Add GWBUF pretty-printing

The gwbuf_hexdump_pretty displays the hex contents of the buffer alongside
the human-readable version of it. The text version helps identify parts of
the buffer that contain text which makes protocol data decoding easier.

include/maxscale/buffer.hh

@@ -165,7 +165,7 @@ inline bool gwbuf_is_contiguous(const GWBUF* b)
 /*< True if all bytes in the buffer have been consumed */
 inline bool gwbuf_link_empty(const GWBUF* b)
 {
-    return ((char*)b->start >= (char*)b->end);
+    return (char*)b->start >= (char*)b->end;
 }
 
 #define GWBUF_EMPTY(b) gwbuf_link_empty(b)
@@ -422,11 +422,22 @@ extern void dprintAllBuffers(void* pdcb);
 /**
  * Debug function for dumping buffer contents to log
  *
+ * @see mxs::Buffer::hexdump
+ *
  * @param buffer    Buffer to dump
  * @param log_level Log priority where the message is written
  */
-void gwbuf_hexdump(GWBUF* buffer, int log_level);
-void gwbuf_hexdump(const mxs::Buffer& buffer, int log_level);
+void gwbuf_hexdump(GWBUF* buffer, int log_level = LOG_INFO);
+
+/**
+ * Debug function for pretty-printing buffer contents to log
+ *
+ * @see mxs::Buffer::hexdump_pretty
+ *
+ * @param buffer    Buffer to dump
+ * @param log_level Log priority where the message is written
+ */
+void gwbuf_hexdump_pretty(GWBUF* buffer, int log_level = LOG_INFO);
 
 /**
  * Return pointer of the byte at offset from start of chained buffer
@@ -1213,6 +1224,24 @@ public:
         }
     }
 
+    /**
+     * Debug function for dumping buffer contents to log
+     *
+     * Prints contents as hexadecimal. Only the first 1024 bytes are dumped to avoid filling up the log.
+     *
+     * @param log_level Log priority where the message is written
+     */
+    void hexdump(int log_level = LOG_INFO) const;
+
+    /**
+     * Debug function for pretty-printing buffer contents to log
+     *
+     * The output format is similar to `hexdump -C` and provides both hex and human-readable values.
+     *
+     * @param log_level Log priority where the message is written
+     */
+    void hexdump_pretty(int log_level = LOG_INFO) const;
+
 private:
     // To prevent @c Buffer from being created on the heap.
     void* operator new(size_t);         // standard new