--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/asn1/der/bit/der_encode_raw_bit_string.c	Sat Feb 17 19:29:51 2018 +0800
@@ -0,0 +1,90 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ */
+#include "tomcrypt.h"
+
+/**
+  @file der_encode_bit_string.c
+  ASN.1 DER, encode a BIT STRING, Tom St Denis
+*/
+
+
+#ifdef LTC_DER
+
+#define getbit(n, k) (((n) & ( 1 << (k) )) >> (k))
+
+/**
+  Store a BIT STRING
+  @param in       The array of bits to store (8 per char)
+  @param inlen    The number of bits to store
+  @param out      [out] The destination for the DER encoded BIT STRING
+  @param outlen   [in/out] The max size and resulting size of the DER BIT STRING
+  @return CRYPT_OK if successful
+*/
+int der_encode_raw_bit_string(const unsigned char *in, unsigned long inlen,
+                                unsigned char *out, unsigned long *outlen)
+{
+   unsigned long len, x, y;
+   unsigned char buf;
+   int           err;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+
+   /* avoid overflows */
+   if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) {
+      return err;
+   }
+
+   if (len > *outlen) {
+      *outlen = len;
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   /* store header (include bit padding count in length) */
+   x = 0;
+   y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1;
+
+   out[x++] = 0x03;
+   if (y < 128) {
+      out[x++] = (unsigned char)y;
+   } else if (y < 256) {
+      out[x++] = 0x81;
+      out[x++] = (unsigned char)y;
+   } else if (y < 65536) {
+      out[x++] = 0x82;
+      out[x++] = (unsigned char)((y>>8)&255);
+      out[x++] = (unsigned char)(y&255);
+   }
+
+   /* store number of zero padding bits */
+   out[x++] = (unsigned char)((8 - inlen) & 7);
+
+   /* store the bits in big endian format */
+   for (y = buf = 0; y < inlen; y++) {
+      buf |= (getbit(in[y/8],7-y%8)?1:0) << (7 - (y & 7));
+      if ((y & 7) == 7) {
+         out[x++] = buf;
+         buf      = 0;
+      }
+   }
+   /* store last byte */
+   if (inlen & 7) {
+      out[x++] = buf;
+   }
+
+   *outlen = x;
+   return CRYPT_OK;
+}
+
+#endif
+
+/* ref:         $Format:%D$ */
+/* git commit:  $Format:%H$ */
+/* commit time: $Format:%ai$ */