[VOL-2831] - Multiple adapter support

This commit introduces the necessary APIs needed to support
multiple adapters.  It uses the number of replicas of a given
adapter and consistent hashing to determine the target of a
given request.

The endpoint_manager.go provides two APIs that will be needed
by components communicating over kafka:
 - GetEndPoint() : to be called before sending a request to kafka
 - IsDeviceOwnedByService(): used during device reconciliation

A change is made to the adapter_proxy.go to use this new mechanism
when sending a request to an adapter from another adapter.

The mocks directory was refactored to get around circular package
dependencies.  This implies any component using these mocks will
need to adjust to the new set of directories when using this
library version.

Change-Id: I470cd62fcfd04edc1fd4508400c9619cadaab25a
diff --git a/vendor/github.com/cespare/xxhash/LICENSE.txt b/vendor/github.com/cespare/xxhash/LICENSE.txt
new file mode 100644
index 0000000..24b5306
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/LICENSE.txt
@@ -0,0 +1,22 @@
+Copyright (c) 2016 Caleb Spare
+
+MIT License
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/vendor/github.com/cespare/xxhash/README.md b/vendor/github.com/cespare/xxhash/README.md
new file mode 100644
index 0000000..0982fd2
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/README.md
@@ -0,0 +1,50 @@
+# xxhash
+
+[![GoDoc](https://godoc.org/github.com/cespare/xxhash?status.svg)](https://godoc.org/github.com/cespare/xxhash)
+
+xxhash is a Go implementation of the 64-bit
+[xxHash](http://cyan4973.github.io/xxHash/) algorithm, XXH64. This is a
+high-quality hashing algorithm that is much faster than anything in the Go
+standard library.
+
+The API is very small, taking its cue from the other hashing packages in the
+standard library:
+
+    $ go doc github.com/cespare/xxhash                                                                                                                                                                                              !
+    package xxhash // import "github.com/cespare/xxhash"
+
+    Package xxhash implements the 64-bit variant of xxHash (XXH64) as described
+    at http://cyan4973.github.io/xxHash/.
+
+    func New() hash.Hash64
+    func Sum64(b []byte) uint64
+    func Sum64String(s string) uint64
+
+This implementation provides a fast pure-Go implementation and an even faster
+assembly implementation for amd64.
+
+## Benchmarks
+
+Here are some quick benchmarks comparing the pure-Go and assembly
+implementations of Sum64 against another popular Go XXH64 implementation,
+[github.com/OneOfOne/xxhash](https://github.com/OneOfOne/xxhash):
+
+| input size | OneOfOne | cespare (purego) | cespare |
+| --- | --- | --- | --- |
+| 5 B   |  416 MB/s | 720 MB/s |  872 MB/s  |
+| 100 B | 3980 MB/s | 5013 MB/s | 5252 MB/s  |
+| 4 KB  | 12727 MB/s | 12999 MB/s | 13026 MB/s |
+| 10 MB | 9879 MB/s | 10775 MB/s | 10913 MB/s  |
+
+These numbers were generated with:
+
+```
+$ go test -benchtime 10s -bench '/OneOfOne,'
+$ go test -tags purego -benchtime 10s -bench '/xxhash,'
+$ go test -benchtime 10s -bench '/xxhash,'
+```
+
+## Projects using this package
+
+- [InfluxDB](https://github.com/influxdata/influxdb)
+- [Prometheus](https://github.com/prometheus/prometheus)
diff --git a/vendor/github.com/cespare/xxhash/go.mod b/vendor/github.com/cespare/xxhash/go.mod
new file mode 100644
index 0000000..10605a6
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/go.mod
@@ -0,0 +1,6 @@
+module github.com/cespare/xxhash
+
+require (
+	github.com/OneOfOne/xxhash v1.2.2
+	github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72
+)
diff --git a/vendor/github.com/cespare/xxhash/go.sum b/vendor/github.com/cespare/xxhash/go.sum
new file mode 100644
index 0000000..f6b5542
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/go.sum
@@ -0,0 +1,4 @@
+github.com/OneOfOne/xxhash v1.2.2 h1:KMrpdQIwFcEqXDklaen+P1axHaj9BSKzvpUUfnHldSE=
+github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72 h1:qLC7fQah7D6K1B0ujays3HV9gkFtllcxhzImRR7ArPQ=
+github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
diff --git a/vendor/github.com/cespare/xxhash/rotate.go b/vendor/github.com/cespare/xxhash/rotate.go
new file mode 100644
index 0000000..f3eac5e
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/rotate.go
@@ -0,0 +1,14 @@
+// +build !go1.9
+
+package xxhash
+
+// TODO(caleb): After Go 1.10 comes out, remove this fallback code.
