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/** @file include/fts0vlc.ic
 Full text variable length integer encoding/decoding.

 Created 2007-03-27 Sunny Bains
 *******************************************************/

#ifndef INNOBASE_FTS0VLC_IC
#define INNOBASE_FTS0VLC_IC

#include "fts0types.h"

/** Return length of val if it were encoded using our VLC scheme.
 FIXME: We will need to be able encode 8 bytes value
 @return length of value encoded, in bytes */
UNIV_INLINE
ulint fts_get_encoded_len(ulint val) /* in: value to encode */
{
  if (val <= 127) {
    return (1);
  } else if (val <= 16383) {
    return (2);
  } else if (val <= 2097151) {
    return (3);
  } else if (val <= 268435455) {
    return (4);
  } else {
    /* Possibly we should care that on 64-bit machines ulint can
    contain values that we can't encode in 5 bytes, but
    fts_encode_int doesn't handle them either so it doesn't much
    matter. */

    return (5);
  }
}

/** Encode an integer using our VLC scheme and return the length in bytes.
 @return length of value encoded, in bytes */
UNIV_INLINE
ulint fts_encode_int(ulint val, /* in: value to encode */
                     byte *buf) /* in: buffer, must have enough space */
{
  ulint len;

  if (val <= 127) {
    *buf = (byte)val;

    len = 1;
  } else if (val <= 16383) {
    *buf++ = (byte)(val >> 7);
    *buf = (byte)(val & 0x7F);

    len = 2;
  } else if (val <= 2097151) {
    *buf++ = (byte)(val >> 14);
    *buf++ = (byte)((val >> 7) & 0x7F);
    *buf = (byte)(val & 0x7F);

    len = 3;
  } else if (val <= 268435455) {
    *buf++ = (byte)(val >> 21);
    *buf++ = (byte)((val >> 14) & 0x7F);
    *buf++ = (byte)((val >> 7) & 0x7F);
    *buf = (byte)(val & 0x7F);

    len = 4;
  } else {
    /* Best to keep the limitations of the 32/64 bit versions
    identical, at least for the time being. */
    ut_ad(val <= 4294967295u);

    *buf++ = (byte)(val >> 28);
    *buf++ = (byte)((val >> 21) & 0x7F);
    *buf++ = (byte)((val >> 14) & 0x7F);
    *buf++ = (byte)((val >> 7) & 0x7F);
    *buf = (byte)(val & 0x7F);

    len = 5;
  }

  /* High-bit on means "last byte in the encoded integer". */
  *buf |= 0x80;

  return (len);
}

/** Decode and return the integer that was encoded using our VLC scheme.
 @return value decoded */
UNIV_INLINE
ulint fts_decode_vlc(byte **ptr) /* in: ptr to decode from, this ptr is
                                 incremented by the number of bytes decoded */
{
  ulint val = 0;

  for (;;) {
    byte b = **ptr;

    ++*ptr;
    val |= (b & 0x7F);

    /* High-bit on means "last byte in the encoded integer". */
    if (b & 0x80) {
      break;
    } else {
      val <<= 7;
    }
  }

  return (val);
}

#endif