What is spaghetti code? [closed]

Answer 1

This is from a MIDI parser I wrote some time ago. It was a quick and dirty proof of concept, but nevertheless, I shall take the blame for its ugliness: 4 levels of nested conditionals plus the dreaded multiple returns. This code was meant to compare 2 MIDI events in order to sort them by priority when writing to a file. Ugly as it was, it did the job decently, though.

internal class EventContainerComparer : IComparer {

    int IComparer.Compare(object a, object b) {
        MIDIEventContainer evt1 = (MIDIEventContainer) a;
        MIDIEventContainer evt2 = (MIDIEventContainer) b;

        ChannelEvent chanEvt1;
        ChannelEvent chanEvt2;

        if (evt1.AbsoluteTime < evt2.AbsoluteTime) {
            return -1;
        } else if (evt1.AbsoluteTime > evt2.AbsoluteTime) {
            return 1;
        } else {    
            // a iguar valor de AbsoluteTime, los channelEvent tienen prioridad
            if(evt1.MidiEvent is ChannelEvent && evt2.MidiEvent is MetaEvent) {
                return -1;
            } else if(evt1.MidiEvent is MetaEvent && evt2.MidiEvent is ChannelEvent){
                return 1;
            //  si ambos son channelEvent, dar prioridad a NoteOn == 0 sobre NoteOn > 0
            } else if(evt1.MidiEvent is ChannelEvent && evt2.MidiEvent is ChannelEvent) {

                chanEvt1 = (ChannelEvent) evt1.MidiEvent;
                chanEvt2 = (ChannelEvent) evt2.MidiEvent;

                // si ambos son NoteOn
                if( chanEvt1.EventType == ChannelEventType.NoteOn 
                    && chanEvt2.EventType == ChannelEventType.NoteOn){

                    //  chanEvt1 en NoteOn(0) y el 2 es NoteOn(>0)
                    if(chanEvt1.Arg1 == 0 && chanEvt2.Arg1 > 0) {
                        return -1;
                    //  chanEvt1 en NoteOn(0) y el 2 es NoteOn(>0)
                    } else if(chanEvt2.Arg1 == 0 && chanEvt1.Arg1 > 0) {
                        return 1;
                    } else {
                        return 0;
                    }
                // son 2 ChannelEvent, pero no son los 2 NoteOn, el orden es indistinto
                } else {
                    return 0;
                }
            //  son 2 MetaEvent, el orden es indistinto
            } else {
                return 0;
            }
        }
    }
}

Answer 2

You've asked for it, you'll get it:

This is the source of a DOS .com file that plays the Blue Danube waltz. The executable is just 176 bytes in size. Code is re-used as data and vice versa.

.286
.model tiny

g4 equ 55-48           ; removed note-decoding !
a4 equ 57-48           ; now: storing midi-notes for octaves 0..2 and convert
h4 equ 59-48           ; to 4..6 with a simple add 48.

c5 equ 60-48
d5 equ 62-48
e5 equ 64-48
g5 equ 67-48
h5 equ 71-48

c6 equ 72-48
d6 equ 74-48
e6 equ 76-48
g6 equ 79-48           ; = 00011111b

pp  equ 0              ;  c4 is not used in the walz, using it as play-pause.
EOM equ 1              ; c#4 is also available... End Of Music
                       ; warning: experts only beyond this point !

pau1 equ 00100000b     ; bitfield definitions for note-compression
pau2 equ 01000000b     ; you can or a pau to each note!
pau3 equ 01100000b

;rep1 equ 01000000b    ; rep1 is history (only used once).
;rep3 equ 11000000b    ; rep3 was never used.

rep2 equ 10000000b     ; or a rep2 to a note to play it 3 times.

drumsize equ 5

.code
org 100h

start:
                mov  ah,9
                mov  dx,offset msg
                int  21h                    ; print our headerstring

                mov  dx,0330h               ; gus midi megaem -port
                mov  si,offset music_code   ; start of music data

mainloop:

    ; get new note (melody)

                xor  bp,bp                  ; bp= repeat-counter

                lodsb                       ; get a new note
                cmp  al, EOM                ; check for end
                jne  continue
                ret

continue:
                jns  no_rep2                ; check for rep2-Bit
                inc  bp
                inc  bp                     ; "build" repeat-counter

no_rep2:
                push ax                     ; save the note for pause

    ; "convert" to midi-note

                and  al,00011111b
                jz   skip_pp                ; check pp, keep it 0
                add  al,48                  ; fix-up oktave

skip_pp:
                xchg ax,bx                  ; bl= midi-note

play_again:
                mov  cl,3
                push cx                     ; patch program (3= piano)
                push 0c8h                   ; program change, channel 9

    ; wait (cx:dx) times

                mov  ah,86h                 ; wait a little bit
                int  15h

    ; prepare drums

                dec  di                     ; get the current drum
                jns  no_drum_underflow
                mov  di,drumsize

no_drum_underflow:

    ; play drum

                push dx                     ; volume drum
                push [word ptr drumtrk+di]  ; note   drum
                mov  al,99h
                push ax                     ; play channel 10

    ; play melody

                push dx                     ; volume melody
                push bx                     ; note   melody

                dec  ax                     ; replaces dec al :)

                push ax                     ; play channel 9

    ; send data to midi-port

                mov  cl,8                   ; we have to send 8 bytes

play_loop:
                pop  ax                     ; get the midi event
                out  dx,al                  ; and send it
                loop play_loop

