--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/if1_unpack.c	Thu May 09 07:06:31 2024 +0000
@@ -0,0 +1,68 @@
+/*
+ * In this module we implement our function for unpacking bits from AMR IF1
+ * and reshuffling them into the codec's natural bit order.
+ */
+
+#include <stdint.h>
+#include "tw_amr.h"
+#include "typedef.h"
+#include "namespace.h"
+#include "int_defs.h"
+#include "if1_func.h"
+
+static inline Word16 msb_get_bit(const uint8_t *buf, Word16 bn)
+{
+	Word16 pos_byte = bn >> 3;
+	Word16 pos_bit  = 7 - (bn & 7);
+
+	return (buf[pos_byte] >> pos_bit) & 1;
+}
+
+static void unpack_bits(const uint8_t *if1_bytes, Word16 *codec_bits,
+			Word16 nbits, const uint8_t *table)
+{
+	Word16 n, nb;
+
+	for (n = 0; n < nbits; n++) {
+		if (table)
+			nb = table[n];
+		else
+			nb = n;
+		codec_bits[nb] = msb_get_bit(if1_bytes, n);
+	}
+}
+
+void if1_unpack_bytes(enum Mode mode, const uint8_t *if1_bytes,
+		      Word16 *serial_bits)
+{
+	switch (mode) {
+	case MR475:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_475, sort_475);
+		return;
+	case MR515:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_515, sort_515);
+		return;
+	case MR59:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_59, sort_59);
+		return;
+	case MR67:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_67, sort_67);
+		return;
+	case MR74:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_74, sort_74);
+		return;
+	case MR795:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_795, sort_795);
+		return;
+	case MR102:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_102, sort_102);
+		return;
+	case MR122:            
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_122, sort_122);
+		return;
+	case MRDTX:
+		unpack_bits(if1_bytes, serial_bits, AMR_NBITS_SID,
+				(const uint8_t *) 0);
+		return;
+	}
+}