1 files changed, 37 insertions, 0 deletions
diff --git a/internal/bufpool/capacity.go b/internal/bufpool/capacity.go
new file mode 100644
index 00000000..ecbd7d76
--- /dev/null
+++ b/internal/bufpool/capacity.go
@@ -0,0 +1,37 @@
+package bufpool
+
+// ensureCapacity grows the underlying buffer to accommodate the requested
+// number of bytes. Growth doubles the capacity by default unless a larger
+// expansion is needed. If the previous storage was pooled and not oversized,
+// it is returned to the pool.
+func (buf *Buffer) ensureCapacity(needed int) {
+	if cap(buf.buf) >= needed {
+		return
+	}
+
+	classIdx, classCap, pooled := classFor(needed)
+
+	var newBuf []byte
+
+	if pooled {
+		//nolint:forcetypeassert
+		raw := bufferPools[classIdx].Get().(*[]byte)
+		if cap(*raw) < classCap {
+			*raw = make([]byte, 0, classCap)
+		}
+
+		newBuf = (*raw)[:len(buf.buf)]
+	} else {
+		newBuf = make([]byte, len(buf.buf), classCap)
+	}
+
+	copy(newBuf, buf.buf)
+	buf.returnToPool()
+
+	buf.buf = newBuf
+	if pooled {
+		buf.pool = poolIndex(classIdx) //#nosec G115
+	} else {
+		buf.pool = unpooled
+	}
+}