added good() to pcm

pcm.hh

@@ -13,6 +13,7 @@ template <typename TYPE>
 struct WritePCM
 {
 	virtual void write(TYPE *, int, int = 1) = 0;
+	virtual bool good() = 0;
 	virtual void silence(int) = 0;
 };
 
@@ -20,6 +21,7 @@ template <typename TYPE>
 struct ReadPCM
 {
 	virtual void read(TYPE *, int, int = 1) = 0;
+	virtual bool good() = 0;
 	virtual void skip(int) = 0;
 	virtual int rate() = 0;
 	virtual int channels() = 0;

wav.hh

@@ -108,6 +108,10 @@ public:
 			}
 		}
 	}
+	bool good()
+	{
+		return is.good();
+	}
 	void skip(int num)
 	{
 		is.seekg(num * channels_ * bytes, std::ios_base::cur);
@@ -204,6 +208,10 @@ public:
 			}
 		}
 	}
+	bool good()
+	{
+		return os.good();
+	}
 	void silence(int num)
 	{
 		for (int i = 0; i < num * channels; ++i)