Tree.java
/*
* 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, so all credit should go authors Jean-loup
* Gailly(jloup@gzip.org) and Mark Adler(madler@alumni.caltech.edu) and contributors of zlib.
*/
package com.jcraft.jsch.jzlib;
final class Tree {
private static final int MAX_BITS = 15;
private static final int BL_CODES = 19;
private static final int D_CODES = 30;
private static final int LITERALS = 256;
private static final int LENGTH_CODES = 29;
private static final int L_CODES = (LITERALS + 1 + LENGTH_CODES);
private static final int HEAP_SIZE = (2 * L_CODES + 1);
// Bit length codes must not exceed MAX_BL_BITS bits
static final int MAX_BL_BITS = 7;
// end of block literal code
static final int END_BLOCK = 256;
// repeat previous bit length 3-6 times (2 bits of repeat count)
static final int REP_3_6 = 16;
// repeat a zero length 3-10 times (3 bits of repeat count)
static final int REPZ_3_10 = 17;
// repeat a zero length 11-138 times (7 bits of repeat count)
static final int REPZ_11_138 = 18;
// extra bits for each length code
static final int[] extra_lbits =
{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
static final int[] extra_dbits = {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
static final int[] extra_blbits = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 3, 7};
static final byte[] bl_order = {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.
static final int Buf_size = 8 * 2;
// see definition of array dist_code below
static final int DIST_CODE_LEN = 512;
static final byte[] _dist_code = {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};
static final byte[] _length_code = {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};
static final int[] base_length = {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};
static final int[] base_dist = {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};
// Mapping from a distance to a distance code. dist is the distance - 1 and
// must not have side effects. _dist_code[256] and _dist_code[257] are never
// used.
static int d_code(int dist) {
return ((dist) < 256 ? _dist_code[dist] : _dist_code[256 + ((dist) >>> 7)]);
}
short[] dyn_tree; // the dynamic tree
int max_code; // largest code with non zero frequency
StaticTree stat_desc; // 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.
void gen_bitlen(Deflate s) {
short[] tree = dyn_tree;
short[] stree = stat_desc.static_tree;
int[] extra = stat_desc.extra_bits;
int base = stat_desc.extra_base;
int max_length = stat_desc.max_length;
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 <= 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)
xbits = extra[n - base];
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] += 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) (((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.
void build_tree(Deflate s) {
short[] tree = dyn_tree;
short[] stree = stat_desc.static_tree;
int elems = stat_desc.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] = (short) (tree[n * 2] + tree[m * 2]);
s.depth[node] = (byte) (Math.max(s.depth[n], 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, s.next_code);
}
// 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.
private static final void gen_codes(short[] tree, // the tree to decorate
int max_code, // largest code with non zero frequency
short[] bl_count, // number of codes at each bit length
short[] next_code) {
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.
next_code[0] = 0;
for (bits = 1; bits <= MAX_BITS; bits++) {
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] = (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
private static final int bi_reverse(int code, // the value to invert
int len // its bit length
) {
int res = 0;
do {
res |= code & 1;
code >>>= 1;
res <<= 1;
} while (--len > 0);
return res >>> 1;
}
}