github.com/iikira/iikira-go-utils@v0.0.0-20230610031953-f2cb11cde33a/utils/checksum/checksum_write.go (about)

     1  package checksum
     2  
     3  import (
     4  	"hash"
     5  	"io"
     6  )
     7  
     8  type (
     9  	ChecksumWriter interface {
    10  		io.Writer
    11  		Sum() interface{}
    12  	}
    13  
    14  	ChecksumWriteUnit struct {
    15  		SliceEnd       int64
    16  		End            int64
    17  		SliceSum       interface{}
    18  		Sum            interface{}
    19  		OnlySliceSum   bool
    20  		ChecksumWriter ChecksumWriter
    21  
    22  		ptr int64
    23  	}
    24  
    25  	hashChecksumWriter struct {
    26  		h hash.Hash
    27  	}
    28  
    29  	hash32ChecksumWriter struct {
    30  		h hash.Hash32
    31  	}
    32  )
    33  
    34  func (wi *ChecksumWriteUnit) handleEnd() error {
    35  	if wi.ptr >= wi.End {
    36  		// 已写完
    37  		if !wi.OnlySliceSum {
    38  			wi.Sum = wi.ChecksumWriter.Sum()
    39  		}
    40  		return ErrChecksumWriteStop
    41  	}
    42  	return nil
    43  }
    44  
    45  func (wi *ChecksumWriteUnit) write(p []byte) (n int, err error) {
    46  	if wi.End <= 0 {
    47  		// do nothing
    48  		err = ErrChecksumWriteStop
    49  		return
    50  	}
    51  	err = wi.handleEnd()
    52  	if err != nil {
    53  		return
    54  	}
    55  
    56  	var (
    57  		i    int
    58  		left = wi.End - wi.ptr
    59  		lenP = len(p)
    60  	)
    61  	if left < int64(lenP) {
    62  		// 读取即将完毕
    63  		i = int(left)
    64  	} else {
    65  		i = lenP
    66  	}
    67  	n, err = wi.ChecksumWriter.Write(p[:i])
    68  	if err != nil {
    69  		return
    70  	}
    71  	wi.ptr += int64(n)
    72  	if left < int64(lenP) {
    73  		err = wi.handleEnd()
    74  		return
    75  	}
    76  	return
    77  }
    78  
    79  func (wi *ChecksumWriteUnit) Write(p []byte) (n int, err error) {
    80  	if wi.SliceEnd <= 0 { // 忽略Slice
    81  		// 读取全部
    82  		n, err = wi.write(p)
    83  		return
    84  	}
    85  
    86  	// 要计算Slice的情况
    87  	// 调整slice
    88  	if wi.SliceEnd > wi.End {
    89  		wi.SliceEnd = wi.End
    90  	}
    91  
    92  	// 计算剩余Slice
    93  	var (
    94  		sliceLeft = wi.SliceEnd - wi.ptr
    95  	)
    96  	if sliceLeft <= 0 {
    97  		// 已处理完Slice
    98  		if wi.OnlySliceSum {
    99  			err = ErrChecksumWriteStop
   100  			return
   101  		}
   102  
   103  		// 继续处理
   104  		n, err = wi.write(p)
   105  		return
   106  	}
   107  
   108  	var (
   109  		lenP = len(p)
   110  	)
   111  	if sliceLeft <= int64(lenP) {
   112  		var n1, n2 int
   113  		n1, err = wi.write(p[:sliceLeft])
   114  		n += n1
   115  		if err != nil {
   116  			return
   117  		}
   118  		wi.SliceSum = wi.ChecksumWriter.Sum().([]byte)
   119  		n2, err = wi.write(p[sliceLeft:])
   120  		n += n2
   121  		if err != nil {
   122  			return
   123  		}
   124  		return
   125  	}
   126  	n, err = wi.write(p)
   127  	return
   128  }
   129  
   130  func NewHashChecksumWriter(h hash.Hash) ChecksumWriter {
   131  	return &hashChecksumWriter{
   132  		h: h,
   133  	}
   134  }
   135  
   136  func (hc *hashChecksumWriter) Write(p []byte) (n int, err error) {
   137  	return hc.h.Write(p)
   138  }
   139  
   140  func (hc *hashChecksumWriter) Sum() interface{} {
   141  	return hc.h.Sum(nil)
   142  }
   143  
   144  func NewHash32ChecksumWriter(h32 hash.Hash32) ChecksumWriter {
   145  	return &hash32ChecksumWriter{
   146  		h: h32,
   147  	}
   148  }
   149  
   150  func (hc *hash32ChecksumWriter) Write(p []byte) (n int, err error) {
   151  	return hc.h.Write(p)
   152  }
   153  
   154  func (hc *hash32ChecksumWriter) Sum() interface{} {
   155  	return hc.h.Sum32()
   156  }