acube1/chip8

Yet another Chip8 "emulator".

Hello humans! I'm aCube!

Hi! I'm a brazillian programmer. I've been involved with game development since 2020, I started with Lua in a Fantasy-Computer called TIC-80. I like game development and low-level coding, my interests are C and C++, as you see on my profile. I'm not open to web development (I really hate it).

Do you want to reach me?

chip8's Issues

Use strlen to fetch string length

Only do memcpy until strlen of args[] do this check what is smaller the strlen result or MAX_FILEPATH_SIZE:

Chip8/src/configs.c

Line 102 in f2a0169

memcpy(config->rom_filepath, argv[context.index], MAX_FILEPATH_SIZE);

Instead of use MAX_FILEPATH_SIZE a better approach would be use strlen to set the string termination (\0) at the end of config->rom_filepath:

Chip8/src/configs.c

Line 103 in f2a0169

config->rom_filepath[MAX_FILEPATH_SIZE - 1] = '\0';

Because the strlen will return the real string length make the termination really meaningful.

Add audio

Add beep audio which is played when the sound timer is greater than 0.

Add Chip8 Instructions

• 00E0 - CLS | Clear the display.
• 00EE - RET | Return from a subroutine.
• 1NNN - JMP | Jump to location NNN.
• 2NNN - CALL | Call subroutine at NNN.
• 3xkk - SE | Skip next instruction if Vx == kk.
• 4xkk - SNE | Skip next instruction if Vx != kk.
• 5xy0 - SEREG | Skip next instruction if Vx == Vy.
• 6xkk - LDIMM | Set Vx = kk.
• 7xkk - ADDIMM | Set Vx = Vx + kk.
• 8xy0 - LDV | Set Vx = Vy.
• 8xy1 - OR | Set Vx = Vx OR Vy.
• 8xy2 - AND | Set Vx = Vx AND Vy.
• 8xy3 - XOR | Set Vx = Vx XOR Vy.
• 8xy4 - ADD | Set Vx = Vx + Vy, set VF = carry.
• 8xy5 - SUB | Set Vx = Vx - Vy, set VF = NOT borrow.
• 8xy6 - SHR | Set Vx = Vx SHR 1.
• 8xy7 - SUBN | Set Vx = Vy - Vx, set VF = NOT borrow.
• 8xyE - SHL | Set Vx = Vx SHL 1.
• 9xy0 - SNEREG | Skip next instruction if Vx != Vy.
• ANNN - LDI | Set Index Register to NNN.
• BNNN - JMPREG | Jump to location NNN + V0.
• Cxkk - RND | Set Vx = random byte AND kk.
• DxyN - DRAW | Display N-byte sprite starting at memory location I at (Vx, Vy), set VF = collision.
• Ex9E - SKEY | Skip next instruction if key with the value of Vx is pressed.
• ExA1 - SNKEY | Skip next instruction if key with the value of Vx is not pressed.
• Fx07 - RDELAY | Set Vx = delay timer value.
• Fx0A - WAITKEY | Wait for a key press, store the value of the key in Vx.
• Fx15 - WDELAY | Set delay timer = Vx.
• Fx18 - WSOUND | Set sound timer = Vx.
• Fx1E - ADDI | Set I = I + Vx.
• Fx29 - LDSPRITE | Set I = location of sprite for digit Vx.
• Fx33 - STBCD | Store BCD representation of Vx in memory locations I, I+1, and I+2.
• Fx55 - STREG | Store registers V0 through Vx in memory starting at location I.
• Fx65 - LDREG | Read registers V0 through Vx from memory starting at location I.

Use SDL_RWFromFile instead of get_file_content.

SDL_RWFromFile seems to be more secure than the internal function get_file_content in utils.c.

I don't really know if this is a good option, more tests are necessary.

Segment fault when no rom is specified

Add an error check if the user not pass any rom to be executed to prevent the segmentation fault.

Add README file.

For now this project doesn't have any documentation.

Add documentation for:

• Building.
• Command-line arguments.

Add keyboard controlling.

Update cpu keystate using key maps.

Default mapping(scancode):

1	2	3	C
4	5	6	D
7	8	9	E
A	0	B	F

1	2	3	4
Q	W	E	R
A	S	D	F
Z	X	C	V

Add clock cycle controlling.

The Chip8 had no specified clock speed. Different games run best at different speeds.

Bugs on command-line arguments.

The width of the window breaks if use the --clock or -c command-line argument.

Reopen the issue: #6

Fix 8xy6 and 8xyE opcodes.

Using the test_suite rom in the roms/demos directory.
The X in the 8xy6 and 8xyE means that the opcode isn't working properly

Improve command-line arguments.

Don't use POSIX header getopt.h, this header isn't portable.

Maybe I can use this library.
https://github.com/cofyc/argparse

Add clock cycle controlling.

The Chip8 had no specified clock speed. Different games run best at different speeds.