如何在Golang中解包字节缓冲区中的各种整数形式？

huangapple
go评论114阅读模式
英文:

How do I unpack various form of integers in a byte buffer in Golang?

问题

我需要从字节缓冲区中提取各种字段。我想出了以下解决方案：

  1. func (fs *FileSystem) readSB() {
  2.  	// fs.f 是一个 *os.File
  3.  	buf := make([]byte, 1024)
  4.  	fs.f.ReadAt(buf, 1024)
  5.  
  6.  	// 偏移量: 类型
  7.  	var p *bytes.Buffer
  8.  
  9.  	// 0: uint32
  10.  	p = bytes.NewBuffer(buf[0:])
  11.  	binary.Read(p, binary.LittleEndian, &fs.sb.inodeCount)
  12.  	// 4: uint32
  13.  	p = bytes.NewBuffer(buf[4:])
  14.  	binary.Read(p, binary.LittleEndian, &fs.sb.blockCount)
  15.  	// 20: uint32
  16.  	p = bytes.NewBuffer(buf[20:])
  17.  	binary.Read(p, binary.LittleEndian, &fs.sb.firstDataBlock)
  18.  	// 24: uint32
  19.  	p = bytes.NewBuffer(buf[24:])
  20.  	binary.Read(p, binary.LittleEndian, &fs.sb.blockSize)
  21.  	fs.sb.blockSize = 1024 << fs.sb.blockSize
  22.  	// 32: uint32
  23.  	p = bytes.NewBuffer(buf[32:])
  24.  	binary.Read(p, binary.LittleEndian, &fs.sb.blockPerGroup)
  25.  	// 40: uint32
  26.  	p = bytes.NewBuffer(buf[40:])
  27.  	binary.Read(p, binary.LittleEndian, &fs.sb.inodePerBlock)
  28. }

有没有更好/更符合惯用方式/更直接的方法来做到这一点？

  • 我希望保持偏移量明确
  • 我希望尽可能从字节缓冲区中读取，而不是从文件中寻找和读取。
英文:

I need to extract various fields in a byte buffer. I came up with this solution:

  1. func (fs *FileSystem) readSB() {
  2.  	// fs.f is a *os.File
  3.  	buf := make([]byte, 1024)
  4.  	fs.f.ReadAt(buf, 1024)
  5.  
  6.  	// Offset: type
  7.  	var p *bytes.Buffer
  8.  
  9.  	// 0: uint32
  10.  	p = bytes.NewBuffer(buf[0:])
  11.  	binary.Read(p, binary.LittleEndian, &amp;fs.sb.inodeCount)
  12.  	// 4: uint32
  13.  	p = bytes.NewBuffer(buf[4:])
  14.  	binary.Read(p, binary.LittleEndian, &amp;fs.sb.blockCount)
  15.  	// 20: uint32
  16.  	p = bytes.NewBuffer(buf[20:])
  17.  	binary.Read(p, binary.LittleEndian, &amp;fs.sb.firstDataBlock)
  18.  	// 24: uint32
  19.  	p = bytes.NewBuffer(buf[24:])
  20.  	binary.Read(p, binary.LittleEndian, &amp;fs.sb.blockSize)
  21.  	fs.sb.blockSize = 1024 &lt;&lt; fs.sb.blockSize
  22.  	// 32: uint32
  23.  	p = bytes.NewBuffer(buf[32:])
  24.  	binary.Read(p, binary.LittleEndian, &amp;fs.sb.blockPerGroup)
  25.  	// 40: uint32
  26.  	p = bytes.NewBuffer(buf[40:])
  27.  	binary.Read(p, binary.LittleEndian, &amp;fs.sb.inodePerBlock)
  28. }

Is there a more better/idiomatic/straightforward way of doing this?

  • I want to keep offsets explicit
  • I want to read from the byte buffer, not seeking and reading from the file when possible.

答案1

得分: 33

你可以通过使用.Next()来跳过不想读取的字节，从而避免每次创建新的缓冲区：

  1. {
  2. 	// 偏移量: 类型
  3. 	p := bytes.NewBuffer(buf)
  5. 	// 0: uint32
  6. 	binary.Read(p, binary.LittleEndian, &fs.sb.inodeCount)
  8. 	// 4: uint32
  9. 	binary.Read(p, binary.LittleEndian, &fs.sb.blockCount)
  11. 	// 跳过 [8:20)
  12. 	p.Next(12)
  14. 	// 20: uint32
  15. 	binary.Read(p, binary.LittleEndian, &fs.sb.firstDataBlock)
  17. 	// 24: uint32
  18. 	binary.Read(p, binary.LittleEndian, &fs.sb.blockSize)
  19. 	fs.sb.blockSize = 1024 << fs.sb.blockSize
  21. 	// 跳过 [28:32)
  22. 	p.Next(4)
  24. 	// 32: uint32
  25. 	binary.Read(p, binary.LittleEndian, &fs.sb.blockPerGroup)
  27. 	// 跳过 [36:40)
  28. 	p.Next(4)
  30. 	// 40: uint32
  31. 	binary.Read(p, binary.LittleEndian, &fs.sb.inodePerBlock)
  32. }

