Fds accessor

pstream.h

@@ -168,6 +168,10 @@ namespace redi
       fopen(FILE*& in, FILE*& out, FILE*& err);
 #endif
 
+      /// Obtain file descriptors for each of the process' standards streams.
+      std::size_t
+      fds(fd_type& in, fd_type& out, fd_type& err);
+
       /// Return the exit status of the process.
       int
       status() const;
@@ -359,6 +363,10 @@ namespace redi
       fopen(FILE*& in, FILE*& out, FILE*& err);
 #endif
 
+      /// Obtain file descriptors for each of the process' standards streams.
+      std::size_t
+      fds(fd_type& in, fd_type& out, fd_type& err);
+
     protected:
       std::string       command_; ///< The command used to start the process.
       streambuf_type    buf_;     ///< The stream buffer.
@@ -2440,6 +2448,63 @@ namespace redi
 
 #endif // REDI_EVISCERATE_PSTREAMS
 
+  /**
+   * @warning  This function exposes the internals of the stream buffer and
+   *           should be used with caution. It is the caller's responsibility
+   *           to manage any interactions between iostream and raw I/O on the
+   *           file descriptors.
+   *
+   * @param   in    An integer that will be the process' stdin.
+   * @param   out   An integer that will be the process' stdout.
+   * @param   err   An integer that will be the process' stderr.
+   * @return  An OR of zero or more of @c pstdin, @c pstdout, @c pstderr.
+   *
+   * For each open stream shared with the child process the file descriptor
+   * used is assigned to the corresponding parameter. For closed
+   * streams @c -1 is assigned to the parameter.
+   * The return value can be tested to see which parameters are valid
+   * by masking with the corresponding @c pmode value.
+   */
+  template <typename C, typename T>
+    std::size_t
+    basic_pstreambuf<C,T>::fds(fd_type& in, fd_type& out, fd_type& err)
+    {
+      in = out = err = -1;
+      std::size_t open_files = 0;
+      if (wpipe() > -1)
+      {
+        in = wpipe();
+        open_files |= pstdin;
+      }
+      if (rpipe(rsrc_out) > -1)
+      {
+        out = rpipe(rsrc_out);
+        open_files |= pstdout;
+      }
+      if (rpipe(rsrc_err) > -1)
+      {
+        err = rpipe(rsrc_err);
+        open_files |= pstderr;
+      }
+      return open_files;
+    }
+
+  /**
+   *  @warning This function exposes the internals of the stream buffer and
+   *  should be used with caution.
+   *
+   *  @param  in   An integer that will refer to the process' stdin.
+   *  @param  out  An integer that will refer to the process' stdout.
+   *  @param  err  An integer that will refer to the process' stderr.
+   *  @return A bitwise-or of zero or more of @c pstdin, @c pstdout, @c pstderr.
+   *  @see    basic_pstreambuf::fds()
+   */
+  template <typename C, typename T>
+    inline std::size_t
+    pstream_common<C,T>::fds(fd_type& fin, fd_type& fout, fd_type& ferr)
+    {
+      return buf_.fds(fin, fout, ferr);
+    }
 
 } // namespace redi
 

test_pstreams.cc

@@ -705,10 +705,12 @@ int main()
 
         const size_t len = 256;
         char buf[len];
+        buf[0] = '\0';
         char* p = fgets(buf, len, out);
         cout << "STDOUT: " << buf;
         print_result(is, p!=NULL);
 
+        buf[0] = '\0';
         p = fgets(buf, len, err);
         cout << "STDERR: " << buf;
         print_result(is, p!=NULL);
@@ -730,17 +732,94 @@ int main()
 #if 0
         size_t len = 256;
         char buf[len];
+        buf[0] = '\0';
         char* p = fgets(buf, len, out);
         cout << "STDOUT: " << buf;
         print_result(ps, p!=NULL);
 
+        buf[0] = '\0';
         p = fgets(buf, len, err);
         cout << "STDERR: " << buf;
         print_result(ps, p!=NULL);
 #endif
     }
+#endif
+
+    clog << "# Testing file descriptor access\n";
+
+    {
+        opstream os("tr '[:lower:]' '[:upper:]' | sed 's/^/STDIN: /'");
+        int in, out, err;
+        size_t res = os.fds(in, out, err);
+        print_result(os, res & pstreambuf::pstdin);
+        print_result(os, in!=-1);
+        const char *msg = "flax\n";
+        ssize_t i = write(in, msg, strlen(msg));
+        print_result(os, i==static_cast<ssize_t>(strlen(msg)));
+    }
+
+    {
+        std::string cmd = "ls /etc/hosts /no/such/file";
+        ipstream is(cmd, pstreambuf::pstdout|pstreambuf::pstderr);
+        int in, out, err;
+        size_t res = is.fds(in, out, err);
+        print_result(is, res & pstreambuf::pstdout);
+        print_result(is, res & pstreambuf::pstderr);
+        print_result(is, out!=-1);
+        print_result(is, err!=-1);
 
+        const size_t len = 256;
+        char buf[len];
+        ssize_t i = read(out, buf, len);
+        ssize_t count = 0;
+        if (i > 0) {
+          count = i;
+        }
+        cout << "STDOUT: " << std::string(buf, count);
+        print_result(is, i>=0);
+
+        i = read(err, buf, len);
+        count = 0;
+        if ( i > 0) {
+          count = i;
+        }
+        cout << "STDERR: " << std::string(buf, count);
+        print_result(is, i>=0);
+    }
+
+    {
+        std::string cmd = "grep 127 -- - /etc/hosts /no/such/file";
+        pstream ps(cmd, all3streams);
+        int in, out, err;
+        size_t res = ps.fds(in, out, err);
+        print_result(ps, res & pstreambuf::pstdin);
+        print_result(ps, res & pstreambuf::pstdout);
+        print_result(ps, res & pstreambuf::pstderr);
+        print_result(ps, in!=-1);
+        print_result(ps, out!=-1);
+        print_result(ps, err!=-1);
+
+        // ps << "12345\n1112777\n0000" << EOF;
+#if 0
+        const size_t len = 256;
+        char buf[len];
+        ssize_t i = read(out, buf, len);
+        ssize_t count = 0;
+        if (i > 0) {
+          count = i;
+        }
+        cout << "STDOUT: " << std::string(buf, count);
+        print_result(is, i>=0);
+
+        i = read(err, buf, len);
+        count = 0;
+        if ( i > 0) {
+          count = i;
+        }
+        cout << "STDERR: " << std::string(buf, count);
+        print_result(is, i>=0);
 #endif
+    }
 
     clog << "# Testing resources freed correctly\n";