Godeps, vendor: convert dependency management to trash (#3198)

This commit converts the dependency management from Godeps to the vendor
folder, also switching the tool from godep to trash. Since the upstream tool
lacks a few features proposed via a few PRs, until those PRs are merged in
(if), use github.com/karalabe/trash.

You can update dependencies via trash --update.

All dependencies have been updated to their latest version.

Parts of the build system are reworked to drop old notions of Godeps and
invocation of the go vet command so that it doesn't run against the vendor
folder, as that will just blow up during vetting.

The conversion drops OpenCL (and hence GPU mining support) from ethash and our
codebase. The short reasoning is that there's noone to maintain and having
opencl libs in our deps messes up builds as go install ./... tries to build
them, failing with unsatisfied link errors for the C OpenCL deps.

golang.org/x/net/context is not vendored in. We expect it to be fetched by the
user (i.e. using go get). To keep ci.go builds reproducible the package is
"vendored" in build/_vendor.

6 files changed, 715 insertions, 0 deletions

diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer.go
new file mode 100644
index 000000000..21de24255
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer.go
@@ -0,0 +1,293 @@
+// 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 util
+
+// This a copy of Go std bytes.Buffer with some modification
+// and some features stripped.
+
+import (
+	"bytes"
+	"io"
+)
+
+// A Buffer is a variable-sized buffer of bytes with Read and Write methods.
+// The zero value for Buffer is an empty buffer ready to use.
+type Buffer struct {
+	buf       []byte   // contents are the bytes buf[off : len(buf)]
+	off       int      // read at &buf[off], write at &buf[len(buf)]
+	bootstrap [64]byte // memory to hold first slice; helps small buffers (Printf) avoid allocation.
+}
+
+// Bytes returns a slice of the contents of the unread portion of the buffer;
+// len(b.Bytes()) == b.Len().  If the caller changes the contents of the
+// returned slice, the contents of the buffer will change provided there
+// are no intervening method calls on the Buffer.
+func (b *Buffer) Bytes() []byte { return b.buf[b.off:] }
+
+// String returns the contents of the unread portion of the buffer
+// as a string.  If the Buffer is a nil pointer, it returns "<nil>".
+func (b *Buffer) String() string {
+	if b == nil {
+		// Special case, useful in debugging.
+		return "<nil>"
+	}
+	return string(b.buf[b.off:])
+}
+
+// Len returns the number of bytes of the unread portion of the buffer;
+// b.Len() == len(b.Bytes()).
+func (b *Buffer) Len() int { return len(b.buf) - b.off }
+
+// Truncate discards all but the first n unread bytes from the buffer.
+// It panics if n is negative or greater than the length of the buffer.
+func (b *Buffer) Truncate(n int) {
+	switch {
+	case n < 0 || n > b.Len():
+		panic("leveldb/util.Buffer: truncation out of range")
+	case n == 0:
+		// Reuse buffer space.
+		b.off = 0
+	}
+	b.buf = b.buf[0 : b.off+n]
+}
+
+// Reset resets the buffer so it has no content.
+// b.Reset() is the same as b.Truncate(0).
+func (b *Buffer) Reset() { b.Truncate(0) }
+
+// grow grows the buffer to guarantee space for n more bytes.
+// It returns the index where bytes should be written.
+// If the buffer can't grow it will panic with bytes.ErrTooLarge.
+func (b *Buffer) grow(n int) int {
+	m := b.Len()
+	// If buffer is empty, reset to recover space.
+	if m == 0 && b.off != 0 {
+		b.Truncate(0)
+	}
+	if len(b.buf)+n > cap(b.buf) {
+		var buf []byte
+		if b.buf == nil && n <= len(b.bootstrap) {
+			buf = b.bootstrap[0:]
+		} else if m+n <= cap(b.buf)/2 {
+			// We can slide things down instead of allocating a new
+			// slice. We only need m+n <= cap(b.buf) to slide, but
+			// we instead let capacity get twice as large so we
+			// don't spend all our time copying.
+			copy(b.buf[:], b.buf[b.off:])
+			buf = b.buf[:m]
+		} else {
+			// not enough space anywhere
+			buf = makeSlice(2*cap(b.buf) + n)
+			copy(buf, b.buf[b.off:])
+		}
+		b.buf = buf
+		b.off = 0
+	}
+	b.buf = b.buf[0 : b.off+m+n]
+	return b.off + m
+}
+
+// Alloc allocs n bytes of slice from the buffer, growing the buffer as
+// needed. If n is negative, Alloc will panic.
