class TS3WebFile: public TWebFile

 Construct a TS3WebFile object. The path argument is a URL of one of the
 following forms:

         s3://host.example.com/bucket/path/to/my/file
     s3http://host.example.com/bucket/path/to/my/file
    s3https://host.example.com/bucket/path/to/my/file
        as3://host.example.com/bucket/path/to/my/file

 For files hosted by Google Storage, use the following forms:

        gs://storage.googleapis.com/bucket/path/to/my/file
    gshttp://storage.googleapis.com/bucket/path/to/my/file
  gsthttps://storage.googleapis.com/bucket/path/to/my/file

 The 'as3' scheme is accepted for backwards compatibility but its usage is
 deprecated.

 The recommended way to create an instance of this class is through
 TFile::Open, for instance:

 TFile* f1 = TFile::Open("s3://host.example.com/bucket/path/to/my/file")
 TFile* f2 = TFile::Open("gs://storage.googleapis.com/bucket/path/to/my/file")

 The specified scheme (i.e. s3, s3http, s3https, ...) determines the underlying
 transport protocol to use for downloading the file contents, namely HTTP or HTTPS.
 The 's3', 's3https', 'gs' and 'gshttps' schemes imply using HTTPS as the transport
 protocol. The 's3http', 'as3' and 'gshttp' schemes imply using HTTP as the transport
 protocol.

 The 'options' argument can contain 'NOPROXY' if you want to bypass
 the HTTP proxy when retrieving this file's contents. As for any TWebFile-derived
 object, the URL of the web proxy can be specified by setting an environmental
 variable 'http_proxy'. If this variable is set, we ask that proxy to route our
 requests HTTP(S) requests to the file server.

 In addition, you can also use the 'options' argument to provide the access key
 and secret key to be used for authentication purposes for this file by using a
 string of the form "AUTH=myAccessKey:mySecretkey". This may be useful to
 open several files hosted by different providers in the same program/macro,
 where the environemntal variables solution is not convenient (see below).

 If you need to specify both NOPROXY and AUTH separate them by ' '
 (blank), for instance:
 "NOPROXY AUTH=F38XYZABCDeFgH4D0E1F:V+frt4re7J1euSNFnmaf8wwmI4AAAE7kzxZ/TTM+"

 Examples:
    TFile* f1 = TFile::Open("s3://host.example.com/bucket/path/to/my/file",
                            "NOPROXY AUTH=F38XYZABCDeFgH4D0E1F:V+frt4re7J1euSNFnmaf8wwmI4AAAE7kzxZ/TTM+");
    TFile* f2 = TFile::Open("s3://host.example.com/bucket/path/to/my/file",
                            "AUTH=F38XYZABCDeFgH4D0E1F:V+frt4re7J1euSNFnmaf8wwmI4AAAE7kzxZ/TTM+");

 If there is no authentication information in the 'options' argument
 (i.e. not AUTH="....") the values of the environmental variables
 S3_ACCESS_KEY and S3_SECRET_KEY (if set) are expected to contain
 the access key id and the secret access key, respectively. You have
 been provided with these credentials by your S3 service provider.

 If neither the AUTH information is provided in the 'options' argument
 nor the environmental variables are set, we try to open the file
 without providing any authentication information to the server. This
 is useful when the file is set an access control that allows for
 any unidentified user to read the file.

 Extracts the S3 authentication key pair (access key and secret key)
 from the options. The authentication credentials can be specified in
 the options provided to the constructor of this class as a string
 containing: "AUTH=<access key>:<secret key>" and can include other
 options, for instance "NOPROXY" for not using the HTTP proxy for
 accessing this file's contents.
 For instance:
 "NOPROXY AUTH=F38XYZABCDeFgHiJkLm:V+frt4re7J1euSNFnmaf8wwmI401234E7kzxZ/TTM+"

 Overwrites TWebFile::GetHead() for retrieving the HTTP headers of this
 file. Uses TS3HTTPRequest to generate an HTTP HEAD request which includes
 the authorization header expected by the S3 server.

 Overwrites TWebFile::SetMsgReadBuffer10() for setting the HTTP GET
 request compliant to the authentication mechanism used by the S3
 protocol. The GET request must contain an "Authorization" header with
 the signature of the request, generated using the user's secret access
 key.

 This method is called by the super-class TWebFile when a HTTP header
 for this file is retrieved. We scan the 'Server' header to detect the
 type of S3 server this file is hosted on and to determine if it is
 known to support multi-range HTTP GET requests. Some S3 servers (for
 instance Amazon's) do not support that feature and when they
 receive a multi-range request they sent back the whole file contents.
 For this class, if the server do not support multirange requests
 we issue multiple single-range requests instead.

 Sets the access and secret keys from the environmental variables, if
 they are both set.

 Modifiers of data members (to be used mainly by subclasses)

 Constructors & Destructor

 Selectors