diff -r 2cfbcbe86a7c -r 9cd98da9ee17 src/buffer.c
--- a/src/buffer.c	Sat Apr 30 09:03:17 2022 +0200
+++ b/src/buffer.c	Sat Apr 30 09:47:20 2022 +0200
@@ -32,6 +32,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
+#include <stdint.h>
 
 int cxBufferInit(
         CxBuffer *buffer,
@@ -53,8 +54,12 @@
     }
     buffer->capacity = capacity;
     buffer->size = 0;
+    buffer->pos = 0;
 
-    buffer->pos = 0;
+    buffer->flush_func = NULL;
+    buffer->flush_blkmax = 0;
+    buffer->flush_blksize = 4096;
+    buffer->flush_threshold = SIZE_MAX;
 
     return 0;
 }
@@ -134,6 +139,7 @@
         size_t nitems,
         CxBuffer *buffer
 ) {
+    // TODO: optimize for special case size == nitems == 1
     size_t len;
     if (cx_szmul(size, nitems, &len)) {
         return 0;
@@ -143,15 +149,27 @@
         return 0;
     }
 
+    bool perform_flush = false;
     if (required > buffer->capacity) {
-        if ((buffer->flags & CX_BUFFER_AUTO_EXTEND) == CX_BUFFER_AUTO_EXTEND) {
-            if (cxBufferMinimumCapacity(buffer, required)) {
-                return 0;
+        if ((buffer->flags & CX_BUFFER_AUTO_EXTEND) == CX_BUFFER_AUTO_EXTEND && required) {
+            if (buffer->flush_blkmax > 0 && required > buffer->flush_threshold) {
+                perform_flush = true;
+            } else {
+                if (cxBufferMinimumCapacity(buffer, required)) {
+                    return 0;
+                }
             }
         } else {
-            len = buffer->capacity - buffer->pos;
-            if (size > 1) {
-                len -= len % size;
+            if (buffer->flush_blkmax > 0) {
+                perform_flush = true;
+            } else {
+                // truncate data to be written, if we can neither extend nor flush
+                len = buffer->capacity - buffer->pos;
+                if (size > 1) {
+                    // TODO: this is bugged - it would only discard one element and not as many as required
+                    len -= len % size;
+                    nitems = len / size;
+                }
             }
         }
     }
@@ -160,13 +178,25 @@
         return len;
     }
 
-    memcpy(buffer->bytes + buffer->pos, ptr, len);
-    buffer->pos += len;
-    if (buffer->pos > buffer->size) {
-        buffer->size = buffer->pos;
+    if (perform_flush) {
+        // TODO: implement flushing
+        // (1) determine how many bytes to flush (use flushmax = blkmax * blksize)
+        // (2) if len is larger than the number computed in (1) we need more flush cycles, compute how many
+        // (3) determine how many bytes from the buffer shall be flushed
+        // (4) if something remains in the buffer, shift the buffer to the left
+        // (4a) if buffer was shifted, append the new data to the buffer
+        // (4b) if the buffer was flushed entirely AND the new data also fits into flushmax,
+        //      directly write the new data to the flush sink
+        return 0; // remove this after implementation
+    } else {
+        memcpy(buffer->bytes + buffer->pos, ptr, len);
+        buffer->pos += len;
+        if (buffer->pos > buffer->size) {
+            buffer->size = buffer->pos;
+        }
     }
 
-    return len / size;
+    return nitems;
 }
 
 int cxBufferPut(