Add DStr sprintf

src/dstr.c

@@ -1,5 +1,7 @@
 #include <string.h>
 #include <stdlib.h>
+#include <stdarg.h>
+#include <stdio.h>
 #include "ucore/dstr.h"
 #include "ucore/utils.h"
 
@@ -26,7 +28,7 @@ int uc_dstr_ensure(struct DStr *str, size_t len)
         //allocate a minimum no. of bytes, and one
         //additional for the common case of nul terminating
         //the string
-        size_t new_len = str->len + UC_MAX(7U, len) + 1;
+        size_t new_len = UC_MAX(7U, len) + 1;
         char *new_str = realloc(str->str, new_len);
 
         if (new_str == NULL) {
@@ -204,4 +206,55 @@ void uc_dstr_trim(struct DStr *str)
     }
 }
 
+int uc_dstr_sprintf(struct DStr *str, const char *fmt, ...)
+{
+    va_list ap;
+    int rc;
+
+    va_start(ap, fmt);
+    rc = uc_dstr_vsprintf(str, fmt, ap);
+    va_end(ap);
+
+    return rc;
+}
+
+int uc_dstr_vsprintf(struct DStr *str, const char *fmt, va_list ap_)
+{
+    va_list ap;
+    int rc;
+    int available;
+    int needed;
+
+    rc = uc_dstr_ensure(str, str->len + 1);
+    if (rc != 0) {
+        return -1;
+    }
+
+    available = uc_dstr_available(str);
+
+    va_copy(ap, ap_);
+    needed = vsnprintf(str->str + str->len, available, fmt, ap);
+    va_end(ap);
+
+    if (needed <= 0) {
+        return needed;
+    }
+
+    if (needed >= available) {
+        rc = uc_dstr_ensure(str, str->len + needed);
+        if (rc != 0) {
+            return -1;
+        }
+
+        available = uc_dstr_available(str);
+
+        va_copy(ap, ap_);
+        needed = vsnprintf(str->str + str->len, available, fmt, ap);
+        va_end(ap);
+    }
+
+    str->len += needed;
+
+    return needed;
+}