1 files changed, 124 insertions, 0 deletions
diff --git a/storage/innobase/include/fts0vlc.h b/storage/innobase/include/fts0vlc.h
new file mode 100644
index 00000000..d6e60377
--- /dev/null
+++ b/storage/innobase/include/fts0vlc.h
@@ -0,0 +1,124 @@
+/**
+
+Copyright (c) 2021, MariaDB Corporation.
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
+**/
+/**
+@file include/fts0vlc.h
+Full text variable length integer encoding/decoding.
+
+Created 2021-10-19 Thirunarayanan Balathandayuthapani
+**/
+
+/** Return length of val if it were encoded using our VLC scheme.
+@param	val	value to encode
+@return length of value encoded, in bytes */
+inline size_t fts_get_encoded_len(doc_id_t val)
+{
+  if (val < static_cast<doc_id_t>(1) << 7)
+    return 1;
+  if (val < static_cast<doc_id_t>(1) << 14)
+    return 2;
+  if (val < static_cast<doc_id_t>(1) << 21)
+    return 3;
+  if (val < static_cast<doc_id_t>(1) << 28)
+    return 4;
+  if (val < static_cast<doc_id_t>(1) << 35)
+    return 5;
+  if (val < static_cast<doc_id_t>(1) << 42)
+    return 6;
+  if (val < static_cast<doc_id_t>(1) << 49)
+    return 7;
+  if (val < static_cast<doc_id_t>(1) << 56)
+    return 8;
+  if (val < static_cast<doc_id_t>(1) << 63)
+    return 9;
+  return 10;
+}
+
+/** Encode an integer using our VLC scheme and return the
+length in bytes.
+@param	val	value to encode
+@param	buf	buffer, must have enough space
+@return length of value encoded, in bytes */
+inline byte *fts_encode_int(doc_id_t val, byte *buf)
+{
+  if (val < static_cast<doc_id_t>(1) << 7)
+    goto add_1;
+  if (val < static_cast<doc_id_t>(1) << 14)
+    goto add_2;
+  if (val < static_cast<doc_id_t>(1) << 21)
+    goto add_3;
+  if (val < static_cast<doc_id_t>(1) << 28)
+    goto add_4;
+  if (val < static_cast<doc_id_t>(1) << 35)
+    goto add_5;
+  if (val < static_cast<doc_id_t>(1) << 42)
+    goto add_6;
+  if (val < static_cast<doc_id_t>(1) << 49)
+    goto add_7;
+  if (val < static_cast<doc_id_t>(1) << 56)
+    goto add_8;
+  if (val < static_cast<doc_id_t>(1) << 63)
+    goto add_9;
+
+  *buf++= static_cast<byte>(val >> 63);
+add_9:
+  *buf++= static_cast<byte>(val >> 56) & 0x7F;
+add_8:
+  *buf++= static_cast<byte>(val >> 49) & 0x7F;
+add_7:
+  *buf++= static_cast<byte>(val >> 42) & 0x7F;
+add_6:
+  *buf++= static_cast<byte>(val >> 35) & 0x7F;
+add_5:
+  *buf++= static_cast<byte>(val >> 28) & 0x7F;
+add_4:
+  *buf++= static_cast<byte>(val >> 21) & 0x7F;
+add_3:
+  *buf++= static_cast<byte>(val >> 14) & 0x7F;
+add_2:
+  *buf++= static_cast<byte>(val >> 7) & 0x7F;
+add_1:
+  *buf++= static_cast<byte>(val) | 0x80;
+  return buf;
+}
+
+/** Decode and return the integer that was encoded using
+our VLC scheme.
+@param	ptr 	pointer to decode from, this ptr is
+		incremented by the number of bytes decoded
+@return value decoded */
+inline doc_id_t fts_decode_vlc(const byte **ptr)
+{
+  ut_d(const byte *const start= *ptr);
+  ut_ad(*start);
+
+  doc_id_t val= 0;
+  for (;;)
+  {
+    byte b= *(*ptr)++;
+    val|= (b & 0x7F);
+
+    /* High-bit on means "last byte in the encoded integer". */
+    if (b & 0x80)
+      break;
+    ut_ad(val < static_cast<doc_id_t>(1) << (64 - 7));
+    val <<= 7;
+  }
+
+  ut_ad(*ptr - start <= 10);
+
+  return(val);
+}