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DoctorWkt.pdp7-unix/bin/cat
2016-03-04 13:41:16 +10:00

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010000: 237777 lac 017777 i
010001: 550407 sad d4 " Skip if we have more than four argument words
010002: 610052 jmp nofiles " Only four argument words, so no arguments
010003: 217777 lac 017777 " Move five words past the argument word count
010004: 350406 tad d1 " so that AC points at the first argument
010005: 350407 tad d4 " and save the pointer in name
010006: 050010 dac name
010007: 020003 sys open; name:0; 0 " Open file, get fd back
010010: 000000
010011: 000000
010012: 741100 spa
010013: 610035 jmp badfile " Negative fd, exit with an error message
010014: 050301 dac fi " Save file descriptor in fi
010015: 110104 jms getc " Get a character in AC
010016: 550407 sad o4
010017: 610022 jmp 1f " Break the loop when we get a ctrl-D
010020: 110140 jms putc " Write the character on stdout
010021: 610015 jmp 1b " and loop back
010022: 210301 lac fi " Close the file descriptor in fi
010023: 020011 sys close
010024: 777774 -4
010025: 377777 tad 017777 i " Subtract 4 from the count of argument words
010026: 077777 dac 017777 i
010027: 550407 sad d4 " Is the value 4, i.e. no args left?
010030: 610064 jmp done " Yes, so exit
010031: 210010 lac name " Still an argument, so move up
010032: 350407 tad d4 " to the next filename argument
010033: 050010 dac name
010034: 610007 jmp loop " and loop back to cat this file
010035: 210010 lac name " Get the pointer to the filename
010036: 050041 dac 1f " Store it in 1f below
010037: 210410 lac d8 " Load fd 8 which is stderr
010040: 020005 sys write; 1:0; 4 " Write the four words of the filename
010041: 000000
010042: 000004
010043: 210410 lac d8
010044: 020005 sys write; 1f; 2 " and then write " ?\n"
010045: 010050
010046: 000002
010047: 610024 jmp loop1 " Now try doing the next argument
010050: 000040 1: 040;077012 " String literal: " ?\n"
010051: 077012
010052: 210410 lac d8
010053: 020005 sys write; 1f; 5 " Write "No files\n" to stderr
010054: 010057
010055: 000005
010056: 020016 sys exit " and exit
010057: 156157 1: <no>; 040; <fi>;<le>;<s 012
010060: 000040
010061: 146151
010062: 154145
010063: 163012
010064: 210404 lac noc " Is the number of characters left zero?
010065: 741200 sna
010066: 020016 sys exit " Yes, exit
010067: 510406 and d1
010070: 751200 sna cla
010071: 610074 jmp 1f
010072: 110140 jms putc " Store the character in the buffer
010073: 610064 jmp done " and loop back
010074: 210404 lac noc " Get the number of characters in the buffer
010075: 744020 rcr " Divide by two to convert to words
010076: 050102 dac 1f " Save in the write's word count below
010077: 210405 lac fo " Load fd 1, stdout
010100: 020005 sys write; iopt+1; 1:.. " Write the leftover buffer and exit
010101: 010304
010102: 010000
010103: 020016 sys exit
010104: 000000 getc: 0
010105: 210176 lac ipt " Load the pointer to the next word in the buffer
010106: 550177 sad eipt
010107: 610123 jmp 1f " We've reached the end of the buffer, so read more
010110: 050174 dac 2f " Save the pointer
010111: 310411 add o400000 " Flip the msb and save into ipt
010112: 050176 dac ipt
010113: 740010 ral " Move the msb into the link register
010114: 230174 lac 2f i " Load the word from the buffer
010115: 741400 szl " Skip if this is the second character in the word
010116: 660511 lrss 9 " It's the first char, shift down the top character
010117: 510412 and o177 " Keep the lowest 7 bits
010120: 741200 sna
010121: 610105 jmp getc+1 " Skip a NUL characters and read another one
010122: 630104 jmp getc i " Return the character from the subroutine
010123: 210301 lac fi " Buffer is empty, read another 64 characters
010124: 020004 sys read; iipt+1; 64
010125: 010201
010126: 000100
010127: 741200 sna
010130: 610136 jmp 1f " No characters were read in
010131: 350200 tad iipt " Add the word count to the base of the buffer
010132: 050177 dac eipt " and store in the end buffer pointer
010133: 210200 lac iipt " Reset the ipt to the base of the buffer
010134: 050176 dac ipt
010135: 610105 jmp getc+1 " and loop back to get one character
010136: 210407 lac o4 " No character, return with ctrl-D
010137: 630104 jmp getc i " return from subroutine
010140: 000000 putc: 0
010141: 510412 and o177 " Keep the lowest 7 bits and save into 2f+1
010142: 050175 dac 2f+1
010143: 210302 lac opt " Save the pointer to the empty buffer
010144: 050174 dac 2f " position to 2f
010145: 310411 add o400000 " Flip the msb and save back into opt
010146: 050302 dac opt " This also has the effect of incrementing
010147: 741100 spa " If the bit was set, we already have one
010150: 610154 jmp 1f " character at 2f+1. If no previous character,
010151: 230174 lac 2f i " merge the old and new character together
010152: 250175 xor 2f+1
010153: 610156 jmp 3f " and go to the "save it in buffer" code
010154: 210175 lac 2f+1 " Move the character up into the top half
010155: 660711 alss 9
010156: 070174 dac 2f i " Save the word into the buffer
010157: 450404 isz noc " Add 1 to the char count, never skipping
010160: 210404 lac noc " Have we reached 128 characters, 64 words?
010161: 550413 sad d128
010162: 741000 skp
010163: 630140 jmp putc i " No, so return (more room still in the buffer)
010164: 210405 lac fo " Load fd1 (i.e stdout)
010165: 020005 sys write; iopt+1; 64 " and write out the 64 words in the buffer
010166: 010304
010167: 000100
010170: 210303 lac iopt
010171: 050302 dac opt " Set opt pointing back to base of buffer
010172: 150404 dzm noc " Set the number of chars in the buffer to 0
010173: 630140 jmp putc i " and return
010174: 000000 2: 0;0 " Current input and output word pointers
010175: 000000
010176: 000000 ipt: 0 " Current input buffer base
010177: 000000 eipt: 0 " Pointer to end of data read in input buffer
010200: 010201 iipt: .+1; .=.+64 " 64 word input buffer and pointer to it
010301: 000000 fi: 0 " Input file descriptor
010302: 010304 opt: .+2 " Current output buffer base
010303: 010304 iopt: .+1; .=.+64 " 64 word output buffer and pointer to it
010404: 000000 noc: 0 " Number of output characters
010405: 000001 fo: 1 " Output file descriptor, fd 1 is stdout
010406: 000001 d1: 1 " Octal and decimal constants
010407: 000004 o4:d4: 4
010410: 000010 d8: 8
010411: 400000 o400000: 0400000 " Msb toggle bit
010412: 000177 o177: 0177 " ASCII mask
010413: 000200 d128: 128 " 128 words in the output buffer