packer-cn/post-processor/atlas/util.go

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package atlas
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import (
"math"
"path/filepath"
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"strings"
)
// longestCommonPrefix finds the longest common prefix for all the strings
// given as an argument, or returns the empty string if a prefix can't be
// found.
//
// This function just uses brute force instead of a more optimized algorithm.
func longestCommonPrefix(vs []string) string {
var length int64
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// Find the shortest string
var shortest string
length = math.MaxUint32
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for _, v := range vs {
if int64(len(v)) < length {
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shortest = v
length = int64(len(v))
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}
}
// Now go through and find a prefix to all the strings using this
// short string, which itself must contain the prefix.
for i := len(shortest); i > 0; i-- {
// We only care about prefixes with path seps
if shortest[i-1] != filepath.Separator {
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continue
}
bad := false
prefix := shortest[0:i]
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for _, v := range vs {
if !strings.HasPrefix(v, prefix) {
bad = true
break
}
}
if !bad {
return prefix
}
}
return ""
}