diff options
Diffstat (limited to 'songdbj/javazoom/jl/decoder/BitReserve.java')
| -rw-r--r-- | songdbj/javazoom/jl/decoder/BitReserve.java | 223 |
1 files changed, 223 insertions, 0 deletions
diff --git a/songdbj/javazoom/jl/decoder/BitReserve.java b/songdbj/javazoom/jl/decoder/BitReserve.java new file mode 100644 index 0000000..a5d3056 --- /dev/null +++ b/songdbj/javazoom/jl/decoder/BitReserve.java @@ -0,0 +1,223 @@ +/* + * 11/19/04 1.0 moved to LGPL. + * + * 12/12/99 0.0.7 Implementation stores single bits + * as ints for better performance. mdm@techie.com. + * + * 02/28/99 0.0 Java Conversion by E.B, javalayer@javazoom.net + * + * Adapted from the public c code by Jeff Tsay. + * + *----------------------------------------------------------------------- + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU Library General Public License as published + * by the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Library General Public License for more details. + * + * You should have received a copy of the GNU Library General Public + * License along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + *---------------------------------------------------------------------- + */ + +package javazoom.jl.decoder; + +/** + * Implementation of Bit Reservoir for Layer III. + * <p> + * The implementation stores single bits as a word in the buffer. If + * a bit is set, the corresponding word in the buffer will be non-zero. + * If a bit is clear, the corresponding word is zero. Although this + * may seem waseful, this can be a factor of two quicker than + * packing 8 bits to a byte and extracting. + * <p> + */ + +// REVIEW: there is no range checking, so buffer underflow or overflow +// can silently occur. +final class BitReserve +{ + /** + * Size of the internal buffer to store the reserved bits. + * Must be a power of 2. And x8, as each bit is stored as a single + * entry. + */ + private static final int BUFSIZE = 4096*8; + + /** + * Mask that can be used to quickly implement the + * modulus operation on BUFSIZE. + */ + private static final int BUFSIZE_MASK = BUFSIZE-1; + + private int offset, totbit, buf_byte_idx; + private final int[] buf = new int[BUFSIZE]; + private int buf_bit_idx; + + BitReserve() + { + + offset = 0; + totbit = 0; + buf_byte_idx = 0; + } + + + /** + * Return totbit Field. + */ + public int hsstell() + { + return(totbit); + } + + /** + * Read a number bits from the bit stream. + * @param N the number of + */ + public int hgetbits(int N) + { + totbit += N; + + int val = 0; + + int pos = buf_byte_idx; + if (pos+N < BUFSIZE) + { + while (N-- > 0) + { + val <<= 1; + val |= ((buf[pos++]!=0) ? 1 : 0); + } + } + else + { + while (N-- > 0) + { + val <<= 1; + val |= ((buf[pos]!=0) ? 1 : 0); + pos = (pos+1) & BUFSIZE_MASK; + } + } + buf_byte_idx = pos; + return val; + } + + + + /** + * Read 1 bit from the bit stream. + */ +/* + public int hget1bit_old() + { + int val; + totbit++; + if (buf_bit_idx == 0) + { + buf_bit_idx = 8; + buf_byte_idx++; + } + // BUFSIZE = 4096 = 2^12, so + // buf_byte_idx%BUFSIZE == buf_byte_idx & 0xfff + val = buf[buf_byte_idx & BUFSIZE_MASK] & putmask[buf_bit_idx]; + buf_bit_idx--; + val = val >>> buf_bit_idx; + return val; + } + */ + /** + * Returns next bit from reserve. + * @returns 0 if next bit is reset, or 1 if next bit is set. + */ + public int hget1bit() + { + totbit++; + int val = buf[buf_byte_idx]; + buf_byte_idx = (buf_byte_idx+1) & BUFSIZE_MASK; + return val; + } + + /** + * Retrieves bits from the reserve. + */ +/* + public int readBits(int[] out, int len) + { + if (buf_bit_idx == 0) + { + buf_bit_idx = 8; + buf_byte_idx++; + current = buf[buf_byte_idx & BUFSIZE_MASK]; + } + + + + // save total number of bits returned + len = buf_bit_idx; + buf_bit_idx = 0; + + int b = current; + int count = len-1; + + while (count >= 0) + { + out[count--] = (b & 0x1); + b >>>= 1; + } + + totbit += len; + return len; + } + */ + + /** + * Write 8 bits into the bit stream. + */ + public void hputbuf(int val) + { + int ofs = offset; + buf[ofs++] = val & 0x80; + buf[ofs++] = val & 0x40; + buf[ofs++] = val & 0x20; + buf[ofs++] = val & 0x10; + buf[ofs++] = val & 0x08; + buf[ofs++] = val & 0x04; + buf[ofs++] = val & 0x02; + buf[ofs++] = val & 0x01; + + if (ofs==BUFSIZE) + offset = 0; + else + offset = ofs; + + } + + /** + * Rewind N bits in Stream. + */ + public void rewindNbits(int N) + { + totbit -= N; + buf_byte_idx -= N; + if (buf_byte_idx<0) + buf_byte_idx += BUFSIZE; + } + + /** + * Rewind N bytes in Stream. + */ + public void rewindNbytes(int N) + { + int bits = (N << 3); + totbit -= bits; + buf_byte_idx -= bits; + if (buf_byte_idx<0) + buf_byte_idx += BUFSIZE; + } +} |