diff -r ee5d668a71e4 -r f024313c08f1 src/cx/buffer.h
--- a/src/cx/buffer.h	Wed Nov 26 23:06:12 2025 +0100
+++ b/src/cx/buffer.h	Wed Nov 26 23:22:03 2025 +0100
@@ -439,11 +439,30 @@
 cx_attr_nonnull cx_attr_nodiscard
 CX_EXPORT bool cxBufferEof(const CxBuffer *buffer);
 
+/**
+ * Ensures that the buffer has the required capacity.
+ *
+ * If the current capacity is not sufficient, the buffer will be extended.
+ *
+ * This function will reserve no more bytes than requested, in contrast to
+ * cxBufferMinimumCapacity(), which may reserve more bytes to improve the
+ * number of future necessary reallocations.
+ *
+ * @param buffer the buffer
+ * @param capacity the required capacity for this buffer
+ * @retval zero the capacity was already sufficient or successfully increased
+ * @retval non-zero on allocation failure
+ * @see cxBufferShrink()
+ * @see cxBufferMinimumCapacity()
+ */
+cx_attr_nonnull
+CX_EXPORT int cxBufferReserve(CxBuffer *buffer, size_t capacity);
 
 /**
  * Ensures that the buffer has a minimum capacity.
  *
- * If the current capacity is not sufficient, the buffer will be extended.
+ * If the current capacity is not sufficient, the buffer will be generously
+ * extended.
  *
  * The new capacity will be a power of two until the system's page size is reached.
  * Then, the new capacity will be a multiple of the page size.
@@ -452,6 +471,7 @@
  * @param capacity the minimum required capacity for this buffer
  * @retval zero the capacity was already sufficient or successfully increased
  * @retval non-zero on allocation failure
+ * @see cxBufferReserve()
  * @see cxBufferShrink()
  */
 cx_attr_nonnull
@@ -471,6 +491,7 @@
  *
  * @param buffer the buffer
  * @param reserve the number of bytes that shall remain reserved
+ * @see cxBufferReserve()
  * @see cxBufferMinimumCapacity()
  */
 cx_attr_nonnull