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* 11/19/04 1.0 moved to LGPL.
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* 12/12/99 0.0.7 Implementation stores single bits
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* as ints for better performance. mdm@techie.com.
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* 02/28/99 0.0 Java Conversion by E.B, javalayer@javazoom.net
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* Adapted from the public c code by Jeff Tsay.
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*-----------------------------------------------------------------------
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Library General Public License as published
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* by the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library General Public License for more details.
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* You should have received a copy of the GNU Library General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*----------------------------------------------------------------------
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package javazoom.jl.decoder;
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* Implementation of Bit Reservoir for Layer III.
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* The implementation stores single bits as a word in the buffer. If a bit is
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* set, the corresponding word in the buffer will be non-zero. If a bit is
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* clear, the corresponding word is zero. Although this may seem waseful, this
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* can be a factor of two quicker than packing 8 bits to a byte and extracting.
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// REVIEW: there is no range checking, so buffer underflow or overflow
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// can silently occur.
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final class BitReserve {
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* Size of the internal buffer to store the reserved bits. Must be a power
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* of 2. And x8, as each bit is stored as a single entry.
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private static final int BUFSIZE = 4096 * 8;
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* Mask that can be used to quickly implement the modulus operation on
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private static final int BUFSIZE_MASK = BUFSIZE - 1;
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private int offset, totbit, buf_byte_idx;
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private final int[] buf = new int[BUFSIZE];
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private int buf_bit_idx;
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* Return totbit Field.
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public int hsstell() {
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* Read a number bits from the bit stream.
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public int hgetbits(int N) {
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int pos = buf_byte_idx;
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if (pos + N < BUFSIZE) {
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val |= ((buf[pos++] != 0) ? 1 : 0);
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val |= ((buf[pos] != 0) ? 1 : 0);
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pos = (pos + 1) & BUFSIZE_MASK;
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* Read 1 bit from the bit stream.
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* public int hget1bit_old() { int val; totbit++; if (buf_bit_idx == 0) {
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* buf_bit_idx = 8; buf_byte_idx++; } // BUFSIZE = 4096 = 2^12, so //
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* buf_byte_idx%BUFSIZE == buf_byte_idx & 0xfff val = buf[buf_byte_idx &
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* BUFSIZE_MASK] & putmask[buf_bit_idx]; buf_bit_idx--; val = val >>>
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* buf_bit_idx; return val; }
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* Returns next bit from reserve.
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* @returns 0 if next bit is reset, or 1 if next bit is set.
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public int hget1bit() {
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int val = buf[buf_byte_idx];
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buf_byte_idx = (buf_byte_idx + 1) & BUFSIZE_MASK;
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* Retrieves bits from the reserve.
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* public int readBits(int[] out, int len) { if (buf_bit_idx == 0) {
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* buf_bit_idx = 8; buf_byte_idx++; current = buf[buf_byte_idx &
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* // save total number of bits returned len = buf_bit_idx; buf_bit_idx =
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* int b = current; int count = len-1;
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* while (count >= 0) { out[count--] = (b & 0x1); b >>>= 1; }
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* totbit += len; return len; }
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* Write 8 bits into the bit stream.
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public void hputbuf(int val) {
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buf[ofs++] = val & 0x80;
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buf[ofs++] = val & 0x40;
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buf[ofs++] = val & 0x20;
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buf[ofs++] = val & 0x10;
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buf[ofs++] = val & 0x08;
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buf[ofs++] = val & 0x04;
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buf[ofs++] = val & 0x02;
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buf[ofs++] = val & 0x01;
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* Rewind N bits in Stream.
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public void rewindNbits(int N) {
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if (buf_byte_idx < 0)
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buf_byte_idx += BUFSIZE;
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* Rewind N bytes in Stream.
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public void rewindNbytes(int N) {
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buf_byte_idx -= bits;
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if (buf_byte_idx < 0)
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buf_byte_idx += BUFSIZE;
added
removed
src/javazoom/jl/decoder/BitReserve.java
