1 // Copyright 2016 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package net 6 7 // parsePort parses service as a decimal integer and returns the 8 // corresponding value as port. It is the caller's responsibility to 9 // parse service as a non-decimal integer when needsLookup is true. 10 // 11 // Some system resolvers will return a valid port number when given a number 12 // over 65536 (see https://golang.org/issues/11715). Alas, the parser 13 // can't bail early on numbers > 65536. Therefore reasonably large/small 14 // numbers are parsed in full and rejected if invalid. 15 func parsePort(service string) (port int, needsLookup bool) { 16 if service == "" { 17 // Lock in the legacy behavior that an empty string 18 // means port 0. See golang.org/issue/13610. 19 return 0, false 20 } 21 const ( 22 max = uint32(1<<32 - 1) 23 cutoff = uint32(1 << 30) 24 ) 25 neg := false 26 if service[0] == '+' { 27 service = service[1:] 28 } else if service[0] == '-' { 29 neg = true 30 service = service[1:] 31 } 32 var n uint32 33 for _, d := range service { 34 if '0' <= d && d <= '9' { 35 d -= '0' 36 } else { 37 return 0, true 38 } 39 if n >= cutoff { 40 n = max 41 break 42 } 43 n *= 10 44 nn := n + uint32(d) 45 if nn < n || nn > max { 46 n = max 47 break 48 } 49 n = nn 50 } 51 if !neg && n >= cutoff { 52 port = int(cutoff - 1) 53 } else if neg && n > cutoff { 54 port = int(cutoff) 55 } else { 56 port = int(n) 57 } 58 if neg { 59 port = -port 60 } 61 return port, false 62 } 63