+
+func rol1(x uint64) uint64  { return (x << 1) | (x >> (64 - 1)) }
+func rol7(x uint64) uint64  { return (x << 7) | (x >> (64 - 7)) }
+func rol11(x uint64) uint64 { return (x << 11) | (x >> (64 - 11)) }
+func rol12(x uint64) uint64 { return (x << 12) | (x >> (64 - 12)) }
+func rol18(x uint64) uint64 { return (x << 18) | (x >> (64 - 18)) }
+func rol23(x uint64) uint64 { return (x << 23) | (x >> (64 - 23)) }
+func rol27(x uint64) uint64 { return (x << 27) | (x >> (64 - 27)) }
+func rol31(x uint64) uint64 { return (x << 31) | (x >> (64 - 31)) }
diff --git a/vendor/github.com/cespare/xxhash/rotate19.go b/vendor/github.com/cespare/xxhash/rotate19.go
new file mode 100644
index 0000000..b99612b
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/rotate19.go
@@ -0,0 +1,14 @@
+// +build go1.9
+
+package xxhash
+
+import "math/bits"
+
+func rol1(x uint64) uint64  { return bits.RotateLeft64(x, 1) }
+func rol7(x uint64) uint64  { return bits.RotateLeft64(x, 7) }
+func rol11(x uint64) uint64 { return bits.RotateLeft64(x, 11) }
+func rol12(x uint64) uint64 { return bits.RotateLeft64(x, 12) }
+func rol18(x uint64) uint64 { return bits.RotateLeft64(x, 18) }
+func rol23(x uint64) uint64 { return bits.RotateLeft64(x, 23) }
+func rol27(x uint64) uint64 { return bits.RotateLeft64(x, 27) }
+func rol31(x uint64) uint64 { return bits.RotateLeft64(x, 31) }
diff --git a/vendor/github.com/cespare/xxhash/xxhash.go b/vendor/github.com/cespare/xxhash/xxhash.go
new file mode 100644
index 0000000..f896bd2
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/xxhash.go
@@ -0,0 +1,168 @@
+// Package xxhash implements the 64-bit variant of xxHash (XXH64) as described
+// at http://cyan4973.github.io/xxHash/.
+package xxhash
+
+import (
+	"encoding/binary"
+	"hash"
+)
+
+const (
+	prime1 uint64 = 11400714785074694791
+	prime2 uint64 = 14029467366897019727
+	prime3 uint64 = 1609587929392839161
+	prime4 uint64 = 9650029242287828579
+	prime5 uint64 = 2870177450012600261
+)
+
+// NOTE(caleb): I'm using both consts and vars of the primes. Using consts where
+// possible in the Go code is worth a small (but measurable) performance boost
+// by avoiding some MOVQs. Vars are needed for the asm and also are useful for
+// convenience in the Go code in a few places where we need to intentionally
+// avoid constant arithmetic (e.g., v1 := prime1 + prime2 fails because the
+// result overflows a uint64).
+var (
+	prime1v = prime1
+	prime2v = prime2
+	prime3v = prime3
+	prime4v = prime4
+	prime5v = prime5
+)
+
+type xxh struct {
+	v1    uint64
+	v2    uint64
+	v3    uint64
+	v4    uint64
+	total int
+	mem   [32]byte
+	n     int // how much of mem is used
+}
+
+// New creates a new hash.Hash64 that implements the 64-bit xxHash algorithm.
