90 lines
2.0 KiB
Go
90 lines
2.0 KiB
Go
package utils
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import (
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"bytes"
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"io"
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)
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// BigEndian is the big-endian implementation of ByteOrder.
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var BigEndian ByteOrder = bigEndian{}
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type bigEndian struct{}
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var _ ByteOrder = &bigEndian{}
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// ReadUintN reads N bytes
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func (bigEndian) ReadUintN(b io.ByteReader, length uint8) (uint64, error) {
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var res uint64
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for i := uint8(0); i < length; i++ {
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bt, err := b.ReadByte()
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if err != nil {
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return 0, err
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}
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res ^= uint64(bt) << ((length - 1 - i) * 8)
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}
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return res, nil
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}
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// ReadUint32 reads a uint32
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func (bigEndian) ReadUint32(b io.ByteReader) (uint32, error) {
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var b1, b2, b3, b4 uint8
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var err error
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if b4, err = b.ReadByte(); err != nil {
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return 0, err
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}
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if b3, err = b.ReadByte(); err != nil {
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return 0, err
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}
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if b2, err = b.ReadByte(); err != nil {
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return 0, err
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}
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if b1, err = b.ReadByte(); err != nil {
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return 0, err
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}
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return uint32(b1) + uint32(b2)<<8 + uint32(b3)<<16 + uint32(b4)<<24, nil
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}
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// ReadUint24 reads a uint24
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func (bigEndian) ReadUint24(b io.ByteReader) (uint32, error) {
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var b1, b2, b3 uint8
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var err error
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if b3, err = b.ReadByte(); err != nil {
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return 0, err
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}
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if b2, err = b.ReadByte(); err != nil {
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return 0, err
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}
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if b1, err = b.ReadByte(); err != nil {
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return 0, err
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}
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return uint32(b1) + uint32(b2)<<8 + uint32(b3)<<16, nil
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}
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// ReadUint16 reads a uint16
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func (bigEndian) ReadUint16(b io.ByteReader) (uint16, error) {
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var b1, b2 uint8
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var err error
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if b2, err = b.ReadByte(); err != nil {
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return 0, err
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}
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if b1, err = b.ReadByte(); err != nil {
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return 0, err
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}
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return uint16(b1) + uint16(b2)<<8, nil
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}
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// WriteUint32 writes a uint32
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func (bigEndian) WriteUint32(b *bytes.Buffer, i uint32) {
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b.Write([]byte{uint8(i >> 24), uint8(i >> 16), uint8(i >> 8), uint8(i)})
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}
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// WriteUint24 writes a uint24
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func (bigEndian) WriteUint24(b *bytes.Buffer, i uint32) {
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b.Write([]byte{uint8(i >> 16), uint8(i >> 8), uint8(i)})
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}
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// WriteUint16 writes a uint16
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func (bigEndian) WriteUint16(b *bytes.Buffer, i uint16) {
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b.Write([]byte{uint8(i >> 8), uint8(i)})
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}
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