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verified gcc-4.6.4.tar.bz2.sig;
imported gcc-4.6.4 source tree from verified upstream tarball.

downloading a git-generated archive based on the 'upstream' tag
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if you have obtained the source via the command 'git clone',
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1 files changed, 373 insertions, 0 deletions

diff --git a/libgo/go/compress/flate/huffman_code.go b/libgo/go/compress/flate/huffman_code.go
new file mode 100644
index 000000000..6be605f0a
--- /dev/null
+++ b/libgo/go/compress/flate/huffman_code.go
@@ -0,0 +1,373 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package flate
+
+import (
+	"math"
+	"sort"
+)
+
+type huffmanEncoder struct {
+	codeBits []uint8
+	code     []uint16
+}
+
+type literalNode struct {
+	literal uint16
+	freq    int32
+}
+
+type chain struct {
+	// The sum of the leaves in this tree
+	freq int32
+
+	// The number of literals to the left of this item at this level
+	leafCount int32
+
+	// The right child of this chain in the previous level.
+	up *chain
+}
+
+type levelInfo struct {
+	// Our level.  for better printing
+	level int32
+
+	// The most recent chain generated for this level
+	lastChain *chain
+
+	// The frequency of the next character to add to this level
+	nextCharFreq int32
+
+	// The frequency of the next pair (from level below) to add to this level.
+	// Only valid if the "needed" value of the next lower level is 0.
+	nextPairFreq int32
+
+	// The number of chains remaining to generate for this level before moving
+	// up to the next level
+	needed int32
+
+	// The levelInfo for level+1
+	up *levelInfo
+
+	// The levelInfo for level-1
+	down *levelInfo
+}
+
+func maxNode() literalNode { return literalNode{math.MaxUint16, math.MaxInt32} }
+
+func newHuffmanEncoder(size int) *huffmanEncoder {
+	return &huffmanEncoder{make([]uint8, size), make([]uint16, size)}
+}
+
+// Generates a HuffmanCode corresponding to the fixed literal table
+func generateFixedLiteralEncoding() *huffmanEncoder {
+	h := newHuffmanEncoder(maxLit)
+	codeBits := h.codeBits
+	code := h.code
+	var ch uint16
+	for ch = 0; ch < maxLit; ch++ {
+		var bits uint16
+		var size uint8
+		switch {
+		case ch < 144:
+			// size 8, 000110000  .. 10111111
+			bits = ch + 48
+			size = 8
+			break
+		case ch < 256:
+			// size 9, 110010000 .. 111111111
+			bits = ch + 400 - 144
+			size = 9
+			break
+		case ch < 280:
+			// size 7, 0000000 .. 0010111
+			bits = ch - 256
+			size = 7
+			break
+		default:
+			// size 8, 11000000 .. 11000111
+			bits = ch + 192 - 280
+			size = 8
+		}
+		codeBits[ch] = size
+		code[ch] = reverseBits(bits, size)
+	}
+	return h
+}
+
+func generateFixedOffsetEncoding() *huffmanEncoder {
+	h := newHuffmanEncoder(30)
+	codeBits := h.codeBits
+	code := h.code
+	for ch := uint16(0); ch < 30; ch++ {
+		codeBits[ch] = 5
+		code[ch] = reverseBits(ch, 5)
+	}
+	return h
+}
+
+var fixedLiteralEncoding *huffmanEncoder = generateFixedLiteralEncoding()
+var fixedOffsetEncoding *huffmanEncoder = generateFixedOffsetEncoding()
+
+func (h *huffmanEncoder) bitLength(freq []int32) int64 {
+	var total int64
+	for i, f := range freq {
+		if f != 0 {
+			total += int64(f) * int64(h.codeBits[i])
+		}
+	}
+	return total
+}
+
+// Generate elements in the chain using an iterative algorithm.
+func (h *huffmanEncoder) generateChains(top *levelInfo, list []literalNode) {
+	n := len(list)
+	list = list[0 : n+1]
+	list[n] = maxNode()
+
+	l := top
+	for {
+		if l.nextPairFreq == math.MaxInt32 && l.nextCharFreq == math.MaxInt32 {
+			// We've run out of both leafs and pairs.
+			// End all calculations for this level.
+			// To m sure we never come back to this level or any lower level,
+			// set nextPairFreq impossibly large.
