BufferChecker.h

#ifndef BUFFER_CHECKER_H_
#define BUFFER_CHECKER_H_

#include <string>

#include "BufferedFileReader.h"

using std::string;

class BufferChecker {
 public:
  BufferChecker(const BufferedFileReader& bf) : bf_(bf) { }

  // Returns true if there is a detectable error
  // False if an error was not detected
  bool check_char_errors(char c, off_t file_offset) {
    size_t index = file_offset % BufferedFileReader::BUF_SIZE;
    if (index == BufferedFileReader::BUF_SIZE - 1) {
      // give some flexibility on how the last character is handled
      return false;
    }
    
    return bf_.buffer_[index] != c;
  }

  // Returns true if there is a detectable error
  // False if an error was not detected
  bool check_token_errors(const string& token, off_t file_offset) {
    size_t end_index = (file_offset + token.length()) % BufferedFileReader::BUF_SIZE;
    size_t start_index = file_offset % BufferedFileReader::BUF_SIZE;

    // Check if we can even check if the token is in the buffer.
    // Can't be checked if token is clipped by buffer length, or token length is
    // greater than buffer length, and other edge cases
    if (start_index > end_index || end_index - start_index != token.length()) {
      return false;
    }

    for (off_t i = 0 ; start_index + i < end_index; i++) {
      if (token[i] != bf_.buffer_[i + start_index]) {
        return true;
      }
    }
    return false;
  }
 private:
  const BufferedFileReader& bf_;
};


#endif  // BUFFER_CHECKER_H_