Testing non-blocking read.

git-svn-id: https://svn.microneil.com/svn/CodeDweller/branches/adeniz_1@54 d34b734f-a00e-4b39-a726-e4eeb87269ab

child.cpp

@@ -25,6 +25,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <signal.h>
+#include <sys/select.h>
 
 #include <cstring>
 #include <cerrno>
@@ -77,6 +78,13 @@ namespace CodeDweller {
     exitCode = 0;
   }
 
+  size_t
+  Child::numBytesAvailable() const {
+
+    return readStreambuf.numBytesAvailable();
+
+  }
+
   void
   Child::run() {
 
@@ -219,7 +227,7 @@ namespace CodeDweller {
       throw std::runtime_error("Error creating pipe for stdin:  " +
 			       getErrorText());
     }
-    if (pipe(childStdOutPipe, O_NONBLOCK) != 0) {
+    if (pipe(childStdOutPipe) != 0) {
       close(childStdInPipe[0]);
       close(childStdInPipe[1]);
       throw std::runtime_error("Error creating pipe for stdout:  " +
@@ -487,9 +495,34 @@ namespace CodeDweller {
   }
 #endif
 
+  size_t
+    Child::ReadStreambuf::numBytesAvailable() const {
+
+    size_t nBytesAvailable =  egptr() - gptr();
+
+    fd_set readFd;
+    int retVal;
+    struct timeval timeout = {0, 0};
+
+    FD_ZERO(&readFd);
+    FD_SET(inputFileDescriptor, &readFd);
+
+    // Check if input is available.
+    retVal = select(inputFileDescriptor + 1, &readFd, NULL, NULL, &timeout);
+
+    if (-1 == retVal) {
+      throw std::runtime_error("Error from select(): " + getErrorText());
+    } else if (retVal > 0) {
+	nBytesAvailable++;
+    }
+
+    return nBytesAvailable;
+
+  }
+
   std::streambuf::int_type
   Child::ReadStreambuf::underflow() {
-
+    std::cout << "underflow()." << std::endl; // debug
     // Check for empty buffer.
     if (gptr() < egptr()) {
 
@@ -497,7 +530,7 @@ namespace CodeDweller {
       return traits_type::to_int_type(*gptr());
 
     }
-
+    std::cout << "need to fill buffer." << std::endl; // debug
     // Need to fill the buffer.
     char *base = &(buffer.front());
     char *start = base;
@@ -523,10 +556,18 @@ namespace CodeDweller {
     }
 #else
     ssize_t nBytesRead;
-
+    std::cout << "Requesting read of " << buffer.size() - (start - base)
+	      << " bytes" << std::endl; // debug
     nBytesRead = read(inputFileDescriptor,
 		      start,
 		      buffer.size() - (start - base));
+    // debug
+    std::cout << "nBytesRead:  " << nBytesRead << std::endl; // debug
+    for (int i = 0; i < nBytesRead; i++) {
+      std::cout << (char) start[i];
+    }
+    std::cout << std::endl;
+    // end of debug
     if (-1 == nBytesRead) {
       return traits_type::eof();
     }
@@ -540,6 +581,8 @@ namespace CodeDweller {
     // Update buffer pointers.
     setg(base, start, start + nBytesRead);
 
+    std::cout << "underflow() return." << std::endl; // debug
+
     return traits_type::to_int_type(*gptr());
 
   }
@@ -598,6 +641,15 @@ namespace CodeDweller {
     ssize_t nBytesWritten;
 
     nBytesWritten = write(outputFileDescriptor, pbase(), nBytes);
+    // debug
+    std::cout << "flushBuffer().  Requested to write " << nBytes << " bytes, "
+	      <<"wrote " << nBytesWritten << " bytes." << std::endl;
+    char *ch = pbase();
+    for (int i = 0; i < nBytesWritten; i++) {
+      std::cout << (char) ch[i];
+    }
+    std::cout << std::endl;
+    // end of debug.
 
 #endif
 

child.hpp

@@ -65,6 +65,8 @@ namespace CodeDweller {
     /// process.
     class ReadStreambuf : public std::streambuf {
 
+      friend class Child;
+
     public:
 
       /// Reader streambuf constructor.
@@ -94,12 +96,23 @@ namespace CodeDweller {
 
     private:
 
+      /** Return the number of bytes that can be read without
+	  blocking.
+
+	  This method checks if any input is available from the pipe,
+	  and returns the number of bytes in the input buffer plus 1.
+	  Reading that number of bytes will not block.  Reading a
+	  larger number of bytes might block.
+
+	  \returns minimum number of bytes that can be read without
+	  blocking.
+
+       */
+      size_t numBytesAvailable() const;
+
       /// Override streambuf::underflow().
       int_type underflow();
 
-      /// Fill the buffer.
-      //void fillBuffer();
-
       /// Copy constructor not implemented.
       ReadStreambuf(const ReadStreambuf &);
 
@@ -231,7 +244,7 @@ namespace CodeDweller {
 	blocking.
 
     */
-    ssize_t inputBytesAvailable();
+    size_t numBytesAvailable() const;
 
     /// Output stream to write data to the child's standard input.
     std::ostream writer;