static int stbi__process_marker()

in Support/STBImage/include/stb_image.h [2984:3084]

• 92 lines of code
• 37 McCabe index (conditional complexity)

static int stbi__process_marker(stbi__jpeg *z, int m)
{
   int L;
   switch (m) {
      case STBI__MARKER_none: // no marker found
         return stbi__err("expected marker","Corrupt JPEG");

      case 0xDD: // DRI - specify restart interval
         if (stbi__get16be(z->s) != 4) return stbi__err("bad DRI len","Corrupt JPEG");
         z->restart_interval = stbi__get16be(z->s);
         return 1;

      case 0xDB: // DQT - define quantization table
         L = stbi__get16be(z->s)-2;
         while (L > 0) {
            int q = stbi__get8(z->s);
            int p = q >> 4, sixteen = (p != 0);
            int t = q & 15,i;
            if (p != 0 && p != 1) return stbi__err("bad DQT type","Corrupt JPEG");
            if (t > 3) return stbi__err("bad DQT table","Corrupt JPEG");

            for (i=0; i < 64; ++i)
               z->dequant[t][stbi__jpeg_dezigzag[i]] = (stbi__uint16)(sixteen ? stbi__get16be(z->s) : stbi__get8(z->s));
            L -= (sixteen ? 129 : 65);
         }
         return L==0;

      case 0xC4: // DHT - define huffman table
         L = stbi__get16be(z->s)-2;
         while (L > 0) {
            stbi_uc *v;
            int sizes[16],i,n=0;
            int q = stbi__get8(z->s);
            int tc = q >> 4;
            int th = q & 15;
            if (tc > 1 || th > 3) return stbi__err("bad DHT header","Corrupt JPEG");
            for (i=0; i < 16; ++i) {
               sizes[i] = stbi__get8(z->s);
               n += sizes[i];
            }
            L -= 17;
            if (tc == 0) {
               if (!stbi__build_huffman(z->huff_dc+th, sizes)) return 0;
               v = z->huff_dc[th].values;
            } else {
               if (!stbi__build_huffman(z->huff_ac+th, sizes)) return 0;
               v = z->huff_ac[th].values;
            }
            for (i=0; i < n; ++i)
               v[i] = stbi__get8(z->s);
            if (tc != 0)
               stbi__build_fast_ac(z->fast_ac[th], z->huff_ac + th);
            L -= n;
         }
         return L==0;
   }

   // check for comment block or APP blocks
   if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE) {
      L = stbi__get16be(z->s);
      if (L < 2) {
         if (m == 0xFE)
            return stbi__err("bad COM len","Corrupt JPEG");
         else
            return stbi__err("bad APP len","Corrupt JPEG");
      }
      L -= 2;

      if (m == 0xE0 && L >= 5) { // JFIF APP0 segment
         static const unsigned char tag[5] = {'J','F','I','F','\0'};
         int ok = 1;
         int i;
         for (i=0; i < 5; ++i)
            if (stbi__get8(z->s) != tag[i])
               ok = 0;
         L -= 5;
         if (ok)
            z->jfif = 1;
      } else if (m == 0xEE && L >= 12) { // Adobe APP14 segment
         static const unsigned char tag[6] = {'A','d','o','b','e','\0'};
         int ok = 1;
         int i;
         for (i=0; i < 6; ++i)
            if (stbi__get8(z->s) != tag[i])
               ok = 0;
         L -= 6;
         if (ok) {
            stbi__get8(z->s); // version
            stbi__get16be(z->s); // flags0
            stbi__get16be(z->s); // flags1
            z->app14_color_transform = stbi__get8(z->s); // color transform
            L -= 6;
         }
      }

      stbi__skip(z->s, L);
      return 1;
   }

   return stbi__err("unknown marker","Corrupt JPEG");
}