1 files changed, 144 insertions, 0 deletions
diff --git a/src/prbs.cpp b/src/prbs.cpp
new file mode 100644
index 0000000..0ac3187
--- /dev/null
+++ b/src/prbs.cpp
@@ -0,0 +1,144 @@
+/*
+   Copyright (C) 2005, 2006, 2007, 2008, 2009 Her Majesty the Queen in Right
+   of Canada (Communications Research Center Canada)
+   */
+/*
+   This file is part of ODR-DabMux.
+
+   ODR-DabMux 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.
+
+   ODR-DabMux 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 ODR-DabMux.  If not, see <http://www.gnu.org/licenses/>.
+   */
+
+#include "prbs.h"
+
+#include <string.h>
+#include <limits.h>
+
+
+/*
+ * Generate a parity check for a 32-bit word.
+ */
+static unsigned long parity_check(unsigned long prbs_accum)
+{
+    unsigned long mask=1UL, parity=0UL;
+    int i;
+    for (i = 0;  i < 32;  ++i) {
+        parity ^= ((prbs_accum & mask) != 0UL);
+        mask <<= 1;
+    }
+    return parity;
+}
+
+void PrbsGenerator::setup(long polynomial)
+{
+    this->polynomial = polynomial;
+    this->accum = 0;
+    gen_prbs_table();
+    gen_weight_table();
+}
+
+uint8_t PrbsGenerator::step()
+{
+    accum = update_prbs();
+    return accum & 0xff;
+}
+
+void PrbsGenerator::rewind()
+{
+    while (accum < polynomial) {
+        accum <<= 1;
+        accum |= 1;
+    }
+}
+
+void PrbsGenerator::gen_prbs_table()
+{
+    for (int i = 0; i < 4; ++i) {
+        for (int j = 0; j < 256; ++j) {
+            unsigned long prbs_accum = ((unsigned long)j << (i * 8));
+            for (int k = 0; k < 8; ++k) {
+                prbs_accum = (prbs_accum << 1)
+                    ^ parity_check(prbs_accum & polynomial);
+            }
+
+            prbs_table[i][j] = (prbs_accum & 0xff);
+        }
+    }
+}
+
+unsigned long PrbsGenerator::update_prbs()
+{
+    unsigned char acc_lsb = 0;
+    int i;
+    for (i = 0;  i < 4;  ++i ) {
+        acc_lsb ^= prbs_table [i] [ (accum >> (i * 8) ) & 0xff ];
+    }
+    return (accum << 8) ^ ((unsigned long)acc_lsb);
+}
+
+void PrbsGenerator::gen_weight_table()
+{
+    for (int i = 0; i < 256; ++i) {
+        unsigned char mask = 1U;
+        unsigned char ones_count = 0U;
+
+        for (int j = 0; j < 8; ++j) {
+            ones_count += ((i & mask) != 0U);
+            mask = mask << 1;
+        }
+        weight[i] = ones_count;
+    }
+}
+
+size_t PrbsGenerator::error_count(
+        unsigned char *rx_data,
+        int rx_data_length)
+{
+    unsigned long error_count = 0U;
+    unsigned long prbs_accum = 0U;
+
+    /* seed the PRBS accumulator */
+    for (int i = 0;  i < 4;  ++i) {
+        prbs_accum = (prbs_accum << 8) ^ (rx_data[i] ^ polarity_mask);
+    }
+
+    /* check the received data */
+    for (int i = 0;  i < rx_data_length;  ++i) {
+        unsigned char error_pattern = (unsigned char)
+                          ((prbs_accum >> 24)
+                          ^ (rx_data[i] ^ polarity_mask));
+        if (error_pattern != 0U) {
+            error_count += weight[error_pattern];
+        }
+        prbs_accum = update_prbs();
+    }
+    return error_count;
+}
+
+void PrbsGenerator::gen_sequence(
+        unsigned char *tx_data,
+        int tx_data_length,
+        unsigned long polynomial)
+{
+    unsigned long prbs_accum = 0U;
+
+    while (prbs_accum < polynomial) {
+        prbs_accum <<= 1;
+        prbs_accum |= 1;
+    }
+
+    while (tx_data_length-- > 0) {
+        prbs_accum = update_prbs();
+        *(tx_data++) = (unsigned char)(prbs_accum & 0xff);
+    }
+}