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AirScout/DotNetZip/Zlib/Tree.cs

423 wiersze
19 KiB
C#
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// Tree.cs
// ------------------------------------------------------------------
//
// Copyright (c) 2009 Dino Chiesa and Microsoft Corporation.
// All rights reserved.
//
// This code module is part of DotNetZip, a zipfile class library.
//
// ------------------------------------------------------------------
//
// This code is licensed under the Microsoft Public License.
// See the file License.txt for the license details.
// More info on: http://dotnetzip.codeplex.com
//
// ------------------------------------------------------------------
//
// last saved (in emacs):
// Time-stamp: <2009-October-28 13:29:50>
//
// ------------------------------------------------------------------
//
// This module defines classes for zlib compression and
// decompression. This code is derived from the jzlib implementation of
// zlib. In keeping with the license for jzlib, the copyright to that
// code is below.
//
// ------------------------------------------------------------------
//
// Copyright (c) 2000,2001,2002,2003 ymnk, JCraft,Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the distribution.
//
// 3. The names of the authors may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
// INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
// OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// -----------------------------------------------------------------------
//
// This program is based on zlib-1.1.3; credit to authors
// Jean-loup Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu)
// and contributors of zlib.
//
// -----------------------------------------------------------------------
using System;
namespace Ionic.Zlib
{
sealed class Tree
{
private static readonly int HEAP_SIZE = (2 * InternalConstants.L_CODES + 1);
// extra bits for each length code
internal static readonly int[] ExtraLengthBits = new int[]
{
0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2,
3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0
};
// extra bits for each distance code
internal static readonly int[] ExtraDistanceBits = new int[]
{
0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6,
7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13
};
// extra bits for each bit length code
internal static readonly int[] extra_blbits = new int[]{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 7};
internal static readonly sbyte[] bl_order = new sbyte[]{16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
// The lengths of the bit length codes are sent in order of decreasing
// probability, to avoid transmitting the lengths for unused bit
// length codes.
internal const int Buf_size = 8 * 2;
// see definition of array dist_code below
//internal const int DIST_CODE_LEN = 512;
private static readonly sbyte[] _dist_code = new sbyte[]
{
0, 1, 2, 3, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7,
8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9,
10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
0, 0, 16, 17, 18, 18, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21,
22, 22, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 23, 23,
24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29
};
internal static readonly sbyte[] LengthCode = new sbyte[]
{
0, 1, 2, 3, 4, 5, 6, 7, 8, 8, 9, 9, 10, 10, 11, 11,
12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15,
16, 16, 16, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17,
18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19,
20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20,
21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 28
};
internal static readonly int[] LengthBase = new int[]
{
0, 1, 2, 3, 4, 5, 6, 7, 8, 10, 12, 14, 16, 20, 24, 28,
32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 0
};
internal static readonly int[] DistanceBase = new int[]
{
0, 1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, 64, 96, 128, 192,
256, 384, 512, 768, 1024, 1536, 2048, 3072, 4096, 6144, 8192, 12288, 16384, 24576
};
/// <summary>
/// Map from a distance to a distance code.
/// </summary>
/// <remarks>
/// No side effects. _dist_code[256] and _dist_code[257] are never used.
/// </remarks>
internal static int DistanceCode(int dist)
{
return (dist < 256)
? _dist_code[dist]
: _dist_code[256 + SharedUtils.URShift(dist, 7)];
}
internal short[] dyn_tree; // the dynamic tree
internal int max_code; // largest code with non zero frequency
internal StaticTree staticTree; // the corresponding static tree
// Compute the optimal bit lengths for a tree and update the total bit length
// for the current block.
// IN assertion: the fields freq and dad are set, heap[heap_max] and
// above are the tree nodes sorted by increasing frequency.
// OUT assertions: the field len is set to the optimal bit length, the
// array bl_count contains the frequencies for each bit length.
// The length opt_len is updated; static_len is also updated if stree is
// not null.
internal void gen_bitlen(DeflateManager s)
{
short[] tree = dyn_tree;
short[] stree = staticTree.treeCodes;
int[] extra = staticTree.extraBits;
int base_Renamed = staticTree.extraBase;
int max_length = staticTree.maxLength;
int h; // heap index
int n, m; // iterate over the tree elements
int bits; // bit length
int xbits; // extra bits
short f; // frequency
int overflow = 0; // number of elements with bit length too large
for (bits = 0; bits <= InternalConstants.MAX_BITS; bits++)
s.bl_count[bits] = 0;
// In a first pass, compute the optimal bit lengths (which may
// overflow in the case of the bit length tree).
tree[s.heap[s.heap_max] * 2 + 1] = 0; // root of the heap
for (h = s.heap_max + 1; h < HEAP_SIZE; h++)
{
n = s.heap[h];
bits = tree[tree[n * 2 + 1] * 2 + 1] + 1;
if (bits > max_length)
{
bits = max_length; overflow++;
}
tree[n * 2 + 1] = (short) bits;
// We overwrite tree[n*2+1] which is no longer needed
if (n > max_code)
continue; // not a leaf node
s.bl_count[bits]++;
xbits = 0;
if (n >= base_Renamed)
xbits = extra[n - base_Renamed];
f = tree[n * 2];
s.opt_len += f * (bits + xbits);
if (stree != null)
s.static_len += f * (stree[n * 2 + 1] + xbits);
}
if (overflow == 0)
return ;
// This happens for example on obj2 and pic of the Calgary corpus
// Find the first bit length which could increase:
do
{
bits = max_length - 1;
while (s.bl_count[bits] == 0)
bits--;
s.bl_count[bits]--; // move one leaf down the tree
s.bl_count[bits + 1] = (short) (s.bl_count[bits + 1] + 2); // move one overflow item as its brother
s.bl_count[max_length]--;
// The brother of the overflow item also moves one step up,
// but this does not affect bl_count[max_length]
overflow -= 2;
}
while (overflow > 0);
for (bits = max_length; bits != 0; bits--)
{
n = s.bl_count[bits];
while (n != 0)
{
m = s.heap[--h];
if (m > max_code)
continue;
if (tree[m * 2 + 1] != bits)
{
s.opt_len = (int) (s.opt_len + ((long) bits - (long) tree[m * 2 + 1]) * (long) tree[m * 2]);
tree[m * 2 + 1] = (short) bits;
}
n--;
}
}
}
// Construct one Huffman tree and assigns the code bit strings and lengths.
