From fe94cfa45ae7134293058132ee7a33c506940f35 Mon Sep 17 00:00:00 2001
From: Jared Boone <jboone@earfeast.com>
Date: Wed, 14 Oct 2015 12:05:09 -0700
Subject: [PATCH] De-std::vector MatchedFilter, was chewing up far too much
 memory.

---
 firmware/baseband/matched_filter.cpp | 19 -------------
 firmware/baseband/matched_filter.hpp | 40 +++++++++++++++++-----------
 firmware/baseband/proc_fsk.cpp       |  3 ---
 firmware/baseband/proc_fsk.hpp       |  4 +--
 4 files changed, 26 insertions(+), 40 deletions(-)

diff --git a/firmware/baseband/matched_filter.cpp b/firmware/baseband/matched_filter.cpp
index 50bfadd3..706d2b89 100644
--- a/firmware/baseband/matched_filter.cpp
+++ b/firmware/baseband/matched_filter.cpp
@@ -24,24 +24,5 @@
 namespace dsp {
 namespace matched_filter {
 
-bool MatchedFilter::execute_once(
-	const sample_t input
-) {
-	samples[samples.size() - decimation_factor + decimation_phase] = input;
-
-	advance_decimation_phase();
-	if( is_new_decimation_cycle() ) {
-		output = std::inner_product(samples.cbegin(), samples.cend(), taps.cbegin(), sample_t { 0.0f, 0.0f });
-		shift_by_decimation_factor();
-		return true;
-	} else {
-		return false;
-	}
-}
-
-void MatchedFilter::shift_by_decimation_factor() {
-	std::rotate(samples.begin(), samples.begin() + decimation_factor, samples.end());
-}
-
 } /* namespace matched_filter */
 } /* namespace dsp */
diff --git a/firmware/baseband/matched_filter.hpp b/firmware/baseband/matched_filter.hpp
index 2a09c4ad..d72e481c 100644
--- a/firmware/baseband/matched_filter.hpp
+++ b/firmware/baseband/matched_filter.hpp
@@ -22,11 +22,12 @@
 #ifndef __MATCHED_FILTER_H__
 #define __MATCHED_FILTER_H__
 
+#include "baseband_ais.hpp"
+
 #include <cstddef>
 
 #include <complex>
 #include <array>
-#include <vector>
 #include <memory>
 
 #include <algorithm>
@@ -35,46 +36,53 @@
 namespace dsp {
 namespace matched_filter {
 
+template<size_t N>
 class MatchedFilter {
 public:
 	using sample_t = std::complex<float>;
 	using tap_t = std::complex<float>;
 
-	using taps_t = std::vector<tap_t>;
+	using taps_t = std::array<tap_t, N>;
 
 	MatchedFilter(
+		const taps_t& taps,
 		size_t decimation_factor = 1
-	) : decimation_factor { decimation_factor }
+	) : taps(taps),
+		decimation_factor { decimation_factor }
 	{
 	}
 
-	template<typename T>
-	void set_taps(const T& new_taps) {
-		taps.assign(new_taps.cbegin(), new_taps.cend());
-		taps.shrink_to_fit();
-		
-		samples.assign(new_taps.size(), 0);		
-		samples.shrink_to_fit();
-	}
-
 	bool execute_once(
 		const sample_t input
-	);
+	) {
+		samples[samples.size() - decimation_factor + decimation_phase] = input;
+
+		advance_decimation_phase();
+		if( is_new_decimation_cycle() ) {
+			output = std::inner_product(samples.cbegin(), samples.cend(), taps.cbegin(), sample_t { 0.0f, 0.0f });
+			shift_by_decimation_factor();
+			return true;
+		} else {
+			return false;
+		}
+	}
 
 	sample_t get_output() const {
 		return output;
 	}
 
 private:
-	using samples_t = std::vector<sample_t>;
+	using samples_t = std::array<sample_t, N>;
 
 	samples_t samples;
-	taps_t taps;
+	const taps_t taps;
 	size_t decimation_factor { 1 };
 	size_t decimation_phase { 0 };
 	sample_t output;
 
-	void shift_by_decimation_factor();
+	void shift_by_decimation_factor() {
+		std::rotate(samples.begin(), samples.begin() + decimation_factor, samples.end());
+	}
 
 	void advance_decimation_phase() {
 		decimation_phase = (decimation_phase + 1) % decimation_factor;
diff --git a/firmware/baseband/proc_fsk.cpp b/firmware/baseband/proc_fsk.cpp
index 55edc77b..4500506d 100644
--- a/firmware/baseband/proc_fsk.cpp
+++ b/firmware/baseband/proc_fsk.cpp
@@ -30,9 +30,6 @@ FSKProcessor::FSKProcessor(
 	MessageHandlerMap& message_handlers
 ) : message_handlers(message_handlers)
 {
-	mf_0.set_taps(baseband::ais::rrc_taps_8_n);
-	mf_1.set_taps(baseband::ais::rrc_taps_8_p);
-
 	message_handlers.register_handler(Message::ID::FSKConfiguration,
 		[this](const Message* const p) {
 			auto m = reinterpret_cast<const FSKConfigurationMessage*>(p);
diff --git a/firmware/baseband/proc_fsk.hpp b/firmware/baseband/proc_fsk.hpp
index 3224581f..f5dddc46 100644
--- a/firmware/baseband/proc_fsk.hpp
+++ b/firmware/baseband/proc_fsk.hpp
@@ -57,8 +57,8 @@ private:
 	const fir_taps_real<64>& channel_filter_taps = taps_64_lp_031_070_tfilter;
 	dsp::decimate::FIRAndDecimateBy2Complex<64> channel_filter { channel_filter_taps.taps };
 
-	dsp::matched_filter::MatchedFilter mf_0 { 1 };
-	dsp::matched_filter::MatchedFilter mf_1 { 1 };
+	dsp::matched_filter::MatchedFilter<8> mf_0 { baseband::ais::rrc_taps_8_n, 1 };
+	dsp::matched_filter::MatchedFilter<8> mf_1 { baseband::ais::rrc_taps_8_p, 1 };
 
 	clock_recovery::ClockRecovery<clock_recovery::FixedErrorFilter> clock_recovery {
 		static_cast<float>(sampling_rate / 4),