First commit

Author: betaWeb

README.md

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+# Implementation of `str_replace` in C
+
+ This is a very naive implementation of the PHP function `str_replace` in C.
+ I wrote it in purpuse to learn C basics.
+ 
+ 
+ Basically, it search for the index of the searched word in the subject string.
+ 
+ If no index found, then it returns the subject.
+ 
+ Otherwize it splits the subject string into 3 parts :
+      - prefix : all chars before the searched word
+      - searched word
+      - suffix : all chars after the searched word
+ and it replaces the searched word by the replace parameter.
+ 
+ Finally, it join prefix with replace and suffix, and returns it as string.

str_replace.c

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+/**
+ * This is a very naive implementation of the PHP function `str_replace` in C.
+ * I wrote it in purpuse to learn C basics.
+ * 
+ * 
+ * Basically, it search for the index of the searched word in the subject string.
+ * 
+ * If no index found, then it returns the subject.
+ * 
+ * Otherwize it splits the subject string into 3 parts :
+ *      - prefix : all chars before the searched word
+ *      - searched word
+ *      - suffix : all chars after the searched word
+ * and it replaces the searched word by the replace parameter.
+ * 
+ * Finally, it join prefix with replace and suffix, and returns it as string.
+ * 
+ * @author BetaWeb / Cyprien GLEPIN
+ **/
+
+#include "str_replace.h"
+
+/**
+ * Returns the first index of a character or a group of characters on a string
+ * 
+ * @param str The string in which to look
+ * @param c The character or group of characters of which we want to found the index
+ * 
+ * @return The found index if it exists, -1 otherwise
+ **/
+int indexOf(char *str, char *c) {
+    char *pointer = strlen(c) > 1 
+        ? strstr(str, c) 
+        : strchr(str, c[0]);
+
+    if (pointer == NULL) {
+        return -1;
+    }
+
+    return pointer - str;
+}
+
+/**
+ * Replaces the first occurrence of the searched string in the subject string.
+ *
+ * @param search The substring to look for
+ * @param replace The substring with which to replace the found substring
+ * @param subject The string in which to look
+ *
+ * @return A new string with the search/replacement performed
+ **/
+char *str_replace(char *search, char *replace, char *subject) {
+    int suffix_len, result_len, search_len, replace_len, subject_len, index;
+    char *result, *prefix, *suffix;
+    
+    search_len = strlen(search);
+    subject_len = strlen(subject);
+    index = indexOf(subject, search);
+
+    if (search_len == 0 || index < 0) {
+        result = malloc(subject_len + 1);
+        strncpy(result, subject, subject_len + 1);
+        
+        return result;
+    }
+
+    prefix = malloc(index + 1);
+    strncpy(prefix, subject, index);
+    
+    suffix_len = subject_len - (index + search_len);
+    suffix = malloc(suffix_len + 1);
+    strncat(suffix, subject + index + search_len, suffix_len);
+
+    replace_len = strlen(replace);
+    result_len = strlen(prefix) + replace_len + suffix_len + 1;    
+    result = malloc(result_len + 1);
+    snprintf(result, result_len, "%s%s%s", prefix, replace, suffix);
+
+    free(prefix);
+    free(suffix);
+
+    return result;
+}
+
+int main(void) {
+    char *original_str, *replaced_str;
+    
+    original_str = "This is a very powerful implementation of str_replace function";
+    replaced_str = str_replace("powerful", "naive", original_str);
+    
+    printf("Original : %s (%d char)\n", original_str, strlen(original_str));
+    printf("Replaced : %s (%d char)\n", replaced_str, strlen(replaced_str));
+
+    free(replaced_str);
+    original_str = NULL;
+
+    return 1;
+}

str_replace.h

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+#include <stdio.h>
+#include <string.h>
+
+int indexOf(char *str, char *c);
+char *str_replace(char *search, char *replace, char *subject);