ファミコンでテトリスをリバースエンジニアリングしてハードドロップを追加

ニンテンドーテトリスは、私のお気に入りのテトリスバージョンの1つです。私の唯一の不満は、現在の形状を即座にドロップして所定の位置にロックする「ハードドロップ」機能がないことです。追加しましょう

, , — «» « » — , , .

. — .

, .

Hard drop . , , , , , .

NES .

rust, NES ROM INES. NES Tetris ( - «Tetris(U)[!].nes»), ROM NES, NES Tetris, .

sha1 a99f922e9da20b2a27e4398348505d2e9d15271b.

$ cargo install nes-tetris-hard-drop-patcher   # install my tool
$ nes-tetris-hard-drop-patcher < 'Tetris (U) [!].nes' > tetris-hd.nes   # patch a NES Tetris ROM
$ fceux tetris-hd.nes   # run the result in an emulator
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, ROM- NES Tetris. . ROM NES — fceux.

, ROM (IPS), . .

NES. , -, . , , , . , .

, Rust. , «» 12:

b.inst(Clc, ());                  // clear carry flag
b.inst(Rol(Accumulator), ());     // rotate accumulator 1 bit to the left (x2)
b.inst(Rol(Accumulator), ());     // rotate accumulator 1 bit to the left (x4)
b.inst(Sta(ZeroPage), 0x20);      // store current accumulator value at address 0x0020
b.inst(Rol(Accumulator), ());     // rotate accumulator 1 bit to the left (x8)
b.inst(Adc(ZeroPage), 0x20);      // add the accumulator with the value at 0x0020 (x12)
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

rust NES. Rust , 1980- .

, NES .

, NES Mesen, . .

NES :

• 8x8 ;

  
  
  
  
  

• — , .

  
  
  
  
  

, — .

, , . , .

, , , , , .

, , :

— , , .

NES (, . .), OAMDMA. ( — OAM — , DMA — , .) OAMDMA NES , .

OAMDMA 0x4014. :

0xAB63  Lda(Immediate) 0x02       # load accumulator with 2
0xAB65  Sta(Absolute) 0x4014      # write accumulator to 0x4014
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

2 OAMDMA, 0x0200 0x02FF OAM. . 0x8A0A , .

0x0040 0x0041, 8 . NES 8x8 , , -, , . : 0x40 — x, 0x41 — Y .

0x42. 0 12, , -, , . (, “S”) 0x42. “ ”.

4 , . 0x40 0x41 — , . 0x8A9C, « ». 13 ( ) 12- . 3 4 :

• y ( 0x41);

  
  
  
  
  

• , ;

  
  
  
  
  

• x ( 0x40).

  
  
  
  
  

OAM DMA . , , , , , , , hard drop. , , / , , .

— mesen, , , . , 0x00 0xFF! , mesen Monospace!

512 , 0xD6D0. , , , DMA OAM:

b.label("oam-dma-buffer-update");

// Call original function
b.inst(Jsr(Absolute), 0x8A0A);
// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

(0x8A0A) .

DMA OAM rust NES.

:

0x8A0A  Lda(ZeroPage) 0x40
0x8A0C  Asl(Accumulator)
0x8A0D  Asl(Accumulator)
0x8A0E  Asl(Accumulator)
0x8A0F  Adc(Immediate) 0x60
0x8A11  Sta(ZeroPage) 0xAA
...
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

:

b.label("render-ghost-piece"); // function label so it can be called by name later

b.inst(Lda(ZeroPage), 0x40);
b.inst(Asl(Accumulator), ());
b.inst(Asl(Accumulator), ());
b.inst(Asl(Accumulator), ());
b.inst(Adc(Immediate), 0x60);
b.inst(Sta(ZeroPage), 0xAA);
...
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

DMA OAM, , . , oam-dma-buffer-update, :

b.label("oam-dma-buffer-update");

// Call new function
b.inst(Jsr(Absolute), "render-ghost-piece");
// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , . , , , , 6.

b.label("oam-dma-buffer-update");  // Call original function first b.inst(Jsr(Absolute), 0x8A0A); // Render the ghost piece, passing the vertical offset argument in address 0x0028. b.inst(Lda(Immediate), 6); b.inst(Sta(ZeroPage), 0x28); b.inst(Jsr(Absolute), "render-ghost-piece"); // Return b.inst(Rts, ());b.label("oam-dma-buffer-update");

// Call original function first
b.inst(Jsr(Absolute), 0x8A0A);
// Render the ghost piece, passing the vertical offset argument in address 0x0028.
b.inst(Lda(Immediate), 6);
b.inst(Sta(ZeroPage), 0x28);
b.inst(Jsr(Absolute), "render-ghost-piece");
// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, . mesen, , , , 0x0020 0x0028. 256 « » , . 8 X, Y , .

