version.go

// Copyright (c) 2013-2014 The btcsuite developers
// Copyright (c) 2015-2017 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package version

import (
	"bytes"
	"fmt"
	"strings"
)

// semverAlphabet is an alphabet of all characters allowed in semver prerelease
// or build metadata identifiers, and the . separator.
const semverAlphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-."

// Constants defining the application version number.
const (
	Major = 1
	Minor = 2
	Patch = 0
)

// PreRelease contains the prerelease name of the application.  It is a variable
// so it can be modified at link time (e.g.
// `-ldflags "-X github.com/decred/dcrwallet/version.PreRelease=rc1"`).
// It must only contain characters from the semantic version alphabet.
var PreRelease = ""

// BuildMetadata defines additional build metadata.  It is modified at link time
// for official releases.  It must only contain characters from the semantic
// version alphabet.
var BuildMetadata = "dev"

// String returns the application version as a properly formed string per the
// semantic versioning 2.0.0 spec (http://semver.org/).
func String() string {
	// Start with the major, minor, and path versions.
	version := fmt.Sprintf("%d.%d.%d", Major, Minor, Patch)

	// Append pre-release version if there is one.  The hyphen called for
	// by the semantic versioning spec is automatically appended and should
	// not be contained in the pre-release string.  The pre-release version
	// is not appended if it contains invalid characters.
	preRelease := normalizeVerString(PreRelease)
	if preRelease != "" {
		version = version + "-" + preRelease
	}

	// Append build metadata if there is any.  The plus called for
	// by the semantic versioning spec is automatically appended and should
	// not be contained in the build metadata string.  The build metadata
	// string is not appended if it contains invalid characters.
	buildMetadata := normalizeVerString(BuildMetadata)
	if buildMetadata != "" {
		version = version + "+" + buildMetadata
	}

	return version
}

// normalizeVerString returns the passed string stripped of all characters which
// are not valid according to the semantic versioning guidelines for pre-release
// version and build metadata strings.  In particular they MUST only contain
// characters in semanticAlphabet.
func normalizeVerString(str string) string {
	var buf bytes.Buffer
	for _, r := range str {
		if strings.ContainsRune(semverAlphabet, r) {
			_, err := buf.WriteRune(r)
			// Writing to a bytes.Buffer panics on OOM, and all
			// errors are unexpected.
			if err != nil {
				panic(err)
			}
		}
	}
	return buf.String()
}