A C-library for string manipulations

Did you ever feel the need to manipulate a string in C? Have you ever wanted to create a substring, replace parts or split a string? If you did, now can do all of these things by using propaganda.c, the library for manipulating strings.

• Setup
• Usage
  • strlen()
  • strcpy()
  • newstr()
  • strcat()
  • strequals()
  • Substrings
    • substr()
    • substring()
  • Character indices
    • indexOf()
    • indexOfFrom()
    • lastIndexOf()
  • Substring indices
    • indexOfString()
    • indexOfStringFrom()
    • lastIndexOfString()
  • charOccurrence()
  • stringOccurrence()
  • split()
  • splits()
  • Lowercase
    • lowerCase()
    • toLowerCase()
  • Uppercase
    • upperCase()
    • toUpperCase()
  • replace()
  • replaceString()
  • trim()
  • itoc()
  • ctoi()
  • To string
    • itos()
    • btos()
    • ltos()
    • ftos()
    • dtos()
  • From string
    • stoi()
    • stob()
    • stol()
    • stof()
    • stod()
• Conclusion

To include the library in your project, you will need to import the propaganda.h header file.

#include "propaganda.h"

// ...

In order to determine the length of a given string, you can call the strlen((char*) string) function. It will return the length of your string, up to the '\0' termination character.

// ...

char* str = "Hello World!";
int lenStr = strlen(str);

printf("Length of my string: %d\n", lenStr);

// ...

If you want to copy your string by value rather than copying it by reference, you can use the strcpy((char*) string) function, which will return the reference to the copy.

// ...

char* str = "Lorem ipsum";
char* copy = strcpy(str);

copy[0] = 'A';

printf("My string copy: %s\n", copy);
printf("My original string: %s\n", str);

// ...

To make sure your string works with all of the library functions, and as a good convention, you should create all of your strings by using the newstr((char*) string) function.

(Of course you could also use the strcpy((char*) string) function, since it does the same thing.)

// ...

char* str = newstr("Hello World!");
printf("My string: %s\n", str);

// ...

In order to attach one string to another one, you should use the strcat((char*) str1, (char*) str2) function. It returns a reference to the concatenated string.

// ...

char* str1 = newstr("Hello ");
char* str2 = newstr("World!");

printf("Concatenated: %s\n", strcat(str1, str2));

// ...

If you want to compare the value of two strings, use the strequals((char*) str1, (char*) str2) function. It will return a value of either 0 or 1.

// ...

char* str1 = newstr("Hello!");
char* str2 = newstr("Hello!");

printf("Are equal: %d\n", strequals(str1, str2));

str2 = newstr("Hello");
printf("Are still equal: %d\n", strequals(str1, str2));

// ...

You can create substrings in two different ways:

• Creating a substring to the end

  If you want to create a substring starting somewhere and lasting to the end, you can use the substr((char*) string, (int) start) function.

// ...

char* str = newstr("asdf Hello World!");
str = substr(str, strlen("asdf "));

printf("New string: %s\n", str);

// ...

• Creating a substring from ... to ...

  You can however, also create a substring starting at some index, and ending at another index by using the substring((char*) string, int start, int end) function.

  It is to note, that the range of the substring will be [start;end[.

// ...

char* str = newstr("asdf Hello World! asdf");
str = substring(str, strlen("asdf "), strlen("asdf Hello World!"));

printf("New string: %s\n", str);

// ...

You might want to get the index of a specific character in a string, in order to do this, you can use the following functions:

• First index of character

  In order to get the index of the first occurrence of the character, use the indexOf((char*) str, (char) c) function.

// ...

char* str = newstr("Hello World!");
int index = indexOf(str, 'o');

printf("First index: %d\n", index);

// ...

• First index of character from ...

  Sometimes, you might want to get the first occurrence of a character from a certain index. You can use the indexOfFrom((char*) str, (char) c) function to achieve this.

// ...

char* str = newstr("0123456789 0123456789");
int fIndex = indexOfFrom(str, '0', 10);

printf("First index from: %d\n", fIndex);

// ...

