diff --git a/ext/bg/bg.h b/ext/bg/bg.h
new file mode 100644
index 0000000..29a6491
--- /dev/null
+++ b/ext/bg/bg.h
@@ -0,0 +1,109 @@
+//#include "defines.h"
+//#include <rw.h>
+#include <stdio.h>
+#include "defines.h"
+//#include "callZlib.h"
+#include <stdint.h>
+//#include <time.h>
+//#include <sys/time.h>
+//#include "conf.h"
+
+#ifndef _BG_H
+#define _BG_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+# define M_LN10      2.30258509299404568401799145468436421   /* loge(10)       */
+# define M_LN2       0.693147180559945309417232121458176568  /* loge(2)        */
+#define int_CEWI 0
+#define NCO_PPC_BIT_XPL_NBR_MIN 2
+
+typedef union lint16
+{
+	unsigned short usvalue;
+	short svalue;
+	unsigned char byte[2];
+} lint16;
+
+typedef union lint32
+{
+	int ivalue;
+	unsigned int uivalue;
+	unsigned char byte[4];
+} lint32;
+
+typedef union lint64
+{
+	long lvalue;
+	unsigned long ulvalue;
+	unsigned char byte[8];
+} lint64;
+
+typedef union ldouble
+{
+    double value;
+    unsigned long lvalue;
+    unsigned char byte[8];
+} ldouble;
+
+typedef union lfloat
+{
+    float value;
+    unsigned int ivalue;
+    unsigned char byte[4];
+} lfloat;
+
+typedef struct bg_params
+{
+	int dataType;
+
+	int sol_ID;// GB
+	int zlibMode; //* four options: Z_NO_COMPRESSION, or Z_BEST_SPEED, Z_BEST_COMPRESSION, Z_DEFAULT_COMPRESSION
+	int bgMode;  //BITGROOM, BITSHAVE or BITSET
+	int errorControlMode;
+	int NSD;
+	int DSD;
+	
+	float fmin, fmax;
+	double dmin, dmax;
+
+} bg_params;
+
+
+typedef struct bg_exedata
+{
+	unsigned int BG_SIZE_TYPE; //the length (# bytes) of the size_t in the system at runtime //4 or 8: sizeof(size_t) 
+} bg_exedata;
+
+
+extern int versionNumber[4];
+
+//-------------------key global variables--------------
+extern int dataEndianType; //*endian type of the data read from disk
+extern int sysEndianType; //*sysEndianType is actually set automatically.
+
+extern bg_params *confparams_cpr;
+extern bg_params *confparams_dec;
+extern bg_exedata *exe_params;
+
+
+//for libpressio
+extern int bgMode_libpressio;
+extern int errorControlMode_libpressio;
+extern int nsd_libpressio;
+extern int dsd_libpressio;
+
+
+unsigned char *BG_compress(int dataType, void *data, size_t *outSize, size_t nbEle);
+
+unsigned char* BG_compress_args(int dataType, void *data, size_t *outSize, int bgMode, int errorControlMode, int nsd, int dsd, size_t nbEle, unsigned char *data_);
+
+//void *BG_decompress(int dataType, unsigned char *bytes, size_t byteLength, size_t nbEle);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ----- #ifndef _BG_H  ----- */