From f8c62753bc30432ef48c00d055551b33121b5535 Mon Sep 17 00:00:00 2001
From: Gerhard Sittig <gerhard.sittig@gmx.net>
Date: Sat, 18 Jul 2020 13:15:41 +0200
Subject: ir_irmp: enforce "one instance" limitation for IRMP library

The IRMP core library is not prepared for threading or interleaved use
by multiple call sites for different data streams, internal state is
kept in global vars (MCU project heritage). Adjust the Python wrapper,
create one usable instance, and several more which fail to execute.
Fail late such that users see error messages.

The approach isn't pretty, but avoids segfaults when re-loaded sessions
assign multiple decoder instances, and raises user's awareness of the
"one instance" limitation by established means: "decoder error" bar, and
log messages, with a description to point out the cause.

This commit implements a dirty modification of a singleton. It's a pity
that Python appears to lack reliable destruction, hence the whole class
remains blocked even if the instance is released. Move all library use
into pd.py:decode() in the hope that Python's 'with' could help in a
future implementation. Prepare to either present a generic message that
is generated by pd.py, or pass on a text that originates in the Python
wrapper for the C library.
---
 decoders/ir_irmp/pd.py | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

(limited to 'decoders/ir_irmp/pd.py')

diff --git a/decoders/ir_irmp/pd.py b/decoders/ir_irmp/pd.py
index cb69fd0..979c1e0 100644
--- a/decoders/ir_irmp/pd.py
+++ b/decoders/ir_irmp/pd.py
@@ -24,6 +24,9 @@ import sigrokdecode as srd
 class SamplerateError(Exception):
     pass
 
+class LibraryError(Exception):
+    pass
+
 class Decoder(srd.Decoder):
     api_version = 3
     id = 'ir_irmp'
@@ -90,12 +93,11 @@ class Decoder(srd.Decoder):
         self.put(ss, es, self.out_ann, [0, txts])
 
     def __init__(self):
-        self.irmp = irmp_library.IrmpLibrary()
-        self.lib_rate = self.irmp.get_sample_rate()
+        self.irmp = None
         self.reset()
 
     def reset(self):
-        self.irmp.reset_state()
+        self.want_reset = True
 
     def start(self):
         self.out_ann = self.register(srd.OUTPUT_ANN)
@@ -105,11 +107,24 @@ class Decoder(srd.Decoder):
             self.samplerate = value
 
     def decode(self):
+        if not self.irmp:
+            try:
+                self.irmp = irmp_library.IrmpLibrary()
+            except Exception as e:
+                txt = e.args[0]
+                raise LibraryError(txt)
+        if self.irmp:
+            self.lib_rate = self.irmp.get_sample_rate()
+        if not self.irmp or not self.lib_rate:
+            raise LibraryError('Cannot access IRMP library. One instance limit exceeded?')
         if not self.samplerate:
             raise SamplerateError('Cannot decode without samplerate.')
         if self.samplerate % self.lib_rate:
-            raise SamplerateError('capture samplerate must be multiple of library samplerate ({})'.format(self.lib_rate))
+            raise SamplerateError('Capture samplerate must be multiple of library samplerate ({})'.format(self.lib_rate))
         self.rate_factor = int(self.samplerate / self.lib_rate)
+        if self.want_reset:
+            self.irmp.reset_state()
+            self.want_reset = False
 
         self.active = 0 if self.options['polarity'] == 'active-low' else 1
         ir, = self.wait()
-- 
cgit v1.2.3-70-g09d2