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I refactored tools/wktcat.s to lose the repeated code, and I also

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improved the comments in the code. I'm happy with it, now.
This commit is contained in:
Warren Toomey
2016-02-27 11:12:16 +10:00
parent fafeae7470
commit 4ee2619b8c
1 changed files with 18 additions and 32 deletions
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50
tools/wktcat.s
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@@ -9,9 +9,6 @@
"
" ./a7out a.out z1 z1
" <the text you typed in will be displayed twice>
"
" Also, the current coding is hideous and needs refactoring.
" I'm still coming to grips with PDP-7 assembly code.
main:
" Load the pointer pointer in 017777 to see if we have any arguments
@@ -19,23 +16,24 @@ main:
sad d4 " Skip if we have more than four argument words
jmp stdinout " Only four argument words, so no arguments
lac 017777
tad d1 " Bump AC up by 5 so that it points at the first argument
lac 017777 " Move five words past the argument word count
tad d1 " so that AC points at the first argument
tad d4
" This section opens files, and copies their contents to standard output
" This section opens files and copies their contents to standard output
catfiles:
" We start with AC pointing to an argument. Save it at label 1f
" We start with AC pointing to an argument. Save it at the "name" label
dac name
" Open the file and get the fd into AC
sys open; name:0; 0; 0
spa
jmp badfile " Bad fd, exit with an error message
jmp badfile " Negative fd, exit with an error message
dac fd " Save the file descriptor
fileloop:
" Read five words into the buffer from the input file
" Five was chosen arbitrarily
lac fd
sys read; buf; 5
spa " Skip if result was >= 0
@@ -76,26 +74,15 @@ end:
sys exit
" This section copies from standard input to standard output
" We cheat by setting the fd value to zero and storing 8
" into the argc word count, so that when the code hits
" fileend, the word count drops to 4 and we exit.
stdinout:
" Read five words into the buffer from stdin
" Five was chosen arbitrarily
lac d8
dac 017777 i " Save 8 into the word count
lac d0
sys read; buf; 5
spa " Skip if result was >= 0
jmp error " Result was -ve, so error result
sna " Skip if result was >0
jmp end " Result was zero, so nothing left to read
" Save the count of words read in
dac 1f
" Write five words from the buffer to stdout
lac d1
sys write; buf; 1:0
" and loop back for more words to read
jmp stdinout
dac fd " Save file descriptor 0
jmp fileloop
" This code comes from the real cat.s
badfile:
@@ -107,12 +94,11 @@ badfile:
sys write; 1f; 2
sys exit " and exit
1: 040; 077012
1: 040; 077012 " String literal: " ?\n"
error:
" Print an "err read" string and exit
lac d1
" Print an "err read" string on stderr and exit
lac d8
sys write; noreadstr; 5
sys exit
@@ -120,11 +106,11 @@ noreadstr:
<er>;<r 040;<re>;<ad>;012000
fd: 0 " fd of the open file
d0: 0 " Constants 0 and 1
d0: 0 " Constants 0, 1, 4 and 8
d1: 1
d4: 4
d8: 8 " stderr seems to have fd 8
minus4: 0777774 " -4 constant
minus4: 0777774 " Constant -4
" Input buffer for read
buf: 0; 0; 0; 0; 0