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Diffstat (limited to 'src/hdlc.c')
-rw-r--r-- | src/hdlc.c | 355 |
1 files changed, 355 insertions, 0 deletions
diff --git a/src/hdlc.c b/src/hdlc.c new file mode 100644 index 0000000..cfc9784 --- /dev/null +++ b/src/hdlc.c @@ -0,0 +1,355 @@ +/* + * Copyright (C) 2016 Paul Kocialkowski <contact@paulk.fr> + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * 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, see <http://www.gnu.org/licenses/>. + */ + +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <endian.h> + +#include "lg-downloader.h" +#include "hdlc.h" + +/* Lookup table for CCITT-16 CRC with generator polynomial 0x8408. */ +static const unsigned short hdlc_crc_table[] = { + 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, + 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, + 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, + 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, + 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, + 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, + 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, + 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, + 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, + 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, + 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, + 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, + 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, + 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, + 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, + 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, + 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, + 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, + 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, + 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, + 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, + 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, + 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, + 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, + 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, + 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, + 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, + 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, + 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, + 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, + 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, + 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 +}; + +static unsigned short hdlc_crc_step(unsigned short crc, unsigned char data) +{ + return ((crc >> 8) ^ hdlc_crc_table[(crc ^ data) & 0xff]); +} + +static unsigned short hdlc_crc_final(unsigned short crc) +{ + return crc ^ HDLC_CRC_SEED; +} + +static unsigned int hdlc_escape_size(const void *data, unsigned int size) +{ + unsigned int length; + unsigned char *p; + unsigned int i; + + if (data == NULL || size == 0) + return 0; + + p = (unsigned char *) data; + length = size; + + for (i = 0; i < size; i++) + if (p[i] == HDLC_FLAG || p[i] == HDLC_ESCAPE) + length++; + + return length; +} + +static int hdlc_escape(const void *data, unsigned int size, void *buffer) +{ + unsigned char *p; + unsigned char *q; + unsigned int i; + unsigned int j; + + if (buffer == NULL) + return -1; + + p = (unsigned char *) data; + q = (unsigned char *) buffer; + + for (i = 0, j = 0; i < size; i++) { + if (p[i] == HDLC_FLAG || p[i] == HDLC_ESCAPE) { + q[j++] = HDLC_ESCAPE; + q[j++] = p[i] ^ HDLC_ESCAPE_MASK; + } else { + q[j++] = p[i]; + } + } + + return 0; +} + +static int hdlc_unescape_size(const void *data, unsigned int size) +{ + if (data == NULL || size == 0) + return 0; + + unsigned int length; + unsigned char *p; + unsigned int i; + + if (data == NULL || size == 0) + return 0; + + p = (unsigned char *) data; + length = size; + + for (i = 0; i < size; i++) + if (p[i] == HDLC_ESCAPE) + length--; + + return length; +} + +static int hdlc_unescape(const void *data, unsigned int size, void *buffer) +{ + unsigned char *p; + unsigned char *q; + unsigned int i; + unsigned int j; + + if (buffer == NULL) + return -1; + + p = (unsigned char *) data; + q = (unsigned char *) buffer; + + for (i = 0, j = 0; i < size; i++) { + if (p[i] == HDLC_ESCAPE && i < (size - 1)) + q[j++] = p[++i] ^ HDLC_ESCAPE_MASK; + else + q[j++] = p[i]; + } + + return 0; +} + +int hdlc_send(struct context *context, const void *data, unsigned int size) +{ + void *buffer = NULL; + unsigned int length; + unsigned short crc; + unsigned char *p; + unsigned short *q; + unsigned int i; + int rc; + + if (data == NULL || size == 0) + return -1; + + /* Escaped length */ + + length = hdlc_escape_size(data, size); + if (length == 0) + return -1; + + /* CRC */ + + crc = HDLC_CRC_SEED; + p = (unsigned char *) data; + + /* CRC is calculated from unescaped data */ + for (i = 0; i < size; i++) + crc = hdlc_crc_step(crc, *p++); + + /* Trailing zeros must be taken in account */ + if (size < HDLC_MIN_SIZE) + for (i = 0; i < (HDLC_MIN_SIZE - size); i++) + crc = hdlc_crc_step(crc, 0); + + crc = hdlc_crc_final(crc); + + /* Final length */ + + /* Minimum size is relative to unescaped data */ + if (size < HDLC_MIN_SIZE); + length = (length - size) + HDLC_MIN_SIZE; + + length = HDLC_HEAD_SIZE + length + HDLC_TAIL_SIZE; + + /* Copy */ + + buffer = calloc(1, length); + + p = (unsigned char *) buffer; + + *p = HDLC_FLAG; + p += HDLC_HEAD_SIZE; + + rc = hdlc_escape(data, size, p); + if (rc < 0) + goto error; + + p += (length - HDLC_HEAD_SIZE - HDLC_TAIL_SIZE); + + q = (unsigned short *) p; + + *q = htole16(crc); + q++; + + p = (unsigned char *) q; + + *p++ = HDLC_FLAG; + + /* USB send */ + + rc = usb_send(context, buffer, length); + if (rc < 0) { + fprintf(stderr, "Sending HDLC data failed\n"); + goto error; + } + + rc = 0; + goto complete; + +error: + rc = -1; + +complete: + if (buffer != NULL) + free(buffer); + + return rc; +} + +int hdlc_recv(struct context *context, void *data, unsigned int size) +{ + void *contents = NULL; + void *buffer = NULL; + unsigned int length; + unsigned int count; + unsigned short crc; + unsigned char *p; + unsigned int i; + int rc; + + if (data == NULL || size == 0) + return -1; + + /* Length and buffer */ + + if (size < HDLC_MIN_SIZE) + length = HDLC_MIN_SIZE; + else + length = size; + + /* Worst case: all bytes are escaped */ + length = 2 * length + HDLC_TAIL_SIZE; + + buffer = calloc(1, length); + + count = 0; + p = (unsigned char *) buffer; + + /* USB recv */ + + while (count < length) { + rc = usb_recv_available(context, p, length - count); + if (rc < 0) { + fprintf(stderr, "Reading HDLC data failed\n"); + fprintf(stderr, "\nYou may want to try disconnecting and reconnecting the USB cable\n"); + goto error; + } + + for (i = 0; i < rc; i++) { + if (p[i] == HDLC_FLAG) { + count += i + 1; + goto check; + } + } + + count += rc; + p += rc; + } + + /* Check */ +check: + p = (unsigned char *) buffer; + + /* Check for bare minimum size and flag */ + if (count < (HDLC_TAIL_SIZE + 1) || p[count - 1] != HDLC_FLAG) { + fprintf(stderr, "Read invalid HDLC data\n"); + goto error; + } + + /* HDLC unescape */ + + /* Eliminate the HDLC flag */ + count--; + + length = hdlc_unescape_size(buffer, count); + if (length < size) + goto error; + + contents = calloc(1, length); + + rc = hdlc_unescape(buffer, count, contents); + if (rc < 0) + goto error; + + /* CRC */ + + crc = HDLC_CRC_SEED; + p = (unsigned char *) contents; + + for (i = 0; i < length; i++) + crc = hdlc_crc_step(crc, *p++); + + if (crc != HDLC_CRC_FINAL) { + fprintf(stderr, "Invalid CRC for HDLC data\n"); + goto error; + } + + /* Copy */ + + memcpy(data, contents, size); + + rc = 0; + goto complete; + +error: + rc = -1; + +complete: + if (contents != NULL) + free(contents); + + if (buffer != NULL) + free(buffer); + + return rc; +} |