From 03653db5a59cd88b481403d312d7c324b56af377 Mon Sep 17 00:00:00 2001
From: Ox Cart <ox.to.a.cart@gmail.com>
Date: Thu, 30 May 2019 12:17:43 -0500
Subject: [PATCH] Added ByteSlice and ByteSlicePool

---
 bytepool.go       |  1 +
 byteslice.go      | 81 +++++++++++++++++++++++++++++++++++++++++++++++
 byteslice_test.go | 38 ++++++++++++++++++++++
 go.mod            |  5 +++
 go.sum            |  7 ++++
 5 files changed, 132 insertions(+)
 create mode 100644 byteslice.go
 create mode 100644 byteslice_test.go
 create mode 100644 go.mod
 create mode 100644 go.sum

diff --git a/bytepool.go b/bytepool.go
index deda16a..a5ebe05 100644
--- a/bytepool.go
+++ b/bytepool.go
@@ -5,6 +5,7 @@ package bpool
 type BytePool struct {
 	c chan []byte
 	w int
+	h int
 }
 
 // NewBytePool creates a new BytePool bounded to the given maxSize, with new
diff --git a/byteslice.go b/byteslice.go
new file mode 100644
index 0000000..7b94b39
--- /dev/null
+++ b/byteslice.go
@@ -0,0 +1,81 @@
+package bpool
+
+// WrapByteSlice wraps a []byte as a ByteSlice
+func WrapByteSlice(full []byte, headerLength int) ByteSlice {
+	return ByteSlice{
+		full:    full,
+		current: full[headerLength:],
+		head:    headerLength,
+		end:     len(full),
+	}
+}
+
+// ByteSlice provides a wrapper around []byte with some added convenience
+type ByteSlice struct {
+	full    []byte
+	current []byte
+	head    int
+	end     int
+}
+
+// ResliceTo reslices the end of the current slice.
+func (b ByteSlice) ResliceTo(end int) ByteSlice {
+	return ByteSlice{
+		full:    b.full,
+		current: b.current[:end],
+		head:    b.head,
+		end:     b.head + end,
+	}
+}
+
+// Bytes returns the current slice
+func (b ByteSlice) Bytes() []byte {
+	return b.current
+}
+
+// BytesWithHeader returns the current slice preceded by the header
+func (b ByteSlice) BytesWithHeader() []byte {
+	return b.full[:b.end]
+}
+
+// Full returns the full original buffer underlying the ByteSlice
+func (b ByteSlice) Full() []byte {
+	return b.full
+}
+
+// ByteSlicePool is a bool of byte slices
+type ByteSlicePool interface {
+	// Get gets a byte slice from the pool
+	GetSlice() ByteSlice
+	// Put returns a byte slice to the pool
+	PutSlice(ByteSlice)
+	// NumPooled returns the number of currently pooled items
+	NumPooled() int
+}
+
+// NewByteSlicePool creates a new ByteSlicePool bounded to the
+// given maxSize, with new byte arrays sized based on width
+func NewByteSlicePool(maxSize int, width int) ByteSlicePool {
+	return NewHeaderPreservingByteSlicePool(maxSize, width, 0)
+}
+
+// NewHeaderPreservingByteSlicePool creates a new ByteSlicePool bounded to the
+// given maxSize, with new byte arrays sized based on width and headerLength
+// preserved at the beginning of the slice.
+func NewHeaderPreservingByteSlicePool(maxSize int, width int, headerLength int) ByteSlicePool {
+	return &BytePool{
+		c: make(chan []byte, maxSize),
+		w: width + headerLength,
+		h: headerLength,
+	}
+}
+
+// GetSlice implements the method from interface ByteSlicePool
+func (bp *BytePool) GetSlice() ByteSlice {
+	return WrapByteSlice(bp.Get(), bp.h)
+}
+
+// PutSlice implements the method from interface ByteSlicePool
+func (bp *BytePool) PutSlice(b ByteSlice) {
+	bp.Put(b.Full())
+}
diff --git a/byteslice_test.go b/byteslice_test.go
new file mode 100644
index 0000000..f7fc31a
--- /dev/null
+++ b/byteslice_test.go
@@ -0,0 +1,38 @@
+package bpool
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestByteSlice(t *testing.T) {
+	full := []byte("abcde")
+	bs := WrapByteSlice(full, 1)
+	assert.EqualValues(t, full[1:], bs.Bytes())
+	assert.EqualValues(t, full, bs.BytesWithHeader())
+	assert.EqualValues(t, full, bs.Full())
+	bs = bs.ResliceTo(2)
+	assert.EqualValues(t, full[1:3], bs.Bytes())
+	assert.EqualValues(t, full[:3], bs.BytesWithHeader())
+	assert.EqualValues(t, full, bs.Full())
+	bs = bs.ResliceTo(1)
+	assert.EqualValues(t, full[1:2], bs.Bytes())
+	assert.EqualValues(t, full[:2], bs.BytesWithHeader())
+	assert.EqualValues(t, full, bs.Full())
+
+}
+
+func TestHeaderPreservingByteSlicePool(t *testing.T) {
+	full := []byte{0, 0, 'a', 'b', 'c'}
+	data := full[2:]
+	pool := NewHeaderPreservingByteSlicePool(1, 3, 2)
+	b := pool.GetSlice()
+	copy(b.Bytes(), data)
+	assert.Equal(t, data, b.Bytes())
+	assert.Equal(t, full, b.Full())
+	pool.PutSlice(b)
+	assert.Equal(t, 1, pool.NumPooled())
+	pool.PutSlice(WrapByteSlice(full, 2))
+	assert.Equal(t, 1, pool.NumPooled(), "Pool should not grow beyond its size limit")
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..9bb3147
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/oxtoacart/bpool
+
+go 1.12
+
+require github.com/stretchr/testify v1.3.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..4347755
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,7 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=