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Task/Queue-Definition/OxygenBasic/queue-definition.basic

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+'==========
+Class Queue
+'==========
+
+ 'FIRST IN FIRST OUT
+
+bstring buf 'buffer to hold queue content
+int    bg   'buffer base offset
+int i       'indexer
+int le      'length of buffer
+
+method constructor()
+====================
+buf=""
+le=0
+bg=0
+i=0
+end method
+
+method destructor()
+===================
+del buf
+le=0
+bg=0
+i=0
+end method
+
+method Encodelength(int ls)
+===========================
+int p at (i+strptr buf)
+p=ls
+i+=sizeof int
+end method
+
+method push(string s)
+=====================
+int ls=len s
+if i+ls+8>le then
+  buf+=nuls 8000+ls*2 'extend buf
+  le=len buf
+end if
+EncodeLength ls 'length of input s
+mid buf,i+1,s   'append input s
+i+=ls
+end method
+
+method popLength() as int
+=========================
+if bg>=i then return -1 'buffer empty
+int p at (bg+strptr buf)
+bg+=sizeof int
+return p
+end method
+
+method pop(string *s) as int
+============================
+int ls=popLength
+if ls<0 then s="" : return ls 'empty buffer
+s=mid buf,bg+1,ls
+bg+=ls
+'cleanup buffer
+if bg>1e6 then
+  buf=mid buf,bg+1
+  le=len buf
+  i-=bg 'shrink buf
+  bg=0
+end if
+end method
+
+method clear()
+==============
+buf=""
+le=0
+bg=0
+i=0
+end method
+
+end class 'Queue
+
+
+'====
+'DEMO
+'====
+
+new Queue  fifo
+string     s
+'
+fifo.push "HumptyDumpty"
+fifo.push "Sat on a wall"
+'
+int er
+do
+  er=fifo.pop s
+  if er then print "(buffer empty)" : exit do
+  print s
+loop
+
+del fifo