diff -r 99a34860c105 -r d938228c382e src/ucx/printf.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ucx/printf.c	Sun Nov 06 15:53:32 2022 +0100
@@ -0,0 +1,109 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   1. Redistributions of source code must retain the above copyright
+ *      notice, this list of conditions and the following disclaimer.
+ *
+ *   2. Redistributions in binary form must reproduce the above copyright
+ *      notice, this list of conditions and the following disclaimer in the
+ *      documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "cx/printf.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#define UCX_PRINTF_BUFSIZE 256
+
+int cx_fprintf(void *stream, cx_write_func wfc, char const *fmt, ...) {
+    int ret;
+    va_list ap;
+    va_start(ap, fmt);
+    ret = cx_vfprintf(stream, wfc, fmt, ap);
+    va_end(ap);
+    return ret;
+}
+
+int cx_vfprintf(void *stream, cx_write_func wfc, char const *fmt, va_list ap) {
+    char buf[UCX_PRINTF_BUFSIZE];
+    va_list ap2;
+    va_copy(ap2, ap);
+    int ret = vsnprintf(buf, UCX_PRINTF_BUFSIZE, fmt, ap);
+    if (ret < 0) {
+        return ret;
+    } else if (ret < UCX_PRINTF_BUFSIZE) {
+        return (int) wfc(buf, 1, ret, stream);
+    } else {
+        int len = ret + 1;
+        char *newbuf = malloc(len);
+        if (!newbuf) {
+            return -1;
+        }
+
+        ret = vsnprintf(newbuf, len, fmt, ap2);
+        if (ret > 0) {
+            ret = (int) wfc(newbuf, 1, ret, stream);
+        }
+        free(newbuf);
+    }
+    return ret;
+}
+
+cxmutstr cx_asprintf_a(CxAllocator *allocator, char const *fmt, ...) {
+    va_list ap;
+    cxmutstr ret;
+    va_start(ap, fmt);
+    ret = cx_vasprintf_a(allocator, fmt, ap);
+    va_end(ap);
+    return ret;
+}
+
+cxmutstr cx_vasprintf_a(CxAllocator *a, char const *fmt, va_list ap) {
+    cxmutstr s;
+    s.ptr = NULL;
+    s.length = 0;
+    char buf[UCX_PRINTF_BUFSIZE];
+    va_list ap2;
+    va_copy(ap2, ap);
+    int ret = vsnprintf(buf, UCX_PRINTF_BUFSIZE, fmt, ap);
+    if (ret > 0 && ret < UCX_PRINTF_BUFSIZE) {
+        s.ptr = cxMalloc(a, ret + 1);
+        if (s.ptr) {
+            s.length = (size_t) ret;
+            memcpy(s.ptr, buf, ret);
+            s.ptr[s.length] = '\0';
+        }
+    } else {
+        int len = ret + 1;
+        s.ptr = cxMalloc(a, len);
+        if (s.ptr) {
+            ret = vsnprintf(s.ptr, len, fmt, ap2);
+            if (ret < 0) {
+                free(s.ptr);
+                s.ptr = NULL;
+            } else {
+                s.length = (size_t) ret;
+            }
+        }
+    }
+    return s;
+}
+