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https://github.com/DoctorWkt/pdp7-unix.git
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536de9ea56
017777, oops. I've added more comments to wktcat.s (renamed from simplecat.s). Now we need to find out how the real PDP-7 Unix does command line arguments.
118 lines
2.7 KiB
ArmAsm
118 lines
2.7 KiB
ArmAsm
" Warren's cat program: cat [arg1 arg2 ...]
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"
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" Because the a7out simulator currently doesn't deal with ASCII files,
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" here is how you can test it:
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" ./as7 wktcat.s > a.out
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"
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" ./a7out a.out > z1
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" <type some lines and end in ctrl-D>
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"
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" ./a7out a.out z1 z1
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" <the text you typed in will be displayed twice>
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"
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" Also, the current coding is hideous and needs refactoring.
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" I'm still coming to grips with PDP-7 assembly code.
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main:
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" Load the pointer pointer in 017777 to see if we have any arguments
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lac 017777 i
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sza " No args, so copy stdin to stdout
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jmp catfiles " Yes args, so deal with them below
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" This section copies from standard input to standard output
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stdinout:
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" Read five words into the buffer from stdin
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" Five was chosen arbitrarily
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lac d0
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sys read; buf; 5
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spa " Skip if result was >= 0
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jmp error " Result was -ve, so error result
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sna " Skip if result was >0
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jmp end " Result was zero, so nothing left to read
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" Save the count of words read in
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dac 1f
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" Write five words from the buffer to stdout
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lac d1
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sys write; buf; 1:0
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" and loop back for more words to read
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jmp stdinout
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" This section opens files, and copies their contents to standard output
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catfiles:
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" We start with AC pointing to an argument. Save it at label 1f
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dac 1f
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" Open the file and get the fd into AC
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sys open; 1:0; 0; 0
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spa
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jmp noopen " Bad fd, exit with an error message
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dac fd " Save the file descriptor
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fileloop:
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" Read five words into the buffer from the input file
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lac fd
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sys read; buf; 5
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spa " Skip if result was >= 0
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jmp error " Result was -ve, so error result
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sna " Skip if result was >0
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jmp fileend " Result was zero, so nothing left to read
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" Save the count of words read in
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dac 1f
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" Write five words from the buffer to stdout
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lac d1
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sys write; buf; 1:0
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" and loop back for more words to read
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jmp fileloop
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fileend:
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" Close the open file descriptor
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lac fd
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sys close
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" Load and increment the 017777 pointer
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lac 017777
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tad d1
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dac 017777
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" Load the pointer pointer in 017777 to see if we have any more arguments
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lac 017777 i
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sna " No args, so end the program
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jmp end
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jmp catfiles " Otherwise loop back to cat this file
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end:
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" exit
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sys exit
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noopen:
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" Print an "err open" string and exit
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lac d1
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sys write; noopenstr; 5
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sys exit
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noopenstr:
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<er>;<r 040;<op>;<en>;012000
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error:
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" Print an "err read" string and exit
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lac d1
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sys write; noreadstr; 5
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sys exit
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noreadstr:
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<er>;<r 040;<re>;<ad>;012000
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fd: 0 " fd of the open file
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d0: 0 " Constants 0 and 1
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d1: 1
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" Input buffer for read
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buf: 0; 0; 0; 0; 0
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