C: add str_replace.*

c-programming/strings/str_replace.c

@@ -0,0 +1,78 @@
+/*
+ * str_replace.c
+ *
+ * Author: Intel A80486DX2-66
+ * License: Creative Commons Zero 1.0 Universal
+ *
+ * To-Do:
+ * - add ability to replace from the end (negative value of max_count)
+ */
+
+#include "str_replace.h"
+
+char* str_replace(
+  const char* str,
+  const char* substr,
+  const char* replacement,
+  ssize_t max_count
+) {
+	/*
+	 * input arguments:
+	 * 	max_count: N <= 0 for all replacements, N > 0 for N replacement
+	 *
+	 * the output string should be freed!
+	 */
+	size_t substr_len = strlen(substr),
+	       replacement_len = strlen(replacement),
+	       count = 0;
+	const char* p = str;
+
+	// count the number of occurrences of the substring
+	for (; (p = strstr(p, substr)) != NULL; count++) {
+		if (max_count >= 0 && count >= (size_t) max_count)
+			break;
+		p += substr_len;
+	}
+
+	// allocate a buffer to hold the modified string
+	size_t new_len = strlen(str) + count * (replacement_len - substr_len);
+
+	char* result = malloc((new_len + 1) * sizeof(char));
+	if (result == NULL) {
+		perror("calloc");
+		exit(EXIT_FAILURE);
+	}
+
+	const char* q = str;
+	char* r = result;
+	for (; (p = strstr(q, substr)) != NULL && count > 0; count--) {
+		size_t len = p - q;
+		memcpy(r, q, len);
+		r += len;
+		memcpy(r, replacement, replacement_len);
+		r += replacement_len;
+		q = p + substr_len;
+	}
+	strcpy(r, q);
+
+	return result;
+}
+
+#ifdef TEST
+#include <stdio.h>
+
+int main(void) {
+	const char* str = "Hello; peace! This is a peaceful test.",
+	          * substr = "peace",
+	          * replacement1 = "universe",
+	          * replacement2 = "_____";
+
+	char* result1 = str_replace(str, substr, replacement1, -1),
+	    * result2 = str_replace(str, substr, replacement2, 1);
+
+	puts(result1); free(result1);
+	puts(result2); free(result2);
+
+	return 0;
+}
+#endif

c-programming/strings/str_replace.h

@@ -0,0 +1,16 @@
+/*
+ * str_replace.h
+ *
+ * Author: Intel A80486DX2-66
+ * License: Creative Commons Zero 1.0 Universal
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+char* str_replace(
+  const char* str,
+  const char* substr,
+  const char* replacement,
+  ssize_t max_count
+);