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// 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 arrio exposes functions to manipulate records, exposing and using
// interfaces not unlike the ones defined in the stdlib io package.
package arrio
import (
"errors"
"io"
"github.com/apache/arrow-go/v18/arrow"
)
// Reader is the interface that wraps the Read method.
type Reader interface {
// Read reads the current record from the underlying stream and an error, if any.
// When the Reader reaches the end of the underlying stream, it returns (nil, io.EOF).
Read() (arrow.Record, error)
}
// ReaderAt is the interface that wraps the ReadAt method.
type ReaderAt interface {
// ReadAt reads the i-th record from the underlying stream and an error, if any.
ReadAt(i int64) (arrow.Record, error)
}
// Writer is the interface that wraps the Write method.
type Writer interface {
Write(rec arrow.Record) error
}
// Copy copies all the records available from src to dst.
// Copy returns the number of records copied and the first error
// encountered while copying, if any.
//
// A successful Copy returns err == nil, not err == EOF. Because Copy is
// defined to read from src until EOF, it does not treat an EOF from Read as an
// error to be reported.
func Copy(dst Writer, src Reader) (n int64, err error) {
for {
rec, err := src.Read()
if err != nil {
if errors.Is(err, io.EOF) {
return n, nil
}
return n, err
}
err = dst.Write(rec)
if err != nil {
return n, err
}
n++
}
}
// CopyN copies n records (or until an error) from src to dst. It returns the
// number of records copied and the earliest error encountered while copying. On
// return, written == n if and only if err == nil.
func CopyN(dst Writer, src Reader, n int64) (written int64, err error) {
for ; written < n; written++ {
rec, err := src.Read()
if err != nil {
if errors.Is(err, io.EOF) && written == n {
return written, nil
}
return written, err
}
err = dst.Write(rec)
if err != nil {
return written, err
}
}
if written != n && err == nil {
err = io.EOF
}
return written, err
}
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