+ /** Header for a single key/data pair within a page.
+ * We guarantee 2-byte alignment for nodes.
+ */
+typedef struct MDB_node {
+ /** lo and hi are used for data size on leaf nodes and for
+ * child pgno on branch nodes. On 64 bit platforms, flags
+ * is also used for pgno. (Branch nodes have no flags).
+ * They are in host byte order in case that lets some
+ * accesses be optimized into a 32-bit word access.
+ */
+#define mn_lo mn_offset[BYTE_ORDER!=LITTLE_ENDIAN]
+#define mn_hi mn_offset[BYTE_ORDER==LITTLE_ENDIAN] /**< part of dsize or pgno */
+ unsigned short mn_offset[2]; /**< storage for #mn_lo and #mn_hi */
+/** @defgroup mdb_node Node Flags
+ * @ingroup internal
+ * Flags for node headers.
+ * @{
+ */
+#define F_BIGDATA 0x01 /**< data put on overflow page */
+#define F_SUBDATA 0x02 /**< data is a sub-database */
+#define F_DUPDATA 0x04 /**< data has duplicates */
+
+/** valid flags for #mdb_node_add() */
+#define NODE_ADD_FLAGS (F_DUPDATA|F_SUBDATA|MDB_RESERVE|MDB_APPEND)
+
+/** @} */
+ unsigned short mn_flags; /**< @ref mdb_node */
+ unsigned short mn_ksize; /**< key size */
+ char mn_data[1]; /**< key and data are appended here */
+} MDB_node;
+
+ /** Size of the node header, excluding dynamic data at the end */
+#define NODESIZE offsetof(MDB_node, mn_data)
+
+ /** Bit position of top word in page number, for shifting mn_flags */
+#define PGNO_TOPWORD ((pgno_t)-1 > 0xffffffffu ? 32 : 0)
+
+ /** Size of a node in a branch page with a given key.
+ * This is just the node header plus the key, there is no data.
+ */
+#define INDXSIZE(k) (NODESIZE + ((k) == NULL ? 0 : (k)->mv_size))
+
+ /** Size of a node in a leaf page with a given key and data.
+ * This is node header plus key plus data size.
+ */
+#define LEAFSIZE(k, d) (NODESIZE + (k)->mv_size + (d)->mv_size)
+
+ /** Address of node \b i in page \b p */
+#define NODEPTR(p, i) ((MDB_node *)((char *)(p) + (p)->mp_ptrs[i]))
+
+ /** Address of the key for the node */
+#define NODEKEY(node) (void *)((node)->mn_data)
+
+ /** Address of the data for a node */
+#define NODEDATA(node) (void *)((char *)(node)->mn_data + (node)->mn_ksize)
+
+ /** Get the page number pointed to by a branch node */
+#define NODEPGNO(node) \
+ ((node)->mn_lo | ((pgno_t) (node)->mn_hi << 16) | \
+ (PGNO_TOPWORD ? ((pgno_t) (node)->mn_flags << PGNO_TOPWORD) : 0))
+ /** Set the page number in a branch node */
+#define SETPGNO(node,pgno) do { \
+ (node)->mn_lo = (pgno) & 0xffff; (node)->mn_hi = (pgno) >> 16; \
+ if (PGNO_TOPWORD) (node)->mn_flags = (pgno) >> PGNO_TOPWORD; } while(0)
+
+ /** Get the size of the data in a leaf node */
+#define NODEDSZ(node) ((node)->mn_lo | ((unsigned)(node)->mn_hi << 16))
+ /** Set the size of the data for a leaf node */
+#define SETDSZ(node,size) do { \
+ (node)->mn_lo = (size) & 0xffff; (node)->mn_hi = (size) >> 16;} while(0)
+ /** The size of a key in a node */
+#define NODEKSZ(node) ((node)->mn_ksize)
+
+ /** Copy a page number from src to dst */
+#ifdef MISALIGNED_OK
+#define COPY_PGNO(dst,src) dst = src
+#else
+#if SIZE_MAX > 4294967295UL
+#define COPY_PGNO(dst,src) do { \
+ unsigned short *s, *d; \
+ s = (unsigned short *)&(src); \
+ d = (unsigned short *)&(dst); \
+ *d++ = *s++; \
+ *d++ = *s++; \
+ *d++ = *s++; \
+ *d = *s; \
+} while (0)
+#else
+#define COPY_PGNO(dst,src) do { \
+ unsigned short *s, *d; \
+ s = (unsigned short *)&(src); \
+ d = (unsigned short *)&(dst); \
+ *d++ = *s++; \
+ *d = *s; \
+} while (0)
+#endif
+#endif
+ /** The address of a key in a LEAF2 page.
+ * LEAF2 pages are used for #MDB_DUPFIXED sorted-duplicate sub-DBs.
+ * There are no node headers, keys are stored contiguously.
+ */
+#define LEAF2KEY(p, i, ks) ((char *)(p) + PAGEHDRSZ + ((i)*(ks)))
+
+ /** Set the \b node's key into \b key, if requested. */
+#define MDB_SET_KEY(node, key) { if ((key) != NULL) { \
+ (key)->mv_size = NODEKSZ(node); (key)->mv_data = NODEKEY(node); } }
+
+ /** Information about a single database in the environment. */