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40 lines
637 B
Go
40 lines
637 B
Go
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package checksum
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// IPv4 implements hash.Hash
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type IPv4 struct {
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sum uint
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odd bool
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}
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func (c *IPv4) Write(p []byte) (n int, err error) {
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for _, b := range p {
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if c.odd {
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c.sum += uint(b)
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if c.sum > 0xffff {
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c.sum++
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c.sum &= 0xffff
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}
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} else {
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c.sum += uint(b) << 8
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}
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c.odd = !c.odd
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}
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return len(p), nil
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}
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func (c *IPv4) Sum(b []byte) []byte {
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s := c.sum
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if c.odd {
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if s > 0xffff {
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s++
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s &= 0xffff
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}
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}
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s ^= 0xffff
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return append(b, byte(s>>8), byte(s))
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}
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func (c *IPv4) Reset() { c.sum = 0 }
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func (c *IPv4) Size() int { return 2 }
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func (c *IPv4) BlockSize() int { return 2 }
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