bufref: buffer reference support

A struct bufref holds a buffer pointer, a data size and a destructor.
When freed or its contents are changed, the previous buffer is implicitly
released by the associated destructor. The data size, although not used
internally, allows binary data support.

A unit test checks its handling methods: test 1661

Closes #6654

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/bufref.h b/lib/bufref.h
new file mode 100644
index 000000000..25f65d894
--- /dev/null
+++ b/lib/bufref.h
@@ -0,0 +1,46 @@
+#ifndef HEADER_CURL_BUFREF_H
+#define HEADER_CURL_BUFREF_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+/*
+ * Generic buffer reference.
+ */
+struct bufref {
+  void (*dtor)(void *);         /* Associated destructor. */
+  const unsigned char *ptr;     /* Referenced data buffer. */
+  size_t len;                   /* The data size in bytes. */
+#ifdef DEBUGBUILD
+  int signature;                /* Detect API use mistakes. */
+#endif
+};
+
+
+void Curl_bufref_init(struct bufref *br);
+void Curl_bufref_set(struct bufref *br, const void *ptr, size_t len,
+                     void (*dtor)(void *));
+const unsigned char *Curl_bufref_ptr(const struct bufref *br);
+size_t Curl_bufref_len(const struct bufref *br);
+CURLcode Curl_bufref_memdup(struct bufref *br, const void *ptr, size_t len);
+void Curl_bufref_free(struct bufref *br);
+
+#endif