// Copyright 2016 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package net // parsePort parses service as a decimal integer and returns the // corresponding value as port. It is the caller's responsibility to // parse service as a non-decimal integer when needsLookup is true. // // Some system resolvers will return a valid port number when given a number // over 65536 (see https://golang.org/issues/11715). Alas, the parser // can't bail early on numbers > 65536. Therefore reasonably large/small // numbers are parsed in full and rejected if invalid. func parsePort(service string) (port int, needsLookup bool) { if service == "" { // Lock in the legacy behavior that an empty string // means port 0. See golang.org/issue/13610. return 0, false } const ( max = uint32(1<<32 - 1) cutoff = uint32(1 << 30) ) neg := false if service[0] == '+' { service = service[1:] } else if service[0] == '-' { neg = true service = service[1:] } var n uint32 for _, d := range service { if '0' <= d && d <= '9' { d -= '0' } else { return 0, true } if n >= cutoff { n = max break } n *= 10 nn := n + uint32(d) if nn < n || nn > max { n = max break } n = nn } if !neg && n >= cutoff { port = int(cutoff - 1) } else if neg && n > cutoff { port = int(cutoff) } else { port = int(n) } if neg { port = -port } return port, false }