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lib.go
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lib.go
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package bstruct
import (
"encoding/binary"
"unsafe"
)
//go:noescape
//go:linkname memmove runtime.memmove
func memmove(to, from unsafe.Pointer, n uintptr)
type Reader struct {
data []byte
pos int
}
func NewReader(data []byte) *Reader {
return &Reader{data: data}
}
func (r *Reader) Data() []byte {
return r.data
}
func (r *Reader) Pos() int {
return r.pos
}
func (r *Reader) ReadLen() int {
l, off := binary.Varint(r.data[r.pos:])
r.pos += off
return int(l)
}
func (r *Reader) Copy(ptr unsafe.Pointer, length int) {
memmove(ptr, unsafe.Pointer(&r.data[r.pos]), uintptr(length))
r.pos += length
}
func (r *Reader) Read(length int) uintptr {
ptr := uintptr(unsafe.Pointer(&r.data[r.pos]))
r.pos += length
return ptr
}
type Writer struct {
data []byte
pos int
}
func NewWriter() *Writer {
return &Writer{data: make([]byte, 16)}
}
func (w *Writer) grow(length int) {
rem := len(w.data) - w.pos
if rem >= length {
w.data = w.data[:len(w.data)]
return
}
w.data = append(w.data, make([]byte, cap(w.data))...)
}
func (w *Writer) Data() []byte {
return w.data
}
func (w *Writer) WriteLen(length int) {
w.grow(9)
w.pos += binary.PutVarint(w.data[w.pos:], int64(length))
}
func (w *Writer) Copy(ptr unsafe.Pointer, length int) {
w.grow(length)
memmove(unsafe.Pointer(&w.data[w.pos]), ptr, uintptr(length))
w.pos += length
}