dotcloud/docker

// Package useragent provides helper functions to pack
// version information into a single User-Agent header.
package useragent // import "github.com/docker/docker/pkg/useragent"

import (
    "strings"
)

// VersionInfo is used to model UserAgent versions.
type VersionInfo struct {
    Name    string
    Version string
}

func (vi *VersionInfo) isValid() bool {
    const stopChars = " \t\r\n/"
    name := vi.Name
    vers := vi.Version
    if len(name) == 0 || strings.ContainsAny(name, stopChars) {
        return false
    }
    if len(vers) == 0 || strings.ContainsAny(vers, stopChars) {
        return false
    }
    return true
}

// AppendVersions converts versions to a string and appends the string to the string base.
//
// Each VersionInfo will be converted to a string in the format of
// "product/version", where the "product" is get from the name field, while
// version is get from the version field. Several pieces of version information
// will be concatenated and separated by space.
//
// Example:
// AppendVersions("base", VersionInfo{"foo", "1.0"}, VersionInfo{"bar", "2.0"})
// results in "base foo/1.0 bar/2.0".
func AppendVersions(base string, versions ...VersionInfo) string {
    if len(versions) == 0 {
        return base
    }

    verstrs := make([]string, 0, 1+len(versions))
    if len(base) > 0 {
        verstrs = append(verstrs, base)
    }

    for _, v := range versions {
        if !v.isValid() {
            continue
        }
        verstrs = append(verstrs, v.Name+"/"+v.Version)
    }
    return strings.Join(verstrs, " ")
}