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Re: How do you understand cryptic code?

11917640 Member 6-Jul-21 19:16

11917640 Member

6-Jul-21 19:16

Understanding an application part - what does this code do (or tries to do). Running many times on different use cases. Adding a lot of logging/trace code and learning a logs in different use cases.

Logging depends on the platform - from OutputDebugString or log file to UART-based printf on embedded device.

Trying to make some simple changes and see what happens. Running and reading a logs again.

And finally, all this doesn't help to understand 10 lines of code written by real C++ guru - template template parameters + traits + 10-20 crazy Boost base classes + SFINAE + RAII + design patters etc. Such code goes to Recycle Bin - it never works. Anyway, I will be in the Recycle Bin soon, so it doesn't matter...

Re: How do you understand cryptic code?

honey the codewitch6-Jul-21 19:38

honey the codewitch

6-Jul-21 19:38

11917640 Member wrote:
template template parameters + traits + 10-20 crazy Boost base classes

Yeah. I do a lot of generic programming (GP) instead of OOP in C++ so templates are par for the course.

However, I dislike boost because of the level of abstraction. I already sideeye the STL for all the allocations it does, and I can't use it when targeting IoT because the Arduino framework doesn't make it available, probably because it can target 8 bit platforms with 8kB of RAM and 256kB of program space.

So I tend to agree. Unfortunately I find myself producing code (sans boost and often sans the STL) like that in order to get the compiler to do what I need. I wish it wasn't necessary because the code becomes so abstract it's really hard to follow.

Real programmers use butterflies

Re: How do you understand cryptic code?

CPallini6-Jul-21 21:26

6-Jul-21 21:26

Quote:
it's really hard to follow C code, so I'm porting it to C# before backporting it to C++ so that I can really understand it.

I try to port it to C code. Smile | :)

Smile | :)

I'm doing a lot of this kind of work, with assembly-like C code.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Re: How do you understand cryptic code?

Rage6-Jul-21 22:26

6-Jul-21 22:26

honey the codewitch wrote:
I'm porting it to C# before backporting it to C++

That's an interesting way of addressing the understanding issue... I still think it is easier to port direct to C++, since C is probably closer to C++ than C#, but then, I do not speak C# much-

Do not escape reality : improve reality !

Re: How do you understand cryptic code?

UnchainedZA6-Jul-21 23:26

6-Jul-21 23:26

I just wish to understand how C is more cryptic than C++?

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 1:28

honey the codewitch

7-Jul-21 1:28

I never said it was. Confused | :confused:

Confused | :confused:

Real programmers use butterflies

Re: How do you understand cryptic code?

UnchainedZA7-Jul-21 1:58

7-Jul-21 1:58

No, you didn't, it just seemed that way to me. I wouldn't even bother with C# in between, but that's a personal opinion, still trying to understand the logic though.

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 2:38

honey the codewitch

7-Jul-21 2:38

The reason I move it between unmanaged and managed code is it forces me to restructure it. I can't just get lazy and copypasta.

In the process of restructuring it, I grok it's machinations.

Furthermore, C# has a library for pretty much everything, so no matter what I'm doing in C++, there is pretty going to be the equiv in the .NET framework that I can rely on, so I can seal it off there and I don't have to import code like say, the code to do an HTTP request from C++, if that's not directly what I'm working on. I hope what I just wrote makes sense! Smile | :)

Smile | :)

Real programmers use butterflies

Re: How do you understand cryptic code?

UnchainedZA7-Jul-21 2:48

7-Jul-21 2:48

Ok, thanks, my bad Smile | :)

Smile | :)

I don't even think of things such as .NET, it doesn't exist in my current life. If I can't find a suitable library, I have to create the functionality. It's just a completely different environment.

Re: How do you understand cryptic code?

Rusty Bullet7-Jul-21 3:01

7-Jul-21 3:01

Besides, "cryptic" usually is a matter of who wrote it and how, not what language it happens to be in. Some of the most cryptic code I have run across was SQL written as a single line. Without parsing it, I would never have figured it out.

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 3:03

honey the codewitch

7-Jul-21 3:03

Yeah. I'm not trying to imply it's a particular language that's cryptic. It's all a matter of the code.

Real programmers use butterflies

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 3:04

honey the codewitch

7-Jul-21 3:04

UnchainedZA wrote:
It's just a completely different environment.

That's exactly why I do it. Big Grin | :-D

Big Grin | :-D

Real programmers use butterflies

Re: How do you understand cryptic code?

Martin ISDN6-Jul-21 23:26

6-Jul-21 23:26

in my head i port c# to c++ and then to c, so i can really understand

Re: How do you understand cryptic code?

Rusty Bullet7-Jul-21 2:56

7-Jul-21 2:56

Yes. Do it often.