或者你可以避免逐块读取并创建一个头部结构，直接使用binary.Read进行读取：

  1. type Head struct {
  2. 	InodeCount		uint32	//  0:4
  3. 	BlockCount		uint32	//  4:8
  4. 	Unknown1		uint32	//  8:12
  5. 	Unknown2 		uint32	// 12:16
  6. 	Unknown3 		uint32	// 16:20
  7. 	FirstBlock		uint32	// 20:24
  8. 	BlockSize		uint32	// 24:28
  9. 	Unknown4		uint32	// 28:32
  10. 	BlocksPerGroup	uint32	// 32:36
  11. 	Unknown5		uint32	// 36:40
  12. 	InodesPerBlock	uint32	// 40:44
  13. }
  15. func main() {
  16. 	var header Head
  18. 	err = binary.Read(file, binary.LittleEndian, &header)
  20. 	if err != nil {
  21. 		log.Fatal(err)
  22. 	}
  24. 	log.Printf("%#v\n", header)
  25. }
英文:

You could avoid creating a new buffer every time by using .Next() to skip the bytes you don't want to read:

  1. {
  2. 	// Offset: type
  3. 	p := bytes.NewBuffer(buf)
  5. 	// 0: uint32
  6. 	binary.Read(p, binary.LittleEndian, &amp;fs.sb.inodeCount)
  8. 	// 4: uint32
  9. 	binary.Read(p, binary.LittleEndian, &amp;fs.sb.blockCount)
  11. 	// Skip [8:20)
  12. 	p.Next(12)
  14. 	// 20: uint32
  15. 	binary.Read(p, binary.LittleEndian, &amp;fs.sb.firstDataBlock)
  17. 	// 24: uint32
  18. 	binary.Read(p, binary.LittleEndian, &amp;fs.sb.blockSize)
  19. 	fs.sb.blockSize = 1024 &lt;&lt; fs.sb.blockSize
  21. 	// Skip [28:32)
  22. 	p.Next(4)
  24. 	// 32: uint32
  25. 	binary.Read(p, binary.LittleEndian, &amp;fs.sb.blockPerGroup)
  27. 	// Skip [36:40)
  28. 	p.Next(4)
  30. 	// 40: uint32
  31. 	binary.Read(p, binary.LittleEndian, &amp;fs.sb.inodePerBlock)
  32. }

Or you could avoid reading chunk by chunk and create a header structure which you read directly using binary.Read:

  1. type Head struct {
  2. 	InodeCount		uint32	//  0:4
  3. 	BlockCount		uint32	//  4:8
  4. 	Unknown1		uint32	//  8:12
  5. 	Unknown2 		uint32	// 12:16
  6. 	Unknown3 		uint32	// 16:20
  7. 	FirstBlock		uint32	// 20:24
  8. 	BlockSize		uint32	// 24:28
  9. 	Unknown4		uint32	// 28:32
  10. 	BlocksPerGroup	uint32	// 32:36
  11. 	Unknown5		uint32	// 36:40
  12. 	InodesPerBlock	uint32	// 40:44
  13. }
  15. func main() {
  16. 	var header Head
  18. 	err = binary.Read(file, binary.LittleEndian, &amp;header)
  20. 	if err != nil {
  21. 		log.Fatal(err)
  22. 	}
  24. 	log.Printf(&quot;%#v\n&quot;, header)
  25. }

答案2

得分: 1

我有一个名为binpacker的包来处理这些情况

示例

示例数据：

  1. buffer := new(bytes.Buffer)
  2. packer := binpacker.NewPacker(buffer)
  3. unpacker := binpacker.NewUnpacker(buffer)
  4. packer.PushByte(0x01)
  5. packer.PushUint16(math.MaxUint16)

解包：

  1. var val1 byte
  2. var val2 uint16
  3. var err error
  4. val1, err = unpacker.ShiftByte()
  5. val2, err = unpacker.ShiftUint16()

或者

  1. var val1 byte
  2. var val2 uint16
  3. var err error
  4. unpacker.FetchByte(&amp;val1).FetchUint16(&amp;val2)
  5. unpacker.Error() // 确保错误为nil
英文:

I have a package binpacker to handle those situations

example

example data:

  1. buffer := new(bytes.Buffer)
  2. packer := binpacker.NewPacker(buffer)
  3. unpacker := binpacker.NewUnpacker(buffer)
  4. packer.PushByte(0x01)
  5. packer.PushUint16(math.MaxUint16)

unpack it:

  1. var val1 byte
  2. var val2 uint16
  3. var err error
  4. val1, err = unpacker.ShiftByte()
  5. val2, err = unpacker.ShiftUint16()

Or

  1. var val1 byte
  2. var val2 uint16
  3. var err error
  4. unpacker.FetchByte(&amp;val1).FetchUint16(&amp;val2)
  5. unpacker.Error() // Make sure error is nil

huangapple
  • 本文由 发表于 2012年9月11日 03:02:46
  • 转载请务必保留本文链接：https://go.coder-hub.com/12357865.html
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