bytebuffer.java

apache 的一个socket框架

    ////////////////////////////////
    // String getters and putters //
    ////////////////////////////////

    /**
     * Reads a <code>NUL</code>-terminated string from this buffer using the
     * specified <code>decoder</code> and returns it.  This method reads
     * until the limit of this buffer if no <tt>NUL</tt> is found.
     */
    public String getString(CharsetDecoder decoder)
            throws CharacterCodingException {
        if (!hasRemaining()) {
            return "";
        }

        boolean utf16 = decoder.charset().name().startsWith("UTF-16");

        int oldPos = position();
        int oldLimit = limit();
        int end;

        if (!utf16) {
            while (hasRemaining()) {
                if (get() == 0) {
                    break;
                }
            }

            end = position();
            if (end == oldLimit && get(end - 1) != 0) {
                limit(end);
            } else {
                limit(end - 1);
            }
        } else {
            while (remaining() >= 2) {
                boolean highZero = (get() == 0);
                boolean lowZero = (get() == 0);
                if (highZero && lowZero) {
                    break;
                }
            }

            end = position();
            if (end == oldLimit || end == oldLimit - 1) {
                limit(end);
            } else {
                limit(end - 2);
            }
        }

        position(oldPos);
        if (!hasRemaining()) {
            limit(oldLimit);
            position(end);
            return "";
        }
        decoder.reset();

        int expectedLength = (int) (remaining() * decoder.averageCharsPerByte()) + 1;
        CharBuffer out = CharBuffer.allocate(expectedLength);
        for (;;) {
            CoderResult cr;
            if (hasRemaining()) {
                cr = decoder.decode(buf(), out, true);
            } else {
                cr = decoder.flush(out);
            }

            if (cr.isUnderflow()) {
                break;
            }

            if (cr.isOverflow()) {
                CharBuffer o = CharBuffer.allocate(out.capacity()
                        + expectedLength);
                out.flip();
                o.put(out);
                out = o;
                continue;
            }

            if (cr.isError()) {
                // Revert the buffer back to the previous state.
                limit(oldLimit);
                position(oldPos);
                cr.throwException();
            }
        }

        limit(oldLimit);
        position(end);
        return out.flip().toString();
    }

    /**
     * Reads a <code>NUL</code>-terminated string from this buffer using the
     * specified <code>decoder</code> and returns it.
     *
     * @param fieldSize the maximum number of bytes to read
     */
    public String getString(int fieldSize, CharsetDecoder decoder)
            throws CharacterCodingException {
        checkFieldSize(fieldSize);

        if (fieldSize == 0) {
            return "";
        }

        if (!hasRemaining()) {
            return "";
        }

        boolean utf16 = decoder.charset().name().startsWith("UTF-16");

        if (utf16 && ((fieldSize & 1) != 0)) {
            throw new IllegalArgumentException("fieldSize is not even.");
        }

        int oldPos = position();
        int oldLimit = limit();
        int end = position() + fieldSize;

        if (oldLimit < end) {
            throw new BufferUnderflowException();
        }

        int i;

        if (!utf16) {
            for (i = 0; i < fieldSize; i++) {
                if (get() == 0) {
                    break;
                }
            }

            if (i == fieldSize) {
                limit(end);
            } else {
                limit(position() - 1);
            }
        } else {
            for (i = 0; i < fieldSize; i += 2) {
                boolean highZero = (get() == 0);
                boolean lowZero = (get() == 0);
                if (highZero && lowZero) {
                    break;
                }
            }

            if (i == fieldSize) {
                limit(end);
            } else {
                limit(position() - 2);
            }
        }

        position(oldPos);
        if (!hasRemaining()) {
            limit(oldLimit);
            position(end);
            return "";
        }
        decoder.reset();

        int expectedLength = (int) (remaining() * decoder.averageCharsPerByte()) + 1;
        CharBuffer out = CharBuffer.allocate(expectedLength);
        for (;;) {
            CoderResult cr;
            if (hasRemaining()) {
                cr = decoder.decode(buf(), out, true);
            } else {
                cr = decoder.flush(out);
            }

            if (cr.isUnderflow()) {
                break;
            }

            if (cr.isOverflow()) {
                CharBuffer o = CharBuffer.allocate(out.capacity()
                        + expectedLength);
                out.flip();
                o.put(out);
                out = o;
                continue;
            }

            if (cr.isError()) {
                // Revert the buffer back to the previous state.
                limit(oldLimit);
                position(oldPos);
                cr.throwException();
            }
        }

        limit(oldLimit);
        position(end);
        return out.flip().toString();
    }

    /**
     * Writes the content of <code>in</code> into this buffer using the
     * specified <code>encoder</code>.  This method doesn't terminate
     * string with <tt>NUL</tt>.  You have to do it by yourself.
     *
     * @throws BufferOverflowException if the specified string doesn't fit
     */
    public ByteBuffer putString(CharSequence val, CharsetEncoder encoder)
            throws CharacterCodingException {
        if (val.length() == 0) {
            return this;
        }