Re: How do you understand cryptic code?

Gary Wheeler7-Jul-21 3:53

7-Jul-21 3:53

I have this precise issue in a legacy project I have inherited. The author wrote the code in a fashion that virtually guaranteed he was the only possible maintainer [approx. 4,000 words of obscenity-laden rant omitted].

On occasion I have copied the relevant source files to another folder and the reformatted and refactored mercilessly. The reformatting is to correct layout issues since his brace style and tabs weren't consistent (I've found tabs of 2, 3, 4, and 8 with tab characters). The refactoring is to give values meaningful names.

The reworked source code lets me understand how the original works when I need to make changes or understand how a feature works. Given the fragility of this towering pile of excreta, I don't use the reformatted code for anything other than my own understanding.

Software Zen: delete this;

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 4:03

honey the codewitch

7-Jul-21 4:03

I have only one thing to say in response, but it's a mouthful:

C++

static int stbtt__run_charstring(const stbtt_fontinfo *info, int glyph_index, stbtt__csctx *c)
{
   int in_header = 1, maskbits = 0, subr_stack_height = 0, sp = 0, v, i, b0;
   int has_subrs = 0, clear_stack;
   float s[48];
   stbtt__buf subr_stack[10], subrs = info->subrs, b;
   float f;

#define STBTT__CSERR(s) (0)

   // this currently ignores the initial width value, which isn't needed if we have hmtx
   b = stbtt__cff_index_get(info->charstrings, glyph_index);
   while (b.cursor < b.size) {
      i = 0;
      clear_stack = 1;
      b0 = stbtt__buf_get8(&b);
      switch (b0) {
      // @TODO implement hinting
      case 0x13: // hintmask
      case 0x14: // cntrmask
         if (in_header)
            maskbits += (sp / 2); // implicit "vstem"
         in_header = 0;
         stbtt__buf_skip(&b, (maskbits + 7) / 8);
         break;

      case 0x01: // hstem
      case 0x03: // vstem
      case 0x12: // hstemhm
      case 0x17: // vstemhm
         maskbits += (sp / 2);
         break;

      case 0x15: // rmoveto
         in_header = 0;
         if (sp < 2) return STBTT__CSERR("rmoveto stack");
         stbtt__csctx_rmove_to(c, s[sp-2], s[sp-1]);
         break;
      case 0x04: // vmoveto
         in_header = 0;
         if (sp < 1) return STBTT__CSERR("vmoveto stack");
         stbtt__csctx_rmove_to(c, 0, s[sp-1]);
         break;
      case 0x16: // hmoveto
         in_header = 0;
         if (sp < 1) return STBTT__CSERR("hmoveto stack");
         stbtt__csctx_rmove_to(c, s[sp-1], 0);
         break;

      case 0x05: // rlineto
         if (sp < 2) return STBTT__CSERR("rlineto stack");
         for (; i + 1 < sp; i += 2)
            stbtt__csctx_rline_to(c, s[i], s[i+1]);
         break;

      // hlineto/vlineto and vhcurveto/hvcurveto alternate horizontal and vertical
      // starting from a different place.

      case 0x07: // vlineto
         if (sp < 1) return STBTT__CSERR("vlineto stack");
         goto vlineto;
      case 0x06: // hlineto
         if (sp < 1) return STBTT__CSERR("hlineto stack");
         for (;;) {
            if (i >= sp) break;
            stbtt__csctx_rline_to(c, s[i], 0);
            i++;
      vlineto:
            if (i >= sp) break;
            stbtt__csctx_rline_to(c, 0, s[i]);
            i++;
         }
         break;

      case 0x1F: // hvcurveto
         if (sp < 4) return STBTT__CSERR("hvcurveto stack");
         goto hvcurveto;
      case 0x1E: // vhcurveto
         if (sp < 4) return STBTT__CSERR("vhcurveto stack");
         for (;;) {
            if (i + 3 >= sp) break;
            stbtt__csctx_rccurve_to(c, 0, s[i], s[i+1], s[i+2], s[i+3], (sp - i == 5) ? s[i + 4] : 0.0f);
            i += 4;
      hvcurveto:
            if (i + 3 >= sp) break;
            stbtt__csctx_rccurve_to(c, s[i], 0, s[i+1], s[i+2], (sp - i == 5) ? s[i+4] : 0.0f, s[i+3]);
            i += 4;
         }
         break;

      case 0x08: // rrcurveto
         if (sp < 6) return STBTT__CSERR("rcurveline stack");
         for (; i + 5 < sp; i += 6)
            stbtt__csctx_rccurve_to(c, s[i], s[i+1], s[i+2], s[i+3], s[i+4], s[i+5]);
         break;

