add other session providers (#5963)

vendor/github.com/siddontang/go-snappy/AUTHORS

@@ -0,0 +1,12 @@
+# This is the official list of Snappy-Go authors for copyright purposes.
+# This file is distinct from the CONTRIBUTORS files.
+# See the latter for an explanation.
+
+# Names should be added to this file as
+#	Name or Organization <email address>
+# The email address is not required for organizations.
+
+# Please keep the list sorted.
+
+Google Inc.
+Jan Mercl <0xjnml@gmail.com>

vendor/github.com/siddontang/go-snappy/CONTRIBUTORS

@@ -0,0 +1,34 @@
+# This is the official list of people who can contribute
+# (and typically have contributed) code to the Snappy-Go repository.
+# The AUTHORS file lists the copyright holders; this file
+# lists people.  For example, Google employees are listed here
+# but not in AUTHORS, because Google holds the copyright.
+#
+# The submission process automatically checks to make sure
+# that people submitting code are listed in this file (by email address).
+#
+# Names should be added to this file only after verifying that
+# the individual or the individual's organization has agreed to
+# the appropriate Contributor License Agreement, found here:
+#
+#     http://code.google.com/legal/individual-cla-v1.0.html
+#     http://code.google.com/legal/corporate-cla-v1.0.html
+#
+# The agreement for individuals can be filled out on the web.
+#
+# When adding J Random Contributor's name to this file,
+# either J's name or J's organization's name should be
+# added to the AUTHORS file, depending on whether the
+# individual or corporate CLA was used.
+
+# Names should be added to this file like so:
+#     Name <email address>
+
+# Please keep the list sorted.
+
+Jan Mercl <0xjnml@gmail.com>
+Kai Backman <kaib@golang.org>
+Marc-Antoine Ruel <maruel@chromium.org>
+Nigel Tao <nigeltao@golang.org>
+Rob Pike <r@golang.org>
+Russ Cox <rsc@golang.org>

vendor/github.com/siddontang/go-snappy/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2011 The Snappy-Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * 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.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS 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 THE COPYRIGHT
+OWNER OR CONTRIBUTORS 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.

vendor/github.com/siddontang/go-snappy/snappy/decode.go

@@ -0,0 +1,124 @@
+// Copyright 2011 The Snappy-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 snappy
+
+import (
+	"encoding/binary"
+	"errors"
+)
+
+// ErrCorrupt reports that the input is invalid.
+var ErrCorrupt = errors.New("snappy: corrupt input")
+
+// DecodedLen returns the length of the decoded block.
+func DecodedLen(src []byte) (int, error) {
+	v, _, err := decodedLen(src)
+	return v, err
+}
+
+// decodedLen returns the length of the decoded block and the number of bytes
+// that the length header occupied.
+func decodedLen(src []byte) (blockLen, headerLen int, err error) {
+	v, n := binary.Uvarint(src)
+	if n == 0 {
+		return 0, 0, ErrCorrupt
+	}
+	if uint64(int(v)) != v {
+		return 0, 0, errors.New("snappy: decoded block is too large")
+	}
+	return int(v), n, nil
+}
+
+// Decode returns the decoded form of src. The returned slice may be a sub-
+// slice of dst if dst was large enough to hold the entire decoded block.
+// Otherwise, a newly allocated slice will be returned.
+// It is valid to pass a nil dst.
+func Decode(dst, src []byte) ([]byte, error) {
+	dLen, s, err := decodedLen(src)
+	if err != nil {
+		return nil, err
+	}
+	if len(dst) < dLen {
+		dst = make([]byte, dLen)
+	}
+
+	var d, offset, length int
+	for s < len(src) {
+		switch src[s] & 0x03 {
+		case tagLiteral:
+			x := uint(src[s] >> 2)
+			switch {
+			case x < 60:
+				s += 1
+			case x == 60:
+				s += 2
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-1])
+			case x == 61:
+				s += 3
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-2]) | uint(src[s-1])<<8
+			case x == 62:
+				s += 4
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-3]) | uint(src[s-2])<<8 | uint(src[s-1])<<16
+			case x == 63:
+				s += 5
+				if s > len(src) {
+					return nil, ErrCorrupt
+				}
+				x = uint(src[s-4]) | uint(src[s-3])<<8 | uint(src[s-2])<<16 | uint(src[s-1])<<24
+			}
+			length = int(x + 1)
+			if length <= 0 {
+				return nil, errors.New("snappy: unsupported literal length")
+			}
+			if length > len(dst)-d || length > len(src)-s {
+				return nil, ErrCorrupt
+			}
+			copy(dst[d:], src[s:s+length])
+			d += length
+			s += length
+			continue
+
+		case tagCopy1:
+			s += 2
+			if s > len(src) {
+				return nil, ErrCorrupt
+			}
+			length = 4 + int(src[s-2])>>2&0x7
+			offset = int(src[s-2])&0xe0<<3 | int(src[s-1])
+
+		case tagCopy2:
+			s += 3
+			if s > len(src) {
+				return nil, ErrCorrupt
+			}
+			length = 1 + int(src[s-3])>>2
+			offset = int(src[s-2]) | int(src[s-1])<<8
+
+		case tagCopy4:
+			return nil, errors.New("snappy: unsupported COPY_4 tag")
+		}
+
+		end := d + length
+		if offset > d || end > len(dst) {
+			return nil, ErrCorrupt
+		}
+		for ; d < end; d++ {
+			dst[d] = dst[d-offset]
+		}
+	}
+	if d != dLen {
+		return nil, ErrCorrupt
+	}
+	return dst[:d], nil
+}

