File Sizes - Newlines

File Sizes - Semicolons

Procedure Counts and Sizes

Write Defensive Code

• Find your mistakes before your users do.

• int main(int argc, char * argv[]) {
    char * title = argv[1];
    ifstream infile(title, ios::in);
    if (!infile) {
      // blah blah blah
      }
  

• i = 0;
  ifstream fin2("int.txt", ios::in);
  while(!fin2.eof()) {
    fin2.getline(tem1[i], 255, '\n');
    // blah blah blah
    i++;
    }
  

• This is just bad programming.

Define and Use Good Names

• enum enum_type_for_chars { CHARACTERS, VAR };
  typedef enum_type_for_chars ETFC;
  

  How about enum char_type { CHARACTERS, VAR };

• No magic numbers.

  char ** pattern = new char*[5000];
  char ** pat_without_spc = new char*[5000];
  char ** tem = new char* [5000];
  char ** tem1 = new char* [5000];
  char ** rep  = new char* [5000];
  for (int i = 0; i < 5000; i++)
  for (int k = 0 ; k < 5000; k++)
  

Don't Duplicate Code

void CharToMatchText(char ch) {
  char* Temp;
  int Length = 0;
  Length = strlen(match_text);
  Temp = new char[Length+1];
  Temp[0] = '\0';
  strcpy(Temp, match_text);
  Temp[Length] = '\0';
  delete [] match_text;
  match_text = new char[Length+2];
  match_text[0] = '\0';
  strcpy(match_text, Temp);
  match_text[Length] = ch;
  match_text[Length+1] = '\0';
  }

void CharToReplacementText(char ch) {
  char* Temp;
  int Length = 0;
  Length = strlen(replc_text);
  Temp = new char[Length+1];
  Temp[0] = '\0';
  strcpy(Temp, replc_text);
  Temp[Length] = '\0';
  delete [] replc_text;
  replc_text = new char[Length+2];
  replc_text[0] = '\0';
  strcpy(replc_text, Temp);
  replc_text[Length] = ch;
  replc_text[Length+1] = '\0';
  }

void CharToInterText(char ch) {
  char* Temp;
  int Length = 0;
  Length = strlen(inter_text);
  Temp = new char[Length+1];
  Temp[0] = '\0';
  strcpy(Temp, inter_text);
  Temp[Length] = '\0';
  delete [] inter_text;
  inter_text = new char[Length+2];
  inter_text[0] = '\0';
  strcpy(inter_text, Temp);
  inter_text[Length] = ch;
  inter_text[Length+1] = '\0';
  }

void CharToInText(char ch) {
  char* Temp;
  int Length = 0;
  Length = strlen(in_text);
  Temp = new char[Length+1];
  Temp[0] = '\0';
  strcpy(Temp, in_text);
  Temp[Length] = '\0';
  delete [] in_text;
  in_text = new char[Length+2];
  in_text[0] = '\0';
  strcpy(in_text, Temp);
  in_text[Length] = ch;
  in_text[Length+1] = '\0';
  }

void CharToMatchText(char ch) {
  CharToText(match_text, ch);
  }

void CharToReplacementText(char ch) {
  CharToText(replc_text, ch);
  }

void CharToInterText(char ch) {
  CharToText(inter_text, ch);
  }

void CharToInText(char ch) {
  CharToText(in_text, ch);
  }

void CharToText(char * & text, char ch) {
  char* Temp;
  int Length = 0;
  Length = strlen(text);
  Temp = new char[Length+1];
  Temp[0] = '\0';
  strcpy(Temp, text);
  Temp[Length] = '\0';
  delete [] text;
  text = new char[Length+2];
  text[0] = '\0';
  strcpy(text, Temp);
  text[Length] = ch;
  text[Length+1] = '\0';
  }

Don't Use char * Strings

void optimize::CharToMatchText(char ch) {
  char* Temp;
  int Length = 0;
  Length = strlen(match_text);
  Temp = new char[Length+1];
  Temp[0] = '\0';
  strcpy(Temp, match_text);
  Temp[Length] = '\0';
  delete [] match_text;
  match_text = new char[Length+2];
  match_text[0] = '\0';
  strcpy(match_text, Temp);
  match_text[Length] = ch;
  match_text[Length+1] = '\0';
  }

void optimize::CharToMatchText(char ch) {
  match_text += ch;
  }

Write Good Code

• Consider

  FILE * imc;
  imc = fopen(argv[2], "r");
  
  while (fgets(line, 80, imc)) {
    if (isspace(line[0])) continue;
    line[strlen(line) - 1] = NULL;
    imc_temp->inter_line = (char *) malloc (strlen(line));
    strcpy(imc_temp->inter_line, line);
  

• Does argv[2] exists? Should it exist?
  Did fopen() succeed or fail?
  80 is a magic number.
  What is being replaced by NULL?
  How much space is being allocated?
  What did malloc() return?
  What is strcpy() doing?
  

Know Your Tools

• What's wrong with this code?
  

  ifstream patternFile( argv[1], ios::in);
  while (!patternFile.eof()) {
    patternFile >> pattern;
    // blah blah blah
    }
  

• Libraries too.
  

  if ((code[0] = '-') & (code[1] >='0') && (code[1] >= '9')) {
    code = pattern;
    return 1;
    }
  if ((code[0] >= '0' && code[0] <= '9') && (pattern[0] == '$')) {
    code = pattern;
    return 1;
    }
  

  How about

  if (((code[0] = '-') && isdigit(code[1])) || {
      (isdigit(code[0]) && (pattern[0] == '$'))) {
    code = pattern;
    return 1;
    }
  

Sometimes Even Strings Don't Help

string match_result;

match_result_length=match_result.length();

for (int check103 = 0; check103 <= match_result_length; check103++) {
  if ((match_result[check103] >= 65) && (match_result[check103] <= 90)) {
    // whatever
    }
  else
    output_result += match_result[check103];
  }

Dynamic Storage

bool readInst(List *L, char *&inst, int noInst) {

  char * line = new char[80];

  inst = new char[80];
  strcpy(inst, "\0");

  line = L->getNext();
  if ( line  == NULL ) {
    inst = NULL;
    return false;
    }

  // blah blah blah
  }

This page last modified on 27 March 2001.