+			l.lastChain = nil
+			l.needed = 0
+			l = l.up
+			l.nextPairFreq = math.MaxInt32
+			continue
+		}
+
+		prevFreq := l.lastChain.freq
+		if l.nextCharFreq < l.nextPairFreq {
+			// The next item on this row is a leaf node.
+			n := l.lastChain.leafCount + 1
+			l.lastChain = &chain{l.nextCharFreq, n, l.lastChain.up}
+			l.nextCharFreq = list[n].freq
+		} else {
+			// The next item on this row is a pair from the previous row.
+			// nextPairFreq isn't valid until we generate two
+			// more values in the level below
+			l.lastChain = &chain{l.nextPairFreq, l.lastChain.leafCount, l.down.lastChain}
+			l.down.needed = 2
+		}
+
+		if l.needed--; l.needed == 0 {
+			// We've done everything we need to do for this level.
+			// Continue calculating one level up.  Fill in nextPairFreq
+			// of that level with the sum of the two nodes we've just calculated on
+			// this level.
+			up := l.up
+			if up == nil {
+				// All done!
+				return
+			}
+			up.nextPairFreq = prevFreq + l.lastChain.freq
+			l = up
+		} else {
+			// If we stole from below, move down temporarily to replenish it.
+			for l.down.needed > 0 {
+				l = l.down
+			}
+		}
+	}
+}
+
+// Return the number of literals assigned to each bit size in the Huffman encoding
+//
+// This method is only called when list.length >= 3
+// The cases of 0, 1, and 2 literals are handled by special case code.
+//
+// list  An array of the literals with non-zero frequencies
+//             and their associated frequencies.  The array is in order of increasing
+//             frequency, and has as its last element a special element with frequency
+//             MaxInt32
+// maxBits     The maximum number of bits that should be used to encode any literal.
+// return      An integer array in which array[i] indicates the number of literals
+//             that should be encoded in i bits.
+func (h *huffmanEncoder) bitCounts(list []literalNode, maxBits int32) []int32 {
+	n := int32(len(list))
+	list = list[0 : n+1]
+	list[n] = maxNode()
+
+	// The tree can't have greater depth than n - 1, no matter what.  This
+	// saves a little bit of work in some small cases
+	maxBits = minInt32(maxBits, n-1)
+
+	// Create information about each of the levels.
+	// A bogus "Level 0" whose sole purpose is so that
+	// level1.prev.needed==0.  This makes level1.nextPairFreq
+	// be a legitimate value that never gets chosen.
+	top := &levelInfo{needed: 0}
+	chain2 := &chain{list[1].freq, 2, new(chain)}
+	for level := int32(1); level <= maxBits; level++ {
+		// For every level, the first two items are the first two characters.
+		// We initialize the levels as if we had already figured this out.
+		top = &levelInfo{
+			level:        level,
+			lastChain:    chain2,
+			nextCharFreq: list[2].freq,
+			nextPairFreq: list[0].freq + list[1].freq,
+			down:         top,
+		}
+		top.down.up = top
+		if level == 1 {
+			top.nextPairFreq = math.MaxInt32
+		}
+	}
+
+	// We need a total of 2*n - 2 items at top level and have already generated 2.
+	top.needed = 2*n - 4
+
+	l := top
+	for {
+		if l.nextPairFreq == math.MaxInt32 && l.nextCharFreq == math.MaxInt32 {
+			// We've run out of both leafs and pairs.
+			// End all calculations for this level.
+			// To m sure we never come back to this level or any lower level,
+			// set nextPairFreq impossibly large.
+			l.lastChain = nil
+			l.needed = 0
+			l = l.up
+			l.nextPairFreq = math.MaxInt32
+			continue
+		}
+
+		prevFreq := l.lastChain.freq
+		if l.nextCharFreq < l.nextPairFreq {
+			// The next item on this row is a leaf node.
+			n := l.lastChain.leafCount + 1
+			l.lastChain = &chain{l.nextCharFreq, n, l.lastChain.up}
+			l.nextCharFreq = list[n].freq
+		} else {
+			// The next item on this row is a pair from the previous row.
+			// nextPairFreq isn't valid until we generate two
+			// more values in the level below
+			l.lastChain = &chain{l.nextPairFreq, l.lastChain.leafCount, l.down.lastChain}
+			l.down.needed = 2
+		}
+
+		if l.needed--; l.needed == 0 {
+			// We've done everything we need to do for this level.
