From 1ede82bb307f8ed8b2b7e4447061054f3ed9c76a Mon Sep 17 00:00:00 2001
From: Francisco <francisco.paisana@softwareradiosystems.com>
Date: Mon, 22 Feb 2021 18:45:52 +0000
Subject: [PATCH] use circular array for buffered PDCP SNs in RLC AM to limit
 memory allocations

---
 lib/include/srslte/upper/rlc_am_lte.h | 26 +++++++++++++++++---------
 lib/src/upper/rlc_am_lte.cc           |  8 +++++---
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/lib/include/srslte/upper/rlc_am_lte.h b/lib/include/srslte/upper/rlc_am_lte.h
index c5c6176eb..e8536f42a 100644
--- a/lib/include/srslte/upper/rlc_am_lte.h
+++ b/lib/include/srslte/upper/rlc_am_lte.h
@@ -129,33 +129,41 @@ public:
   void add_pdcp_sdu(uint32_t sn)
   {
     assert(not has_pdcp_sn(sn));
-    uint32_t sn_idx          = get_idx(sn);
-    buffered_pdus[sn_idx].sn = sn_idx;
+    buffered_pdus[get_idx(sn)].sn = sn;
     count++;
   }
   void clear_pdcp_sdu(uint32_t sn)
   {
     uint32_t sn_idx = get_idx(sn);
     buffered_pdus[sn_idx].rlc_sn_info_list.clear();
-    buffered_pdus[sn_idx].sn = -1;
+    buffered_pdus[sn_idx].sn = invalid_sn;
     count--;
   }
 
   pdcp_sdu_info_t& operator[](uint32_t sn)
   {
     assert(has_pdcp_sn(sn));
-    uint32_t sn_idx = get_idx(sn);
-    return buffered_pdus[sn_idx];
+    return buffered_pdus[get_idx(sn)];
+  }
+  bool has_pdcp_sn(uint32_t pdcp_sn) const
+  {
+    assert(pdcp_sn <= max_pdcp_sn or pdcp_sn == status_report_sn);
+    return buffered_pdus[get_idx(pdcp_sn)].sn == pdcp_sn;
   }
-  bool     has_pdcp_sn(uint32_t pdcp_sn) const { return buffered_pdus[get_idx(pdcp_sn)].sn < max_pdcp_sn; }
   uint32_t nof_sdus() const { return count; }
 
 private:
-  // TODO: Set size based on PDCP config
-  const static size_t max_pdcp_sn = 262143;
+  const static size_t   max_pdcp_sn      = 262143u;
+  const static size_t   max_buffer_idx   = 4096u;
+  const static uint32_t status_report_sn = std::numeric_limits<uint32_t>::max();
+  const static uint32_t invalid_sn       = std::numeric_limits<uint32_t>::max() - 1;
 
-  uint32_t get_idx(uint32_t sn) const { return std::min(sn, static_cast<uint32_t>(buffered_pdus.size() - 1)); }
+  size_t get_idx(uint32_t sn) const
+  {
+    return (sn != status_report_sn) ? static_cast<size_t>(sn % max_buffer_idx) : max_buffer_idx;
+  }
 
+  // size equal to buffer_size + 1 (last element for Status Report)
   std::vector<pdcp_sdu_info_t> buffered_pdus;
   uint32_t                     count = 0;
 };
diff --git a/lib/src/upper/rlc_am_lte.cc b/lib/src/upper/rlc_am_lte.cc
index a2a9d8865..397f9b0c4 100644
--- a/lib/src/upper/rlc_am_lte.cc
+++ b/lib/src/upper/rlc_am_lte.cc
@@ -2013,10 +2013,12 @@ void rlc_am_lte::rlc_am_lte_rx::debug_state()
   logger.debug("%s vr_r = %d, vr_mr = %d, vr_x = %d, vr_ms = %d, vr_h = %d", RB_NAME, vr_r, vr_mr, vr_x, vr_ms, vr_h);
 }
 
-buffered_pdcp_pdu_list::buffered_pdcp_pdu_list() : buffered_pdus(max_pdcp_sn + 2)
+const size_t buffered_pdcp_pdu_list::max_buffer_idx;
+
+buffered_pdcp_pdu_list::buffered_pdcp_pdu_list() : buffered_pdus(max_buffer_idx + 1)
 {
   for (size_t i = 0; i < buffered_pdus.size(); ++i) {
-    buffered_pdus[i].sn = -1;
+    buffered_pdus[i].sn = invalid_sn;
     buffered_pdus[i].rlc_sn_info_list.reserve(5);
   }
 }
@@ -2024,7 +2026,7 @@ buffered_pdcp_pdu_list::buffered_pdcp_pdu_list() : buffered_pdus(max_pdcp_sn + 2
 void buffered_pdcp_pdu_list::clear()
 {
   for (auto& b : buffered_pdus) {
-    b.sn = -1;
+    b.sn = invalid_sn;
     b.rlc_sn_info_list.clear();
   }
 }