+func New() hash.Hash64 {
+	var x xxh
+	x.Reset()
+	return &x
+}
+
+func (x *xxh) Reset() {
+	x.n = 0
+	x.total = 0
+	x.v1 = prime1v + prime2
+	x.v2 = prime2
+	x.v3 = 0
+	x.v4 = -prime1v
+}
+
+func (x *xxh) Size() int      { return 8 }
+func (x *xxh) BlockSize() int { return 32 }
+
+// Write adds more data to x. It always returns len(b), nil.
+func (x *xxh) Write(b []byte) (n int, err error) {
+	n = len(b)
+	x.total += len(b)
+
+	if x.n+len(b) < 32 {
+		// This new data doesn't even fill the current block.
+		copy(x.mem[x.n:], b)
+		x.n += len(b)
+		return
+	}
+
+	if x.n > 0 {
+		// Finish off the partial block.
+		copy(x.mem[x.n:], b)
+		x.v1 = round(x.v1, u64(x.mem[0:8]))
+		x.v2 = round(x.v2, u64(x.mem[8:16]))
+		x.v3 = round(x.v3, u64(x.mem[16:24]))
+		x.v4 = round(x.v4, u64(x.mem[24:32]))
+		b = b[32-x.n:]
+		x.n = 0
+	}
+
+	if len(b) >= 32 {
+		// One or more full blocks left.
+		b = writeBlocks(x, b)
+	}
+
+	// Store any remaining partial block.
+	copy(x.mem[:], b)
+	x.n = len(b)
+
+	return
+}
+
+func (x *xxh) Sum(b []byte) []byte {
+	s := x.Sum64()
+	return append(
+		b,
+		byte(s>>56),
+		byte(s>>48),
+		byte(s>>40),
+		byte(s>>32),
+		byte(s>>24),
+		byte(s>>16),
+		byte(s>>8),
+		byte(s),
+	)
+}
+
+func (x *xxh) Sum64() uint64 {
+	var h uint64
+
+	if x.total >= 32 {
+		v1, v2, v3, v4 := x.v1, x.v2, x.v3, x.v4
+		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
+		h = mergeRound(h, v1)
+		h = mergeRound(h, v2)
+		h = mergeRound(h, v3)
+		h = mergeRound(h, v4)
+	} else {
+		h = x.v3 + prime5
+	}
+
+	h += uint64(x.total)
+
+	i, end := 0, x.n
+	for ; i+8 <= end; i += 8 {
+		k1 := round(0, u64(x.mem[i:i+8]))
+		h ^= k1
+		h = rol27(h)*prime1 + prime4
+	}
+	if i+4 <= end {
+		h ^= uint64(u32(x.mem[i:i+4])) * prime1
+		h = rol23(h)*prime2 + prime3
+		i += 4
+	}
+	for i < end {
+		h ^= uint64(x.mem[i]) * prime5
+		h = rol11(h) * prime1
+		i++
+	}
+
+	h ^= h >> 33
+	h *= prime2
+	h ^= h >> 29
+	h *= prime3
+	h ^= h >> 32
+
+	return h
+}
+
+func u64(b []byte) uint64 { return binary.LittleEndian.Uint64(b) }
+func u32(b []byte) uint32 { return binary.LittleEndian.Uint32(b) }
+
+func round(acc, input uint64) uint64 {
+	acc += input * prime2
+	acc = rol31(acc)
+	acc *= prime1
+	return acc
+}
+
+func mergeRound(acc, val uint64) uint64 {
+	val = round(0, val)
+	acc ^= val
+	acc = acc*prime1 + prime4
+	return acc
+}
diff --git a/vendor/github.com/cespare/xxhash/xxhash_amd64.go b/vendor/github.com/cespare/xxhash/xxhash_amd64.go
new file mode 100644
index 0000000..d617652
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/xxhash_amd64.go
@@ -0,0 +1,12 @@
+// +build !appengine
+// +build gc
+// +build !purego
+
+package xxhash
+
+// Sum64 computes the 64-bit xxHash digest of b.
