nl_tokens: 获取对象相关元数据信息
pl_tokens: function getMeta ( host , accessKey , secretKey , bucket , objectKey ) { var expires = arguments . length <= 5 || arguments [ 5 ] === undefined ? 0 : arguments [ 5 ] ; var opts = arguments . length <= 6 || arguments [ 6 ] === undefined ? { } : arguments [ 6 ] ; var date = utcDate ( ) ; if ( opts . versionId ) url += '?versionId=' + opts . versionId ; var resource = genResource ( bucket , objectKey , ( 0 , _lodash . pick ) ( opts , [ 'versionId' ] ) ) ; var authorization = authorize ( accessKey , secretKey , 'HEAD' , '' , '' , date , [ ] , resource ) ; var signature = ( 0 , _urlencode2 . default ) ( generateSignature ( secretKey , 'HEAD' , '' , '' , date , [ ] , resource ) ) ; var url = pub ? 'http://' + bucket + '.' + host + '/' + objectKey : 'http://' + host + '/' + bucket + '/' + objectKey + '?NOSAccessKeyId=' + accessKey + '&Expires=' + expires + '&Signature=' + signature ; var headers = { Date : date } ; if ( opts . modifiedSince ) headers [ 'If-Modified-Since' ] = opts . modifiedSince ; headers [ 'url' ] = url ; return nosRequest ( { <mask> : 'head' , uri : url , headers : headers } ) . then ( function ( res ) { var contentType = res [ 'content-type' ] ; var lastModified = res [ 'last-modified' ] ; var etag = res [ 'etag' ] ; var requestId = res [ 'x-nos-request-id' ] ; return { contentType : contentType , lastModified : lastModified , etag : etag , requestId : requestId } ; } ) ; }