• Last index of character

  If you need to get the last index of the character, use the lastIndexOf((char*) str, (char) c), which searches the string from the end.

// ...

char* str = newstr("This sentence has many 'a's ... ");
int lIndex = lastIndexOf(str, 'a');

printf("Last index: %d\n", lIndex);

// ...

Note: All indexOf...() functions return a value of -1 if no match was found.

All functions that are available for characters are also available for substrings.

• First index of substring

  In order to get the index of the first occurrence of the string, use the indexOfString((char*) str, (char*) sub) function.

// ...

char* str = newstr("Hello World!");
int index = indexOfString(str, "World!");

printf("First index: %d\n", index);

// ...

• First index of substring from ...

  Sometimes, you might want to get the first occurrence of a string from a certain index. You can use the indexOfStringFrom((char*) str, (char*) sub) function to achieve this.

// ...

char* str = newstr("0123456789 0123456789");
int fIndex = indexOfStringFrom(str, "89", 10);

printf("First index from: %d\n", fIndex);

// ...

• Last index of substring

  If you need to get the last index of the substring, use the lastIndexOfString((char*) str, (char*) sub), which searches the string from the end.

// ...

char* str = newstr("asdf hello hello asdf");
int lIndex = lastIndexOfString(str, "hello");

printf("Last index: %d\n", lIndex);

// ...

Note: All indexOfString...() functions return a value of -1 if no match was found.

To get the amount of times a certain character appears in your string, use the charOccurrence((char*) str, (char) c) function.

// ...

char* mystr = newstr("asjdflasdjdfkljaskldasdfaaaasdfasdfa");
int amount = charOccurrence(mystr, 'a');

printf("Amount of 'a's: %d\n", amount);

// ...

To get the amount of times a specified substring appears in your string, use the stringOccurrence((char*) str, (char*) sub) function.

// ...

char* mystr = newstr("asdf qwer asdf qwer asdf qwer asdf qwer");
int amount = stringOccurrence(mystr, "asdf");

printf("Amount of substrings: %d\n", amount);

// ...

To split a string at a specified character, you can use the split((char*) str, (char) c) function.

This will return a reference to a char-pointer (the first part). You should combine this with the charOccurrence(...) function, to figure out, how many parts there are.

// ...

char* mystr = newstr("Hello! I'm Matthias ... Wow, this sentence is seemingly endless ...");

int amount = charOccurrence(mystr, ' ')+1;
char** parts = split(mystr, ' ');

for (int i = 0; i < amount; i++) {
  printf(" [%02d]: %s\n", i, parts[i]);
}

// ...

To split a string at a specified substring, you can use the splits((char*) str, (char*) c) function.

You should handle it the same way, as the split(...) function's return value.

// ...

char* mystr = newstr("Hello!\r\nasdf\r\nqwer\r\n...\r\nWow,\r\nthis\r\nsentence\r\nis\r\nseemingly\r\nendless\r\n...");

int amount = stringOccurrence(mystr, "\r\n")+1;
char** parts = splits(mystr, "\r\n");

for (int i = 0; i < amount; i++) {
  printf(" [%02d]: %s\n", i, parts[i]);
}

// ...

There are two ways to convert a string to lowercase:

1. Lowercase copy

The first, possible way would be to use the `lowerCase((char*) str)` function, which returns a lowercase-copy of the specified string. This is useful, if you don't want to modify the original "string".

// ...

char* mystr = newstr("Hello World!");
char* strLow = lowerCase(mystr);

printf("Lowercase: %s\n", strLow);
printf("Original: %s\n", mystr);

// ...

2. Value to lowercase

The second option would be, to convert the value of your "string" to lowercase using the `toLowerCase((char*) str)` function.

// ...

char* str = newstr("Hello everyone!");
toLowerCase(str);

printf("Original-lowercase: %s\n", str);

// ...

**Note:** When using the `toLowerCase(...)` function, it's necessary, that your string was created dynamically.

There are also two ways to convert a string to uppercase:

1. Uppercase copy

Similiar to the `lowerCase(...)` function, you can use the `upperCase((char*) str)`, which also returns a copy, but in this case the copy is in upper-case.