+//
+//go:noescape
+func Sum64(b []byte) uint64
+
+func writeBlocks(x *xxh, b []byte) []byte
diff --git a/vendor/github.com/cespare/xxhash/xxhash_amd64.s b/vendor/github.com/cespare/xxhash/xxhash_amd64.s
new file mode 100644
index 0000000..757f201
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/xxhash_amd64.s
@@ -0,0 +1,233 @@
+// +build !appengine
+// +build gc
+// +build !purego
+
+#include "textflag.h"
+
+// Register allocation:
+// AX	h
+// CX	pointer to advance through b
+// DX	n
+// BX	loop end
+// R8	v1, k1
+// R9	v2
+// R10	v3
+// R11	v4
+// R12	tmp
+// R13	prime1v
+// R14	prime2v
+// R15	prime4v
+
+// round reads from and advances the buffer pointer in CX.
+// It assumes that R13 has prime1v and R14 has prime2v.
+#define round(r) \
+	MOVQ  (CX), R12 \
+	ADDQ  $8, CX    \
+	IMULQ R14, R12  \
+	ADDQ  R12, r    \
+	ROLQ  $31, r    \
+	IMULQ R13, r
+
+// mergeRound applies a merge round on the two registers acc and val.
+// It assumes that R13 has prime1v, R14 has prime2v, and R15 has prime4v.
+#define mergeRound(acc, val) \
+	IMULQ R14, val \
+	ROLQ  $31, val \
+	IMULQ R13, val \
+	XORQ  val, acc \
+	IMULQ R13, acc \
+	ADDQ  R15, acc
+
+// func Sum64(b []byte) uint64
+TEXT ·Sum64(SB), NOSPLIT, $0-32
+	// Load fixed primes.
+	MOVQ ·prime1v(SB), R13
+	MOVQ ·prime2v(SB), R14
+	MOVQ ·prime4v(SB), R15
+
+	// Load slice.
+	MOVQ b_base+0(FP), CX
+	MOVQ b_len+8(FP), DX
+	LEAQ (CX)(DX*1), BX
+
+	// The first loop limit will be len(b)-32.
+	SUBQ $32, BX
+
+	// Check whether we have at least one block.
+	CMPQ DX, $32
+	JLT  noBlocks
+
+	// Set up initial state (v1, v2, v3, v4).
+	MOVQ R13, R8
+	ADDQ R14, R8
+	MOVQ R14, R9
+	XORQ R10, R10
+	XORQ R11, R11
+	SUBQ R13, R11
+
+	// Loop until CX > BX.
+blockLoop:
+	round(R8)
+	round(R9)
+	round(R10)
+	round(R11)
+
+	CMPQ CX, BX
+	JLE  blockLoop
+
+	MOVQ R8, AX
+	ROLQ $1, AX
+	MOVQ R9, R12
+	ROLQ $7, R12
+	ADDQ R12, AX
+	MOVQ R10, R12
+	ROLQ $12, R12
+	ADDQ R12, AX
+	MOVQ R11, R12
+	ROLQ $18, R12
+	ADDQ R12, AX
+
+	mergeRound(AX, R8)
+	mergeRound(AX, R9)
+	mergeRound(AX, R10)
+	mergeRound(AX, R11)
+
+	JMP afterBlocks
+
+noBlocks:
+	MOVQ ·prime5v(SB), AX
+
+afterBlocks:
+	ADDQ DX, AX
+
+	// Right now BX has len(b)-32, and we want to loop until CX > len(b)-8.
+	ADDQ $24, BX
+
+	CMPQ CX, BX
+	JG   fourByte
+
+wordLoop:
+	// Calculate k1.