0x20 0x27 X, Y :

b.label("compute-hard-drop-distance"); // function label so it can be called by name later

const SHAPE_TABLE: Address = 0x8A9C;
const ZP_PIECE_COORD_X: u8 = 0x40;
const ZP_PIECE_COORD_Y: u8 = 0x41;
const ZP_PIECE_SHAPE: u8 = 0x42;
// Multiply the shape by 12 to make an offset into the shape table,
// storing the result in IndexRegisterX.
b.inst(Lda(ZeroPage), ZP_PIECE_SHAPE);  // read shape index into accumulator
b.inst(Clc, ());               // clear carry flag to prepare for arithmetic
b.inst(Rol(Accumulator), ());  // rotate left: index * 2
b.inst(Rol(Accumulator), ());  // rotate left: index * 4
b.inst(Sta(ZeroPage), 0x20);   // store index * 4 at 0x0020
b.inst(Rol(Accumulator), ());  // rotate left: index * 8
b.inst(Adc(ZeroPage), 0x20);   // add to 0x0020: index * 12
b.inst(Tax, ());               // transfer accumulator to IndexRegisterX
// Store absolute X,Y coords of each tile by reading relative coordinates from shape table
// and adding the piece offset, storing the result in zero page 0x20..=0x27.
for i in 0..4 { // this is a rust loop - the assembly generated inside will be generated 4 times
    b.inst(Lda(AbsoluteXIndexed), Addr(SHAPE_TABLE)); // read Y offset from shape table
    b.inst(Clc, ());                                  // clear carry flag to prepare for addition
    b.inst(Adc(ZeroPage), ZP_PIECE_COORD_Y);          // add to Y coordinate of piece
    b.inst(Sta(ZeroPage), 0x21 + (i  2));            // store the result in zero page
    b.inst(Inx, ());                                  // increment IndexRegisterX to sprite index
    b.inst(Inx, ());                                  // increment IndexRegisterX to X offset
    b.inst(Lda(AbsoluteXIndexed), Addr(SHAPE_TABLE)); // read X offset from shape table
    b.inst(Clc, ());                                  // clear carry flag to prepare for addition
    b.inst(Adc(ZeroPage), ZP_PIECE_COORD_X);          // add to X coordinate of piece
    b.inst(Sta(ZeroPage), 0x20 + (i  2));            // store the result in zero page
    b.inst(Inx, ());                                  // increment IndexRegisterX to next tile
}
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

! Y 0x20 0x27, . mesen, , , 0x0400, 0xEF — « ». , - 0xEF.

, , for rust, . . rust 4 , .

const BOARD_TILES: Address = 0x0400;
const EMPTY_TILE: u8 = 0xEF;
const BOARD_HEIGHT: u8 = 20;

b.inst(Ldx(Immediate), 0);   // Load 0 into IndexRegisterX - this will be our loop counter

b.label("start-ghost-depth-loop"); // This is a label - a target for branch instructions

for i in 0..4 { // the assembly in this rust loop will be emitted 4 times

    // Increment the Y component of the coordinate
    b.inst(Inc(ZeroPage), 0x21 + (i * 2));

    // Break out of the loop if the tile is off the bottom of the board
    b.inst(Lda(ZeroPage), 0x21 + (i * 2));
    b.inst(Cmp(Immediate), BOARD_HEIGHT);
    b.inst(Bpl, LabelRelativeOffset("end-ghost-depth-loop"));

    // Multiply the Y component of the coordinate by 10 (the number of columns)
    b.inst(Asl(Accumulator), ());
    b.inst(Sta(ZeroPage), 0x28); // store Y * 2
    b.inst(Asl(Accumulator), ());
    b.inst(Asl(Accumulator), ()); // accumulator now contains Y * 8
    b.inst(Clc, ());
    b.inst(Adc(ZeroPage), 0x28); // accumulator now contains Y * 10

    // Now add the X component to get the row-major index of the cell
    b.inst(Adc(ZeroPage), 0x20 + (i * 2));

    // Load the tile at that coordinate
    b.inst(Tay, ());
    b.inst(Lda(AbsoluteYIndexed), BOARD_TILES);

    // Test whether the tile is empty, breaking out of the loop if it is not
    b.inst(Cmp(Immediate), EMPTY_TILE);
    b.inst(Bne, LabelRelativeOffset("end-ghost-depth-loop"));
}
// Increment counter and loop
b.inst(Inx, ());
b.inst(Jmp(Absolute), "start-ghost-depth-loop");

b.label("end-ghost-depth-loop");
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, IndexRegisterX , , . :