      case 0x18: // rcurveline
         if (sp < 8) return STBTT__CSERR("rcurveline stack");
         for (; i + 5 < sp - 2; i += 6)
            stbtt__csctx_rccurve_to(c, s[i], s[i+1], s[i+2], s[i+3], s[i+4], s[i+5]);
         if (i + 1 >= sp) return STBTT__CSERR("rcurveline stack");
         stbtt__csctx_rline_to(c, s[i], s[i+1]);
         break;

      case 0x19: // rlinecurve
         if (sp < 8) return STBTT__CSERR("rlinecurve stack");
         for (; i + 1 < sp - 6; i += 2)
            stbtt__csctx_rline_to(c, s[i], s[i+1]);
         if (i + 5 >= sp) return STBTT__CSERR("rlinecurve stack");
         stbtt__csctx_rccurve_to(c, s[i], s[i+1], s[i+2], s[i+3], s[i+4], s[i+5]);
         break;

      case 0x1A: // vvcurveto
      case 0x1B: // hhcurveto
         if (sp < 4) return STBTT__CSERR("(vv|hh)curveto stack");
         f = 0.0;
         if (sp & 1) { f = s[i]; i++; }
         for (; i + 3 < sp; i += 4) {
            if (b0 == 0x1B)
               stbtt__csctx_rccurve_to(c, s[i], f, s[i+1], s[i+2], s[i+3], 0.0);
            else
               stbtt__csctx_rccurve_to(c, f, s[i], s[i+1], s[i+2], 0.0, s[i+3]);
            f = 0.0;
         }
         break;

      case 0x0A: // callsubr
         if (!has_subrs) {
            if (info->fdselect.size)
               subrs = stbtt__cid_get_glyph_subrs(info, glyph_index);
            has_subrs = 1;
         }
         // fallthrough
      case 0x1D: // callgsubr
         if (sp < 1) return STBTT__CSERR("call(g|)subr stack");
         v = (int) s[--sp];
         if (subr_stack_height >= 10) return STBTT__CSERR("recursion limit");
         subr_stack[subr_stack_height++] = b;
         b = stbtt__get_subr(b0 == 0x0A ? subrs : info->gsubrs, v);
         if (b.size == 0) return STBTT__CSERR("subr not found");
         b.cursor = 0;
         clear_stack = 0;
         break;

      case 0x0B: // return
         if (subr_stack_height <= 0) return STBTT__CSERR("return outside subr");
         b = subr_stack[--subr_stack_height];
         clear_stack = 0;
         break;

      case 0x0E: // endchar
         stbtt__csctx_close_shape(c);
         return 1;

      case 0x0C: { // two-byte escape
         float dx1, dx2, dx3, dx4, dx5, dx6, dy1, dy2, dy3, dy4, dy5, dy6;
         float dx, dy;
         int b1 = stbtt__buf_get8(&b);
         switch (b1) {
         // @TODO These "flex" implementations ignore the flex-depth and resolution,
         // and always draw beziers.
         case 0x22: // hflex
            if (sp < 7) return STBTT__CSERR("hflex stack");
            dx1 = s[0];
            dx2 = s[1];
            dy2 = s[2];
            dx3 = s[3];
            dx4 = s[4];
            dx5 = s[5];
            dx6 = s[6];
            stbtt__csctx_rccurve_to(c, dx1, 0, dx2, dy2, dx3, 0);
            stbtt__csctx_rccurve_to(c, dx4, 0, dx5, -dy2, dx6, 0);
            break;

         case 0x23: // flex
            if (sp < 13) return STBTT__CSERR("flex stack");
            dx1 = s[0];
            dy1 = s[1];
            dx2 = s[2];
            dy2 = s[3];
            dx3 = s[4];
            dy3 = s[5];
            dx4 = s[6];
            dy4 = s[7];
            dx5 = s[8];
            dy5 = s[9];
            dx6 = s[10];
            dy6 = s[11];
            //fd is s[12]
            stbtt__csctx_rccurve_to(c, dx1, dy1, dx2, dy2, dx3, dy3);
            stbtt__csctx_rccurve_to(c, dx4, dy4, dx5, dy5, dx6, dy6);
            break;

         case 0x24: // hflex1
            if (sp < 9) return STBTT__CSERR("hflex1 stack");
            dx1 = s[0];
            dy1 = s[1];
            dx2 = s[2];
            dy2 = s[3];
            dx3 = s[4];
            dx4 = s[5];
            dx5 = s[6];
            dy5 = s[7];
            dx6 = s[8];
            stbtt__csctx_rccurve_to(c, dx1, dy1, dx2, dy2, dx3, 0);
            stbtt__csctx_rccurve_to(c, dx4, 0, dx5, dy5, dx6, -(dy1+dy2+dy5));
            break;