+	MOVQ  (CX), R8
+	ADDQ  $8, CX
+	IMULQ R14, R8
+	ROLQ  $31, R8
+	IMULQ R13, R8
+
+	XORQ  R8, AX
+	ROLQ  $27, AX
+	IMULQ R13, AX
+	ADDQ  R15, AX
+
+	CMPQ CX, BX
+	JLE  wordLoop
+
+fourByte:
+	ADDQ $4, BX
+	CMPQ CX, BX
+	JG   singles
+
+	MOVL  (CX), R8
+	ADDQ  $4, CX
+	IMULQ R13, R8
+	XORQ  R8, AX
+
+	ROLQ  $23, AX
+	IMULQ R14, AX
+	ADDQ  ·prime3v(SB), AX
+
+singles:
+	ADDQ $4, BX
+	CMPQ CX, BX
+	JGE  finalize
+
+singlesLoop:
+	MOVBQZX (CX), R12
+	ADDQ    $1, CX
+	IMULQ   ·prime5v(SB), R12
+	XORQ    R12, AX
+
+	ROLQ  $11, AX
+	IMULQ R13, AX
+
+	CMPQ CX, BX
+	JL   singlesLoop
+
+finalize:
+	MOVQ  AX, R12
+	SHRQ  $33, R12
+	XORQ  R12, AX
+	IMULQ R14, AX
+	MOVQ  AX, R12
+	SHRQ  $29, R12
+	XORQ  R12, AX
+	IMULQ ·prime3v(SB), AX
+	MOVQ  AX, R12
+	SHRQ  $32, R12
+	XORQ  R12, AX
+
+	MOVQ AX, ret+24(FP)
+	RET
+
+// writeBlocks uses the same registers as above except that it uses AX to store
+// the x pointer.
+
+// func writeBlocks(x *xxh, b []byte) []byte
+TEXT ·writeBlocks(SB), NOSPLIT, $0-56
+	// Load fixed primes needed for round.
+	MOVQ ·prime1v(SB), R13
+	MOVQ ·prime2v(SB), R14
+
+	// Load slice.
+	MOVQ b_base+8(FP), CX
+	MOVQ CX, ret_base+32(FP) // initialize return base pointer; see NOTE below
+	MOVQ b_len+16(FP), DX
+	LEAQ (CX)(DX*1), BX
+	SUBQ $32, BX
+
+	// Load vN from x.
+	MOVQ x+0(FP), AX
+	MOVQ 0(AX), R8   // v1
+	MOVQ 8(AX), R9   // v2
+	MOVQ 16(AX), R10 // v3
+	MOVQ 24(AX), R11 // v4
+
+	// We don't need to check the loop condition here; this function is
+	// always called with at least one block of data to process.
+blockLoop:
+	round(R8)
+	round(R9)
+	round(R10)
+	round(R11)
+
+	CMPQ CX, BX
+	JLE  blockLoop
+
+	// Copy vN back to x.
+	MOVQ R8, 0(AX)
+	MOVQ R9, 8(AX)
+	MOVQ R10, 16(AX)
+	MOVQ R11, 24(AX)
+
+	// Construct return slice.
+	// NOTE: It's important that we don't construct a slice that has a base
+	// pointer off the end of the original slice, as in Go 1.7+ this will
+	// cause runtime crashes. (See discussion in, for example,
+	// https://github.com/golang/go/issues/16772.)
+	// Therefore, we calculate the length/cap first, and if they're zero, we
+	// keep the old base. This is what the compiler does as well if you
+	// write code like
+	//   b = b[len(b):]
+
+	// New length is 32 - (CX - BX) -> BX+32 - CX.
+	ADDQ $32, BX
+	SUBQ CX, BX
+	JZ   afterSetBase
+
+	MOVQ CX, ret_base+32(FP)
+
+afterSetBase:
+	MOVQ BX, ret_len+40(FP)
+	MOVQ BX, ret_cap+48(FP) // set cap == len
+
+	RET
diff --git a/vendor/github.com/cespare/xxhash/xxhash_other.go b/vendor/github.com/cespare/xxhash/xxhash_other.go
new file mode 100644
index 0000000..c68d13f
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/xxhash_other.go
@@ -0,0 +1,75 @@
+// +build !amd64 appengine !gc purego
+
+package xxhash
+
+// Sum64 computes the 64-bit xxHash digest of b.
+func Sum64(b []byte) uint64 {
+	// A simpler version would be
+	//   x := New()
+	//   x.Write(b)
+	//   return x.Sum64()
+	// but this is faster, particularly for small inputs.