// Return depth via accumulator
b.inst(Txa, ());  // transfer IndexRegisterX to accumulator
b.inst(Rts, ());  // return
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

DMA OAM:

b.label("oam-dma-buffer-update");

// Call original function first
b.inst(Jsr(Absolute), 0x8A0A);
// Compute distance from current piece to drop destination, placing result in accumulator
b.inst(Jsr(Absolute), "compute-hard-drop-distance");
// Check if the distance is 0, and skip rendering the ghost piece in this case
b.inst(Beq, LabelRelativeOffset("after-render-ghost-piece"));
// Render the ghost piece, passing the vertical offset argument in address 0x0028.
b.inst(Sta(ZeroPage), 0x28);
b.inst(Jsr(Absolute), "render-ghost-piece");
b.label("after-render-ghost-piece");
// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

:

Hard Drop 

, , — , «» . «» , , hard drop.

, , , , — , «», , .

, , 0x4016, , , , .

, . , , . . 20 , , . , 20 . — , — . , , .

:

@@ -116912,9 +116912,175 @@
 0x89B8  Lda(ZeroPage) 0xB5
 0x89BA  And(Immediate) 0x03
 0x89BC  Bne(Relative) 0x15
-0x89BE  Lda(ZeroPage) 0xB6
-0x89C0  And(Immediate) 0x03
-0x89C2  Beq(Relative) 0x45
+0x89D3  Lda(Immediate) 0x00
+0x89D5  Sta(ZeroPage) 0x46
+0x89D7  Lda(ZeroPage) 0xB6
+0x89D9  And(Immediate) 0x01
+0x89DB  Beq(Relative) 0x0F
...
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, :

0x89AE  Lda(ZeroPage) 0x40
0x89B0  Sta(ZeroPage) 0xAE
0x89B2  Lda(ZeroPage) 0xB6
0x89B4  And(Immediate) 0x04
0x89B6  Bne(Relative) 0x51 (relative: 0x51, absolute: 0x8A09)
0x89B8  Lda(ZeroPage) 0xB5
0x89BA  And(Immediate) 0x03
0x89BC  Bne(Relative) 0x15 (relative: 0x15, absolute: 0x89D3)
0x89BE  Lda(ZeroPage) 0xB6
0x89C0  And(Immediate) 0x03
0x89C2  Beq(Relative) 0x45 (relative: 0x45, absolute: 0x8A09)
...
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

0x00B5 0x00B6. mesen , 0xB5 , 0xB6 . , «» .

, DMA OAM. , , — :

b.label("handle-controls");

// Call the original function
b.inst(Jsr(Absolute), 0x89AE);

// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, «». :

b.label("handle-controls");

const CONTROLLER_STATE: u8 = 0xB6;
const CONTROLLER_BIT_UP: u8 = 0x08;

// Call the original function
b.inst(Jsr(Absolute), 0x89AE);

// Skip to the end if the UP bit of the controller state is not set
b.inst(Lda(ZeroPage), CONTROLLER_STATE);
b.inst(And(Immediate), CONTROLLER_BIT_UP);
b.inst(Beq, LabelRelativeOffset("controller-end"));

// Set the current piece's Y coordinate to 7
b.inst(Lda(Immediate), 7);
b.inst(Sta(ZeroPage), ZP_PIECE_COORD_Y);

b.label("controller-end");

// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, «»:

7 , . compute-hard-drop-distance, , , Y, :

b.label("handle-controls");

const CONTROLLER_STATE: u8 = 0xB6;
const CONTROLLER_BIT_UP: u8 = 0x08;

// Call the original function
b.inst(Jsr(Absolute), 0x89AE);

// Skip to the end if the UP bit of the controller state is not set
b.inst(Lda(ZeroPage), CONTROLLER_STATE);
b.inst(And(Immediate), CONTROLLER_BIT_UP);
b.inst(Beq, LabelRelativeOffset("controller-end"));

// Compute distance from current piece to drop destination, placing result in accumulator
b.inst(Jsr(Absolute), "compute-hard-drop-distance");

// Add the current piece's Y coordinate
b.inst(Clc, ());
b.inst(Adc(ZeroPage), ZP_PIECE_COORD_Y);

// Update the current piece's Y coordinate with the result
b.inst(Sta(ZeroPage), ZP_PIECE_COORD_Y);

b.label("controller-end");

// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

!

. , «», . hard drop’a .

mesen, , 0x0045, , ( ). , 13 . 13, , .

13 . - , 13 . !

