strjoin()

ccan/string/string.c

@@ -30,4 +30,15 @@ char **strsplit(const void *ctx, const char *string, const char *delims,
 		*nump = num;
 	return lines;
 }
-	
+
+char *strjoin(const void *ctx, char *strings[], const char *delim)
+{
+	unsigned int i;
+	char *ret = talloc_strdup(ctx, "");
+
+	for (i = 0; strings[i]; i++) {
+		ret = talloc_append_string(ret, strings[i]);
+		ret = talloc_append_string(ret, delim);
+	}
+	return ret;
+}

ccan/string/string.h

@@ -54,7 +54,8 @@ static inline bool strends(const char *str, const char *postfix)
  * This function splits a single string into multiple strings.  The
  * original string is untouched: an array is allocated (using talloc)
  * pointing to copies of each substring.  Multiple delimiters result
- * in empty substrings.
+ * in empty substrings.  By definition, no delimiters will appear in
+ * the substrings.
  *
  * The final char * in the array will be NULL, so you can use this or
  * @nump to find the array length.
@@ -76,4 +77,29 @@ static inline bool strends(const char *str, const char *postfix)
  */
 char **strsplit(const void *ctx, const char *string, const char *delims,
 		 unsigned int *nump);
+
+/**
+ * strjoin - Join an array of substrings into one long string
+ * @ctx: the context to tallocate from (often NULL)
+ * @strings: the NULL-terminated array of strings to join
+ * @delim: the delimiter to insert between the strings
+ *
+ * This function joins an array of strings into a single string.  The
+ * return value is allocated using talloc.  Each string in @strings is
+ * followed by a copy of @delim.
+ *
+ * Example:
+ *	// Append the string "--EOL" to each line.
+ *	char *append_to_all_lines(const char *string)
+ *	{
+ *		char **lines, *ret;
+ *		unsigned int i, num, newnum;
+ *
+ *		lines = strsplit(NULL, string, "\n", NULL);
+ *		ret = strjoin(NULL, lines, "-- EOL\n");
+ *		talloc_free(lines);
+ *		return ret;
+ *	}
+ */
+char *strjoin(const void *ctx, char *strings[], const char *delim);
 #endif /* CCAN_STRING_H */

ccan/string/test/run.c

@@ -7,7 +7,9 @@
 /* FIXME: ccanize */
 #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof(arr[0]))
 
-static char *substrings[] = { "far", "bar", "baz", "b", "ba", "z", "ar" };
+static char *substrings[] = { "far", "bar", "baz", "b", "ba", "z", "ar", NULL };
+
+#define NUM_SUBSTRINGS (ARRAY_SIZE(substrings) - 1)
 
 static char *strdup_rev(const char *s)
 {
@@ -22,13 +24,13 @@ static char *strdup_rev(const char *s)
 int main(int argc, char *argv[])
 {
 	unsigned int i, j, n;
-	char **split;
+	char **split, *str;
 	void *ctx;
-	char *strings[ARRAY_SIZE(substrings) * ARRAY_SIZE(substrings)];
+	char *strings[NUM_SUBSTRINGS * NUM_SUBSTRINGS];
 
 	n = 0;
-	for (i = 0; i < ARRAY_SIZE(substrings); i++) {
-		for (j = 0; j < ARRAY_SIZE(substrings); j++) {
+	for (i = 0; i < NUM_SUBSTRINGS; i++) {
+		for (j = 0; j < NUM_SUBSTRINGS; j++) {
 			strings[n] = malloc(strlen(substrings[i])
 					    + strlen(substrings[j]) + 1);
 			sprintf(strings[n++], "%s%s",
@@ -36,7 +38,7 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	plan_tests(n * n * 5 + 16);
+	plan_tests(n * n * 5 + 19);
 	for (i = 0; i < n; i++) {
 		for (j = 0; j < n; j++) {
 			unsigned int k, identical = 0;
@@ -104,6 +106,16 @@ int main(int argc, char *argv[])
 	split = strsplit(ctx, "hello  world", "o ", NULL);
 	ok1(talloc_parent(split) == ctx);
 	talloc_free(ctx);
+
+	str = strjoin(NULL, substrings, ", ");
+	ok1(streq(str, "far, bar, baz, b, ba, z, ar, "));
+	ctx = str;
+	str = strjoin(ctx, substrings, "");
+	ok1(streq(str, "farbarbazbbazar"));
+	ok1(talloc_parent(str) == ctx);
+	talloc_free(ctx);
+
+
 	
 	return exit_status();
 }