C - Stacks, Queues - LIFO, FIFO

• A project done during my Full-Stack Software Engineering studies at ALX Africa, a course offered by Holberton School.

Technologies

• Files written in vi, vim, and emacs editors.
• C files compiled using gcc 9.4.0.
• C files wriiten according to the betty coding style. Checked using betty-style.pl and betty-doc.pl.
• Files tested on Ubuntu 20.04 LTS using gcc.
• Outpus are printed on stdout
• Error messages printed on stderr

The Monty language

• Monty 0.98 is a scripting language that is first compiled into Monty byte codes (Just like Python). It relies on a unique stack, with specific instructions to manipulate it. The goal of this project is to create an interpreter for Monty ByteCodes files.

A. Monty byte code files

• Files containing Monty byte codes usually have the .m extension. Most of the industry uses this standard but it is not required by the specification of the language. There is not more than one instruction per line. There can be any number of spaces before or after the opcode and its argument
• Monty byte code files can contain blank lines (empty or made of spaces only, and any additional text after the opcode or its required argument is not taken into account.

B. The monty program

• Usage: monty file
  • where file is the path to the file containing Monty byte code.

Compilation

$ gcc -Wall -Werror -Wextra -pedantic *.c -o monty
$

Run

$ ./monty monty_file.m
5
7
1
2

Interpreter Synopsis

$ ./monty [montyfilename]
$

• If the user does not give any file or more than one argument to your program, print the error message USAGE: monty file, followed by a new line, and exit with the status EXIT_FAILURE
• If, for any reason, it’s not possible to open the file, print the error message Error: Can't open file <file>, followed by a new line, and exit with the status EXIT_FAILURE.
  • where <file> is the name of the file.
• If the file contains an invalid instruction, print the error message L<line_number>: unknown instruction <opcode>, followed by a new line, and exit with the status EXIT_FAILURE
  • where is the line number where the instruction appears.
  • Line numbers always start at 1
• The monty program runs the bytecodes line by line and stop if either:
  • it executed properly every line of the file
  • it finds an error in the file
  • an error occured
• If you can’t malloc anymore, the program prints the error message Error: malloc failed, followed by a new line, and exit with status EXIT_FAILURE.

C. Opcodes

1. pint

• The opcode pint prints the value at the top of the stack, followed by a new line.

Usage: pint

• If the stack is empty, print the error message L<line_number>: can't pint, stack empty, followed by a new line, and exit with the status EXIT_FAILURE
• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/06.m 
push 1
pint
push 2
pint
push 3
pint
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/06.m 
1
2
3
micahondiwa@ubuntu:~/monty$ 

2. pop

• The opcode pop removes the top element of the stack.

Usage: pop

• If the stack is empty, print the error message L<line_number>: can't pop an empty stack, followed by a new line, and exit with the status EXIT_FAILURE
• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/07.m 
push 1
push 2
push 3
pall
pop
pall
pop
pall
pop
pall
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/07.m 
3
2
1
2
1
1
micahondiwa@ubuntu:~/monty$ 

3. swap

• The opcode swap swaps the top two elements of the stack.

Usage: swap

• If the stack contains less than two elements, print the error message L<line_number>: can't swap, stack too short, followed by a new line, and exit with the status EXIT_FAILURE -Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/09.m 
push 1
push 2
push 3
pall
swap
pall
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/09.m 
3
2
1
2
3
1
micahondiwa@ubuntu:~/monty$ 

4. add

• The opcode add adds the top two elements of the stack.

Usage: add

• If the stack contains less than two elements, print the error message L<line_number>: can't add, stack too short, followed by a new line, and exit with the status EXIT_FAILURE -The result is stored in the second top element of the stack, and the top element is removed, so that at the end:

  • The top element of the stack contains the result
  • The stack is one element shorter

• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/12.m 
push 1
push 2
push 3
pall
add
pall
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/12.m 
3
2
1
5
micahondiwa@ubuntu:~/monty$

5. nop

• The opcode nop doesn’t do anything!

Usage: nop

6. sub

• The opcode sub subtracts the top element of the stack from the second top element of the stack.

Usage: sub

• If the stack contains less than two elements, print the error message L<line_number>: can't sub, stack too short, followed by a new line, and exit with the status EXIT_FAILURE
• The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
  • The top element of the stack contains the result
  • The stack is one element shorter
• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/19.m 
push 1
push 2
push 10
push 3
sub
pall
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/19.m 
7
2
1

7. div

• The opcode div divides the second top element of the stack by the top element of the stack.

Usage: div

• If the stack contains less than two elements, print the error message L<line_number>: can't div, stack too short, followed by a new line, and exit with the status EXIT_FAILURE
• The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
  • The top element of the stack contains the result
  • The stack is one element shorter
• If the top element of the stack is 0, print the error message L<line_number>: division by zero, followed by a new line, and exit with the status EXIT_FAILURE

8. mul

• The opcode ```mul`` multiplies the second top element of the stack with the top element of the stack.

