charset}. The charset that it uses
+ * may be specified by name or may be given explicitly, or the platform's
+ * default charset may be accepted.
+ *
+ * Each invocation of one of an InputStreamReader's read() methods may + * cause one or more bytes to be read from the underlying byte-input stream. + * To enable the efficient conversion of bytes to characters, more bytes may + * be read ahead from the underlying stream than are necessary to satisfy the + * current read operation. + * + *
For top efficiency, consider wrapping an InputStreamReader within a + * BufferedReader. For example: + * + *
+ * BufferedReader in + * = new BufferedReader(new InputStreamReader(System.in)); + *+ * + * @see BufferedReader + * @see InputStream + * @see java.nio.charset.Charset + * + * @author Mark Reinhold + * @since JDK1.1 + */ + +public class InputStreamReader extends Reader { + + /** + * Creates an InputStreamReader that uses the default charset. + * + * @param in An InputStream + */ + public InputStreamReader(InputStream in) { + super(in); + } + + /** + * Creates an InputStreamReader that uses the named charset. + * + * @param in + * An InputStream + * + * @param charsetName + * The name of a supported + * {@link java.nio.charset.Charset charset
}
+ *
+ * @exception UnsupportedEncodingException
+ * If the named charset is not supported
+ */
+ public InputStreamReader(InputStream in, String charsetName)
+ throws UnsupportedEncodingException
+ {
+ super(in);
+ if (!charsetName.toUpperCase().equals("UTF-8")) {
+ throw new UnsupportedEncodingException(charsetName);
+ }
+ }
+
+ /**
+ * Creates an InputStreamReader that uses the given charset.
+ *
+ * @param in An InputStream
+ * @param cs A charset
+ *
+ * @since 1.4
+ * @spec JSR-51
+ */
+/* XXX:
+ public InputStreamReader(InputStream in, Charset cs) {
+ super(in);
+ if (cs == null)
+ throw new NullPointerException("charset");
+ sd = StreamDecoder.forInputStreamReader(in, this, cs);
+ }
+*/
+ /**
+ * Creates an InputStreamReader that uses the given charset decoder.
+ *
+ * @param in An InputStream
+ * @param dec A charset decoder
+ *
+ * @since 1.4
+ * @spec JSR-51
+ */
+/* XXX:
+ public InputStreamReader(InputStream in, CharsetDecoder dec) {
+ super(in);
+ if (dec == null)
+ throw new NullPointerException("charset decoder");
+ sd = StreamDecoder.forInputStreamReader(in, this, dec);
+ }
+*/
+
+ /**
+ * Returns the name of the character encoding being used by this stream.
+ *
+ * If the encoding has an historical name then that name is returned;
+ * otherwise the encoding's canonical name is returned.
+ *
+ *
If this instance was created with the {@link
+ * #InputStreamReader(InputStream, String)} constructor then the returned
+ * name, being unique for the encoding, may differ from the name passed to
+ * the constructor. This method will return null if the
+ * stream has been closed.
+ *
+ * @return The historical name of this encoding, or
+ * null if the stream has been closed
+ *
+ * @see java.nio.charset.Charset
+ *
+ * @revised 1.4
+ * @spec JSR-51
+ */
+ public String getEncoding() {
+ return "UTF-8";
+ }
+
+ /**
+ * Reads a single character.
+ *
+ * @return The character read, or -1 if the end of the stream has been
+ * reached
+ *
+ * @exception IOException If an I/O error occurs
+ */
+ public int read() throws IOException {
+ final InputStream is = (InputStream)lock;
+ int c = is.read();
+ if (c == -1) {
+ return -1;
+ }
+ c = (int) c & 0xff;
+ switch (c >> 4) {
+ case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
+ /* 0xxxxxxx*/
+ return c;
+ case 12: case 13: {
+ /* 110x xxxx 10xx xxxx*/
+ int char2 = (int) is.read();
+ if ((char2 & 0xC0) != 0x80)
+ throw new UTFDataFormatException("malformed input");
+ return (((c & 0x1F) << 6) | (char2 & 0x3F));
+ }
+ case 14: {
+ /* 1110 xxxx 10xx xxxx 10xx xxxx */
+ int char2 = is.read();
+ int char3 = is.read();
+ if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
+ throw new UTFDataFormatException("malformed input");
+ return (((c & 0x0F) << 12) |
+ ((char2 & 0x3F) << 6) |
+ ((char3 & 0x3F) << 0));
+ }
+ default:
+ /* 10xx xxxx, 1111 xxxx */
+ throw new UTFDataFormatException("malformed input");
+ }
+ }
+
+ /**
+ * Reads characters into a portion of an array.
+ *
+ * @param cbuf Destination buffer
+ * @param offset Offset at which to start storing characters
+ * @param length Maximum number of characters to read
+ *
+ * @return The number of characters read, or -1 if the end of the
+ * stream has been reached
+ *
+ * @exception IOException If an I/O error occurs
+ */
+ public int read(char cbuf[], int offset, int length) throws IOException {
+ for (int i = 0; i < length; i++) {
+ int ch = read();
+ if (ch == -1) {
+ if (i == 0) return -1;
+ return i;
+ }
+ cbuf[offset++] = (char) ch;
+ }
+ return length;
+ }
+
+ /**
+ * Tells whether this stream is ready to be read. An InputStreamReader is
+ * ready if its input buffer is not empty, or if bytes are available to be
+ * read from the underlying byte stream.
+ *
+ * @exception IOException If an I/O error occurs
+ */
+ public boolean ready() throws IOException {
+ return ((InputStream)lock).available() > 0;
+ }
+
+ public void close() throws IOException {
+ ((InputStream)lock).close();
+ }
+}