Package org.python.modules._io

Class OpenMode

java.lang.Object
org.python.modules._io.OpenMode
public class OpenMode extends Object
An object able to check a file access mode provided as a String and represent it as boolean attributes and in a normalised form. Such a string is the the mode argument of the several open() functions available in Python and certain constructors for streams-like objects.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    boolean
    appending
    Whether this file is opened in appending mode ('a')
    boolean
    binary
    Whether this file is opened in binary mode ('b')
    boolean
    invalid
    Set true when any invalid symbol or combination is discovered
    String
    message
    Error message describing the way in which the mode is invalid, or null if no problem has been found.
    final String
    originalModeString
    Original string supplied as the mode
    boolean
    other
    Whether the mode contained some other symbol from the allowed ones
    boolean
    reading
    Whether this file is opened for reading ('r')
    boolean
    text
    Whether this file is opened in text mode ('t')
    boolean
    universal
    Whether this file is opened in universal newlines mode ('U')
    boolean
    updating
    Whether this file is opened for updating ('+')
    boolean
    writing
    Whether this file is opened for writing ('w')

  • Constructor Summary

    Constructors
    Constructor
    Description
    OpenMode(String mode)
    Decode the given string to an OpenMode object, checking for duplicate or unrecognised mode letters.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    checkValid()
    Call validate() and raise an exception if the mode string is not valid, as signalled by either invalid or other being true after that call.
    String
    forFileIO()
    The mode string we need when constructing a FileIO initialised with the present mode.
    String
    text()
    The mode string that a text file should claim to have, when initialised with the present mode.
    String
    toString()
     
    void
    validate()
    Adjust and validate the flags decoded from the mode string.
    void
    validate(String encoding, String errors, String newline)
    Perform additional validation of the flags relevant to text files.

    Methods inherited from class java.lang.Object

    equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

  • Field Details

    • originalModeString

      public final String originalModeString
      Original string supplied as the mode

    • reading

      public boolean reading
      Whether this file is opened for reading ('r')

    • writing

      public boolean writing
      Whether this file is opened for writing ('w')

    • appending

      public boolean appending
      Whether this file is opened in appending mode ('a')

    • updating

      public boolean updating
      Whether this file is opened for updating ('+')

    • binary

      public boolean binary
      Whether this file is opened in binary mode ('b')

    • text

      public boolean text
      Whether this file is opened in text mode ('t')

    • universal

      public boolean universal
      Whether this file is opened in universal newlines mode ('U')

    • other

      public boolean other
      Whether the mode contained some other symbol from the allowed ones

    • invalid

      public boolean invalid
      Set true when any invalid symbol or combination is discovered

    • message

      public String message
      Error message describing the way in which the mode is invalid, or null if no problem has been found. This field may be set by the constructor (in the case of duplicate or unrecognised mode letters), by the validate() method, or by client code.

  • Constructor Details

    • OpenMode

      public OpenMode(String mode)
      Decode the given string to an OpenMode object, checking for duplicate or unrecognised mode letters. Valid letters are those in "rwa+btU". Errors in the mode string do not raise an exception, they simply generate an appropriate error message in message. After construction, a client should always call validate() to complete validity checks.
      Parameters:
      mode -

  • Method Details

    • validate

      public void validate()
      Adjust and validate the flags decoded from the mode string. The method affects the flags where the presence of one flag implies another, then if the invalid flag is not already true, it checks the validity of the flags against combinations allowed by the Python io.open() function. In the case of a violation, it sets the invalid flag, and sets message to a descriptive message. The point of the qualification "if the invalid flag is not already true" is that the message should always describe the first problem discovered. If left blank, as in fact the constructor does, it will be filled by the generic message when checkValid() is finally called. Clients may override this method (by sub-classing) to express the validation correct in their context.

      The invalid combinations enforced here are those for the "raw" (ie non-text) file types:

      • universal & (writing | appending),
      • text & binary,
      • reading & writing,
      • appending & (reading | writing)
      See also validate(String, String, String) for additional checks relevant to text files.

    • validate

      public void validate(String encoding, String errors, String newline)
      Perform additional validation of the flags relevant to text files. If invalid is not already true, and the mode includes binary, then all the arguments to this call must be null. If the criterion is not met, then on return from the method, invalid==true and message is set to a standard error message. This is the standard additional validation applicable to text files. (By "standard" we mean the test and messages that CPython io.open uses.)
      Parameters:
      encoding - argument to open()
      errors - argument to open()
      newline - argument to open()

    • checkValid

      public void checkValid() throws PyException
      Call validate() and raise an exception if the mode string is not valid, as signalled by either invalid or other being true after that call. If no more specific message has been assigned in message, report the original mode string.
      Throws:
      PyException - ValueError if the mode string was invalid.

    • forFileIO

      public String forFileIO()
      The mode string we need when constructing a FileIO initialised with the present mode. Note that this is not the same as the full open mode because it omits the text-based attributes.
      Returns:
      "r", "w", or "a" with optional "+".

    • text

      public String text()
      The mode string that a text file should claim to have, when initialised with the present mode. Note that this only contains text-based attributes. Since mode 't' has no effect, except to produce an error if specified with 'b', we don't reproduce it.
      Returns:
      "", or "U".

    • toString

      public String toString()
      Overrides:
      toString in class Object