+// If the buffer can't grow it will panic with bytes.ErrTooLarge.
+func (b *Buffer) Alloc(n int) []byte {
+	if n < 0 {
+		panic("leveldb/util.Buffer.Alloc: negative count")
+	}
+	m := b.grow(n)
+	return b.buf[m:]
+}
+
+// Grow grows the buffer's capacity, if necessary, to guarantee space for
+// another n bytes. After Grow(n), at least n bytes can be written to the
+// buffer without another allocation.
+// If n is negative, Grow will panic.
+// If the buffer can't grow it will panic with bytes.ErrTooLarge.
+func (b *Buffer) Grow(n int) {
+	if n < 0 {
+		panic("leveldb/util.Buffer.Grow: negative count")
+	}
+	m := b.grow(n)
+	b.buf = b.buf[0:m]
+}
+
+// Write appends the contents of p to the buffer, growing the buffer as
+// needed. The return value n is the length of p; err is always nil. If the
+// buffer becomes too large, Write will panic with bytes.ErrTooLarge.
+func (b *Buffer) Write(p []byte) (n int, err error) {
+	m := b.grow(len(p))
+	return copy(b.buf[m:], p), nil
+}
+
+// MinRead is the minimum slice size passed to a Read call by
+// Buffer.ReadFrom.  As long as the Buffer has at least MinRead bytes beyond
+// what is required to hold the contents of r, ReadFrom will not grow the
+// underlying buffer.
+const MinRead = 512
+
+// ReadFrom reads data from r until EOF and appends it to the buffer, growing
+// the buffer as needed. The return value n is the number of bytes read. Any
+// error except io.EOF encountered during the read is also returned. If the
+// buffer becomes too large, ReadFrom will panic with bytes.ErrTooLarge.
+func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
+	// If buffer is empty, reset to recover space.
+	if b.off >= len(b.buf) {
+		b.Truncate(0)
+	}
+	for {
+		if free := cap(b.buf) - len(b.buf); free < MinRead {
+			// not enough space at end
+			newBuf := b.buf
+			if b.off+free < MinRead {
+				// not enough space using beginning of buffer;
+				// double buffer capacity
+				newBuf = makeSlice(2*cap(b.buf) + MinRead)
+			}
+			copy(newBuf, b.buf[b.off:])
+			b.buf = newBuf[:len(b.buf)-b.off]
+			b.off = 0
+		}
+		m, e := r.Read(b.buf[len(b.buf):cap(b.buf)])
+		b.buf = b.buf[0 : len(b.buf)+m]
+		n += int64(m)
+		if e == io.EOF {
+			break
+		}
+		if e != nil {
+			return n, e
+		}
+	}
+	return n, nil // err is EOF, so return nil explicitly
+}
+
+// makeSlice allocates a slice of size n. If the allocation fails, it panics
+// with bytes.ErrTooLarge.
+func makeSlice(n int) []byte {
+	// If the make fails, give a known error.
+	defer func() {
+		if recover() != nil {
+			panic(bytes.ErrTooLarge)
+		}
+	}()
+	return make([]byte, n)
+}
+
+// WriteTo writes data to w until the buffer is drained or an error occurs.
+// The return value n is the number of bytes written; it always fits into an
+// int, but it is int64 to match the io.WriterTo interface. Any error
+// encountered during the write is also returned.
+func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
+	if b.off < len(b.buf) {
+		nBytes := b.Len()
+		m, e := w.Write(b.buf[b.off:])
+		if m > nBytes {
+			panic("leveldb/util.Buffer.WriteTo: invalid Write count")
+		}
+		b.off += m
+		n = int64(m)
+		if e != nil {
+			return n, e
+		}
+		// all bytes should have been written, by definition of
+		// Write method in io.Writer
+		if m != nBytes {
+			return n, io.ErrShortWrite
+		}
+	}
+	// Buffer is now empty; reset.
+	b.Truncate(0)
+	return
+}
+
+// WriteByte appends the byte c to the buffer, growing the buffer as needed.
+// The returned error is always nil, but is included to match bufio.Writer's
+// WriteByte. If the buffer becomes too large, WriteByte will panic with
+// bytes.ErrTooLarge.
+func (b *Buffer) WriteByte(c byte) error {
+	m := b.grow(1)
+	b.buf[m] = c
+	return nil
+}
+
+// Read reads the next len(p) bytes from the buffer or until the buffer
+// is drained.  The return value n is the number of bytes read.  If the
+// buffer has no data to return, err is io.EOF (unless len(p) is zero);
+// otherwise it is nil.
