Add eof() support to SGIOChannel/SGFile.

simgear/io/iochannel.cxx

@@ -70,3 +70,9 @@ int SGIOChannel::writestring( const char *str ) {
 bool SGIOChannel::close() {
     return false;
 }
+
+
+// dummy eof routine
+bool SGIOChannel::eof() {
+    return false;
+}

simgear/io/iochannel.hxx

@@ -152,6 +152,14 @@ public:
      */
     virtual bool close();
 
+    /**
+     * The eof() method returns true if end of file has been reached
+     * in a context where that makes sense.  Otherwise it returns
+     * false.
+     * @return result of eof check
+     */
+    virtual bool eof();
+
     inline void set_type( SGChannelType t ) { type = t; }
     inline SGChannelType get_type() const { return type; }
 

simgear/io/sg_file.cxx

@@ -80,7 +80,7 @@ bool SGFile::open( const SGProtocolDir d ) {
 int SGFile::read( char *buf, int length ) {
     // read a chunk
     ssize_t result = ::read( fp, buf, length );
-    if ( result == 0 ) {
+    if ( length > 0 && result == 0 ) {
         eof_flag = true;
     }
     return result;
@@ -94,7 +94,7 @@ int SGFile::readline( char *buf, int length ) {
 
     // read a chunk
     ssize_t result = ::read( fp, buf, length );
-    if ( result == 0 ) {
+    if ( length > 0 && result == 0 ) {
         eof_flag = true;
     }