arrow/memory/go_allocator.go

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package memory

// GoAllocator is an Allocator backed by the Go heap. Buffers it returns start
// at a 64-byte boundary; Free is a no-op because the garbage collector reclaims
// the memory. Its buffers must not be retained by C code beyond a single cgo
// call; see the package documentation for allocators that return C memory.
type GoAllocator struct{}

// NewGoAllocator returns a GoAllocator.
func NewGoAllocator() *GoAllocator { return &GoAllocator{} }

func (a *GoAllocator) Allocate(size int) []byte {
	buf := make([]byte, size+alignment) // padding for 64-byte alignment
	addr := int(addressOf(buf))
	next := roundUpToMultipleOf64(addr)
	shift := next - addr
	return buf[shift : size+shift : size+shift]
}

func (a *GoAllocator) Reallocate(size int, b []byte) []byte {
	if cap(b) >= size {
		return b[:size]
	}
	newBuf := a.Allocate(size)
	copy(newBuf, b)
	return newBuf
}

func (a *GoAllocator) Free(b []byte) {}

var (
	_ Allocator = (*GoAllocator)(nil)
)