+func (b *Buffer) Read(p []byte) (n int, err error) {
+	if b.off >= len(b.buf) {
+		// Buffer is empty, reset to recover space.
+		b.Truncate(0)
+		if len(p) == 0 {
+			return
+		}
+		return 0, io.EOF
+	}
+	n = copy(p, b.buf[b.off:])
+	b.off += n
+	return
+}
+
+// Next returns a slice containing the next n bytes from the buffer,
+// advancing the buffer as if the bytes had been returned by Read.
+// If there are fewer than n bytes in the buffer, Next returns the entire buffer.
+// The slice is only valid until the next call to a read or write method.
+func (b *Buffer) Next(n int) []byte {
+	m := b.Len()
+	if n > m {
+		n = m
+	}
+	data := b.buf[b.off : b.off+n]
+	b.off += n
+	return data
+}
+
+// ReadByte reads and returns the next byte from the buffer.
+// If no byte is available, it returns error io.EOF.
+func (b *Buffer) ReadByte() (c byte, err error) {
+	if b.off >= len(b.buf) {
+		// Buffer is empty, reset to recover space.
+		b.Truncate(0)
+		return 0, io.EOF
+	}
+	c = b.buf[b.off]
+	b.off++
+	return c, nil
+}
+
+// ReadBytes reads until the first occurrence of delim in the input,
+// returning a slice containing the data up to and including the delimiter.
+// If ReadBytes encounters an error before finding a delimiter,
+// it returns the data read before the error and the error itself (often io.EOF).
+// ReadBytes returns err != nil if and only if the returned data does not end in
+// delim.
+func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
+	slice, err := b.readSlice(delim)
+	// return a copy of slice. The buffer's backing array may
+	// be overwritten by later calls.
+	line = append(line, slice...)
+	return
+}
+
+// readSlice is like ReadBytes but returns a reference to internal buffer data.
+func (b *Buffer) readSlice(delim byte) (line []byte, err error) {
+	i := bytes.IndexByte(b.buf[b.off:], delim)
+	end := b.off + i + 1
+	if i < 0 {
+		end = len(b.buf)
+		err = io.EOF
+	}
+	line = b.buf[b.off:end]
+	b.off = end
+	return line, err
+}
+
+// NewBuffer creates and initializes a new Buffer using buf as its initial
+// contents.  It is intended to prepare a Buffer to read existing data.  It
+// can also be used to size the internal buffer for writing. To do that,
+// buf should have the desired capacity but a length of zero.
+//
+// In most cases, new(Buffer) (or just declaring a Buffer variable) is
+// sufficient to initialize a Buffer.
+func NewBuffer(buf []byte) *Buffer { return &Buffer{buf: buf} }
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go
new file mode 100644
index 000000000..2f3db974a
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go
@@ -0,0 +1,239 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+import (
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+type buffer struct {
+	b    []byte
+	miss int
+}
+
+// BufferPool is a 'buffer pool'.
+type BufferPool struct {
+	pool      [6]chan []byte
+	size      [5]uint32
+	sizeMiss  [5]uint32
+	sizeHalf  [5]uint32
+	baseline  [4]int
+	baseline0 int
+
+	mu     sync.RWMutex
+	closed bool
+	closeC chan struct{}
+
+	get     uint32
+	put     uint32
+	half    uint32
+	less    uint32
+	equal   uint32
+	greater uint32
+	miss    uint32
+}
+
+func (p *BufferPool) poolNum(n int) int {
+	if n <= p.baseline0 && n > p.baseline0/2 {
+		return 0
+	}
+	for i, x := range p.baseline {
+		if n <= x {
+			return i + 1
+		}
+	}
+	return len(p.baseline) + 1
+}
+
+// Get returns buffer with length of n.
+func (p *BufferPool) Get(n int) []byte {
+	if p == nil {
+		return make([]byte, n)
+	}
+
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	if p.closed {
+		return make([]byte, n)
+	}
+
+	atomic.AddUint32(&p.get, 1)
+
+	poolNum := p.poolNum(n)
+	pool := p.pool[poolNum]
+	if poolNum == 0 {
+		// Fast path.
