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

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2014-12-09 18:00:03 -05:00
package main
import (
"math"
"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 {
// Find the shortest string
var shortest string
length := math.MaxUint32
for _, v := range vs {
if len(v) < length {
shortest = v
length = len(v)
}
}
// 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] != '/' {
continue
}
bad := false
prefix := shortest[0 : i]
for _, v := range vs {
if !strings.HasPrefix(v, prefix) {
bad = true
break
}
}
if !bad {
return prefix
}
}
return ""
}