TagStore的构造

const DEFAULT_TAG = "latest"

type TagStore struct {
    path         string
    //# 记录`image`本地`graph`的信息
    graph        *Graph
    Repositories map[string]Repository
}

type Repository map[string]string

TagStore的方法

//# Save 将`store`哈希成json保存到`store.path`中。
func (store *TagStore) Save() error {
    // 保存json
    jsonData, err := json.Marshal(store)
    if err != nil {
        return err
    }
    if err := ioutil.WriteFile(store.path, jsonData, 0600); err != nil {
        return err
    }
    return nil
}

//# Reload 重新从`store.path`中读取json并赋值给`store`。
func (store *TagStore) Reload() error {
    jsonData, err := ioutil.ReadFile(store.path)
    if err != nil {
        return err
    }
    if err := json.Unmarshal(jsonData, store); err != nil {
        return err
    }
    return nil
}

//# LookupImage 根据名称搜索`image`
func (store *TagStore) LookupImage(name string) (*Image, error) {
    img, err := store.graph.Get(name)
    if err != nil {
        // FIXME: standardize on returning nil when the image doesn't exist, and err for everything else
        // (so we can pass all errors here)
        repoAndTag := strings.SplitN(name, ":", 2)
        if len(repoAndTag) == 1 {
            repoAndTag = append(repoAndTag, DEFAULT_TAG)
        }
        if i, err := store.GetImage(repoAndTag[0], repoAndTag[1]); err != nil {
            return nil, err
        } else if i == nil {
            return nil, fmt.Errorf("No such image: %s", name)
        } else {
            img = i
        }
    }
    return img, nil
}

// 返回所有名称的反序查找表， 指向每一个`image`
// 例子 {"43b5f19b10584": {"base:latest", "base:v1"}}
func (store *TagStore) ById() map[string][]string {
    byId := make(map[string][]string)
    for repoName, repository := range store.Repositories {
        for tag, id := range repository {
            name := repoName + ":" + tag
            if _, exists := byId[id]; !exists {
                byId[id] = []string{name}
            } else {
                byId[id] = append(byId[id], name)
            }
        }
    }
    return byId
}

//# ImageName 返回镜像名称
func (store *TagStore) ImageName(id string) string {
    if names, exists := store.ById()[id]; exists && len(names) > 0 {
        return names[0]
    }
    return id
}

//# Set 设置一个标签`tag`
func (store *TagStore) Set(repoName, tag, imageName string, force bool) error {
    img, err := store.LookupImage(imageName)
    if err != nil {
        return err
    }
    if tag == "" {
        tag = DEFAULT_TAG
    }
    if err := validateRepoName(repoName); err != nil {
        return err
    }
    if err := validateTagName(tag); err != nil {
        return err
    }
    if err := store.Reload(); err != nil {
        return err
    }
    var repo Repository
    if r, exists := store.Repositories[repoName]; exists {
        repo = r
    } else {    
        //# 如果`tag`不存在, 则创建一个仓库， 并存储在`store.Repositories`中
        repo = make(map[string]string)
        if old, exists := store.Repositories[repoName]; exists && !force {
            return fmt.Errorf("Tag %s:%s is already set to %s", repoName, tag, old)
        }
        store.Repositories[repoName] = repo
    }
    repo[tag] = img.Id
    return store.Save()
}

//# 
func (store *TagStore) Get(repoName string) (Repository, error) {
    if err := store.Reload(); err != nil {
        return nil, err
    }
    if r, exists := store.Repositories[repoName]; exists {
        return r, nil
    }
    return nil, nil
}

//# GetImage 根据`repo`和版本查找`image`
func (store *TagStore) GetImage(repoName, tag string) (*Image, error) {
    repo, err := store.Get(repoName)
    if err != nil {
        return nil, err
    } else if repo == nil {
        return nil, nil
    }
    if revision, exists := repo[tag]; exists {
        return store.graph.Get(revision)
    }
    return nil, nil
}

//# 验证仓库名称
func validateRepoName(name string) error {
    if name == "" {
        return fmt.Errorf("Repository name can't be empty")
    }
    if strings.Contains(name, ":") {
        return fmt.Errorf("Illegal repository name: %s", name)
    }
    return nil
}

// 验证标签名称
func validateTagName(name string) error {
    if name == "" {
        return fmt.Errorf("Tag name can't be empty")
    }
    if strings.Contains(name, "/") || strings.Contains(name, ":") {
        return fmt.Errorf("Illegal tag name: %s", name)
    }
    return nil
}