CODEWITHSUNDEEP
cpointersbyte
Texasy04
Texasy04

Reputation: 3

C: finding occurrences of bytes in a block of memory

I am trying to write a function that uses only pointer-based logic to search through a region of memory (blockAddress) for a certain byte (Byte), counts the occurrences, and stores the offsets in an array (pOffsets). Here is what I have so far: 

// blockLength is the number of bytes in the memory region;
// Byte is the value to be searched for
// maxBytes is the maximum number of bytes that are to be copied
// Returns: the number of occurrences of Byte found in the memory region

uint32_t findOccurrencesOfByte(uint32_t *const pOffsets,
                               const uint8_t *const blockAddress,
                               uint32_t blockLength, uint8_t Byte,
                               uint32_t maxBytes) {
  uint32_t count, read;
  count = 0;

  for (read = 0; read < blockLength && read < maxBytes; read++) {
    if (*(blockAddress + read) == Byte) {
      *(pOffsets + count) = read;
      count++;
    } // if
  } // for

  return count;
} // findOccurrencesOfByte

I'm not sure how to implement a condition that if maxBytes == 3 and there are more than 3 occurrences it would stop after recording 3 times. I'm also still new to pointers and not sure if what I did is correct.

Upvotes: 0

Views: 566

Answers (1)

Barmar
Barmar

Reputation: 781833

Your pointer code is correct.

You should be comparing count to maxBytes, not read.

  for (read = 0; read < blockLength && count < maxBytes; read++) {
    if (*(blockAddress + read) == Byte) {
      *(pOffsets + count) = read;
      count++;
    } // if
  } // for

Upvotes: 3

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