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

Method Summary

Methods

Modifier and Type	Method and 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 Detail

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 Detail

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 Detail

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