/*****************************************************************************

Copyright (c) 1995, 2022, Oracle and/or its affiliates.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License, version 2.0, as published by the
Free Software Foundation.

This program is also distributed with certain software (including but not
limited to OpenSSL) that is licensed under separate terms, as designated in a
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FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
for more details.

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this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

*****************************************************************************/

/** @file mach/mach0data.cc
 Utilities for converting data from the database file
 to the machine format.

 Created 11/28/1995 Heikki Tuuri
 ***********************************************************************/

#include "mach0data.h"
#include "log0log.h"

#include <stddef.h>

/** Read a 64-bit integer in a much compressed form.
@param[in,out]  ptr     pointer to memory from where to read,
advanced by the number of bytes consumed, or set NULL if out of space
@param[in]      end_ptr end of the buffer
@return unsigned 64-bit integer */
uint64_t mach_parse_u64_much_compressed(const byte **ptr, const byte *end_ptr) {
  ulint val;

  if (*ptr >= end_ptr) {
    *ptr = nullptr;
    return (0);
  }

  val = mach_read_from_1(*ptr);

  if (val != 0xFF) {
    return (mach_parse_compressed(ptr, end_ptr));
  }

  ++*ptr;

  uint64_t n = mach_parse_compressed(ptr, end_ptr);
  if (*ptr == nullptr) {
    return (0);
  }

  n <<= 32;

  n |= mach_parse_compressed(ptr, end_ptr);
  if (*ptr == nullptr) {
    return (0);
  }

  return (n);
}

/** Read a 32-bit integer in a compressed form.
@param[in,out]  ptr     pointer to memory from where to read;
advanced by the number of bytes consumed, or set NULL if out of space
@param[in]      end_ptr end of the buffer
@return unsigned value */
static uint32_t mach_parse_compressed_v3(const byte **ptr,
                                         const byte *end_ptr) {
  ulint val;

  if (*ptr >= end_ptr) {
    *ptr = NULL;
    return (0);
  }

  val = mach_read_from_1(*ptr);

  if (val < 0x80) {
    /* 0nnnnnnn (7 bits) */
    ++*ptr;
    return (static_cast<uint32_t>(val));
  }

  /* Workaround GCC bug
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77673:
  the compiler moves mach_read_from_4 right to the beginning of the
  function, causing and out-of-bounds read if we are reading a short
  integer close to the end of buffer. */
#if defined(__GNUC__) && (__GNUC__ >= 5) && !defined(__clang__)
#define DEPLOY_FENCE
#endif

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xC0) {
    /* 10nnnnnn nnnnnnnn (14 bits) */
    if (end_ptr >= *ptr + 2) {
      val = mach_read_from_2(*ptr) & 0x3FFF;
      ut_ad(val > 0x7F);
      *ptr += 2;
      return (static_cast<uint32_t>(val));
    }
    *ptr = NULL;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xE0) {
    /* 110nnnnn nnnnnnnn nnnnnnnn (21 bits) */
    if (end_ptr >= *ptr + 3) {
      val = mach_read_from_3(*ptr) & 0x1FFFFF;
      ut_ad(val > 0x3FFF);
      *ptr += 3;
      return (static_cast<uint32_t>(val));
    }
    *ptr = NULL;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xF0) {
    /* 1110nnnn nnnnnnnn nnnnnnnn nnnnnnnn (28 bits) */
    if (end_ptr >= *ptr + 4) {
      val = mach_read_from_4(*ptr) & 0xFFFFFFF;
      ut_ad(val > 0x1FFFFF);
      *ptr += 4;
      return (static_cast<uint32_t>(val));
    }
    *ptr = NULL;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

#undef DEPLOY_FENCE

  ut_ad(val == 0xF0);

  /* 11110000 nnnnnnnn nnnnnnnn nnnnnnnn nnnnnnnn (32 bits) */
  if (end_ptr >= *ptr + 5) {
    val = mach_read_from_4(*ptr + 1);
    ut_ad(val > 0xFFFFFFF);
    *ptr += 5;
    return (static_cast<uint32_t>(val));
  }