    ; repeat "bp" times

                dec  bp                     ; repeat the note
                jns  play_again

    ; check and "play" pause

                xor  bx,bx                  ; clear the note, so we can hear
                                            ; a pause
    ; decode pause value

                pop  ax
                test al,01100000b
                jz   mainloop               ; no pause, get next note

    ; decrement pause value and save on stack

                sub  al,20h
                push ax
                jmp  play_again             ; and play next drum

; don't change the order of the following data, it is heavily crosslinked !
music_code      db pp or rep2

                db g4 or rep2 or pau1
                db h4 or pau1, d5 or pau1, d5 or pau3
                db d6 or pau1, d6 or pau3, h5 or pau1, h5 or pau3

                db g4 or rep2 or pau1
                db h4 or pau1, d5 or pau1, d5 or pau3
                db d6 or pau1, d6 or pau3, c6 or pau1, c6 or pau3

                db a4 or rep2 or pau1
                db c5 or pau1, e5 or pau1, e5 or pau3
                db e6 or pau1, e6 or pau3, c6 or pau1, c6 or pau3

                db a4 or rep2 or pau1
                db c5 or pau1, e5 or pau1, e5 or pau3
                db e6 or pau1, e6 or pau3, h5 or pau1, h5 or pau3

                db g4 or rep2 or pau1
                db h4 or pau1, g5 or pau1, g5 or pau3
                db g6 or pau1, g6 or pau3, d6 or pau1, d6 or pau3

                db g4 or rep2 or pau1
                db h4 or pau1, g5 or pau1, g5 or pau3
                db g6 or pau1, g6 or pau3, e6 or pau1, e6 or pau3

                db a4 or rep2 or pau1
                db c5 or pau1, e5 or pau1, e5 or pau3, pp or pau3
                db c5 or pau1, e5 or pau1, h5 or pau3, pp or pau3, d5 or pau1

                db h4 or pau1, h4 or pau3
                db a4 or pau1, e5 or pau3
                db d5 or pau1, g4 or pau2

;                db g4 or rep1 or pau1
; replace this last "rep1"-note with two (equal-sounding) notes
                db g4
                db g4 or pau1

msg             db EOM, 'Docking Station',10,'doj&sub'
drumtrk         db 36, 42, 38, 42, 38, 59  ; reversed order to save some bytes !

end start

Answer 3

Real spaghetti code was done in COBOL and used the ALTER statement.

Here's an example, while listed a "humor", I've seen this kind of thing. Almost got fired once for noting that any program with an Alter statement was obviously in a state of sin. I refused to "maintain" that program, it was quicker to replace it than understand it.

Answer 4

I'm not pulling this out of my head. This is what I have had to work with, albeit simplified. Let's say that basically you have a program that needs an enum:

enum {
   a, b, c;
} myenum;

But instead what we have is

HashTable t;
t["a"] = 0;
t["b"] = 1;
t["c"] = 2;

But of course, no implementation of a hash table is good enough so there is a local implementation of hash tables, which contains about 10 times more code than an average open source implementation with half the features and double the number of bugs. The HashTable is actually defined virtual, and there's a factory HashTableFactory to create instances of HashTables, but true to the pattern HashTableFactory is also virtual. To prevent an infite cascade of virtual classes there's a function

HashTableFactory *makeHashTableFactor();

Thus everywhere where the code needs myenum's it carries a reference to the instance of a HashTable and HashTableFactory, in case you want to make more HashTable's. But wait, that's not all! This is not how the hash table is initialized, but it's done by writing a code that reads XML:

<enum>
  <item name="a" value="0"/>
  <item name="b" value="1"/>
  <item name="c" value="2"/>
</enum>

and inserts into a hash table. But the code is "optimised" so that it doesn't read an ascii file myenum.xml, but instead there's a compile time script which generates:

const char* myenumXML = [13, 32, 53 ....];

from myenum.xml and the hash table is initialized by a function:

void xmlToHashTable(char *xml, HashTable *h, HashTableFactory *f);

which is called:

HashTableFactory *factory = makeHashTableFactory();
HashTable *t = facotry.make();
xmlToHashTable(myenumXML, t, f);

Ok, so we have a lot of code to get an enum structure. It's basically used in a function:

void printStuff(int c) {
   switch (c) {
   case a: print("a");
   case b: print("b");
   case c: print("c");
   }
}

and this is called in a context where:

void stuff(char* str) {
   int c = charToEnum(str);
   printStuff(c);
}

So what we actually have is instead of

void stuff(char *str) {
   printf(str);
}

we have manged to generate thousands of lines of code (private new, buggy, complex, implementation of hashtables, and xml readers, and writer) in place of the above 3.

Answer 5

Here is the Duff's Device, from Matt's answer to this question:

int n = (count + 7) / 8;
switch (count % 8) {
case 0: do { *to = *from++;
case 7:      *to = *from++;
case 6:      *to = *from++;
case 5:      *to = *from++;
case 4:      *to = *from++;
case 3:      *to = *from++;
case 2:      *to = *from++;
case 1:      *to = *from++;
           } while (--n > 0);
}

Answer 6

Have you ever looked at code generated by Flex/Bison scanner and generator? A plethora of labels and preprocessor directives.

It's absolutely impossible to understand what's inside.. and absolutely impossible to follow flow of the program.

That's definetely spaghetti code.