+		select {
+		case b := <-pool:
+			switch {
+			case cap(b) > n:
+				if cap(b)-n >= n {
+					atomic.AddUint32(&p.half, 1)
+					select {
+					case pool <- b:
+					default:
+					}
+					return make([]byte, n)
+				} else {
+					atomic.AddUint32(&p.less, 1)
+					return b[:n]
+				}
+			case cap(b) == n:
+				atomic.AddUint32(&p.equal, 1)
+				return b[:n]
+			default:
+				atomic.AddUint32(&p.greater, 1)
+			}
+		default:
+			atomic.AddUint32(&p.miss, 1)
+		}
+
+		return make([]byte, n, p.baseline0)
+	} else {
+		sizePtr := &p.size[poolNum-1]
+
+		select {
+		case b := <-pool:
+			switch {
+			case cap(b) > n:
+				if cap(b)-n >= n {
+					atomic.AddUint32(&p.half, 1)
+					sizeHalfPtr := &p.sizeHalf[poolNum-1]
+					if atomic.AddUint32(sizeHalfPtr, 1) == 20 {
+						atomic.StoreUint32(sizePtr, uint32(cap(b)/2))
+						atomic.StoreUint32(sizeHalfPtr, 0)
+					} else {
+						select {
+						case pool <- b:
+						default:
+						}
+					}
+					return make([]byte, n)
+				} else {
+					atomic.AddUint32(&p.less, 1)
+					return b[:n]
+				}
+			case cap(b) == n:
+				atomic.AddUint32(&p.equal, 1)
+				return b[:n]
+			default:
+				atomic.AddUint32(&p.greater, 1)
+				if uint32(cap(b)) >= atomic.LoadUint32(sizePtr) {
+					select {
+					case pool <- b:
+					default:
+					}
+				}
+			}
+		default:
+			atomic.AddUint32(&p.miss, 1)
+		}
+
+		if size := atomic.LoadUint32(sizePtr); uint32(n) > size {
+			if size == 0 {
+				atomic.CompareAndSwapUint32(sizePtr, 0, uint32(n))
+			} else {
+				sizeMissPtr := &p.sizeMiss[poolNum-1]
+				if atomic.AddUint32(sizeMissPtr, 1) == 20 {
+					atomic.StoreUint32(sizePtr, uint32(n))
+					atomic.StoreUint32(sizeMissPtr, 0)
+				}
+			}
+			return make([]byte, n)
+		} else {
+			return make([]byte, n, size)
+		}
+	}
+}
+
+// Put adds given buffer to the pool.
+func (p *BufferPool) Put(b []byte) {
+	if p == nil {
+		return
+	}
+
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	if p.closed {
+		return
+	}
+
+	atomic.AddUint32(&p.put, 1)
+
+	pool := p.pool[p.poolNum(cap(b))]
+	select {
+	case pool <- b:
+	default:
+	}
+
+}
+
+func (p *BufferPool) Close() {
+	if p == nil {
+		return
+	}
+
+	p.mu.Lock()
+	if !p.closed {
+		p.closed = true
+		p.closeC <- struct{}{}
+	}
+	p.mu.Unlock()
+}
+
+func (p *BufferPool) String() string {
+	if p == nil {
+		return "<nil>"
+	}
+
+	return fmt.Sprintf("BufferPool{B·%d Z·%v Zm·%v Zh·%v G·%d P·%d H·%d <·%d =·%d >·%d M·%d}",
+		p.baseline0, p.size, p.sizeMiss, p.sizeHalf, p.get, p.put, p.half, p.less, p.equal, p.greater, p.miss)
+}
+
+func (p *BufferPool) drain() {
+	ticker := time.NewTicker(2 * time.Second)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			for _, ch := range p.pool {
+				select {
+				case <-ch:
+				default:
+				}
+			}
+		case <-p.closeC:
+			close(p.closeC)
+			for _, ch := range p.pool {
+				close(ch)
+			}
+			return
+		}
+	}
+}
+
+// NewBufferPool creates a new initialized 'buffer pool'.
+func NewBufferPool(baseline int) *BufferPool {
+	if baseline <= 0 {
+		panic("baseline can't be <= 0")
+	}
+	p := &BufferPool{
+		baseline0: baseline,
+		baseline:  [...]int{baseline / 4, baseline / 2, baseline * 2, baseline * 4},
+		closeC:    make(chan struct{}, 1),
+	}
+	for i, cap := range []int{2, 2, 4, 4, 2, 1} {
+		p.pool[i] = make(chan []byte, cap)
+	}
+	go p.drain()
+	return p
+}
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/crc32.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/crc32.go
new file mode 100644
index 000000000..631c9d610
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/crc32.go
@@ -0,0 +1,30 @@
+// Copyright 2011 The LevelDB-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 util
+
+import (
+	"hash/crc32"
+)
+
+var table = crc32.MakeTable(crc32.Castagnoli)
+
+// CRC is a CRC-32 checksum computed using Castagnoli's polynomial.
+type CRC uint32
+
+// NewCRC creates a new crc based on the given bytes.
