Added convenience method gpr_strjoin_sep

src/core/support/string.c

@@ -153,6 +153,12 @@ int gpr_ltoa(long value, char *string) {
 }
 
 char *gpr_strjoin(const char **strs, size_t nstrs, size_t *final_length) {
+  return gpr_strjoin_sep(strs, nstrs, "", final_length);
+}
+
+char *gpr_strjoin_sep(const char **strs, size_t nstrs, const char *sep,
+                      size_t *final_length) {
+  const size_t sep_len = strlen(sep);
   size_t out_length = 0;
   size_t i;
   char *out;
@@ -160,12 +166,19 @@ char *gpr_strjoin(const char **strs, size_t nstrs, size_t *final_length) {
     out_length += strlen(strs[i]);
   }
   out_length += 1;  /* null terminator */
+  if (nstrs > 0) {
+    out_length += sep_len * (nstrs - 1);  /* separators */
+  }
   out = gpr_malloc(out_length);
   out_length = 0;
   for (i = 0; i < nstrs; i++) {
-    size_t slen = strlen(strs[i]);
+    const size_t slen = strlen(strs[i]);
     memcpy(out + out_length, strs[i], slen);
     out_length += slen;
+    if (sep_len > 0 && nstrs > 0 && i < nstrs - 1) {
+      memcpy(out + out_length, sep, sep_len);
+      out_length += sep_len;
+    }
   }
   out[out_length] = 0;
   if (final_length != NULL) {

src/core/support/string.h

@@ -72,6 +72,12 @@ void gpr_reverse_bytes(char *str, int len);
    if it is non-null. */
 char *gpr_strjoin(const char **strs, size_t nstrs, size_t *total_length);
 
+/* Join a set of strings using a separator, returning the resulting string.
+   Total combined length (excluding null terminator) is returned in total_length
+   if it is non-null. */
+char *gpr_strjoin_sep(const char **strs, size_t nstrs, const char *sep,
+                      size_t *total_length);
+
 /* A vector of strings... for building up a final string one piece at a time */
 typedef struct {
   char **strs;

test/core/support/string_test.c

@@ -145,11 +145,53 @@ static void test_asprintf(void) {
   }
 }
 
+static void test_strjoin(void) {
+  const char *parts[4] = {"one", "two", "three", "four"};
+  size_t joined_len;
+  char *joined;
+
+  LOG_TEST_NAME("test_strjoin");
+
+  joined = gpr_strjoin(parts, 4, &joined_len);
+  GPR_ASSERT(0 == strcmp("onetwothreefour", joined));
+  gpr_free(joined);
+
+  joined = gpr_strjoin(parts, 0, &joined_len);
+  GPR_ASSERT(0 == strcmp("", joined));
+  gpr_free(joined);
+
+  joined = gpr_strjoin(parts, 1, &joined_len);
+  GPR_ASSERT(0 == strcmp("one", joined));
+  gpr_free(joined);
+}
+
+static void test_strjoin_sep(void) {
+  const char *parts[4] = {"one", "two", "three", "four"};
+  size_t joined_len;
+  char *joined;
+
+  LOG_TEST_NAME("test_strjoin_sep");
+
+  joined = gpr_strjoin_sep(parts, 4, ", ", &joined_len);
+  GPR_ASSERT(0 == strcmp("one, two, three, four", joined));
+  gpr_free(joined);
+
+  joined = gpr_strjoin_sep(parts, 0, ", ", &joined_len);
+  GPR_ASSERT(0 == strcmp("", joined));
+  gpr_free(joined);
+
+  joined = gpr_strjoin_sep(parts, 1, ", ", &joined_len);
+  GPR_ASSERT(0 == strcmp("one", joined));
+  gpr_free(joined);
+}
+
 int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
   test_strdup();
   test_hexdump();
   test_parse_uint32();
   test_asprintf();
+  test_strjoin();
+  test_strjoin_sep();
   return 0;
 }