henge.h initial

diff --git a/src/henge.h b/src/henge.h
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+/*!@file
+  \brief   HENGE Memory Definition in common with STON Asset Packages
+  \details C Aligned memory structures used to define datatypes in the STON
+           Asset Package format, used for reading asset packages as runtime 
+           memory.
+  \author  Ken Grimes
+  \date    Feb 2017
+  ----------------------------------------------------------------------------*/
+#ifndef _HENGE_H_
+#define _HENGE_H_
+
+/* Henge Generic Hashtable 
+
+   Hashtables are stored as dynamically sized two dimensional arrays, whose
+   columns are provided, and whose rows, and sizes, are derived.
+
+   ht_size = header.ht_columns << header.ht_2pow;
+   ht_rows = 0x1 << header.ht_2pow;
+
+   All generic hashtables in henge must have a power-of-two number of rows.  An
+   ht_columns value that is also a power-of-two will result in a power-of-two
+   sized memory imprint for the structure, making it easy to page align.
+
+   Elements in the columns may be of any arbitrary size.
+
+   typedef uint32_t my_ht_type;
+   ht_bytes = ht_size * sizeof(my_ht_type);
+*/
+struct hng_ht_header_t
+{ uint16_t ht_columns;
+  uint8_t  ht_2pow, ht_flags;
+};
+
+#define hng_ht_size(_HEADER)             ((_HEADER)->ht_columns << (_HEADER)->ht_2pow)
+#define hng_ht_rows(_HEADER)             (0x1 << (_HEADER)->ht_2pow)
+#define hng_ht_cols(_HEADER)             (_HEADER->ht_columns)
+#define hng_ht_start(_HEADER)            (_HEADER + sizeof(*_HEADER))
+#define hng_ht_array(_HEADER,_UNIT)      ((_UNIT*)hng_ht_start(_HEADER))
+#define hng_ht_bytes(_HEADER,_UNIT)      (hng_ht_size(_HEADER) * sizeof(_UNIT))
+#define hng_ht_2bytes(_HEADER,_UNIT2POW) (hng_ht_size(_HEADER) << _UNIT2POW)
+
+#endif //_HENGE_H_