+func NewCRC(b []byte) CRC {
+	return CRC(0).Update(b)
+}
+
+// Update updates the crc with the given bytes.
+func (c CRC) Update(b []byte) CRC {
+	return CRC(crc32.Update(uint32(c), table, b))
+}
+
+// Value returns a masked crc.
+func (c CRC) Value() uint32 {
+	return uint32(c>>15|c<<17) + 0xa282ead8
+}
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/hash.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/hash.go
new file mode 100644
index 000000000..7f3fa4e2c
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/hash.go
@@ -0,0 +1,48 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+import (
+	"encoding/binary"
+)
+
+// Hash return hash of the given data.
+func Hash(data []byte, seed uint32) uint32 {
+	// Similar to murmur hash
+	const (
+		m = uint32(0xc6a4a793)
+		r = uint32(24)
+	)
+	var (
+		h = seed ^ (uint32(len(data)) * m)
+		i int
+	)
+
+	for n := len(data) - len(data)%4; i < n; i += 4 {
+		h += binary.LittleEndian.Uint32(data[i:])
+		h *= m
+		h ^= (h >> 16)
+	}
+
+	switch len(data) - i {
+	default:
+		panic("not reached")
+	case 3:
+		h += uint32(data[i+2]) << 16
+		fallthrough
+	case 2:
+		h += uint32(data[i+1]) << 8
+		fallthrough
+	case 1:
+		h += uint32(data[i])
+		h *= m
+		h ^= (h >> r)
+	case 0:
+	}
+
+	return h
+}
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/range.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/range.go
new file mode 100644
index 000000000..85159583d
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/range.go
@@ -0,0 +1,32 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+// Range is a key range.
+type Range struct {
+	// Start of the key range, include in the range.
+	Start []byte
+
+	// Limit of the key range, not include in the range.
+	Limit []byte
+}
+
+// BytesPrefix returns key range that satisfy the given prefix.
+// This only applicable for the standard 'bytes comparer'.
+func BytesPrefix(prefix []byte) *Range {
+	var limit []byte
+	for i := len(prefix) - 1; i >= 0; i-- {
+		c := prefix[i]
+		if c < 0xff {
+			limit = make([]byte, i+1)
+			copy(limit, prefix)
+			limit[i] = c + 1
+			break
+		}
+	}
+	return &Range{prefix, limit}
+}
diff --git a/vendor/github.com/syndtr/goleveldb/leveldb/util/util.go b/vendor/github.com/syndtr/goleveldb/leveldb/util/util.go
new file mode 100644
index 000000000..f35976865
--- /dev/null
+++ b/vendor/github.com/syndtr/goleveldb/leveldb/util/util.go
@@ -0,0 +1,73 @@
+// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package util provides utilities used throughout leveldb.
+package util
+
+import (
+	"errors"
+)
+
+var (
+	ErrReleased    = errors.New("leveldb: resource already relesed")
+	ErrHasReleaser = errors.New("leveldb: releaser already defined")
+)
+
+// Releaser is the interface that wraps the basic Release method.
+type Releaser interface {
+	// Release releases associated resources. Release should always success
+	// and can be called multipe times without causing error.
+	Release()
+}
+
+// ReleaseSetter is the interface that wraps the basic SetReleaser method.
+type ReleaseSetter interface {
+	// SetReleaser associates the given releaser to the resources. The
+	// releaser will be called once coresponding resources released.
+	// Calling SetReleaser with nil will clear the releaser.
+	//
+	// This will panic if a releaser already present or coresponding
+	// resource is already released. Releaser should be cleared first
+	// before assigned a new one.
+	SetReleaser(releaser Releaser)
+}
+
+// BasicReleaser provides basic implementation of Releaser and ReleaseSetter.
+type BasicReleaser struct {
+	releaser Releaser
+	released bool
+}
+
+// Released returns whether Release method already called.
+func (r *BasicReleaser) Released() bool {
+	return r.released
+}
+
+// Release implements Releaser.Release.
+func (r *BasicReleaser) Release() {
+	if !r.released {
+		if r.releaser != nil {
+			r.releaser.Release()
+			r.releaser = nil
+		}
+		r.released = true
+	}
+}
+
+// SetReleaser implements ReleaseSetter.SetReleaser.
+func (r *BasicReleaser) SetReleaser(releaser Releaser) {
+	if r.released {
+		panic(ErrReleased)
+	}
+	if r.releaser != nil && releaser != nil {
+		panic(ErrHasReleaser)
+	}
+	r.releaser = releaser
+}
+
+type NoopReleaser struct{}
+
+func (NoopReleaser) Release() {}