (byte >> 2) & 1; |
| 170 | if (cur >= limit) |
| 171 | break; |
| 172 | *cur++ = (byte >> 1) & 1; |
| 173 | if (cur >= limit) |
| 174 | break; |
| 175 | *cur++ = (byte >> 0) & 1; |
| 176 | if (cur >= limit) |
| 177 | break; |
| 178 | } |
| 179 | return cur - out; |
| 180 | } |
| 181 | |
| 182 | /*! convert unpacked bits to packed bits (extended options) |
| 183 | * \param[out] out output buffer of packed bits |
| 184 | * \param[in] out_ofs offset into output buffer |
| 185 | * \param[in] in input buffer of unpacked bits |
| 186 | * \param[in] in_ofs offset into input buffer |
| 187 | * \param[in] num_bits number of bits |
| 188 | * \param[in] lsb_mode Encode bits in LSB orde instead of MSB |
| 189 | * \returns length in bytes (max written offset of output buffer + 1) |
| 190 | */ |
| 191 | int osmo_ubit2pbit_ext(pbit_t *out, unsigned int out_ofs, |
| 192 | const ubit_t *in, unsigned int in_ofs, |
| 193 | unsigned int num_bits, int lsb_mode) |
| 194 | { |
| 195 | int i, op, bn; |
| 196 | for (i=0; i<num_bits; i++) { |
| 197 | op = out_ofs + i; |
| 198 | bn = lsb_mode ? (op&7) : (7-(op&7)); |
| 199 | if (in[in_ofs+i]) |
| 200 | out[op>>3] |= 1 << bn; |
| 201 | else |
| 202 | out[op>>3] &= ~(1 << bn); |
| 203 | } |
| 204 | return ((out_ofs + num_bits - 1) >> 3) + 1; |
| 205 | } |
| 206 | |
| 207 | /*! convert packed bits to unpacked bits (extended options) |
| 208 | * \param[out] out output buffer of unpacked bits |
| 209 | * \param[in] out_ofs offset into output buffer |
| 210 | * \param[in] in input buffer of packed bits |
| 211 | * \param[in] in_ofs offset into input buffer |
| 212 | * \param[in] num_bits number of bits |
| 213 | * \param[in] lsb_mode Encode bits in LSB orde instead of MSB |
| 214 | * \returns length in bytes (max written offset of output buffer + 1) |
| 215 | */ |
| 216 | int osmo_pbit2ubit_ext(ubit_t *out, unsigned int out_ofs, |
| 217 | const pbit_t *in, unsigned int in_ofs, |
| 218 | unsigned int num_bits, int lsb_mode) |
| 219 | { |
| 220 | int i, ip, bn; |
| 221 | for (i=0; i<num_bits; i++) { |
| 222 | ip = in_ofs + i; |
| 223 | bn = lsb_mode ? (ip&7) : (7-(ip&7)); |
| 224 | out[out_ofs+i] = !!(in[ip>>3] & (1<<bn)); |
| 225 | } |
| 226 | return out_ofs + num_bits; |
| 227 | } |
| 228 | |
| 229 | /*! generalized bit reversal function |
| 230 | * \param[in] x the 32bit value to be reversed |
| 231 | * \param[in] k the type of reversal requested |
| 232 | * \returns the reversed 32bit dword |
| 233 | * |
| 234 | * This function reverses the bit order within a 32bit word. Depending |
| 235 | * on "k", it either reverses all bits in a 32bit dword, or the bytes in |
| 236 | * the dword, or the bits in each byte of a dword, or simply swaps the |
| 237 | * two 16bit words in a dword. See Chapter 7 "Hackers Delight" |
| 238 | */ |
| 239 | uint32_t osmo_bit_reversal(uint32_t x, enum osmo_br_mode k) |
| 240 | { |
| 241 | if (k & 1) x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1; |
| 242 | if (k & 2) x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2; |
| 243 | if (k & 4) x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4; |
| 244 | if (k & 8) x = (x & 0x00FF00FF) << 8 | (x & 0xFF00FF00) >> 8; |
| 245 | if (k & 16) x = (x & 0x0000FFFF) << 16 | (x & 0xFFFF0000) >> 16; |
| 246 | |
| 247 | return x; |
| 248 | } |
| 249 | |
| 250 | /*! reverse the bit-order in each byte of a dword |
| 251 | * \param[in] x 32bit input value |
| 252 | * \returns 32bit value where bits of each byte have been reversed |
| 253 | * |
| 254 | * See Chapter 7 "Hackers Delight" |
| 255 | */ |
| 256 | uint32_t osmo_revbytebits_32(uint32_t x) |
| 257 | { |
| 258 | x = (x & 0x55555555) << 1 | (x & 0xAAAAAAAA) >> 1; |
| 259 | x = (x & 0x33333333) << 2 | (x & 0xCCCCCCCC) >> 2; |
| 260 | x = (x & 0x0F0F0F0F) << 4 | (x & 0xF0F0F0F0) >> 4; |
| 261 | |
| 262 | return x; |
| 263 | } |
| 264 | |
| 265 | /*! reverse the bit order in a byte |
| 266 | * \param[in] x 8bit input value |
| 267 | * \returns 8bit value where bits order has been reversed |
| 268 | * |
| 269 | * See Chapter 7 "Hackers Delight" |
| 270 | */ |
| 271 | uint32_t osmo_revbytebits_8(uint8_t x) |
| 272 | { |
| 273 | x = (x & 0x55) << 1 | (x & 0xAA) >> 1; |
| 274 | x = (x & 0x33) << 2 | (x & 0xCC) >> 2; |
| 275 | x = (x & 0x0F) << 4 | (x & 0xF0) >> 4; |
| 276 | |
| 277 | return x; |
| 278 | } |
| 279 | |
| 280 | /*! reverse bit-order of each byte in a buffer |
| 281 | * \param[in] buf buffer containing bytes to be bit-reversed |
| 282 | * \param[in] len length of buffer in bytes |
| 283 | * |
| 284 | * This function reverses the bits in each byte of the buffer |
| 285 | */ |
| 286 | void osmo_revbytebits_buf(uint8_t *buf, int len) |
| 287 | { |
| 288 | unsigned int i; |
| 289 | unsigned int unaligned_cnt; |
| 290 | int len_remain = len; |
| 291 | |
| 292 | unaligned_cnt = ((unsigned long)buf & 3); |
| 293 | for (i = 0; i < unaligned_cnt; i++) { |
| 294 | buf[i] = osmo_revbytebits_8(buf[i]); |
| 295 | len_remain--; |
| 296 | if (len_remain <= 0) |
| 297 | return; |
| 298 | } |
| 299 | |
| 300 | for (i = unaligned_cnt; i + 3 < len; i += 4) { |
| 301 | osmo_store32be(osmo_revbytebits_32(osmo_load32be(buf + i)), buf + i); |
| 302 | len_remain -= 4; |
| 303 | } |
| 304 | |
| 305 | for (i = len - len_remain; i < len; i++) { |
| 306 | buf[i] = osmo_revbytebits_8(buf[i]); |
| 307 | len_remain--; |
| 308 | } |
| 309 | } |
| 310 | |
| 311 | /*! @} */ |