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Format/typo fixes in 1994/shapiro

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This completes 1994/shapiro as long as a formatting change in shapiro.md
is correct. That will be checked and if necessary it will be fixed.
This commit is contained in:
Cody Boone Ferguson committed 2023-11-10 09:38:35 -08:00
1 parent eb5845072e
commit e25615b987
2 files changed
+48 -48
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1994/shapiro/README.md
+17 -17
View File
@@ -30,12 +30,14 @@ For more detailed information see [1994 shapiro in bugs.md](/bugs.md#1994-shapir
^Z
bg
ps x
fg
^C
./shapiro_t1
```
Notice what you see in the output of `ps`!
Notice what you see in the output of `ps`! Observe too that after you bring it
back to the foreground what happens.
## Judges' remarks:
@@ -60,29 +62,27 @@ The basic theme (pun) of this program is:
> ~~~~
My entry ([shapiro.c](shapiro.c)) is mostly comment, formatted in the shape of a\
clock. If you strip out the comments and look at the code you will\
quickly realize that the comments were the important part and that\
the code does very little (see pun above). It writes (to stdout)\
another C program ([shapiro_t2.c](shapiro_t2.c)). This is the first level of\
My entry ([shapiro.c](shapiro.c)) is mostly comments, formatted in the shape of a
clock. If you strip out the comments and look at the code you will
quickly realize that the comments were the important part and that
the code does very little (see pun above). It writes (to `stdout`)
another C program ([shapiro_t2.c](shapiro_t2.c)). This is the first level of
obfuscation.
The second program ([shapiro_t2.c](shapiro_t2.c) if you use the Makefile
The second program ([shapiro_t2.c](shapiro_t2.c) (use `make everything` first)
prints a clock in the upper right hand corner of your VTxxx/ANSI display.
Most of the surface obfuscation in the second program
([shapiro_t2.c](shapiro_t2.c))\
was an attempt to make it as small as possible. You should be able to\
see around this with cb(1) and some more intelligent variable names.\
Once you get past this you will realize that the third level of\
obfuscation is a six member client/server hierarchy.\
(See the [shapiro.md](shapiro.md) file for a detailed description of the
algorithm.)
([shapiro_t2.c](shapiro_t2.c)) was an attempt to make it as small as possible.
You should be able to see around this with `cb(1)` and some more intelligent
variable names. Once you get past this you will realize that the third level of
obfuscation is a six member client/server hierarchy. (See the
[shapiro.md](shapiro.md) file for a detailed description of the algorithm.)
`lint` complains about: precedence confusion, `K` may be used before set,
main() returns random value to invocation environment, value type used\
inconsistently, value type declared inconsistently, function argument\
(number) used inconsistently, function returns value which is always\
`main()` returns random value to invocation environment, value type used
inconsistently, value type declared inconsistently, function argument
(number) used inconsistently, function returns value which is always
ignored, function returns value which is sometimes ignored.
All of which are harmless (famous last words).
1994/shapiro/shapiro.md
+31 -31
View File
@@ -1,6 +1,6 @@
# HINTS
For the first program (prog.c):
For the first program ([shapiro.c](shapiro.c)):
This is a very simple program:
@@ -20,15 +20,14 @@ This is a very simple program:
12. exit(0);}
```
Lines 1-5 are basic stuff. Line 6 opens the source code for input. Line 7
is the loop. Line 8 is read in each character in the file (placed in `L`)
while not `EOF` (usually `-1`). Line 9 is an if expression which filters out all
characters not between `J` and `J + 15`. Line 10 uses `M` to execute two different
paths the first just stores the character in `K`. The second path combines
the last two characters read in as high and low nibbles of a byte and
outputs them. In effect this is a very poor ASCII to binary decoder.
The last line is necessary so that make will not stop when it executes
this program.
Lines 1-5 are basic stuff. Line 6 opens the source code for input. Line 7 is the
loop. Line 8 reads in each character in the file (placed in `L`) while not >= 0.
Line 9 is an `if` expression which filters out all characters not between `J`
and `J + 15`. Line 10 uses `M` to execute two different paths; the first just
stores the character in `K` and the second path combines the last two characters
read in as high and low nibbles of a byte and outputs them. In effect this is a
very poor ASCII to binary decoder. The last line is necessary so that make will
not stop when it executes this program.
The second program is encoded into this format and then included (mostly)
as a comment.
@@ -38,6 +37,7 @@ contiguous ASCII characters free for the encoding. Because of this the
second program is mostly included as a comment. However, some of the
characters of the encoded program are also source code for the decoder.
### For the second program (with time.h):
```
@@ -72,37 +72,37 @@ characters of the encoded program are also source code for the decoder.
```
Lines 1 and 2 have to be. Think of `o` in line 3 as send message with
`j`,`k` and `m` as where, format and what. Lines 4 and 5 are all the text
strings. Line 6 is the offsets into the time string for the hours,
minutes and seconds. Lines 7-13 are basic stuff. Line 14 is the crux of
the biscuit. 14 forks off `f` (6) processes each of which is connected to
the ones above and below it with a Unix pipe. It was too difficult to
recover the actual FD numbers for the pipe ends in line 14 so I regenerate
them and `fdopen()` them (for use with the standard C library functions) on lines
15 and 16. Now we have six almost identical processes. Each of which has
two files open `h` and `i` (up and down). The only difference in each process
is the value of `f` (`0 <= f < 6`). The five processes where `f !=0` are the
slave processes and `f == 0` is the master. Line 17 says we are going to do
this forever. Lines 18 and 23 differentiate between the master and the
slaves.
Lines 1 and 2 have to be there. Think of `o` in line 3 as send message with
`j`,`k` and `m` as where, format and what. Lines 4 and 5 are all the text
strings. Line 6 is the offsets into the time string for the hours, minutes and
seconds. Lines 7-13 are basic stuff. Line 14 is the crux of the biscuit. 14
forks off `f` (6) processes each of which is connected to the ones above and
below it with a Unix pipe. It was too difficult to recover the actual FD numbers
for the pipe ends in line 14 so I regenerate them and `fdopen()` them (for use
with the standard C library functions) on lines 15 and 16. Now we have six
almost identical processes each of which has two files open, `h` and `i` (up and
down). The only difference in each process is the value of `f` (`0 <= f < 6`).
The five processes where `f !=0` are the slave processes and `f == 0` is the
master. Line 17 says we are going to do this forever. Lines 18 and 23
differentiate between the master and the slaves.
Lines 19 to 22 are the slave code. Here we read in a line of text from
`i` (down)(line 19) and remove the end of line char (line 20). On line
`i` (down, line 19) and remove the newline char (line 20). On line
21 if this message is for us (if the first character is our number, `f`,
in ASCII) we do two things:
1. We copy the text of the message to `*c` which is really argv[0]. If you are
1. We copy the text of the message to `*c` which is really `argv[0]`. If you are
on the correct flavor of Unix this will change the output of the `ps(1)` command
to the string we just put there.
2. We send the message (not including the number) to stdout with format number 6
2. We send the message (not including the number) to `stdout` with format number 6
(`"\0337\033[%d;65;H%s\0338"`) If you can read VTxxx (and I read books printed
as ANSI/VTxxx codes for fun :-) ) you know this is the sequence for:
remember where we are,
go somewhere else,
print the message,
and return to where we started.
remember where we are,\
go somewhere else,\
print the message,\
and return to where we started.
Line 22 says if this message is not for us (the number is bigger than ours)
send it to `h` (up).