mirror of
https://github.com/DoctorWkt/pdp7-unix.git
synced 2026-04-15 16:19:44 +00:00
I've added tad and sza to the a7out simulator, and I also added some
code to place command-line arguments into the simulated memory. I'm trying to write my own version of cat so I can compare mine to the real one. Right now there's a bug when simplecat has two arguments. Zero and one arguments are OK! Saving so I have a backup before proceeding.
This commit is contained in:
Warren Toomey
111
tools/a7out
111
tools/a7out
@@ -27,11 +27,12 @@ if ( ( @ARGV > 0 ) && ( $ARGV[0] eq "-d" ) ) {
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}
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# Check the arguments
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die("Usage: $0 [-d] a.outfile\n") if ( @ARGV != 1 );
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die("Usage: $0 [-d] a.outfile [arg1 arg2 ...]\n") if ( @ARGV < 1 );
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# Load the a.out file into memory
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# and simulate it
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load_code( $ARGV[0] );
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load_code( shift(@ARGV) );
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set_arguments(@ARGV);
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simulate();
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exit(0);
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@@ -67,6 +68,62 @@ sub load_code {
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close($IN);
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}
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### Copy the arguments into the PDP-7 memory space, and build
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### an array of pointers to these arguments. Build a pointer
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### at 017777 that points at the array.
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###
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### At the moment, this is NOT what PDP-7 Unix uses, but it's
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### a start and it will help us to grok the real thing.
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###
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### For now, assume abc, def and ghi are stored in memory.
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### The layout of the pointers and strings would be:
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###
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### +-------+
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### | |
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### | +-----|---------+
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### | | | |
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### | | +---|---------|---------+
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### | | | | | |
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### | | | V V V
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### |o|o|o|0|<ab>|<c 0|<de>|<f 0|<gh>|<i 0|o|
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### ^ |
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### | |
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### +-------------------------------------+
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### 0 0 0 0 0 0 0 0 0 0 0
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### 1 1 1 1 1 1 1 1 1 1 1
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### 7 7 7 7 7 7 7 7 7 7 7
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### 7 7 7 7 7 7 7 7 7 7 7
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### 6 6 6 7 7 7 7 7 7 7 7
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### 5 6 7 0 1 2 3 4 5 6 7
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###
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sub set_arguments {
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# No arguments, set the 017777 pointer to 017776 which is NULL
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if (@ARGV==0) {
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$Mem[ 017777 ] = 017776;
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print( STDERR "No arguments, so NULL 017777 pointer\n") if ($debug);
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return;
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}
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# Count the number of words to store each string and its pointer
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my $wordcount=1; # 1 as we count the NULL pointer at end of array
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my $argcount= @ARGV;
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foreach my $arg (@ARGV) {
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# +1 before /2 to allow for the NUL character at end of string
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# += +1 to include the pointer to the string
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$wordcount += 1 + ( (length($arg) +1)/2);
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}
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my $arraybase= 017777 - $wordcount;
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my $stringbase= $arraybase + $argcount + 1; # include NULL pointer
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$Mem[ 017777 ] = $arraybase;
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# Now copy each string into memory and initialise the pointer
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foreach my $arg (@ARGV) {
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$Mem[$arraybase++]= $stringbase;
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$stringbase= string2mem($arg, $stringbase);
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}
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}
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### Simulate the machine code loaded into memory
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sub simulate {
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@@ -74,6 +131,7 @@ sub simulate {
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my %Oplist = (
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oct("004") => \&dac,
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oct("020") => \&lac,
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oct("034") => \&tad,
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oct("060") => \&jmp,
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oct("070") => \&iot,
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oct("074") => \&special,
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@@ -123,7 +181,7 @@ sub lac {
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# Deposit AC
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sub dac {
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my ( $instruction, $indirect, $addr ) = @_;
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printf( STDERR "PC %06o: dac AC (value %08o) into %05o into AC\n",
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printf( STDERR "PC %06o: dac AC (value %08o) into %05o\n",
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$PC, $AC, $addr )
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if ($debug);
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if ($indirect) {
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@@ -134,6 +192,20 @@ sub dac {
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$PC++;
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}
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# Add to AC
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sub tad {
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my ( $instruction, $indirect, $addr ) = @_;
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printf( STDERR "PC %06o: tac AC (value %08o) from addr %05o\n",
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$PC, $AC, $addr )
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if ($debug);
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if ($indirect) {
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$AC += $Mem[ $Mem[$addr] & 017777 ];
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} else {
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$AC+= $Mem[$addr];
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}
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$PC++;
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}
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# Jump
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sub jmp {
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my ( $instruction, $indirect, $addr ) = @_;
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@@ -153,15 +225,20 @@ sub special {
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exit(1);
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}
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if ( $instruction == 0741100 ) { # spa: skip on positive AC
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printf( STDERR "PC %06o: spa\n", $PC ) if ($debug);
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printf( STDERR "PC %06o: spa AC %06o\n", $PC, $AC ) if ($debug);
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$PC += ( $AC >= 0 ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0741200 ) { # sna: skip on non-zero AC
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printf( STDERR "PC %06o: sna\n", $PC ) if ($debug);
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printf( STDERR "PC %06o: sna AC %06o\n", $PC, $AC ) if ($debug);
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$PC += ( $AC != 0 ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0740200 ) { # sza: skip on zero AC
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printf( STDERR "PC %06o: sza AC %06o\n", $PC, $AC ) if ($debug);
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$PC += ( $AC == 0 ) ? 2 : 1;
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return;
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}
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printf( STDERR "PC %06o: unknown instruction %08o\n", $PC, $instruction );
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exit(1);
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}
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@@ -237,14 +314,13 @@ sub sys_open {
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if ( open( my $FH, "<", $filename ) ) {
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# Find a place in the @FD array to store this filehandle. 99 is arbitrary
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my $fd;
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foreach $fd ( 0 .. 99 ) {
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foreach my $fd ( 0 .. 99 ) {
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if ( !defined( $FD[$fd] ) ) {
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$FD[$fd] = $FH;
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$AC = $fd;
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last;
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}
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}
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$AC = $fd;
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return;
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} else {
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# No filehandle, so it's an error
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@@ -393,3 +469,22 @@ sub mem2string {
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$addr++;
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}
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}
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# Given a string and the address of a word in memory, copy
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# the string into memory starting at that address and NUL
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# terminate the string. Return the first address after the string.
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#
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# We will go off the end of the string: suppress warnings
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no warnings ('substr');
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sub string2mem {
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my ($str, $base)= @_;
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# <= length so we go off the end and insert a NUL
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for (my $i=0; $i <= length($str); $i += 2) {
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my $c1= substr($str, $i, 1) || "";
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my $c2= substr($str, $i+1, 1) || "";
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#printf("Saving %06o to %05o\n", (ord($c1) << 9 ) | ord($c2), $base);
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$Mem[$base++]= (ord($c1) << 9 ) | ord($c2);
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}
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return($base);
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}
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@@ -1,6 +1,13 @@
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" Simple cat program: echo stdin to stdout until no more words to read
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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
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" This section copies from standard input to standard output
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stdinout:
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" Read 5 words into the buffer from stdin
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lac d0
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sys read; buf; 5
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@@ -15,15 +22,81 @@ main:
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" Write 5 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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jmp main
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error:
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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 5 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 5 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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d0: 0
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d1: 1
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fd: 0 " fd of the open file
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" Input buffer for read
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buf: 0; 0; 0; 0; 0
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