python: read automata from pipes

* src/hoaparse/hoaparse.yy, src/hoaparse/hoascan.ll,
src/hoaparse/parsedecl.hh, src/hoaparse/public.hh:
Add a way to read automata from a file descriptor.
* wrap/python/spot.py: Add machinery to read from
pipes.
* wrap/python/tests/piperead.ipynb: New file.
* wrap/python/tests/Makefile.am: Add it.
* wrap/python/tests/run.in: Setup PATH.

src/hoaparse/hoaparse.yy

@@ -1620,6 +1620,15 @@ namespace spot
       throw std::runtime_error(std::string("Cannot open file ") + name);
   }
 
+  hoa_stream_parser::hoa_stream_parser(int fd,
+				       const std::string& name,
+				       bool ignore_abort)
+    : filename_(name), ignore_abort_(ignore_abort)
+  {
+    if (hoayyopen(fd))
+      throw std::runtime_error(std::string("Cannot open file ") + name);
+  }
+
   hoa_stream_parser::~hoa_stream_parser()
   {
     hoayyclose();

src/hoaparse/hoascan.ll

@@ -388,6 +388,31 @@ namespace spot
     return 0;
   }
 
+  int
+  hoayyopen(int fd)
+  {
+    bool want_interactive = false;
+
+    yyin = fdopen(fd, "r");
+
+    // If the input is a pipe, make the scanner
+    // interactive so that it does not wait for the input
+    // buffer to be full to process automata.
+    struct stat s;
+    if (fstat(fd, &s) < 0)
+      throw std::runtime_error("fstat failed");
+    if (S_ISFIFO(s.st_mode))
+      want_interactive = true;
+
+    // Reset the lexer in case a previous parse
+    // ended badly.
+    YY_NEW_FILE;
+    hoayyreset();
+    if (want_interactive)
+      yy_set_interactive(true);
+    return 0;
+  }
+
   void
   hoayyclose()
   {

src/hoaparse/parsedecl.hh

@@ -1,5 +1,5 @@
 // -*- coding: utf-8 -*-
-// Copyright (C) 2014 Laboratoire de Recherche et Développement
+// Copyright (C) 2014, 2015 Laboratoire de Recherche et Développement
 // de l'EPITA.
 //
 // This file is part of Spot, a model checking library.
@@ -33,6 +33,7 @@ namespace spot
 {
   void hoayyreset();
   int hoayyopen(const std::string& name);
+  int hoayyopen(int fd);
   void hoayyclose();
 
   // This exception is thrown by the lexer when it reads "--ABORT--".

src/hoaparse/public.hh

@@ -64,6 +64,10 @@ namespace spot
     bool ignore_abort_;
   public:
     hoa_stream_parser(const std::string& filename, bool ignore_abort = false);
+    // Read from an already open file descriptor.
+    // Use filename in error messages.
+    hoa_stream_parser(int fd, const std::string& filename,
+		      bool ignore_abort = false);
     ~hoa_stream_parser();
     hoa_aut_ptr parse(hoa_parse_error_list& error_list,
 		      const bdd_dict_ptr& dict,