org.apache.flex.compiler.internal.parsing.as

Class OffsetCue

java.lang.Object

org.apache.flex.compiler.internal.parsing.as.OffsetCue

public class OffsetCue
extends Object

Background

Imagine an ActionScript source as a character stream (include directives are expanded and merged into the main file), each character's offset number is an "absolute" offset. It differs from the "local" offset of a character in an included file.

For example, when "version.as" is included in "Button.as" at offset 10 in "Button.as", the first character in "version.as" has local offset "0", but its "absolute" offset in "Button.as" is "10". Suppose keyword var is after the include statement, and its "local" offset is "20", since "version.as" has 100 characters in it, the "absolute" offset of var becomes "120".

Computing absolute offsets

The OffsetCue objects are markers on the "absolute" offset axis. It records the adjustment between an "local" offset and its "absolute" offset.

The formula is:
local = absolute - adjustment

The JFlex-generated lexer sets the local offset when it tokenizes a file. Meanwhile, IncludeHandler records the "adjustment" to compute the "absolute" offset.

Besides offset adjustment, an OffsetCue also records the name of the file the character is from.

Example

Suppose "main.as" includes "A.as"; "A.as" includes "B.as".

Imagine the following character stream and the tuples inside parentheses are OffsetCue.

 --------->        ----------->  ----------->  ------>     ----------->
 (0:main.as)_______(2:A.as)______(4:B.as)______(6:A.as)____(7:main.as)_______
 [local]     0   1          0  1         0 1 2 3         2            2  3
 [absolute]  0   1          2  3         4 5 6 7         8            9  10
 [file] main.as    in "A"         in "B"        back to "A"   back to "main"
 

1. 0:main.as - the root file.
2. 2:A.as - main.as includes A.as. Local offset "1" in A.as is absolute offset "3" in parsing main.as, because the adjustment is "2";
3. 4:B.as - A.as includes B.as. Local offset "0" in B.as is absolute offset "4" in parsing main.as, because the adjustment is "4"
4. 6:A.as - return to A.as from B.as. The adjustments change because characters in B.as advance absolute offsets.
5. 7:main.as - return to main.as from A.as.

An OffsetCue applies to all the characters/tokens after itself (inclusive) until the next OffsetCue (exclusive).

OffsetCue is an immutable class. It is created in IncludeHandler.

Field Summary

Fields

Modifier and Type	Field and Description
int	absolute Absolute offset.
int	adjustment Adjustment between absolute offset and local offset.
String	filename File that contains the characters after this cue point until the next cue point.
int	local Local offset.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	OffsetCue(String filename, int absolute, int adjustment)

Method Summary

Methods

Modifier and Type	Method and Description
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

filename

public final String filename

File that contains the characters after this cue point until the next cue point.

adjustment

public final int adjustment

Adjustment between absolute offset and local offset.
local = absolute - adjustment

absolute

public final int absolute

Absolute offset.

local

public final int local

Local offset.

Constructor Detail

OffsetCue

protected OffsetCue(String filename,
         int absolute,
         int adjustment)

Method Detail

toString

public String toString()

Overrides:

toString in class Object