         case 0x25: // flex1
            if (sp < 11) return STBTT__CSERR("flex1 stack");
            dx1 = s[0];
            dy1 = s[1];
            dx2 = s[2];
            dy2 = s[3];
            dx3 = s[4];
            dy3 = s[5];
            dx4 = s[6];
            dy4 = s[7];
            dx5 = s[8];
            dy5 = s[9];
            dx6 = dy6 = s[10];
            dx = dx1+dx2+dx3+dx4+dx5;
            dy = dy1+dy2+dy3+dy4+dy5;
            if (STBTT_fabs(dx) > STBTT_fabs(dy))
               dy6 = -dy;
            else
               dx6 = -dx;
            stbtt__csctx_rccurve_to(c, dx1, dy1, dx2, dy2, dx3, dy3);
            stbtt__csctx_rccurve_to(c, dx4, dy4, dx5, dy5, dx6, dy6);
            break;

         default:
            return STBTT__CSERR("unimplemented");
         }
      } break;

      default:
         if (b0 != 255 && b0 != 28 && (b0 < 32 || b0 > 254))
            return STBTT__CSERR("reserved operator");

         // push immediate
         if (b0 == 255) {
            f = (float)(stbtt_int32)stbtt__buf_get32(&b) / 0x10000;
         } else {
            stbtt__buf_skip(&b, -1);
            f = (float)(stbtt_int16)stbtt__cff_int(&b);
         }
         if (sp >= 48) return STBTT__CSERR("push stack overflow");
         s[sp++] = f;
         clear_stack = 0;
         break;
      }
      if (clear_stack) sp = 0;
   }
   return STBTT__CSERR("no endchar");

#undef STBTT__CSERR
}

Laugh | :laugh:

Laugh | :laugh:

Laugh | :laugh:

I laugh so I don't cry.

Real programmers use butterflies

Re: How do you understand cryptic code?

Julian Ragan7-Jul-21 4:24

7-Jul-21 4:24

I either write code analysis report, where I divide code into sections and write section by section, what I think it does, then verify with debugger, or I create a good old flow diagram, if it is really cryptic (even for OO this will work for extracting actual algorithms, if you can identify sequence first).

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 4:27

honey the codewitch

7-Jul-21 4:27

I can totally see the sense in that, but I could never do it. Too rigorous for me. Laugh | :laugh:

Laugh | :laugh:

I am good at improvisation and creativity, but I am no good at being methodical.

Real programmers use butterflies

Re: How do you understand cryptic code?

Julian Ragan7-Jul-21 4:47

7-Jul-21 4:47

Yeah, it is exhausting to do in a complex code base.

Re: How do you understand cryptic code?

JP Reyes7-Jul-21 4:34

7-Jul-21 4:34

Not exactly. I used to use C to spit out ARM16 Assembler so I got an idea how I could program what I needed in assembler...then I yanked out all the stuff I didn't need (Like when you throw out all the useless HTML an editor generates). Smaller, faster, optimized and straight to the point (well for me...anybody else would also have to be comfortable with ARM16 as well)

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 4:39

honey the codewitch

7-Jul-21 4:39

I rarely write in assembly these days but I read it a lot. I've focused more on getting C and particularly C++ to generate the exact machine code I intended if I'd have written by hand, or as is often the case, better.

Real programmers use butterflies

Re: How do you understand cryptic code?

englebart7-Jul-21 4:35

7-Jul-21 4:35

Do you port all pointers to array access?
Pointers are always the pain for this type of exercise. Some algorithms are easier to understand that way. Multilevel pointers are the worst.

Re: How do you understand cryptic code?

honey the codewitch7-Jul-21 4:38

honey the codewitch

7-Jul-21 4:38

Whenever I can, that's what I do. I turn it to arrays and indices. It is difficult but actually that process is critical for me to understand it. It's one of the most important parts of the port.

And yeah, double indirection and such gets tricky fast.

Real programmers use butterflies

Re: How do you understand cryptic code?

NightPen7-Jul-21 6:44

7-Jul-21 6:44

Start by determining what data it works with. Then split out the functions and start figuring out the inputs and outputs from each function. Finally, make a process and data flow diagrams for the code. This process makes short work of understanding even the most cryptic code.

If you don't want to spend a day or two doing this process there are tools like sourcetrail that will do the work for you.

Re: How do you understand cryptic code?

hur10forcer108-Jul-21 2:38

8-Jul-21 2:38

If the project is fairly significant in size with multiple .c and .h files with many functions, I will often turn doxygen (with graphviz) loose on it. Even though the code may not have any doxygen tags or doxygen-compatible comment blocks to generate function and API documentation, it can still give you an idea of "what calls what" in a graphical context.

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