Transceiver52M: Dynamically allocate convolution input vectors

This prevents the use of a copy constructor in the downlink
modulator and prevents a secondary memory allocation during
the convolution. Avoid both cases by dynamically allocating
with preloaded head room. The latter provides enough memory
before the first sample in the burst to cover the length
of the filter taps.

Signed-off-by: Thomas Tsou <tom@tsou.cc>

2 files changed, 31 insertions, 21 deletions

diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp
index ab421b6..23538f3 100644
--- a/Transceiver52M/sigProcLib.cpp
+++ b/Transceiver52M/sigProcLib.cpp
@@ -369,9 +369,11 @@ signalVector *convolve(const signalVector *x,
   switch (spanType) {
   case START_ONLY:
     start = 0;
-    head = h->size();
+    head = h->size() - 1;
     len = x->size();
-    append = true;
+
+    if (x->getStartIndex() < head)
+      append = true;
     break;
   case NO_DELAY:
     start = h->size() / 2;
@@ -681,7 +683,8 @@ static signalVector *modulateBurstLaurent(const BitVector &bits,
 {
   int burst_len;
   float phase;
-  signalVector *c0_pulse, *c1_pulse, c0_burst, c1_burst, *c0_shaped, *c1_shaped;
+  signalVector *c0_pulse, *c1_pulse, *c0_burst;
+  signalVector *c1_burst, *c0_shaped, *c1_shaped;
   signalVector::iterator c0_itr, c1_itr;
 
   /*
@@ -696,13 +699,13 @@ static signalVector *modulateBurstLaurent(const BitVector &bits,
 
   burst_len = sps * (bits.size() + guard_len);
 
-  c0_burst = signalVector(burst_len);
-  c0_burst.isRealOnly(true);
-  c0_itr = c0_burst.begin();
+  c0_burst = new signalVector(burst_len, c0_pulse->size());
+  c0_burst->isRealOnly(true);
+  c0_itr = c0_burst->begin();
 
-  c1_burst = signalVector(burst_len);
-  c1_burst.isRealOnly(true);
-  c1_itr = c1_burst.begin();
+  c1_burst = new signalVector(burst_len, c1_pulse->size());
+  c1_burst->isRealOnly(true);
+  c1_itr = c1_burst->begin();
 
   /* Padded differential start bits */
   *c0_itr = 2.0 * (0x00 & 0x01) - 1.0;
@@ -718,10 +721,10 @@ static signalVector *modulateBurstLaurent(const BitVector &bits,
   *c0_itr = 2.0 * (0x01 & 0x01) - 1.0;
 
   /* Generate C0 phase coefficients */
-  GMSKRotate(c0_burst, sps);
-  c0_burst.isRealOnly(false);
+  GMSKRotate(*c0_burst, sps);
+  c0_burst->isRealOnly(false);
 
-  c0_itr = c0_burst.begin();
+  c0_itr = c0_burst->begin();
   c0_itr += sps * 2;
   c1_itr += sps * 2;
 
@@ -746,8 +749,8 @@ static signalVector *modulateBurstLaurent(const BitVector &bits,
   *c1_itr = *c0_itr * Complex<float>(0, phase);
 
   /* Primary (C0) and secondary (C1) pulse shaping */
-  c0_shaped = convolve(&c0_burst, c0_pulse, NULL, START_ONLY);
-  c1_shaped = convolve(&c1_burst, c1_pulse, NULL, START_ONLY);
+  c0_shaped = convolve(c0_burst, c0_pulse, NULL, START_ONLY);
+  c1_shaped = convolve(c1_burst, c1_pulse, NULL, START_ONLY);
 
   /* Sum shaped outputs into C0 */
   c0_itr = c0_shaped->begin();
@@ -755,6 +758,8 @@ static signalVector *modulateBurstLaurent(const BitVector &bits,
   for (unsigned i = 0; i < c0_shaped->size(); i++ )
     *c0_itr++ += *c1_itr++;
 
+  delete c0_burst;
+  delete c1_burst;
   delete c1_shaped;
 
   return c0_shaped;
@@ -764,7 +769,7 @@ static signalVector *modulateBurstBasic(const BitVector &bits,
 					int guard_len, int sps)
 {
   int burst_len;
-  signalVector *pulse, burst, *shaped;
+  signalVector *pulse, *burst, *shaped;
   signalVector::iterator burst_itr;
 
   if (sps == 1)
@@ -774,9 +779,9 @@ static signalVector *modulateBurstBasic(const BitVector &bits,
 
   burst_len = sps * (bits.size() + guard_len);
 
-  burst = signalVector(burst_len);
-  burst.isRealOnly(true);
-  burst_itr = burst.begin();
+  burst = new signalVector(burst_len, pulse->size());
+  burst->isRealOnly(true);
+  burst_itr = burst->begin();
 
   /* Raw bits are not differentially encoded */
   for (unsigned i = 0; i < bits.size(); i++) {
@@ -784,11 +789,13 @@ static signalVector *modulateBurstBasic(const BitVector &bits,
     burst_itr += sps;
   }
 
-  GMSKRotate(burst, sps);
-  burst.isRealOnly(false);
+  GMSKRotate(*burst, sps);
+  burst->isRealOnly(false);
 
   /* Single Gaussian pulse approximation shaping */
-  shaped = convolve(&burst, pulse, NULL, START_ONLY);
+  shaped = convolve(burst, pulse, NULL, START_ONLY);
+
+  delete burst;
 
   return shaped;
 }
diff --git a/Transceiver52M/sigProcLib.h b/Transceiver52M/sigProcLib.h
index 516d352..ebe7519 100644
--- a/Transceiver52M/sigProcLib.h
+++ b/Transceiver52M/sigProcLib.h
@@ -95,6 +95,9 @@ class signalVector: public Vector<complex>
       symmetry = NONE;
     };
 
+  /** start index */
+  int getStartIndex() const { return mStart - mData; };
+
   /** symmetry operators */
   Symmetry getSymmetry() const { return symmetry;};
   void setSymmetry(Symmetry wSymmetry) { symmetry = wSymmetry;};