        CharBuffer in = CharBuffer.wrap(val);
        encoder.reset();

        int expandedState = 0;

        for (;;) {
            CoderResult cr;
            if (in.hasRemaining()) {
                cr = encoder.encode(in, buf(), true);
            } else {
                cr = encoder.flush(buf());
            }

            if (cr.isUnderflow()) {
                break;
            }
            if (cr.isOverflow()) {
                if (isAutoExpand()) {
                    switch (expandedState) {
                    case 0:
                        autoExpand((int) Math.ceil(in.remaining()
                                * encoder.averageBytesPerChar()));
                        expandedState++;
                        break;
                    case 1:
                        autoExpand((int) Math.ceil(in.remaining()
                                * encoder.maxBytesPerChar()));
                        expandedState++;
                        break;
                    default:
                        throw new RuntimeException("Expanded by "
                                + (int) Math.ceil(in.remaining()
                                        * encoder.maxBytesPerChar())
                                + " but that wasn't enough for '" + val + "'");
                    }
                    continue;
                }
            } else {
                expandedState = 0;
            }
            cr.throwException();
        }
        return this;
    }

    /**
     * Writes the content of <code>in</code> into this buffer as a
     * <code>NUL</code>-terminated string using the specified
     * <code>encoder</code>.
     * <p>
     * If the charset name of the encoder is UTF-16, you cannot specify
     * odd <code>fieldSize</code>, and this method will append two
     * <code>NUL</code>s as a terminator.
     * <p>
     * Please note that this method doesn't terminate with <code>NUL</code>
     * if the input string is longer than <tt>fieldSize</tt>.
     *
     * @param fieldSize the maximum number of bytes to write
     */
    public ByteBuffer putString(CharSequence val, int fieldSize,
            CharsetEncoder encoder) throws CharacterCodingException {
        checkFieldSize(fieldSize);

        if (fieldSize == 0)
            return this;

        autoExpand(fieldSize);

        boolean utf16 = encoder.charset().name().startsWith("UTF-16");

        if (utf16 && ((fieldSize & 1) != 0)) {
            throw new IllegalArgumentException("fieldSize is not even.");
        }

        int oldLimit = limit();
        int end = position() + fieldSize;

        if (oldLimit < end) {
            throw new BufferOverflowException();
        }

        if (val.length() == 0) {
            if (!utf16) {
                put((byte) 0x00);
            } else {
                put((byte) 0x00);
                put((byte) 0x00);
            }
            position(end);
            return this;
        }

        CharBuffer in = CharBuffer.wrap(val);
        limit(end);
        encoder.reset();

        for (;;) {
            CoderResult cr;
            if (in.hasRemaining()) {
                cr = encoder.encode(in, buf(), true);
            } else {
                cr = encoder.flush(buf());
            }

            if (cr.isUnderflow() || cr.isOverflow()) {
                break;
            }
            cr.throwException();
        }

        limit(oldLimit);

        if (position() < end) {
            if (!utf16) {
                put((byte) 0x00);
            } else {
                put((byte) 0x00);
                put((byte) 0x00);
            }
        }

        position(end);
        return this;
    }

    /**
     * Reads a string which has a 16-bit length field before the actual
     * encoded string, using the specified <code>decoder</code> and returns it.
     * This method is a shortcut for <tt>getPrefixedString(2, decoder)</tt>.
     */
    public String getPrefixedString(CharsetDecoder decoder)
            throws CharacterCodingException {
        return getPrefixedString(2, decoder);
    }

    /**
     * Reads a string which has a length field before the actual
     * encoded string, using the specified <code>decoder</code> and returns it.
     *
     * @param prefixLength the length of the length field (1, 2, or 4)
     */
    public String getPrefixedString(int prefixLength, CharsetDecoder decoder)
            throws CharacterCodingException {
        if (!prefixedDataAvailable(prefixLength)) {
            throw new BufferUnderflowException();
        }

        int fieldSize = 0;

        switch (prefixLength) {
        case 1:
            fieldSize = getUnsigned();
            break;
        case 2:
            fieldSize = getUnsignedShort();
            break;
        case 4:
            fieldSize = getInt();
            break;
        }

        if (fieldSize == 0) {
            return "";
        }

        boolean utf16 = decoder.charset().name().startsWith("UTF-16");

        if (utf16 && ((fieldSize & 1) != 0)) {
            throw new BufferDataException(
                    "fieldSize is not even for a UTF-16 string.");
        }

        int oldLimit = limit();
        int end = position() + fieldSize;

        if (oldLimit < end) {
            throw new BufferUnderflowException();
        }

        limit(end);
        decoder.reset();

        int expectedLength = (int) (remaining() * decoder.averageCharsPerByte()) + 1;
        CharBuffer out = CharBuffer.allocate(expectedLength);
        for (;;) {
            CoderResult cr;
            if (hasRemaining()) {
                cr = decoder.decode(buf(), out, true);
            } else {
                cr = decoder.flush(out);
            }

            if (cr.isUnderflow()) {
                break;
            }

            if (cr.isOverflow()) {
                CharBuffer o = CharBuffer.allocate(out.capacity()
                        + expectedLength);
                out.flip();
                o.put(out);
                out = o;
                continue;
            }

            cr.throwException();
        }

        limit(oldLimit);
        position(end);
        return out.flip().toString();
    }

    /**
     * Writes the content of <code>in</code> into this buffer as a
     * string which has a 16-bit length field before the actual
     * encoded string, using the specified <code>encoder</code>.