+			// Continue calculating one level up.  Fill in nextPairFreq
+			// of that level with the sum of the two nodes we've just calculated on
+			// this level.
+			up := l.up
+			if up == nil {
+				// All done!
+				break
+			}
+			up.nextPairFreq = prevFreq + l.lastChain.freq
+			l = up
+		} else {
+			// If we stole from below, move down temporarily to replenish it.
+			for l.down.needed > 0 {
+				l = l.down
+			}
+		}
+	}
+
+	// Somethings is wrong if at the end, the top level is null or hasn't used
+	// all of the leaves.
+	if top.lastChain.leafCount != n {
+		panic("top.lastChain.leafCount != n")
+	}
+
+	bitCount := make([]int32, maxBits+1)
+	bits := 1
+	for chain := top.lastChain; chain.up != nil; chain = chain.up {
+		// chain.leafCount gives the number of literals requiring at least "bits"
+		// bits to encode.
+		bitCount[bits] = chain.leafCount - chain.up.leafCount
+		bits++
+	}
+	return bitCount
+}
+
+// Look at the leaves and assign them a bit count and an encoding as specified
+// in RFC 1951 3.2.2
+func (h *huffmanEncoder) assignEncodingAndSize(bitCount []int32, list []literalNode) {
+	code := uint16(0)
+	for n, bits := range bitCount {
+		code <<= 1
+		if n == 0 || bits == 0 {
+			continue
+		}
+		// The literals list[len(list)-bits] .. list[len(list)-bits]
+		// are encoded using "bits" bits, and get the values
+		// code, code + 1, ....  The code values are
+		// assigned in literal order (not frequency order).
+		chunk := list[len(list)-int(bits):]
+		sortByLiteral(chunk)
+		for _, node := range chunk {
+			h.codeBits[node.literal] = uint8(n)
+			h.code[node.literal] = reverseBits(code, uint8(n))
+			code++
+		}
+		list = list[0 : len(list)-int(bits)]
+	}
+}
+
+// Update this Huffman Code object to be the minimum code for the specified frequency count.
+//
+// freq  An array of frequencies, in which frequency[i] gives the frequency of literal i.
+// maxBits  The maximum number of bits to use for any literal.
+func (h *huffmanEncoder) generate(freq []int32, maxBits int32) {
+	list := make([]literalNode, len(freq)+1)
+	// Number of non-zero literals
+	count := 0
+	// Set list to be the set of all non-zero literals and their frequencies
+	for i, f := range freq {
+		if f != 0 {
+			list[count] = literalNode{uint16(i), f}
+			count++
+		} else {
+			h.codeBits[i] = 0
+		}
+	}
+	// If freq[] is shorter than codeBits[], fill rest of codeBits[] with zeros
+	h.codeBits = h.codeBits[0:len(freq)]
+	list = list[0:count]
+	if count <= 2 {
+		// Handle the small cases here, because they are awkward for the general case code.  With
+		// two or fewer literals, everything has bit length 1.
+		for i, node := range list {
+			// "list" is in order of increasing literal value.
+			h.codeBits[node.literal] = 1
+			h.code[node.literal] = uint16(i)
+		}
+		return
+	}
+	sortByFreq(list)
+
+	// Get the number of literals for each bit count
+	bitCount := h.bitCounts(list, maxBits)
+	// And do the assignment
+	h.assignEncodingAndSize(bitCount, list)
+}
+
+type literalNodeSorter struct {
+	a    []literalNode
+	less func(i, j int) bool
+}
+
+func (s literalNodeSorter) Len() int { return len(s.a) }
+
+func (s literalNodeSorter) Less(i, j int) bool {
+	return s.less(i, j)
+}
+
+func (s literalNodeSorter) Swap(i, j int) { s.a[i], s.a[j] = s.a[j], s.a[i] }
+
+func sortByFreq(a []literalNode) {
+	s := &literalNodeSorter{a, func(i, j int) bool { return a[i].freq < a[j].freq }}
+	sort.Sort(s)
+}
+
+func sortByLiteral(a []literalNode) {
+	s := &literalNodeSorter{a, func(i, j int) bool { return a[i].literal < a[j].literal }}
+	sort.Sort(s)
+}