Class: ImmutableByteArray

• Inheritance
• Description
• Related information
• Class protocol
  • instance creation
  • queries
  • testing
• Instance protocol
  • accessing
  • converting
  • copying
  • copying-private
  • printing & storing
  • private
  • queries
  • specials

Inheritance:

   Object
   |
   +--Collection
      |
      +--SequenceableCollection
         |
         +--ArrayedCollection
            |
            +--UninterpretedBytes
               |
               +--ByteArray
                  |
                  +--ImmutableByteArray

Package:

stx:libbasic

Category:

System-Compiler-Support

Version:

rev: 1.29 date: 2019/07/21 06:31:35

user: cg

file: ImmutableByteArray.st directory: libbasic

module: stx stc-classLibrary: libbasic

Author:

Claus Gittinger

Description:

By default, byte array literals in smalltalk are mutable objects. That
may lead to some subtle (and hard to find errors), if some method passes
a literal byte-array object as argument to someone else, who changes the
bytearray using at:put: like messages. Since the bytearray object is kept in
the first methods literals, the bytearray constant has now been changed without
having the method's sourcecode reflect this. Thus, the method will
behave differently from what its source may make you think.

To help finding this kind of 'feature/bug', the compiler can be
configured to create instances of this ImmutableByteArray instead of ByteArrays
for literals. Instances of ImmutableByteArray catch storing accesses and
enter the debugger. Although useful, this feature is disabled by default
for compatibility to other smalltalk implementations.
(Also, if turned on, this makes inspecting bytearray literals entered in
 a workspace somewhat strange: you cannot modify it any longer).

Turn the ImmutableArray feature on, by setting the Parser's class variable
'ArraysAreImmutable' to true or use the new launchers settings menu.

This class should be used only by the compiler.

ATTENTION:
    there may be still code around which checks for explicit class being ByteArray
    (both in Smalltalk and in primitive code). All code like foo 'class == ByteArray'
    or '__isByteArray()' will not work with ImmutableByteArrays - consider using '__isByteArrayLike()'.
    A somewhat better approach would be to either add a flag to the object (mutability)
    and check this dynamically (expensive) or to place immutable objects into a readonly
    memory segment (the good solution). We will eventually implement the second in the future...

Related information:

    ImmutableString
    ImmutableArray
    Parser
    Scanner

Class protocol:

 fromPackedString: aString

(comment from inherited method)
ST-80 compatibility: decode a byteArray from a packed string in which
6bits are encoded per character. The argument, aString must be a multiple
of 4 in size (since 24 is the lcm of 6 and 8).
Every 6 bit packet is encoded as a character in 32..95.
Characters below 32 are ignored (so line breaks can be inserted at any place).
An addition final byte defines how many bytes of the last triple are valid.
This is somewhat like the radix-encoding used in good old PDP11 times ;-)
ST-80 uses this encoding for Images ...
This is a base64 encoding, very similar (but not equal) to the algorithm used in RFC1421.
PS: It took a while to figure that one out ...
PPS: I don't like it ;-)

 mutableClass

answer an equivalent mustable class

 hasImmutableInstances

Instance protocol:

 at: index put: value

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 basicAt: index put: value

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 byteAt: index put: value

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 doubleAt: index put: anInteger

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 doubleAt: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 floatAt: index put: anInteger

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 floatAt: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 signedInt128At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 signedInt16At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 signedInt32At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 signedInt64At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt128At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt16At: index put: anInteger

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt16At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt32At: index put: anInteger

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt32At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt64At: index put: anInteger

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 unsignedInt64At: index put: anInteger MSB: msb

Trigger an error if an immutable bytearray is stored into.
The store will be performed (for compatibility reasons) if you continue
in the debugger (or proceed in an exception handler).

 asByteArray

return the receiver as a (mutable) byteArray

usage example(s):

#[1 2 3 4] asImmutableByteArray asByteArray

 asImmutableByteArray

that's what I am-

 asImmutableCollection

(comment from inherited method)
return a write-protected copy of myself

 asMutableCollection

return a writable copy of myself

 beImmutable

that's what I am

 beMutable

you never go back

 beUnsigned

that's what I am-

usage example(s):

#[1 2 3 128 255] asImmutableByteArray beUnsigned

 shallowCopy

when copying, return a real (mutable) ByteArray

usage example(s):

#[1 2 3 4] asImmutableByteArray shallowCopy

 postCopy

when copied, make me a real (mutable) ByteArray

 postDeepCopy

when copied, make me a real (mutable) ByteArray

 displayOn: aGCOrStream

what a kludge - Dolphin and Squeak mean: printOn: a stream;

 species

Copies should be mutable

 speciesForCopy

Copies should be mutable

 isImmutable

return true, if the receiver is immutable.
Since I am an immutable byte array, return always true here

 isLiteral

return true, if the receiver can be used as a literal constant in ST syntax
(i.e. can be used in constant arrays)

 become: anotherObject

trigger an error if I should become something else
(this would be an even more tricky manipulation)

 becomeNil

trigger an error if I should become nil
(this would be an even more tricky manipulation)

 becomeSameAs: anotherObject

trigger an error if I should become something else
(this would be an even more tricky manipulation)