From 00974d4f49dd666112a297cb9ec1eb9f891b64e0 Mon Sep 17 00:00:00 2001
From: sawinglogz <3787776-sawinglogz@users.noreply.gitlab.com>
Date: Thu, 9 Dec 2021 12:23:08 -0500
Subject: [PATCH] Skip empty DS2 files.

Also update comments based on further testing.
---
 oscar/SleepLib/loader_plugins/prs1_loader.cpp | 12 +++++++-----
 oscar/SleepLib/loader_plugins/prs1_parser.cpp |  6 +++---
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/oscar/SleepLib/loader_plugins/prs1_loader.cpp b/oscar/SleepLib/loader_plugins/prs1_loader.cpp
index d305c57b..a3842cbe 100644
--- a/oscar/SleepLib/loader_plugins/prs1_loader.cpp
+++ b/oscar/SleepLib/loader_plugins/prs1_loader.cpp
@@ -413,6 +413,10 @@ bool PRDS2File::initializeKey()
 
 bool PRDS2File::parseDS2Header()
 {
+    if (m_device.size() == 0) {
+        qWarning() << name() << "is empty, skipping";
+        return false;
+    }
     int a = read16();
     int b = read16();
     int c = read16();
@@ -2551,11 +2555,9 @@ void PRS1Import::ImportWaveforms()
             }
 
             if (s2 > 0) {
-                // NOTE: The 900X (F5V3) clamps the values at 127 (15.875 cmH2O) for some reason.
-                //
-                // Previous autoSV machines (950P-961P, F5V0-F5V2) didn't, nor do 1030X (F3V6).
-                // 1130X (also F3V6) is unknown, but likely follows the 1030X. Older ventilators
-                // (F3V3) are also unknown.
+                // NOTE: The 900X (F5V3) firmware V1.0.1 clamps the values at 127 (15.875 cmH2O)
+                // due to incorrectly treating this value as a signed integer. This bug is fixed
+                // in firmware V1.0.6.
                 EventList * pres = session->AddEventList(CPAP_MaskPressureHi, EVL_Waveform, pressure_gain, 0.0f, 0.0f, 0.0f, double(dur) / double(s2));
                 pres->AddWaveform(ti, (unsigned char *)data[1].data(), data[1].size(), dur);
             }
diff --git a/oscar/SleepLib/loader_plugins/prs1_parser.cpp b/oscar/SleepLib/loader_plugins/prs1_parser.cpp
index 44b785ee..3667d5d0 100644
--- a/oscar/SleepLib/loader_plugins/prs1_parser.cpp
+++ b/oscar/SleepLib/loader_plugins/prs1_parser.cpp
@@ -1395,9 +1395,9 @@ static crc32_t CRC32(const unsigned char *data, size_t data_len, crc32_t crc)
 }
 
 
-// Strangely, the PRS1 CRC32 appears to consider every byte a 32-bit wchar_t.
-// Nothing like trying a bunch of encodings and CRC32 variants on PROP.TXT files
-// until you find a winner.
+// The PRS1 CRC32 considers every byte a 32-bit wchar_t, presumably due to
+// use of the STM32 CRC calculation unit, in which "CRC computation is done
+// on the whole 32-bit data word, and not byte per byte".
 
 static crc32_t CRC32wchar(const unsigned char *data, size_t data_len, crc32_t crc)
 {