+
+	n := len(b)
+	var h uint64
+
+	if n >= 32 {
+		v1 := prime1v + prime2
+		v2 := prime2
+		v3 := uint64(0)
+		v4 := -prime1v
+		for len(b) >= 32 {
+			v1 = round(v1, u64(b[0:8:len(b)]))
+			v2 = round(v2, u64(b[8:16:len(b)]))
+			v3 = round(v3, u64(b[16:24:len(b)]))
+			v4 = round(v4, u64(b[24:32:len(b)]))
+			b = b[32:len(b):len(b)]
+		}
+		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
+		h = mergeRound(h, v1)
+		h = mergeRound(h, v2)
+		h = mergeRound(h, v3)
+		h = mergeRound(h, v4)
+	} else {
+		h = prime5
+	}
+
+	h += uint64(n)
+
+	i, end := 0, len(b)
+	for ; i+8 <= end; i += 8 {
+		k1 := round(0, u64(b[i:i+8:len(b)]))
+		h ^= k1
+		h = rol27(h)*prime1 + prime4
+	}
+	if i+4 <= end {
+		h ^= uint64(u32(b[i:i+4:len(b)])) * prime1
+		h = rol23(h)*prime2 + prime3
+		i += 4
+	}
+	for ; i < end; i++ {
+		h ^= uint64(b[i]) * prime5
+		h = rol11(h) * prime1
+	}
+
+	h ^= h >> 33
+	h *= prime2
+	h ^= h >> 29
+	h *= prime3
+	h ^= h >> 32
+
+	return h
+}
+
+func writeBlocks(x *xxh, b []byte) []byte {
+	v1, v2, v3, v4 := x.v1, x.v2, x.v3, x.v4
+	for len(b) >= 32 {
+		v1 = round(v1, u64(b[0:8:len(b)]))
+		v2 = round(v2, u64(b[8:16:len(b)]))
+		v3 = round(v3, u64(b[16:24:len(b)]))
+		v4 = round(v4, u64(b[24:32:len(b)]))
+		b = b[32:len(b):len(b)]
+	}
+	x.v1, x.v2, x.v3, x.v4 = v1, v2, v3, v4
+	return b
+}
diff --git a/vendor/github.com/cespare/xxhash/xxhash_safe.go b/vendor/github.com/cespare/xxhash/xxhash_safe.go
new file mode 100644
index 0000000..dfa15ab
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/xxhash_safe.go
@@ -0,0 +1,10 @@
+// +build appengine
+
+// This file contains the safe implementations of otherwise unsafe-using code.
+
+package xxhash
+
+// Sum64String computes the 64-bit xxHash digest of s.
+func Sum64String(s string) uint64 {
+	return Sum64([]byte(s))
+}
diff --git a/vendor/github.com/cespare/xxhash/xxhash_unsafe.go b/vendor/github.com/cespare/xxhash/xxhash_unsafe.go
new file mode 100644
index 0000000..d2b64e8
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/xxhash_unsafe.go
@@ -0,0 +1,30 @@
+// +build !appengine
+
+// This file encapsulates usage of unsafe.
+// xxhash_safe.go contains the safe implementations.
+
+package xxhash
+
+import (
+	"reflect"
+	"unsafe"
+)
+
+// Sum64String computes the 64-bit xxHash digest of s.
+// It may be faster than Sum64([]byte(s)) by avoiding a copy.
+//
+// TODO(caleb): Consider removing this if an optimization is ever added to make
+// it unnecessary: https://golang.org/issue/2205.
+//
+// TODO(caleb): We still have a function call; we could instead write Go/asm
+// copies of Sum64 for strings to squeeze out a bit more speed.
+func Sum64String(s string) uint64 {
+	// See https://groups.google.com/d/msg/golang-nuts/dcjzJy-bSpw/tcZYBzQqAQAJ
+	// for some discussion about this unsafe conversion.
+	var b []byte
+	bh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
+	bh.Data = (*reflect.StringHeader)(unsafe.Pointer(&s)).Data
+	bh.Len = len(s)
+	bh.Cap = len(s)
+	return Sum64(b)
+}