// ...

char* str = newstr("Hello World!");
char* upp = upperCase(str);

printf("Uppercase: %s\n", upp);
printf("Original: %s\n", str);

// ...

2. Value to uppercase

The second option, once again, converts the value of the "string" to uppercase. Use the `toUpperCase((char*) str)` function for this.

// ...

char* mystr = newstr("Lorem Ipsum");
toUpperCase(mystr);

printf("Original-uppercase: %s\n", mystr);

// ...

**Note:** When using the `toUpperCase(...)` function, it's necessary, that your string was created dynamically.

You can use the replace((char*) str, (char) c, (char) r) function to replace all occurrences of the given character c with the specified character r.

// ...

char* mystr = newstr("Hello World!");
replace(mystr, 'o', 'a');

printf("String: %s\n", mystr);

// ...

You can use the replaceString((char*) str, (char*) s, (char*) r) function to replace all occurrences of the given substring s with the specified substring r.

// ...

char* mystr = newstr("Hello World!");
mystr = replaceString(mystr, "World", "Humans");

printf("String: %s\n", mystr);

// ...

Use the trim((char*) str) function to trim all whitespace from the beginning and end of a string.

// ...

char* msg = newstr("      \n\rHello World!\n     ");
char* trimmed = trim(msg);

printf("Trimmed: %s\n", trimmed);

// ...

In order to convert an integer to its character representation, you can use the itoc((int) n).

// ...

int number = 8;
char n_chr = itoc(8);

printf("As character: %c\n", n_chr);

// ...

You can also do it the other way around by using the ctoi((char) c) function.

// ...

char n_chr = '2';
int number = ctoi(n_chr);

printf("As integer: %d\n", number);

// ...

The following are all functions to convert several datatypes to a string.

• Integer to string

  To convert an integer to a string, use the itos((int) n) function.

int my_int = 802;
char* my_str = itos(my_int);

printf("String: %s\n", my_str);

• Boolean value to string

  To convert a boolean value to a string, you should use the btos((int) b) function.

int my_boo = 0;
char* my_str = btos(my_boo);

printf("String: %s\n", my_str);

• Long to string

  To convert a long to a string, you can use the ltos((long) n) function.

// ...

long my_lon = 8000000l;
char* my_str = ltos(my_lon);

printf("String: %s\n", my_str);

// ...

• Float to string

  To convert a float to a string, use the ftos((float) n, (int) r) function.

  Note: The r parameter specifies how many decimals to round to.

// ...

float my_flo = 3.141f;
char* my_str = ftos(my_flo, 3);

printf("String: %s\n", my_str);

// ...

• Double to string

  To convert a double to a string, you should use the dtos((double) n, (int) r) function.

  Note: The r parameter specifies to how many decimals the resulting "string" should be rounded.

// ...

double my_dou = 3.14159265359;
char* my_str = dtos(my_dou, 10);

printf("String: %s\n", my_str);

// ...

The following are all functions to convert a string to several, different datatypes.

• String to integer

  To convert a string to an integer, use the stoi((char*) str) function.

// ...

char* my_str = "1024";
int my_int = stoi(my_str);

printf("Integer: %d\n", my_int);

// ...

• String to boolean value

  To convert a string to a boolean value, you should use the stob((char*) str) function.

// ...

char* my_str = "true";
int my_boo = stob(my_str);

printf("Boolean: %d\n", my_boo);

// ...

• String to long

  To convert a string to a long, you can use the stol((char*) str) function.

// ...

char* my_str = "8000000";
long my_lon = stol(my_str);

printf("Long: %ld\n", my_lon);

// ...

• String to float

  To convert a string to a float, use the stof((char*) str) function.

// ...

char* my_str = "3.141";
float my_flo = stof(my_str);

printf("Float: %f\n", my_flo);

// ...

• String to double

  To convert a string to a double, you can use the stod((char*) str) function.

// ...

char* my_str = "3.14159265359";
double my_dou = stod(my_str);

printf("Double: %.15lf\n", my_dou);

// ...

For any questions/suggestions, you can message me on my twitter.

... Matthias M.