/tmp/log.txt:

cat /tmp/log.txt | sort | uniq --count | sort --numeric-sort
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

. , 13 , :

13 0x8958  Lda(Immediate) 0x00
13 0x895A  Sta(ZeroPage) 0x45
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, 0x0045!

:

0x8980  Lda(ZeroPage) 0x45    # load the timer value
0x8982  Cmp(ZeroPage) 0xAF    # compare with the value at 0x00AF
0x8984  Bpl(Relative) 0xD2 (relative: D2, absolute: 8958)  # branch if it was higher
0x8986  Jmp(Absolute) 0x8972
0x8972  Rts(Implied)
0x8958  Lda(Immediate) 0x00  # load 0 into the accumulator
0x895A  Sta(ZeroPage) 0x45   # store the accumulator (0) in the timer
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

0, 13 . — (0x8984), , 13 — , . , , , , 0xAF, , , .

0x00AF mesen, , , , 0x0045. , , 0x00AF , ! hard drop 0x00AF:

b.label("handle-controls");

const CONTROLLER_STATE: u8 = 0xB6;
const CONTROLLER_BIT_UP: u8 = 0x08;
const TIMER: u8 = 0x45;
const TIMER_MAX: u8 = 0xAF;

// Call the original function
b.inst(Jsr(Absolute), 0x89AE);

// Skip to the end if the UP bit of the controller state is not set
b.inst(Lda(ZeroPage), CONTROLLER_STATE);
b.inst(And(Immediate), CONTROLLER_BIT_UP);
b.inst(Beq, LabelRelativeOffset("controller-end"));

// Compute distance from current piece to drop destination, placing result in accumulator
b.inst(Jsr(Absolute), "compute-hard-drop-distance");

// Add the current piece's Y coordinate
b.inst(Clc, ());
b.inst(Adc(ZeroPage), ZP_PIECE_COORD_Y);

// Update the current piece's Y coordinate with the result
b.inst(Sta(ZeroPage), ZP_PIECE_COORD_Y);

// Set the timer to its maximum value
b.inst(Lda(ZeroPage), TIMER);
b.inst(Sta(ZeroPage), TIMER_MAX);

b.label("controller-end");

// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, , . , , . mesen, , 0x004E . 0. 0 hard drop’a .

b.label("handle-controls");

const CONTROLLER_STATE: u8 = 0xB6;
const CONTROLLER_BIT_UP: u8 = 0x08;
const TIMER: u8 = 0x45;
const TIMER_MAX: u8 = 0xAF;
const TIMER_FIRST_TICK: u8 = 0x4E;

// Call the original function
b.inst(Jsr(Absolute), 0x89AE);

// Skip to the end if the UP bit of the controller state is not set
b.inst(Lda(ZeroPage), CONTROLLER_STATE);
b.inst(And(Immediate), CONTROLLER_BIT_UP);
b.inst(Beq, LabelRelativeOffset("controller-end"));

// Compute distance from current piece to drop destination, placing result in accumulator
b.inst(Jsr(Absolute), "compute-hard-drop-distance");

// Add the current piece's Y coordinate
b.inst(Clc, ());
b.inst(Adc(ZeroPage), ZP_PIECE_COORD_Y);

// Update the current piece's Y coordinate with the result
b.inst(Sta(ZeroPage), ZP_PIECE_COORD_Y);

// Set the timer to its maximum value
b.inst(Lda(ZeroPage), TIMER);
b.inst(Sta(ZeroPage), TIMER_MAX);

// Clear the first tick timer
b.inst(Lda(Immediate), 0x00);
b.inst(Sta(ZeroPage), TIMER_FIRST_TICK);

b.label("controller-end");

// Return
b.inst(Rts, ());
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
    

, !

github. IPS, , , . , hard drop, , .



, , — « Unity», .

, :

• Data Scientist

  
  
  
  
  

• Data Analyst

  
  
  
  
  

• Data Engineering

  
  
  
  
  

• Fullstack- Python

  
  
  
  
  

• Java-

  
  
  
  
  

• QA- JAVA

  
  
  
  
  

• Frontend-

  
  
  
  
  

• 
  
  
  
  

• C++

  
  
  
  
  

• Unity

  
  
  
  
  

• -

  
  
  
  
  

• iOS-

  
  
  
  
  

• Android-

  
  
  
  
  

• Machine Learning

  
  
  
  
  

• "Machine Learning Deep Learning"

  
  
  
  
  

• " Data Science"

  
  
  
  
  

• " Machine Learning Data Science" 

  
  
  
  
  

• "Python -"

  
  
  
  
  

• " "

  
  
  
  
  

• 
  
  
  
  

• DevOps