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;
+}