The Piet programming language is similar to Brainf*ck, except it is way more interesting. Piet programs are pictures!
SysPiet respects all the rules of the Piet programming language. However, it adds one single instruction: Syscall. Syscall is represented by a Smoke codel. The smoke codel has the color #C0C0C0. When encountered the smoke codel behaves as follow:
- The first value of the stack is popped and used as the number of the syscall to be called.
- The second value of the stack is popped and used as the number of arguments to be used as a syscall.
- Two times the number of arguments are popped.
- For each couple of values, the first one is the type of the argument.
- The second is the argument itself.
- The syscall is called.
- The return value of the syscall is pushed in the stack.
- Resume execution, do not try to use the difference between the Smoke codel and the next codel as an operation (same behavior as when going from a white codel to a colored codel).
There are two types of arguments:
- 1: The argument is a regular number
- 2: The argument is a pointer. This means that the address of the beginning of the piet stack has to be added to the argument
Here's an example:
+-----+-------------------+-------------------------------------------+----------------------------------------+
| pos | Stack (grows up ) | What it means to the interpreter | What it means to the syscall |
+-----+-------------------+-------------------------------------------+---------------------------------------+
| 8 | 0 | Number of the syscall | Syscall nb. 0 is read() |
| 7 | 3 | Number of arguments for the syscall | |
| 6 | 1 | The first argument is a number | First arg is the file descriptor, |
| 5 | 0 | The first argument is 0 | 0 means stdin |
| 4 | 2 | The second argument is a pointer | Second arg is the buffer that should |
| 3 | 0 | The second argument is the address of the | be filled, here it's the beginning |
| | | first element of the piet stack plus 0 | of the piet stack |
| 2 | 1 | The third argument is a number | Third arg is the number of bytes |
| 1 | 1 | The third argument is 1 | that should be read |
| 0 | 42 | Doesn't mean anything | This is where the data will be placed |
+-----+-------------------+-------------------------------------------+---------------------------------------+
If the stack looks like this when arriving on a Smoke codel, the read(stdin, piet_stack, 1) syscall will be executed. If the string "Hello world!" is available in stdin, the piet_stack will look like this once leaving the smoke codel:
+-----+-------------------+-----------------------------------------------------------------------------------+
| pos | Stack (grows up ) | What it means |
+-----+-------------------+-------------------------------------------+---------------------------------------+
| 1 | 1 | Return value of the syscall, here it is 1 because read() read a single byte. |
| 0 | 72 | This is the byte read by read(), H is '72' in the ascii table. |
+-----+-------------------+-------------------------------------------+---------------------------------------+
This is an example syspiet program with a codel size of 1 and a codel size of
10 that will execute write(stdin, piet_stack, 1):
Clone this repository, cd into the directory, build using a nightly version of the rust toolchain and you should be good to go!
git clone 'https://github.com/glacambre/piet'
cd piet
cargo build --release
target/release/pieti $piet_program.png- Codel size defaults to 1. In order to change it, use the -c flag.
- Unknow codels default to white. In order to default to black, use the -b flag.
- Syspiet is disabled by default. In order to enable it, use the -s flag.
The program and its execution can be displayed using the --view flag. This should show the picture and highlight the current codel. Using syspiet to access stdin/stdout might make the display crash. Currently only the png format is supported. This might change.