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dev:crosscompiler:strings [2015/04/06 16:14] – [Erzeugung] ursgrafdev:crosscompiler:strings [2016/02/25 13:33] (current) – external edit 127.0.0.1
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 The field //size// holds the number of bytes of the whole object. This is analogous to other objects (see [[dev:rts:heap|Heap Manager and Garbage Collection]]). It is used for an efficient sweep phase. The field //size// holds the number of bytes of the whole object. This is analogous to other objects (see [[dev:rts:heap|Heap Manager and Garbage Collection]]). It is used for an efficient sweep phase.
  
-===== Erzeugung =====+===== Creation =====
 The Bytecode for the creation of a string is The Bytecode for the creation of a string is
 <code> <code>
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   * initialize the string.   * initialize the string.
 Finally, the reference to the newly created string has to be put into the result register of the //sCnew// instruction.   Finally, the reference to the newly created string has to be put into the result register of the //sCnew// instruction.  
-===== Feldzugriffe ===== +===== Access to Fields ===== 
-Sobald auf Felder des Stringarrays zugegriffen werden sollmuss das im Codegenerator speziell berücksichtigt werdenEin solcher Zugriff hat in der SSA die Form+When accessing fields of a stringthe code generator has to modify the codeSuch an access shows up in the SSA as follows
 <code> <code>
 1: MonadicRef[sCloadFromField] {0} <value([C)> (Char-Array) 1: MonadicRef[sCloadFromField] {0} <value([C)> (Char-Array)
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 3: Dyadic[sCloadFromArray] {1, 2} (Char) 3: Dyadic[sCloadFromArray] {1, 2} (Char)
 </code> </code>
-Zuerst wird also das Feld //value// geladen. //value// ist eine ReferenzAnschliessend wird über die Referenz und ein Index auf das Array zugegriffenIm Codegenerator muss bei einer Instruktion //sCloadFromField// geprüft werden, ob auf das Feld //String.value// zugegriffen wirdFalls jawird dieser Zugriff weggelassen und der Offset von //value// gemerktBei der darauffolgenden Instruktion //sCloadFromArray// muss dieser Offset zum Index dazuaddiert werdenEbenfalls darf als Arrayreferenz nicht das //value// dienen, sondern die Referenz auf den String. \\ +The field //value// is loaded. //value// is a referenceWith this reference and an index into the array the proper character can be accessedThe code generator has to check for the instruction //sCloadFromField// if the field is  //String.value//If truethe fetching is ommited and the offset of //value// is storedWith the subsequent instruction //sCloadFromArray//, the offset must be added to the indexAt the same time one cannot use //value// as the array reference but must use the reference to the string. \\ 
-Analog muss auch das Schreiben auf die Stringzeichen angepasst werdenHier gibt es aber noch eine Besonderheit. Weil Strings immutable sindwerden nur beim Initialisieren in den Fabrikmethoden die Arrayfelder geschriebenDarum kann die Prüfung auf Arrayüberschreitung weggelassen werden.+Similarly, writing to a string must be customizedHoweverstrings in java are immutable. Writing to strings happens only in the factory methods during initializationChecking for array index out of bounds may be ommited as well.
  
 ===== Constant String ===== ===== Constant String =====
-Constant strings are stored in the constant block of a class, see [[Linker32]]. The layout there must be identical to the layout on the heap as given above.+Constant strings are stored in the constant block of a class, see [[dev:crosscompiler:backend_ppc:linker32|Linker32]]. The layout there must be identical to the layout on the heap as given above.
  
 ===== Special Linking ===== ===== Special Linking =====
 The type descriptor of the class //String// must have its field //nofInstPtr// set to 0. Though there is a field //char[] values// we access this field in an omtimized way as decribed above. The garbage collector must not follow this field! The type descriptor of the class //String// must have its field //nofInstPtr// set to 0. Though there is a field //char[] values// we access this field in an omtimized way as decribed above. The garbage collector must not follow this field!
dev/crosscompiler/strings.1428329647.txt.gz · Last modified: 2016/02/25 13:33 (external edit)