70 lines
1.9 KiB
Batchfile
70 lines
1.9 KiB
Batchfile
@echo off
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setlocal enableDelayedExpansion
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:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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:: FIFO queue usage
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:: Define the queue
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call :newQueue myQ
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:: Populate the queue
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for %%A in (value1 value2 value3) do call :enqueue myQ %%A
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:: Test if queue is empty by examining the tail "attribute"
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if myQ.tail==0 (echo myQ is empty) else (echo myQ is NOT empty)
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:: Peek at the head of the queue
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call:peekQueue myQ val && echo a peek at the head of myQueue shows !val!
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:: Process the first queue value
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call :dequeue myQ val && echo dequeued myQ value=!val!
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:: Add some more values to the queue
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for %%A in (value4 value5 value6) do call :enqueue myQ %%A
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:: Process the remainder of the queue
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:processQueue
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call :dequeue myQ val || goto :queueEmpty
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echo dequeued myQ value=!val!
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goto :processQueue
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:queueEmpty
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:: Test if queue is empty using the empty "method"/"macro". Use of the
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:: second IF statement serves to demonstrate the negation of the empty
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:: "method". A single IF could have been used with an ELSE clause instead.
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if %myQ.empty% echo myQ is empty
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if not %myQ.empty% echo myQ is NOT empty
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exit /b
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:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
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:: FIFO queue definition
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:newQueue qName
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set /a %~1.head=1, %~1.tail=0
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:: Define an empty "method" for this queue as a sort of macro
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set "%~1.empty=^!%~1.tail^! == 0"
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exit /b
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:enqueue qName value
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set /a %~1.tail+=1
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set %~1.!%~1.tail!=%2
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exit /b
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:dequeue qName returnVar
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:: Sets errorlevel to 0 if success
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:: Sets errorlevel to 1 if failure because queue was empty
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if !%~1.tail! equ 0 exit /b 1
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for %%N in (!%~1.head!) do (
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set %~2=!%~1.%%N!
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set %~1.%%N=
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)
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if !%~1.head! == !%~1.tail! (set /a "%~1.head=1, %~1.tail=0") else set /a %~1.head+=1
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exit /b 0
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:peekQueue qName returnVar
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:: Sets errorlevel to 0 if success
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:: Sets errorlevel to 1 if failure because queue was empty
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if !%~1.tail! equ 0 exit /b 1
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for %%N in (!%~1.head!) do set %~2=!%~1.%%N!
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exit /b 0
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