--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtwamr/if1_pack.c	Thu May 09 07:06:31 2024 +0000
@@ -0,0 +1,81 @@
+/*
+ * In this module we implement our function for packing AMR codec bits
+ * from an array containing them in the codec's natural bit order
+ * into the octet form of AMR IF1 and RFC 4867.
+ */
+
+#include <stdint.h>
+#include "tw_amr.h"
+#include "typedef.h"
+#include "namespace.h"
+#include "int_defs.h"
+#include "if1_func.h"
+
+static inline void msb_set_bit(uint8_t *buf, Word16 bn, Word16 bit)
+{
+	Word16 pos_byte = bn >> 3;
+	Word16 pos_bit  = 7 - (bn & 7);
+
+	if (bit)
+		buf[pos_byte] |= (1 << pos_bit);
+	else
+		buf[pos_byte] &= ~(1 << pos_bit);
+}
+
+static void pack_bits(uint8_t *if1_bytes, const Word16 *src_bits, Word16 nbits,
+		      const uint8_t *table)
+{
+	Word16 n, nb;
+
+	for (n = 0; n < nbits; n++) {
+		if (table)
+			nb = table[n];
+		else
+			nb = n;
+		msb_set_bit(if1_bytes, n, src_bits[nb]);
+	}
+}
+
+void if1_pack_bytes(enum Mode mode, const Word16 *serial_bits,
+		    uint8_t *if1_bytes)
+{
+	switch (mode) {
+	case MR475:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_475, sort_475);
+		if1_bytes[11] &= 0xFE;
+		return;
+	case MR515:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_515, sort_515);
+		if1_bytes[12] &= 0xFE;
+		return;
+	case MR59:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_59, sort_59);
+		if1_bytes[14] &= 0xFC;
+		return;
+	case MR67:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_67, sort_67);
+		if1_bytes[16] &= 0xFC;
+		return;
+	case MR74:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_74, sort_74);
+		if1_bytes[18] &= 0xF0;
+		return;
+	case MR795:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_795, sort_795);
+		if1_bytes[19] &= 0xFE;
+		return;
+	case MR102:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_102, sort_102);
+		if1_bytes[25] &= 0xF0;
+		return;
+	case MR122:            
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_122, sort_122);
+		if1_bytes[30] &= 0xF0;
+		return;
+	case MRDTX:
+		pack_bits(if1_bytes, serial_bits, AMR_NBITS_SID,
+				(const uint8_t *) 0);
+		if1_bytes[4] &= 0xE0;
+		return;
+	}
+}