Rewrite of touchstone parser

- keeped compatible with previous version
- add test examples of touchstone files
- commented out writing to loaded file to fix bug #99

NanoVNASaver/NanoVNASaver.py

@@ -905,7 +905,8 @@ class NanoVNASaver(QtWidgets.QWidget):
             self.data21 = []
             t = Touchstone(filename)
             t.load()
-            self.saveData(t.s11data, t.s21data, filename)
+            # shouldn't modify read file. even destroys it if read fails 
+            # self.saveData(t.s11data, t.s21data, filename)
             self.dataUpdated()
 
     def sizeHint(self) -> QtCore.QSize:

NanoVNASaver/Touchstone.py

@@ -16,6 +16,7 @@
 #  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 import logging
 import cmath
+import io
 from NanoVNASaver.RFTools import Datapoint
 
 logger = logging.getLogger(__name__)
@@ -61,30 +62,73 @@ class Options:
 
 class Touchstone:
 
-    def __init__(self, filename):
+    def __init__(self, filename: str):
         self.filename = filename
-        self.s11data = []
-        self.s21data = []
-        self.s12data = []
-        self.s22data = []
+        self.sdata = [[], [], [], []]  # at max 4 data pairs
         self.comments = []
         self.opts = Options()
 
+    @property
+    def s11data(self) -> list:
+        return self.sdata[0]
+
+    @s11data.setter
+    def s11data(self, data: list):
+        self.sdata[0] = data[:]
+
+    @property
+    def s21data(self) -> list:
+        return self.sdata[1]
+
+    @s21data.setter
+    def s21data(self, data: list):
+        self.sdata[1] = data[:]
+
+    @property
+    def s12data(self) -> list:
+        return self.sdata[2]
+
+    @s12data.setter
+    def s12data(self, data: list):
+        self.sdata[2] = data[:]
+
+    @property
+    def s22data(self) -> list:
+        return self.sdata[3]
+
+    @s22data.setter
+    def s22data(self, data: list):
+        self.sdata[3] = data[:]
+
+    def _parse_comments(self, fp) -> str:
+        for line in fp:
+            line = line.strip()
+            if line.startswith("!"):
+                logger.info(line)
+                self.comments.append(line)
+            else:
+                return line
+
     def load(self):
         logger.info("Attempting to open file %s", self.filename)
-        sdata = [[], [], [], []]  # at max 4 data pairs
+        try:
+            with open(self.filename) as infile:
+                self.loads(infile.read())
+        except TypeError as e:
+            logger.exception("Failed to parse %s: %s", self.filename, e)
+        except IOError as e:
+            logger.exception("Failed to open %s: %s", self.filename, e)
 
-        with open(self.filename, "r") as file:
-            for line in file:
-                line = line.strip()
-                if line.startswith("!"):
-                    logger.info(line)
-                    self.comments.append(line)
-                    continue
-                break
-            self.opts.parse(line)
+    def loads(self, s: str):
+        """Parse touchstone 1.1 string input
+           appends to existing sdata if Touchstone object exists
+        """
+        with io.StringIO(s) as file:
+            opts_line = self._parse_comments(file)
+            self.opts.parse(opts_line)
 
-            prev_freq = prev_len = 0
+            prev_freq = 0.0
+            prev_len = 0
             for line in file:
                 # ignore empty lines (even if not specified)
                 if not line.strip():
@@ -108,7 +152,7 @@ class Touchstone:
                 elif data_len != prev_len:
                     raise TypeError("Inconsistent number of pairs: " + line)
 
-                data_list = iter(sdata)
+                data_list = iter(self.sdata)
                 vals = iter(data)
                 for v in vals:
                     if self.opts.format == "ri":
@@ -118,7 +162,5 @@ class Touchstone:
                         z = cmath.polar(float(v), float(next(vals)))
                         next(data_list).append(Datapoint(freq, z.real, z.imag))
 
-                self.s11data, self.s21data, self.s12data, self.s22data = sdata[:]
-
     def setFilename(self, filename):
         self.filename = filename

test/data/broken_pair.s1p

@@ -0,0 +1,9 @@
+# Hz S RI R 50
+140000000 -0.720544874 -0.074467673
+140307234 -0.707615315 -0.045678697
+140614468 -0.694235622 -0.017205553
+140921702 -0.679476678 0.011064857
+141228936  0.037949264
+141536169 -0.645231842 0.06495472
+141843404 -0.625548779 0.090901531
+142150638 -0.605278372 0.116493001

test/data/missing_pair.s2p

@@ -0,0 +1,16 @@
+! Vector Network Analyzer VNA R2
+! Tucson Amateur Packet Radio
+! Saturday, 9 November, 2019   17:48:47
+! Frequency              S11                           S21                            S12                            S22
+! ListType=Lin
+# HZ  S  RI R 50
+000500000    -3.33238E-001  1.80018E-004    6.74780E-001  -8.19510E-007    6.75290E-001  -8.20129E-007    -3.33238E-001  3.08078E-004
+001382728    -3.33017E-001  6.89580E-004    6.74251E-001  -3.70855E-004    6.74761E-001  -5.04361E-004    -3.33016E-001  9.45694E-004
+002265456    -3.33136E-001  1.06095E-003    6.74766E-001  -1.00228E-003    6.75276E-001  -1.00304E-003    -3.33136E-001  1.06095E-003
+003148184    -3.33120E-001  1.97467E-003    6.74773E-001  -1.65230E-003    6.74773E-001  -1.65230E-003    -3.33121E-001  1.91064E-003
+004030912    -3.32847E-001  2.45743E-003    6.74777E-001  -2.28839E-003    6.75288E-001  -2.15679E-003    
+004913640    -3.32746E-001  2.93382E-003    6.75260E-001  -2.94645E-003    6.75261E-001  -2.81312E-003    -3.32990E-001  3.06364E-003
+005796368    -3.33479E-001  3.06528E-003    6.75798E-001  -2.32365E-003    6.76309E-001  -2.32540E-003    -3.33479E-001  3.06528E-003
+006679097    -3.32609E-001  3.80377E-003    6.74764E-001  -4.08250E-003    6.74764E-001  -4.08250E-003    -3.32854E-001  3.80608E-003
+007561825    -3.32448E-001  4.35906E-003    6.75247E-001  -4.96650E-003    6.75249E-001  -4.69986E-003    -3.32692E-001  4.36169E-003
+008444553    -3.32510E-001  4.94361E-003    6.74737E-001  -5.33508E-003    6.75248E-001  -5.20579E-003    -3.32508E-001  5.13540E-003

test/data/unordered.s1p

@@ -0,0 +1,8 @@
+# Hz S RI R 50
+140000000 -0.720544874 -0.074467673
+140307234 -0.707615315 -0.045678697
+140921702 -0.679476678 0.011064857
+140614468 -0.694235622 -0.017205553
+141536169 -0.645231842 0.06495472
+141843404 -0.625548779 0.090901531
+142150638 -0.605278372 0.116493001

test/data/valid_with_datacomment.s1p

@@ -0,0 +1,12 @@
+# Hz S RI R 50
+140000000 -0.720544874 -0.074467673
+140307234 -0.707615315 -0.045678697
+140614468 -0.694235622 -0.017205553
+140921702 -0.679476678 0.011064857
+141228936 -0.662805676 0.037949264
+141536169 -0.645231842 0.06495472  ! just a test comment
+141843404 -0.625548779 0.090901531
+142150638 -0.605278372 0.116493001
+142457872 -0.583680212 0.140287563
+142765106 -0.560637235 0.16401714
+143072339 -0.536502182 0.186390563