Demonstrate bugs in Wikipedia's cobsDecode C sample

cobs.c

#include <assert.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>

#define USE_WIKIPEDIA_COBS_DECODE 1

#if USE_WIKIPEDIA_COBS_DECODE
size_t cobsDecode(const uint8_t *buffer, size_t length, void *data) {
  assert(buffer && data);

  const uint8_t *byte = buffer;      // Encoded input byte pointer
  uint8_t *decode = (uint8_t *)data; // Decoded output byte pointer

  for (uint8_t code = 0xff, block = 0; byte < buffer + length; --block) {
    if (block) // Decode block byte
      *decode++ = *byte++;
    else {
      if (code != 0xff) // Encoded zero, write it
        *decode++ = 0;
      block = code = *byte++; // Next block length
      if (!code)              // Delimiter code found
        break;
    }
  }

  return (size_t)(decode - (uint8_t *)data);
}
#else
size_t cobsDecode(const uint8_t *buffer, size_t length, void *data) {
  assert(buffer && data);

  const uint8_t *byte = buffer;      // Encoded input byte pointer
  uint8_t *decode = (uint8_t *)data; // Decoded output byte pointer

  for (uint8_t code = 0xff, block = 0; byte < buffer + length; --block) {
    if (block) // Decode block byte
      *decode++ = *byte++;
    else {
      block = *byte++;             // Fetch the next block length
      if (block && (code != 0xff)) // Encoded zero, write it unless it's final.
        *decode++ = 0;
      code = block;
      if (!code) // Delimiter code found
        break;
    }
  }

  return (size_t)(decode - (uint8_t *)data);
}
#endif

unsigned char s_decoded[1024];

void wikipedia_example(unsigned index, unsigned char const *encoded,
                       size_t encoded_len, unsigned char const *expected,
                       unsigned expected_len) {
  size_t const len = cobsDecode(encoded, encoded_len, s_decoded);
  printf("Example %u: Expected (%u)", index, expected_len);
  for (size_t i = 0; i < expected_len; ++i) {
    printf(" 0x%02X", expected[i]);
  }
  printf(", Actual (%u)", (unsigned)len);
  for (size_t i = 0; i < len; ++i) {
    printf(" 0x%02X", s_decoded[i]);
  }
  printf("\n");
}

void wikipedia_example_1(void) {
  unsigned char const encoded[] = {0x01, 0x01, 0x00};
  unsigned char const expected[] = {0x00};
  wikipedia_example(1, encoded, sizeof(encoded), expected, sizeof(expected));
}

void wikipedia_example_2(void) {
  unsigned char const encoded[] = {0x01, 0x01, 0x00, 0x00};
  unsigned char const expected[] = {0x00, 0x00};
  wikipedia_example(2, encoded, sizeof(encoded), expected, sizeof(expected));
}

void wikipedia_example_3(void) {
  unsigned char const encoded[] = {0x01, 0x02, 0x11, 0x01, 0x00};
  unsigned char const expected[] = {0x00, 0x11, 0x00};
  wikipedia_example(3, encoded, sizeof(encoded), expected, sizeof(expected));
}

void wikipedia_example_4(void) {
  unsigned char const encoded[] = {0x03, 0x11, 0x22, 0x02, 0x33, 0x00};
  unsigned char const expected[] = {0x11, 0x22, 0x00, 0x33};
  wikipedia_example(4, encoded, sizeof(encoded), expected, sizeof(expected));
}

void wikipedia_example_5(void) {
  unsigned char const encoded[] = {0x05, 0x11, 0x22, 0x33, 0x44, 0x00};
  unsigned char const expected[] = {0x11, 0x22, 0x33, 0x44};
  wikipedia_example(5, encoded, sizeof(encoded), expected, sizeof(expected));
}

void wikipedia_example_6(void) {
  unsigned char const encoded[] = {0x02, 0x11, 0x01, 0x01, 0x01, 0x00};
  unsigned char const expected[] = {0x11, 0x00, 0x00, 0x00};
  wikipedia_example(6, encoded, sizeof(encoded), expected, sizeof(expected));
}

int main(int argc, char const *argv[]) {
  (void)argc;
  (void)argv;
  wikipedia_example_1();
  wikipedia_example_2();
  wikipedia_example_3();
  wikipedia_example_4();
  wikipedia_example_5();
  wikipedia_example_6();
  return 0;
}

Hi Wikipedia folks- I don't have an account over there but am happy to discuss over here if that's interesting / helpful. I hope this example displays the bug well enough.