Usage: mul

• If the stack contains less than two elements, print the error message L<line_number>: can't mul, stack too short, followed by a new line, and exit with the status EXIT_FAILURE.
• The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
  • The top element of the stack contains the result
  • nThe stack is one element shorter

9. mod

• The opcode mod computes the rest of the division of the second top element of the stack by the top element of the stack.

Usage: mod

• If the stack contains less than two elements, print the error message L<line_number>: can't mod, stack too short, followed by a new line, and exit with the status EXIT_FAILURE.
• The result is stored in the second top element of the stack, and the top element is removed, so that at the end:
  • The top element of the stack contains the result
  • The stack is one element shorter
• If the top element of the stack is 0, print the error message L<line_number>: division by zero, followed by a new line, and exit with the status EXIT_FAILURE

10. pchar

• The opcode pchar prints the char at the top of the stack.

• Usage: pchar

• The integer stored at the top of the stack is treated as the ascii value of the character to be printed

• If the value is not in the ascii table (man ascii) print the error message L<line_number>: can't pchar, value out of range, followed by a new line, and exit with the status EXIT_FAILURE

• If the stack is empty, print the error message L<line_number>: can't pchar, stack empty, followed by a new line, and exit with the status EXIT_FAILURE

• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/28.m 
push 72
pchar
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/28.m 
H
micahondiwa@ubuntu:~/monty$

11. pstr

• The opcode pstr prints the string starting at the top of the stack, followed by a new line.

Usage: pstr

• The integer stored in each element of the stack is treated as the ascii value of the character to be printed
• The string stops when either:
  • the stack is over
  • the value of the element is 0
  • the value of the element is not in the ascii table
• If the stack is empty, print only a new line
• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/31.m 
push 1
push 2
push 3
push 4
push 0
push 110
push 0
push 108
push 111
push 111
push 104
push 99
push 83
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/31.m 
School
micahondiwa@ubuntu:~/monty$ 

12. rotl

• The opcode rotl rotates the stack to the top.

Usage: rotl

• The top element of the stack becomes the last one, and the second top element of the stack becomes the first one rotl never fails
• Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/35.m 
push 1
push 2
push 3
push 4
push 5
push 6
push 7
push 8
push 9
push 0
pall
rotl
pall
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/35.m 
0
9
8
7
6
5
4
3
2
1
9
8
7
6
5
4
3
2
1
0
micahondiwa@ubuntu:~/monty$ 

13. rotr

• The opcode rotr rotates the stack to the bottom.

Usage: rotr

• The last element of the stack becomes the top element of the stack rotr never fails

14. stack, queue

The stack opcode

• The opcode stack sets the format of the data to a stack (LIFO). This is the default behavior of the program.

• Usage: ```stack``

The queue opcode

• The opcode queue sets the format of the data to a queue (FIFO).

• Usage: queue

When switching mode:

• The top of the stack becomes the front of the queue
• The front of the queue becomes the top of the stack

-Example:

micahondiwa@ubuntu:~/monty$ cat bytecodes/47.m
queue
push 1
push 2
push 3
pall
stack
push 4
push 5
push 6
pall
add
pall
queue
push 11111
add
pall
micahondiwa@ubuntu:~/monty$ ./monty bytecodes/47.m
1
2
3
6
5
4
1
2
3
11
4
1
2
3
15
1
2
3
11111
micahondiwa@ubuntu:~/monty$ 

Files and Directories

Directory/File	Description
bf	Codes implenting the Brainfuck Langauge
bytecodes	Contains bytecode files for the monty language
doubly_functions.c	A C program implementing doubly-linked list: adding a note at the end of the doubly link list, adding a note at the begining of the doubly link list, frees the doubly linked list
get_opcodes.c	A C program that selects the correct opcode to perform and returns a pointer to the function that executes the opcode.
main.c	A C program that frees the global variables, initializes the global variables, checks if the file exists and if the file can be opened and provides the entry point.
malloc_functions.c	A C program that concatenates two strings specially and changes the size and copy the content.
monty.h	The header file containing the prototypes of all your functions
opcode_instructions.c	A C program containing push, pall, pint, pop, and swap opcode functions.
opcode_instructions2.c	A C program containing queue, stack, add, nop, and sub opcode functions.
opcode_instructions3.c	A C program containinbg div, mul, mod, pchar, and pstr opcode functions.
opcode_instructions4.c	A C program containing rotl, and rotr opcode functions
str_functions.c	A C program with strcmp-a function that compares two strings, sch-search if a char is inside a string and strtoky - function that cut a string into tokens depending of the delimit

Author: micahondiwa