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Diffstat (limited to 'libjava/classpath/java/util/zip/StreamManipulator.java')
| -rw-r--r-- | libjava/classpath/java/util/zip/StreamManipulator.java | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/libjava/classpath/java/util/zip/StreamManipulator.java b/libjava/classpath/java/util/zip/StreamManipulator.java new file mode 100644 index 00000000000..57d15ae283b --- /dev/null +++ b/libjava/classpath/java/util/zip/StreamManipulator.java @@ -0,0 +1,216 @@ +/* java.util.zip.StreamManipulator + Copyright (C) 2001 Free Software Foundation, Inc. + +This file is part of GNU Classpath. + +GNU Classpath is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License as published by +the Free Software Foundation; either version 2, or (at your option) +any later version. + +GNU Classpath 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 +General Public License for more details. + +You should have received a copy of the GNU General Public License +along with GNU Classpath; see the file COPYING. If not, write to the +Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301 USA. + +Linking this library statically or dynamically with other modules is +making a combined work based on this library. Thus, the terms and +conditions of the GNU General Public License cover the whole +combination. + +As a special exception, the copyright holders of this library give you +permission to link this library with independent modules to produce an +executable, regardless of the license terms of these independent +modules, and to copy and distribute the resulting executable under +terms of your choice, provided that you also meet, for each linked +independent module, the terms and conditions of the license of that +module. An independent module is a module which is not derived from +or based on this library. If you modify this library, you may extend +this exception to your version of the library, but you are not +obligated to do so. If you do not wish to do so, delete this +exception statement from your version. */ + +package java.util.zip; + +/** + * This class allows us to retrieve a specified amount of bits from + * the input buffer, as well as copy big byte blocks. + * + * It uses an int buffer to store up to 31 bits for direct + * manipulation. This guarantees that we can get at least 16 bits, + * but we only need at most 15, so this is all safe. + * + * There are some optimizations in this class, for example, you must + * never peek more then 8 bits more than needed, and you must first + * peek bits before you may drop them. This is not a general purpose + * class but optimized for the behaviour of the Inflater. + * + * @author John Leuner, Jochen Hoenicke + */ + +class StreamManipulator +{ + private byte[] window; + private int window_start = 0; + private int window_end = 0; + + private int buffer = 0; + private int bits_in_buffer = 0; + + /** + * Get the next n bits but don't increase input pointer. n must be + * less or equal 16 and if you if this call succeeds, you must drop + * at least n-8 bits in the next call. + * + * @return the value of the bits, or -1 if not enough bits available. */ + public final int peekBits(int n) + { + if (bits_in_buffer < n) + { + if (window_start == window_end) + return -1; + buffer |= (window[window_start++] & 0xff + | (window[window_start++] & 0xff) << 8) << bits_in_buffer; + bits_in_buffer += 16; + } + return buffer & ((1 << n) - 1); + } + + /* Drops the next n bits from the input. You should have called peekBits + * with a bigger or equal n before, to make sure that enough bits are in + * the bit buffer. + */ + public final void dropBits(int n) + { + buffer >>>= n; + bits_in_buffer -= n; + } + + /** + * Gets the next n bits and increases input pointer. This is equivalent + * to peekBits followed by dropBits, except for correct error handling. + * @return the value of the bits, or -1 if not enough bits available. + */ + public final int getBits(int n) + { + int bits = peekBits(n); + if (bits >= 0) + dropBits(n); + return bits; + } + /** + * Gets the number of bits available in the bit buffer. This must be + * only called when a previous peekBits() returned -1. + * @return the number of bits available. + */ + public final int getAvailableBits() + { + return bits_in_buffer; + } + + /** + * Gets the number of bytes available. + * @return the number of bytes available. + */ + public final int getAvailableBytes() + { + return window_end - window_start + (bits_in_buffer >> 3); + } + + /** + * Skips to the next byte boundary. + */ + public void skipToByteBoundary() + { + buffer >>= (bits_in_buffer & 7); + bits_in_buffer &= ~7; + } + + public final boolean needsInput() { + return window_start == window_end; + } + + + /* Copies length bytes from input buffer to output buffer starting + * at output[offset]. You have to make sure, that the buffer is + * byte aligned. If not enough bytes are available, copies fewer + * bytes. + * @param length the length to copy, 0 is allowed. + * @return the number of bytes copied, 0 if no byte is available. + */ + public int copyBytes(byte[] output, int offset, int length) + { + if (length < 0) + throw new IllegalArgumentException("length negative"); + if ((bits_in_buffer & 7) != 0) + /* bits_in_buffer may only be 0 or 8 */ + throw new IllegalStateException("Bit buffer is not aligned!"); + + int count = 0; + while (bits_in_buffer > 0 && length > 0) + { + output[offset++] = (byte) buffer; + buffer >>>= 8; + bits_in_buffer -= 8; + length--; + count++; + } + if (length == 0) + return count; + + int avail = window_end - window_start; + if (length > avail) + length = avail; + System.arraycopy(window, window_start, output, offset, length); + window_start += length; + + if (((window_start - window_end) & 1) != 0) + { + /* We always want an even number of bytes in input, see peekBits */ + buffer = (window[window_start++] & 0xff); + bits_in_buffer = 8; + } + return count + length; + } + + public StreamManipulator() + { + } + + public void reset() + { + window_start = window_end = buffer = bits_in_buffer = 0; + } + + public void setInput(byte[] buf, int off, int len) + { + if (window_start < window_end) + throw new IllegalStateException + ("Old input was not completely processed"); + + int end = off + len; + + /* We want to throw an ArrayIndexOutOfBoundsException early. The + * check is very tricky: it also handles integer wrap around. + */ + if (0 > off || off > end || end > buf.length) + throw new ArrayIndexOutOfBoundsException(); + + if ((len & 1) != 0) + { + /* We always want an even number of bytes in input, see peekBits */ + buffer |= (buf[off++] & 0xff) << bits_in_buffer; + bits_in_buffer += 8; + } + + window = buf; + window_start = off; + window_end = end; + } +} + |