vendor/github.com/siddontang/go-snappy/snappy/encode.go

@@ -0,0 +1,174 @@
+// Copyright 2011 The Snappy-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 snappy
+
+import (
+	"encoding/binary"
+)
+
+// We limit how far copy back-references can go, the same as the C++ code.
+const maxOffset = 1 << 15
+
+// emitLiteral writes a literal chunk and returns the number of bytes written.
+func emitLiteral(dst, lit []byte) int {
+	i, n := 0, uint(len(lit)-1)
+	switch {
+	case n < 60:
+		dst[0] = uint8(n)<<2 | tagLiteral
+		i = 1
+	case n < 1<<8:
+		dst[0] = 60<<2 | tagLiteral
+		dst[1] = uint8(n)
+		i = 2
+	case n < 1<<16:
+		dst[0] = 61<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		i = 3
+	case n < 1<<24:
+		dst[0] = 62<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		dst[3] = uint8(n >> 16)
+		i = 4
+	case int64(n) < 1<<32:
+		dst[0] = 63<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		dst[3] = uint8(n >> 16)
+		dst[4] = uint8(n >> 24)
+		i = 5
+	default:
+		panic("snappy: source buffer is too long")
+	}
+	if copy(dst[i:], lit) != len(lit) {
+		panic("snappy: destination buffer is too short")
+	}
+	return i + len(lit)
+}
+
+// emitCopy writes a copy chunk and returns the number of bytes written.
+func emitCopy(dst []byte, offset, length int) int {
+	i := 0
+	for length > 0 {
+		x := length - 4
+		if 0 <= x && x < 1<<3 && offset < 1<<11 {
+			dst[i+0] = uint8(offset>>8)&0x07<<5 | uint8(x)<<2 | tagCopy1
+			dst[i+1] = uint8(offset)
+			i += 2
+			break
+		}
+
+		x = length
+		if x > 1<<6 {
+			x = 1 << 6
+		}
+		dst[i+0] = uint8(x-1)<<2 | tagCopy2
+		dst[i+1] = uint8(offset)
+		dst[i+2] = uint8(offset >> 8)
+		i += 3
+		length -= x
+	}
+	return i
+}
+
+// Encode returns the encoded form of src. The returned slice may be a sub-
+// slice of dst if dst was large enough to hold the entire encoded block.
+// Otherwise, a newly allocated slice will be returned.
+// It is valid to pass a nil dst.
+func Encode(dst, src []byte) ([]byte, error) {
+	if n := MaxEncodedLen(len(src)); len(dst) < n {
+		dst = make([]byte, n)
+	}
+
+	// The block starts with the varint-encoded length of the decompressed bytes.
+	d := binary.PutUvarint(dst, uint64(len(src)))
+
+	// Return early if src is short.
+	if len(src) <= 4 {
+		if len(src) != 0 {
+			d += emitLiteral(dst[d:], src)
+		}
+		return dst[:d], nil
+	}
+
+	// Initialize the hash table. Its size ranges from 1<<8 to 1<<14 inclusive.
+	const maxTableSize = 1 << 14
+	shift, tableSize := uint(32-8), 1<<8
+	for tableSize < maxTableSize && tableSize < len(src) {
+		shift--
+		tableSize *= 2
+	}
+	var table [maxTableSize]int
+
+	// Iterate over the source bytes.
+	var (
+		s   int // The iterator position.
+		t   int // The last position with the same hash as s.
+		lit int // The start position of any pending literal bytes.
+	)
+	for s+3 < len(src) {
+		// Update the hash table.
+		b0, b1, b2, b3 := src[s], src[s+1], src[s+2], src[s+3]
+		h := uint32(b0) | uint32(b1)<<8 | uint32(b2)<<16 | uint32(b3)<<24
+		p := &table[(h*0x1e35a7bd)>>shift]
+		// We need to to store values in [-1, inf) in table. To save
+		// some initialization time, (re)use the table's zero value
+		// and shift the values against this zero: add 1 on writes,
+		// subtract 1 on reads.
+		t, *p = *p-1, s+1
+		// If t is invalid or src[s:s+4] differs from src[t:t+4], accumulate a literal byte.
+		if t < 0 || s-t >= maxOffset || b0 != src[t] || b1 != src[t+1] || b2 != src[t+2] || b3 != src[t+3] {
+			s++
+			continue
+		}
+		// Otherwise, we have a match. First, emit any pending literal bytes.
+		if lit != s {
+			d += emitLiteral(dst[d:], src[lit:s])
+		}
+		// Extend the match to be as long as possible.
+		s0 := s
+		s, t = s+4, t+4
+		for s < len(src) && src[s] == src[t] {
+			s++
+			t++
+		}
+		// Emit the copied bytes.
+		d += emitCopy(dst[d:], s-t, s-s0)
+		lit = s
+	}
+
+	// Emit any final pending literal bytes and return.
+	if lit != len(src) {
+		d += emitLiteral(dst[d:], src[lit:])
+	}
+	return dst[:d], nil
+}
+
+// MaxEncodedLen returns the maximum length of a snappy block, given its
+// uncompressed length.
+func MaxEncodedLen(srcLen int) int {
+	// Compressed data can be defined as:
+	//    compressed := item* literal*
+	//    item       := literal* copy
+	//
+	// The trailing literal sequence has a space blowup of at most 62/60
+	// since a literal of length 60 needs one tag byte + one extra byte
+	// for length information.
+	//
+	// Item blowup is trickier to measure. Suppose the "copy" op copies
+	// 4 bytes of data. Because of a special check in the encoding code,
+	// we produce a 4-byte copy only if the offset is < 65536. Therefore
+	// the copy op takes 3 bytes to encode, and this type of item leads
+	// to at most the 62/60 blowup for representing literals.
+	//
+	// Suppose the "copy" op copies 5 bytes of data. If the offset is big
+	// enough, it will take 5 bytes to encode the copy op. Therefore the
+	// worst case here is a one-byte literal followed by a five-byte copy.
+	// That is, 6 bytes of input turn into 7 bytes of "compressed" data.
+	//
+	// This last factor dominates the blowup, so the final estimate is:
+	return 32 + srcLen + srcLen/6
+}

