Reader interface
// Reader is the interface that wraps the basic Read method.
//
// Read reads up to len(p) bytes into p. It returns the number of bytes
// read (0 <= n <= len(p)) and any error encountered. Even if Read
// returns n < len(p), it may use all of p as scratch space during the call.
// If some data is available but not len(p) bytes, Read conventionally
// returns what is available instead of waiting for more.
//
// When Read encounters an error or end-of-file condition after
// successfully reading n > 0 bytes, it returns the number of
// bytes read. It may return the (non-nil) error from the same call
// or return the error (and n == 0) from a subsequent call.
// An instance of this general case is that a Reader returning
// a non-zero number of bytes at the end of the input stream may
// return either err == EOF or err == nil. The next Read should
// return 0, EOF.
//
// Callers should always process the n > 0 bytes returned before
// considering the error err. Doing so correctly handles I/O errors
// that happen after reading some bytes and also both of the
// allowed EOF behaviors.
//
// Implementations of Read are discouraged from returning a
// zero byte count with a nil error, except when len(p) == 0.
// Callers should treat a return of 0 and nil as indicating that
// nothing happened; in particular it does not indicate EOF.
//
// Implementations must not retain p.
type Reader interface {
Read(p []byte) (n int, err error)
}
Writer interface
// Writer is the interface that wraps the basic Write method.
//
// Write writes len(p) bytes from p to the underlying data stream.
// It returns the number of bytes written from p (0 <= n <= len(p))
// and any error encountered that caused the write to stop early.
// Write must return a non-nil error if it returns n < len(p).
// Write must not modify the slice data, even temporarily.
//
// Implementations must not retain p.
type Writer interface {
Write(p []byte) (n int, err error)
}
Closer interface
// Closer is the interface that wraps the basic Close method.
//
// The behavior of Close after the first call is undefined.
// Specific implementations may document their own behavior.
type Closer interface {
Close() error
}
Seeker Interface
// Seeker is the interface that wraps the basic Seek method.
//
// Seek sets the offset for the next Read or Write to offset,
// interpreted according to whence:
// SeekStart means relative to the start of the file,
// SeekCurrent means relative to the current offset, and
// SeekEnd means relative to the end.
// Seek returns the new offset relative to the start of the
// file and an error, if any.
//
// Seeking to an offset before the start of the file is an error.
// Seeking to any positive offset is legal, but the behavior of subsequent
// I/O operations on the underlying object is implementation-dependent.
type Seeker interface {
Seek(offset int64, whence int) (int64, error)
}
Reference