dynstr_prepend(), fixed typo in comment

1 files changed, 45 insertions, 0 deletions

diff --git a/dynstr.c b/dynstr.c
index 847b75f..97f03bc 100644
--- a/dynstr.c
+++ b/dynstr.c
@@ -59,6 +59,51 @@ enum dynstr_err dynstr_append(struct dynstr *const d, const char *const format,
     return DYNSTR_OK;
 }
 
+enum dynstr_err dynstr_prepend(struct dynstr *const d, const char *const format, ...)
+{
+    va_list ap;
+
+    va_start(ap, format);
+
+    {
+        const size_t src_len = vsnprintf(NULL, 0, format, ap);
+        const size_t new_len = d->len + src_len + 1;
+        va_end(ap);
+
+        d->str = realloc(d->str, new_len * sizeof *d->str);
+
+        if (d->str && d->len)
+        {
+            /* Keep byte that will be removed by later call to vsprintf. */
+            const char c = *d->str;
+
+            for (size_t i = new_len - 1, j = d->len; j <= d->len; i--, j--)
+            {
+                d->str[i] = d->str[j];
+            }
+
+            va_start(ap, format);
+            vsprintf(d->str, format, ap);
+            va_end(ap);
+            d->str[src_len] = c;
+        }
+        else if (!d->len)
+        {
+            va_start(ap, format);
+            vsprintf(d->str + d->len, format, ap);
+            va_end(ap);
+        }
+        else
+        {
+            return DYNSTR_ERR_ALLOC;
+        }
+
+        d->len += src_len;
+    }
+
+    return DYNSTR_OK;
+}
+
 enum dynstr_err dynstr_dup(struct dynstr *const dst, const struct dynstr *const src)
 {
     if (!dst->str && !dst->len)