147 lines
3.1 KiB
Go
147 lines
3.1 KiB
Go
package rifs
|
|
|
|
import (
|
|
"io"
|
|
"os"
|
|
|
|
"github.com/dsoprea/go-logging"
|
|
)
|
|
|
|
// SeekableBuffer is a simple memory structure that satisfies
|
|
// `io.ReadWriteSeeker`.
|
|
type SeekableBuffer struct {
|
|
data []byte
|
|
position int64
|
|
}
|
|
|
|
// NewSeekableBuffer is a factory that returns a `*SeekableBuffer`.
|
|
func NewSeekableBuffer() *SeekableBuffer {
|
|
data := make([]byte, 0)
|
|
|
|
return &SeekableBuffer{
|
|
data: data,
|
|
}
|
|
}
|
|
|
|
// NewSeekableBufferWithBytes is a factory that returns a `*SeekableBuffer`.
|
|
func NewSeekableBufferWithBytes(originalData []byte) *SeekableBuffer {
|
|
data := make([]byte, len(originalData))
|
|
copy(data, originalData)
|
|
|
|
return &SeekableBuffer{
|
|
data: data,
|
|
}
|
|
}
|
|
|
|
func len64(data []byte) int64 {
|
|
return int64(len(data))
|
|
}
|
|
|
|
// Bytes returns the underlying slice.
|
|
func (sb *SeekableBuffer) Bytes() []byte {
|
|
return sb.data
|
|
}
|
|
|
|
// Len returns the number of bytes currently stored.
|
|
func (sb *SeekableBuffer) Len() int {
|
|
return len(sb.data)
|
|
}
|
|
|
|
// Write does a standard write to the internal slice.
|
|
func (sb *SeekableBuffer) Write(p []byte) (n int, err error) {
|
|
defer func() {
|
|
if state := recover(); state != nil {
|
|
err = log.Wrap(state.(error))
|
|
}
|
|
}()
|
|
|
|
// The current position we're already at is past the end of the data we
|
|
// actually have. Extend our buffer up to our current position.
|
|
if sb.position > len64(sb.data) {
|
|
extra := make([]byte, sb.position-len64(sb.data))
|
|
sb.data = append(sb.data, extra...)
|
|
}
|
|
|
|
positionFromEnd := len64(sb.data) - sb.position
|
|
tailCount := positionFromEnd - len64(p)
|
|
|
|
var tailBytes []byte
|
|
if tailCount > 0 {
|
|
tailBytes = sb.data[len64(sb.data)-tailCount:]
|
|
sb.data = append(sb.data[:sb.position], p...)
|
|
} else {
|
|
sb.data = append(sb.data[:sb.position], p...)
|
|
}
|
|
|
|
if tailBytes != nil {
|
|
sb.data = append(sb.data, tailBytes...)
|
|
}
|
|
|
|
dataSize := len64(p)
|
|
sb.position += dataSize
|
|
|
|
return int(dataSize), nil
|
|
}
|
|
|
|
// Read does a standard read against the internal slice.
|
|
func (sb *SeekableBuffer) Read(p []byte) (n int, err error) {
|
|
defer func() {
|
|
if state := recover(); state != nil {
|
|
err = log.Wrap(state.(error))
|
|
}
|
|
}()
|
|
|
|
if sb.position >= len64(sb.data) {
|
|
return 0, io.EOF
|
|
}
|
|
|
|
n = copy(p, sb.data[sb.position:])
|
|
sb.position += int64(n)
|
|
|
|
return n, nil
|
|
}
|
|
|
|
// Truncate either chops or extends the internal buffer.
|
|
func (sb *SeekableBuffer) Truncate(size int64) (err error) {
|
|
defer func() {
|
|
if state := recover(); state != nil {
|
|
err = log.Wrap(state.(error))
|
|
}
|
|
}()
|
|
|
|
sizeInt := int(size)
|
|
if sizeInt < len(sb.data)-1 {
|
|
sb.data = sb.data[:sizeInt]
|
|
} else {
|
|
new := make([]byte, sizeInt-len(sb.data))
|
|
sb.data = append(sb.data, new...)
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// Seek does a standard seek on the internal slice.
|
|
func (sb *SeekableBuffer) Seek(offset int64, whence int) (n int64, err error) {
|
|
defer func() {
|
|
if state := recover(); state != nil {
|
|
err = log.Wrap(state.(error))
|
|
}
|
|
}()
|
|
|
|
if whence == os.SEEK_SET {
|
|
sb.position = offset
|
|
} else if whence == os.SEEK_END {
|
|
sb.position = len64(sb.data) + offset
|
|
} else if whence == os.SEEK_CUR {
|
|
sb.position += offset
|
|
} else {
|
|
log.Panicf("seek whence is not valid: (%d)", whence)
|
|
}
|
|
|
|
if sb.position < 0 {
|
|
sb.position = 0
|
|
}
|
|
|
|
return sb.position, nil
|
|
}
|