vendor/github.com/siddontang/go-snappy/snappy/snappy.go

@@ -0,0 +1,38 @@
+// Copyright 2011 The Snappy-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 snappy implements the snappy block-based compression format.
+// It aims for very high speeds and reasonable compression.
+//
+// The C++ snappy implementation is at http://code.google.com/p/snappy/
+package snappy
+
+/*
+Each encoded block begins with the varint-encoded length of the decoded data,
+followed by a sequence of chunks. Chunks begin and end on byte boundaries. The
+first byte of each chunk is broken into its 2 least and 6 most significant bits
+called l and m: l ranges in [0, 4) and m ranges in [0, 64). l is the chunk tag.
+Zero means a literal tag. All other values mean a copy tag.
+
+For literal tags:
+  - If m < 60, the next 1 + m bytes are literal bytes.
+  - Otherwise, let n be the little-endian unsigned integer denoted by the next
+    m - 59 bytes. The next 1 + n bytes after that are literal bytes.
+
+For copy tags, length bytes are copied from offset bytes ago, in the style of
+Lempel-Ziv compression algorithms. In particular:
+  - For l == 1, the offset ranges in [0, 1<<11) and the length in [4, 12).
+    The length is 4 + the low 3 bits of m. The high 3 bits of m form bits 8-10
+    of the offset. The next byte is bits 0-7 of the offset.
+  - For l == 2, the offset ranges in [0, 1<<16) and the length in [1, 65).
+    The length is 1 + m. The offset is the little-endian unsigned integer
+    denoted by the next 2 bytes.
+  - For l == 3, this tag is a legacy format that is no longer supported.
+*/
+const (
+	tagLiteral = 0x00
+	tagCopy1   = 0x01
+	tagCopy2   = 0x02
+	tagCopy4   = 0x03
+)