// Update the total bit length for the current block.
// IN assertion: the field freq is set for all tree elements.
// OUT assertions: the fields len and code are set to the optimal bit length
// and corresponding code. The length opt_len is updated; static_len is
// also updated if stree is not null. The field max_code is set.
internal void build_tree(DeflateManager s)
{
short[] tree = dyn_tree;
short[] stree = staticTree.treeCodes;
int elems = staticTree.elems;
int n, m; // iterate over heap elements
int max_code = -1; // largest code with non zero frequency
int node; // new node being created
// Construct the initial heap, with least frequent element in
// heap[1]. The sons of heap[n] are heap[2*n] and heap[2*n+1].
// heap[0] is not used.
s.heap_len = 0;
s.heap_max = HEAP_SIZE;
for (n = 0; n < elems; n++)
{
if (tree[n * 2] != 0)
{
s.heap[++s.heap_len] = max_code = n;
s.depth[n] = 0;
}
else
{
tree[n * 2 + 1] = 0;
}
}
// The pkzip format requires that at least one distance code exists,
// and that at least one bit should be sent even if there is only one
// possible code. So to avoid special checks later on we force at least
// two codes of non zero frequency.
while (s.heap_len < 2)
{
node = s.heap[++s.heap_len] = (max_code < 2?++max_code:0);
tree[node * 2] = 1;
s.depth[node] = 0;
s.opt_len--;
if (stree != null)
s.static_len -= stree[node * 2 + 1];
// node is 0 or 1 so it does not have extra bits
}
this.max_code = max_code;
// The elements heap[heap_len/2+1 .. heap_len] are leaves of the tree,
// establish sub-heaps of increasing lengths:
for (n = s.heap_len / 2; n >= 1; n--)
s.pqdownheap(tree, n);
// Construct the Huffman tree by repeatedly combining the least two
// frequent nodes.
node = elems; // next internal node of the tree
do
{
// n = node of least frequency
n = s.heap[1];
s.heap[1] = s.heap[s.heap_len--];
s.pqdownheap(tree, 1);
m = s.heap[1]; // m = node of next least frequency
s.heap[--s.heap_max] = n; // keep the nodes sorted by frequency
s.heap[--s.heap_max] = m;
// Create a new node father of n and m
tree[node * 2] = unchecked((short) (tree[n * 2] + tree[m * 2]));
s.depth[node] = (sbyte) (System.Math.Max((byte) s.depth[n], (byte) s.depth[m]) + 1);
tree[n * 2 + 1] = tree[m * 2 + 1] = (short) node;
// and insert the new node in the heap
s.heap[1] = node++;
s.pqdownheap(tree, 1);
}
while (s.heap_len >= 2);
s.heap[--s.heap_max] = s.heap[1];
// At this point, the fields freq and dad are set. We can now
// generate the bit lengths.
gen_bitlen(s);
// The field len is now set, we can generate the bit codes
gen_codes(tree, max_code, s.bl_count);
}
// Generate the codes for a given tree and bit counts (which need not be
// optimal).
// IN assertion: the array bl_count contains the bit length statistics for
// the given tree and the field len is set for all tree elements.
// OUT assertion: the field code is set for all tree elements of non
// zero code length.
internal static void gen_codes(short[] tree, int max_code, short[] bl_count)
{
short[] next_code = new short[InternalConstants.MAX_BITS + 1]; // next code value for each bit length
short code = 0; // running code value
int bits; // bit index
int n; // code index
// The distribution counts are first used to generate the code values
// without bit reversal.
for (bits = 1; bits <= InternalConstants.MAX_BITS; bits++)
unchecked {
next_code[bits] = code = (short) ((code + bl_count[bits - 1]) << 1);
}
// Check that the bit counts in bl_count are consistent. The last code
// must be all ones.
//Assert (code + bl_count[MAX_BITS]-1 == (1<<MAX_BITS)-1,
// "inconsistent bit counts");
//Tracev((stderr,"\ngen_codes: max_code %d ", max_code));
for (n = 0; n <= max_code; n++)
{
int len = tree[n * 2 + 1];
if (len == 0)
continue;
// Now reverse the bits
tree[n * 2] = unchecked((short) (bi_reverse(next_code[len]++, len)));
}
}
// Reverse the first len bits of a code, using straightforward code (a faster
// method would use a table)
// IN assertion: 1 <= len <= 15
internal static int bi_reverse(int code, int len)
{
int res = 0;
do
{
res |= code & 1;
code >>= 1; //SharedUtils.URShift(code, 1);
res <<= 1;
}
while (--len > 0);
return res >> 1;
}
}
}
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