116 lines
2.7 KiB
C
116 lines
2.7 KiB
C
#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <osmocom/core/utils.h>
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#include <osmocom/core/bits.h>
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#include "hdlc.h"
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#if 0
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#define DEBUGP(x, args ...) fprintf(stderr, x, ## args)
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#else
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#define DEBUGP(x, args ...) do {} while (0)
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#endif
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static const ubit_t flag_octet[] = { 0,1,1,1,1,1,1,0 };
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static const ubit_t five_ones_zero[] = { 0,1,1,1,1,1 };
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static void append_bit_history(struct hdlc_proc *hdlc, uint8_t bit)
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{
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/* we always add the bit to the history */
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memmove(hdlc->history+1, hdlc->history, sizeof(hdlc->history)-1);
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hdlc->history[0] = bit;
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}
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static int append_bit_out(struct hdlc_proc *hdlc, uint8_t bit)
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{
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memmove(hdlc->next_outbyte+1, hdlc->next_outbyte, sizeof(hdlc->next_outbyte)-1);
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hdlc->next_outbyte[0] = bit;
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hdlc->num_bits++;
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if (hdlc->num_bits == 8) {
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pbit_t out;
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hdlc->num_bits = 0;
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/* generate one output byte */
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osmo_ubit2pbit_ext(&out, 0, hdlc->next_outbyte, 0, 8, 0);
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/* append to output buffer */
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OSMO_ASSERT(hdlc->out.len < sizeof(hdlc->out.buf));
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hdlc->out.buf[hdlc->out.len++] = out;
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return out;
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}
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return -1;
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}
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static int process_hdlc_bit(struct hdlc_proc *hdlc, uint8_t bit)
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{
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int out = -1, flag = 0;
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DEBUGP("bit=%u, history_in = %s, ", bit, osmo_ubit_dump(hdlc->history, sizeof(hdlc->history)));
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/* always append bit to history */
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append_bit_history(hdlc, bit);
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if (!memcmp(flag_octet, hdlc->history, sizeof(flag_octet))) {
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hdlc->num_bits = 0;
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DEBUGP("S ");
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flag = 1;
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if (hdlc->out.len) {
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/* call output function if any frame was
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* received before the flag octet */
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if (hdlc->out_cb)
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hdlc->out_cb(hdlc->out.buf, hdlc->out.len,
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hdlc->priv);
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hdlc->out.len = 0;
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}
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} else if (!memcmp(five_ones_zero, hdlc->history, sizeof(five_ones_zero))) {
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/* 4.3.1 Synchronous transmission: receiver shall
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* discard any "0" bit after five contiguous ones */
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DEBUGP("I ");
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} else {
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out = append_bit_out(hdlc, bit);
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}
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DEBUGP("history_out = %s", osmo_ubit_dump(hdlc->history, sizeof(hdlc->history)));
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if (out >= 0)
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DEBUGP(", out 0x%02x\n", out);
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else
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DEBUGP("\n");
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if (flag)
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return -123;
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else
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return out;
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}
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int process_raw_hdlc(struct hdlc_proc *hdlc, ubit_t *bits, unsigned int len)
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{
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unsigned int i;
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int out;
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static int last_out;
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DEBUGP("process_raw_hdlc(%s)\n", osmo_hexdump(bits, len));
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for (i = 0; i < len; i ++) {
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out = process_hdlc_bit(hdlc, bits[i]);
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if (out == -123) {
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/* suppress repeating Flag characters */
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if (last_out != out)
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printf("\nF ");
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last_out = out;
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} else if (out >= 0) {
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/* suppress 0xAA and 0x55 bit pattern */
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//if (out != 0xaa && out != 0x55)
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printf("%02x ", out);
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last_out = out;
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}
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}
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return 0;
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}
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