61 lines
1.3 KiB
Go
61 lines
1.3 KiB
Go
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//go:build purego || !amd64
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// +build purego !amd64
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package ascii
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// EqualFoldString is a version of strings.EqualFold designed to work on ASCII
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// input instead of UTF-8.
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//
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// When the program has guarantees that the input is composed of ASCII
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// characters only, it allows for greater optimizations.
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func EqualFoldString(a, b string) bool {
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if len(a) != len(b) {
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return false
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}
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var cmp byte
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for len(a) >= 8 {
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cmp |= lowerCase[a[0]] ^ lowerCase[b[0]]
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cmp |= lowerCase[a[1]] ^ lowerCase[b[1]]
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cmp |= lowerCase[a[2]] ^ lowerCase[b[2]]
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cmp |= lowerCase[a[3]] ^ lowerCase[b[3]]
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cmp |= lowerCase[a[4]] ^ lowerCase[b[4]]
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cmp |= lowerCase[a[5]] ^ lowerCase[b[5]]
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cmp |= lowerCase[a[6]] ^ lowerCase[b[6]]
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cmp |= lowerCase[a[7]] ^ lowerCase[b[7]]
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if cmp != 0 {
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return false
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}
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a = a[8:]
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b = b[8:]
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}
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switch len(a) {
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case 7:
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cmp |= lowerCase[a[6]] ^ lowerCase[b[6]]
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fallthrough
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case 6:
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cmp |= lowerCase[a[5]] ^ lowerCase[b[5]]
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fallthrough
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case 5:
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cmp |= lowerCase[a[4]] ^ lowerCase[b[4]]
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fallthrough
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case 4:
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cmp |= lowerCase[a[3]] ^ lowerCase[b[3]]
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fallthrough
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case 3:
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cmp |= lowerCase[a[2]] ^ lowerCase[b[2]]
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fallthrough
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case 2:
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cmp |= lowerCase[a[1]] ^ lowerCase[b[1]]
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fallthrough
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case 1:
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cmp |= lowerCase[a[0]] ^ lowerCase[b[0]]
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}
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return cmp == 0
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}
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