1 files changed, 33 insertions, 0 deletions
diff --git a/sys/base/string/grow.c b/sys/base/string/grow.c
new file mode 100644
index 0000000..39a9d2f
--- /dev/null
+++ b/sys/base/string/grow.c
@@ -0,0 +1,33 @@
+#include "internal.h"
+
+// grow ensures that the string can encompass at least delta bytes.
+// if it already can, this is a no op.
+// if it can't, the string will be reallocated.
+void
+str·grow(string *s, vlong delta)
+{
+    Hdr *h, *newh;
+    vlong cap = str·cap(*s);
+    vlong len = str·len(*s);
+    assert(cap >= len); // To prevent unsigned behavior
+
+    if (cap - len >= delta) return;
+
+    h = (Hdr*)(*s - sizeof(Hdr));
+
+    vlong newCap = cap + delta;
+    assert(newCap >= cap); // To prevent unsigned behavior
+    if (newCap < MAX_STRING_ALLOC) {
+        newCap *= 2;
+    } else
+        newCap += MAX_STRING_ALLOC;
+
+    newh = (Hdr*)realloc(h, sizeof(*h) + newCap + 1);
+    if (newh == nil) return;
+
+    memset(newh->buf + len, '\0', newCap - len);
+    newh->cap = newCap;
+    newh->len = len;
+
+    *s = newh->buf;
+}