| // 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 array |
| |
| import ( |
| "sync/atomic" |
| |
| "github.com/apache/arrow/go/arrow/bitutil" |
| "github.com/apache/arrow/go/arrow/internal/debug" |
| "github.com/apache/arrow/go/arrow/memory" |
| ) |
| |
| // A bufferBuilder provides common functionality for populating memory with a sequence of type-specific values. |
| // Specialized implementations provide type-safe APIs for appending and accessing the memory. |
| type bufferBuilder struct { |
| refCount int64 |
| mem memory.Allocator |
| buffer *memory.Buffer |
| length int |
| capacity int |
| |
| bytes []byte |
| } |
| |
| // Retain increases the reference count by 1. |
| // Retain may be called simultaneously from multiple goroutines. |
| func (b *bufferBuilder) Retain() { |
| atomic.AddInt64(&b.refCount, 1) |
| } |
| |
| // Release decreases the reference count by 1. |
| // When the reference count goes to zero, the memory is freed. |
| // Release may be called simultaneously from multiple goroutines. |
| func (b *bufferBuilder) Release() { |
| debug.Assert(atomic.LoadInt64(&b.refCount) > 0, "too many releases") |
| |
| if atomic.AddInt64(&b.refCount, -1) == 0 { |
| if b.buffer != nil { |
| b.buffer.Release() |
| b.buffer, b.bytes = nil, nil |
| } |
| } |
| } |
| |
| // Len returns the length of the memory buffer in bytes. |
| func (b *bufferBuilder) Len() int { return b.length } |
| |
| // Cap returns the total number of bytes that can be stored without allocating additional memory. |
| func (b *bufferBuilder) Cap() int { return b.capacity } |
| |
| // Bytes returns a slice of length b.Len(). |
| // The slice is only valid for use until the next buffer modification. That is, until the next call |
| // to Advance, Reset, Finish or any Append function. The slice aliases the buffer content at least until the next |
| // buffer modification. |
| func (b *bufferBuilder) Bytes() []byte { return b.bytes[:b.length] } |
| |
| func (b *bufferBuilder) resize(elements int) { |
| if b.buffer == nil { |
| b.buffer = memory.NewResizableBuffer(b.mem) |
| } |
| |
| b.buffer.Resize(elements) |
| oldCapacity := b.capacity |
| b.capacity = b.buffer.Cap() |
| b.bytes = b.buffer.Buf() |
| |
| if b.capacity > oldCapacity { |
| memory.Set(b.bytes[oldCapacity:], 0) |
| } |
| } |
| |
| // Advance increases the buffer by length and initializes the skipped bytes to zero. |
| func (b *bufferBuilder) Advance(length int) { |
| if b.capacity < b.length+length { |
| newCapacity := bitutil.NextPowerOf2(b.length + length) |
| b.resize(newCapacity) |
| } |
| b.length += length |
| } |
| |
| // Append appends the contents of v to the buffer, resizing it if necessary. |
| func (b *bufferBuilder) Append(v []byte) { |
| if b.capacity < b.length+len(v) { |
| newCapacity := bitutil.NextPowerOf2(b.length + len(v)) |
| b.resize(newCapacity) |
| } |
| b.unsafeAppend(v) |
| } |
| |
| // Reset returns the buffer to an empty state. Reset releases the memory and sets the length and capacity to zero. |
| func (b *bufferBuilder) Reset() { |
| if b.buffer != nil { |
| b.buffer.Release() |
| } |
| b.buffer, b.bytes = nil, nil |
| b.capacity, b.length = 0, 0 |
| } |
| |
| // Finish TODO(sgc) |
| func (b *bufferBuilder) Finish() (buffer *memory.Buffer) { |
| if b.length > 0 { |
| b.buffer.ResizeNoShrink(b.length) |
| } |
| buffer = b.buffer |
| b.buffer = nil |
| b.Reset() |
| return |
| } |
| |
| func (b *bufferBuilder) unsafeAppend(data []byte) { |
| copy(b.bytes[b.length:], data) |
| b.length += len(data) |
| } |