HeapCharBuffer源码解读

class HeapCharBuffer extends CharBuffer {

	//  调用CharBuffer的构造函数
	//	CharBuffer(int mark, int pos, int lim, int cap, char[] hb, int offset) {
	//		super(mark, pos, lim, cap);
	//		this.hb = hb;
	//		this.offset = offset;
	//	}
	HeapCharBuffer(int cap, int lim) { 
		super(-1, 0, lim, cap, new char[cap], 0);
	}
	
	
	HeapCharBuffer(char[] buf, int off, int len) { 
		super(-1, off, off + len, buf.length, buf, 0);
	}

	protected HeapCharBuffer(char[] buf, int mark, int pos, int lim, int cap,
			int off) {
		super(mark, pos, lim, cap, buf, off);
	}

	//返回
	public CharBuffer slice() {
		return new HeapCharBuffer(hb, -1, 0, this.remaining(),
				this.remaining(), this.position() + offset);
	}

	public CharBuffer duplicate() {
		return new HeapCharBuffer(hb, this.markValue(), this.position(),
				this.limit(), this.capacity(), offset);
	}

	public CharBuffer asReadOnlyBuffer() {
		return new HeapCharBufferR(hb, this.markValue(), this.position(),
				this.limit(), this.capacity(), offset);

	}

	
	protected int ix(int i) {
		return i + offset;
	}

	//获取缓冲区中当前位置的元素，然后pos++
	public char get() {
		return hb[ix(nextGetIndex())];
	}
	//返回当前位置的元素
	public char get(int i) {
		return hb[ix(checkIndex(i))];
	}

	//
	public CharBuffer get(char[] dst, int offset, int length) {
		checkBounds(offset, length, dst.length);
		if (length > remaining())
			throw new BufferUnderflowException();
		System.arraycopy(hb, ix(position()), dst, offset, length);
		position(position() + length);
		return this;
	}

	public boolean isDirect() {
		return false;
	}

	public boolean isReadOnly() {
		return false;
	}

	//
	public CharBuffer put(char x) {
		hb[ix(nextPutIndex())] = x;
		return this;

	}

	public CharBuffer put(int i, char x) {

		hb[ix(checkIndex(i))] = x;
		return this;

	}

	public CharBuffer put(char[] src, int offset, int length) {

		checkBounds(offset, length, src.length);
		if (length > remaining())
			throw new BufferOverflowException();
		System.arraycopy(src, offset, hb, ix(position()), length);
		position(position() + length);
		return this;

	}

	public CharBuffer put(CharBuffer src) {

		if (src instanceof HeapCharBuffer) {
			if (src == this)
				throw new IllegalArgumentException();
			HeapCharBuffer sb = (HeapCharBuffer) src;
			int n = sb.remaining();
			if (n > remaining())
				throw new BufferOverflowException();
			System.arraycopy(sb.hb, sb.ix(sb.position()), hb, ix(position()), n);
			sb.position(sb.position() + n);
			position(position() + n);
		} else if (src.isDirect()) {
			int n = src.remaining();
			if (n > remaining())
				throw new BufferOverflowException();
			src.get(hb, ix(position()), n);
			position(position() + n);
		} else {
			super.put(src);
		}
		return this;

	}

	public CharBuffer compact() {

		System.arraycopy(hb, ix(position()), hb, ix(0), remaining());
		position(remaining());
		limit(capacity());
		return this;

	}

	String toString(int start, int end) { // package-private
		try {
			return new String(hb, start + offset, end - start);
		} catch (StringIndexOutOfBoundsException x) {
			throw new IndexOutOfBoundsException();
		}
	}

	// --- Methods to support CharSequence ---

	public CharSequence subSequence(int start, int end) {
		if ((start < 0) || (end > length()) || (start > end))
			throw new IndexOutOfBoundsException();
		int pos = position();
		return new HeapCharBuffer(hb, -1, pos + start, pos + end, capacity(),
				offset);
	}

	public ByteOrder order() {
		return ByteOrder.nativeOrder();
	}

}