// Package ioutil contains various constructs for io operations
package ioutil
import (
"io"
)
// An function alias type that implements io.Writer
type WriterFunc func([]byte) (int, error)
// Delegates the call to the WriterFunc while implementing io.Writer
func (w WriterFunc) Write(b []byte) (int, error) {
return w(b)
}
// An function alias type that implements io.Reader
type ReaderFunc func([]byte) (int, error)
// Delegates the call to the WriterFunc while implementing io.Reader
func (r ReaderFunc) Read(b []byte) (int, error) {
return r(b)
}
// Returns a reader that will delegate calls to Read(...) while ensuring
// that the output buffer will never be smaller than the required size
func MinReader(reader io.Reader, size int) io.Reader {
var buffer []byte = make([]byte, 0, size)
return ReaderFunc(func(output []byte) (readCount int, e error) {
var (
bufferLength int = len(buffer)
err error
)
start:
// Reply with the buffered data if there is any
if bufferLength > 0 {
readCount = copy(output, buffer)
if readCount < bufferLength {
// Advance the data in the buffer
buffer = buffer[:copy(buffer, buffer[readCount:])]
} else {
// Clear the buffer
buffer = buffer[:0]
}
// Stage any error for returning
e, err = err, nil
return readCount, e
}
// Delegate if the buffer is empty and the destination buffer is large enough
if len(output) >= size {
return reader.Read(output[:len(output)/size])
}
// Extend the buffer up to the desired size and perform a Read
buffer = buffer[:size]
readCount, err = reader.Read(buffer)
// Size the buffer down to the read data size and restart
buffer = buffer[:readCount]
bufferLength = len(buffer)
if bufferLength > 0 {
goto start
}
// Stage any error for returning
e, err = err, nil
return 0, e
})
}