func (c *Client) tryLoadCacheThenRemote(consistentInfo tuf.ConsistentInfo) ([]byte, error) {
cachedTS, err := c.cache.GetMeta(consistentInfo.RoleName, consistentInfo.Length())
if err != nil {
logrus.Debugf("no %s in cache, must download", consistentInfo.RoleName)
return c.tryLoadRemote(consistentInfo, nil)
}
if err = c.newBuilder.Load(consistentInfo.RoleName, cachedTS, 1, false); err == nil {
logrus.Debugf("successfully verified cached %s", consistentInfo.RoleName)
return cachedTS, nil
}
logrus.Debugf("cached %s is invalid (must download): %s", consistentInfo.RoleName, err)
return c.tryLoadRemote(consistentInfo, cachedTS)
}
func (c *TUFClient) tryLoadRemote(consistentInfo tuf.ConsistentInfo, old []byte) ([]byte, error) {
consistentName := consistentInfo.ConsistentName()
raw, err := c.remote.GetSized(consistentName, consistentInfo.Length())
if err != nil {
logrus.Debugf("error downloading %s: %s", consistentName, err)
return old, err
}
// try to load the old data into the old builder - only use it to validate
// versions if it loads successfully. If it errors, then the loaded version
// will be 1
c.oldBuilder.Load(consistentInfo.RoleName, old, 1, true)
minVersion := c.oldBuilder.GetLoadedVersion(consistentInfo.RoleName)
if err := c.newBuilder.Load(consistentInfo.RoleName, raw, minVersion, false); err != nil {
logrus.Debugf("downloaded %s is invalid: %s", consistentName, err)
return raw, err
}
logrus.Debugf("successfully verified downloaded %s", consistentName)
if err := c.cache.Set(consistentInfo.RoleName, raw); err != nil {
logrus.Debugf("Unable to write %s to cache: %s", consistentInfo.RoleName, err)
}
return raw, nil
}