78 lines
1.8 KiB
Go
78 lines
1.8 KiB
Go
package util
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import (
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"encoding/binary"
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"errors"
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"io"
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)
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//BinWriter is a convenient wrapper around a io.Writer and err object
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// Used to simplify error handling when writing into a io.Writer
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// from a struct with many fields
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type BinWriter struct {
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W io.Writer
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Err error
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}
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// WriteLE writes into the underlying io.Writer from an object v in little-endian format
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func (w *BinWriter) WriteLE(v interface{}) {
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if w.Err != nil {
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return
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}
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w.Err = binary.Write(w.W, binary.LittleEndian, v)
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}
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// WriteBE writes into the underlying io.Writer from an object v in big-endian format
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func (w *BinWriter) WriteBE(v interface{}) {
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if w.Err != nil {
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return
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}
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w.Err = binary.Write(w.W, binary.BigEndian, v)
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}
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// WriteVarUint writes a uint64 into the underlying writer using variable-length encoding
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func (w *BinWriter) WriteVarUint(val uint64) {
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if w.Err != nil {
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return
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}
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if val < 0 {
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w.Err = errors.New("value out of range")
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return
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}
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if w.Err != nil {
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return
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}
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if val < 0xfd {
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w.Err = binary.Write(w.W, binary.LittleEndian, uint8(val))
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return
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}
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if val < 0xFFFF {
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w.Err = binary.Write(w.W, binary.LittleEndian, byte(0xfd))
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w.Err = binary.Write(w.W, binary.LittleEndian, uint16(val))
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return
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}
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if val < 0xFFFFFFFF {
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w.Err = binary.Write(w.W, binary.LittleEndian, byte(0xfe))
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w.Err = binary.Write(w.W, binary.LittleEndian, uint32(val))
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return
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}
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w.Err = binary.Write(w.W, binary.LittleEndian, byte(0xff))
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w.Err = binary.Write(w.W, binary.LittleEndian, val)
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}
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// WriteBytes writes a variable length byte array into the underlying io.Writer
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func (w *BinWriter) WriteBytes(b []byte) {
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w.WriteVarUint(uint64(len(b)))
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w.WriteLE(b)
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}
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// WriteString writes a variable length string into the underlying io.Writer
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func (w *BinWriter) WriteString(s string) {
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w.WriteBytes([]byte(s))
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}
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