Convert CharSequence to StringBuffer

Conv.hs

charSeqToStringBuffer :: CharSequence -> StringBuffer
charSeqToStringBuffer cs = unsafePerformJava $ do
  bytes <- charSequenceBytes cs
  len   <- bytes <.> alength
  buf   <- mallocForeignPtrArray len
  io $ withForeignPtr buf $ putBytesIntoPtr bytes
  return $ StringBuffer { cur = 0, .. }


foreign import java unsafe "@static Utils.charSequenceBytes" charSequenceBytes
  :: CharSequence -> Java a JByteArray

foreign import java unsafe "@static Utils.putBytesIntoPtr" putBytesIntoPtr
  :: Ptr Word8 -> IO ()

Utils.java

import eta.runtime.io.MemoryManager;
import java.io.UnsupportedEncodingException;

public class Utils {
    public static byte[] charSequenceBytes(CharSequence cs)
        throws UnsupportedEncodingException {
        return cs.toString().getBytes("UTF-8");
    }

    public static void putBytesIntoPtr(long address, byte[] bytes) {
        MemoryManager.getBoundedBuffer(address).put(bytes);
    }
}