  *ptr = NULL;
  return (0);
}

/** Read a 32-bit integer in a compressed form.
@param[in,out]	ptr	pointer to memory where to read;
advanced by the number of bytes consumed, or set NULL if out of space
@param[in]	end_ptr	end of the buffer
@return unsigned value */
uint32_t mach_parse_compressed_v4(const byte **ptr, const byte *end_ptr) {
  ulint val;

  if (*ptr >= end_ptr) {
    *ptr = nullptr;
    return (0);
  }

  val = mach_read_from_1(*ptr);

  if (val < 0x80) {
    /* 0nnnnnnn (7 bits) */
    ++*ptr;
    return (static_cast<uint32_t>(val));
  }

  /* Workaround GCC bug
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77673:
  the compiler moves mach_read_from_4 right to the beginning of the
  function, causing and out-of-bounds read if we are reading a short
  integer close to the end of buffer. */
#if defined(__GNUC__) && (__GNUC__ >= 5) && !defined(__clang__)
#define DEPLOY_FENCE
#endif

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xC0) {
    /* 10nnnnnn nnnnnnnn (14 bits) */
    if (end_ptr >= *ptr + 2) {
      val = mach_read_from_2(*ptr) & 0x3FFF;
      ut_ad(val > 0x7F);
      *ptr += 2;
      return (static_cast<uint32_t>(val));
    }
    *ptr = nullptr;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xE0) {
    /* 110nnnnn nnnnnnnn nnnnnnnn (21 bits) */
    if (end_ptr >= *ptr + 3) {
      val = mach_read_from_3(*ptr) & 0x1FFFFF;
      ut_ad(val > 0x3FFF);
      *ptr += 3;
      return (static_cast<uint32_t>(val));
    }
    *ptr = nullptr;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xF0) {
    /* 1110nnnn nnnnnnnn nnnnnnnn nnnnnnnn (28 bits) */
    if (end_ptr >= *ptr + 4) {
      val = mach_read_from_4(*ptr) & 0xFFFFFFF;
      ut_ad(val > 0x1FFFFF);
      *ptr += 4;
      return (static_cast<uint32_t>(val));
    }
    *ptr = nullptr;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xF8) {
    ut_ad(val == 0xF0);

    /* 11110000 nnnnnnnn nnnnnnnn nnnnnnnn nnnnnnnn (32 bits) */
    if (end_ptr >= *ptr + 5) {
      val = mach_read_from_4(*ptr + 1);
      ut_ad(val > 0xFFFFFFF);
      *ptr += 5;
      return (static_cast<uint32_t>(val));
    }

    *ptr = nullptr;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xFC) {
    /* 111110nn nnnnnnnn (10 bits) (extended) */
    if (end_ptr >= *ptr + 2) {
      val = (mach_read_from_2(*ptr) & 0x3FF) | 0xFFFFFC00;
      *ptr += 2;
      return (static_cast<uint32_t>(val));
    }
    *ptr = nullptr;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

  if (val < 0xFE) {
    /* 1111110n nnnnnnnn nnnnnnnn (17 bits) (extended) */
    if (end_ptr >= *ptr + 3) {
      val = (mach_read_from_3(*ptr) & 0x1FFFF) | 0xFFFE0000;
      ut_ad(val < 0xFFFFFC00);
      *ptr += 3;
      return (static_cast<uint32_t>(val));
    }
    *ptr = nullptr;
    return (0);
  }

#ifdef DEPLOY_FENCE
  __atomic_thread_fence(__ATOMIC_ACQUIRE);
#endif

#undef DEPLOY_FENCE

  ut_ad(val == 0xFE);

  /* 11111110 nnnnnnnn nnnnnnnn nnnnnnnn (24 bits) (extended) */
  if (end_ptr >= *ptr + 4) {
    val = mach_read_from_3(*ptr + 1) | 0xFF000000;
    ut_ad(val < 0xFFFE0000);
    *ptr += 4;
    return (static_cast<uint32_t>(val));
  }

  *ptr = nullptr;
  return (0);
}

/** Read a 32-bit integer in a compressed form.
@param[in,out]	ptr	pointer to memory where to read;
advanced by the number of bytes consumed, or set NULL if out of space
@param[in]	end_ptr	end of the buffer
@return unsigned value */
uint32_t mach_parse_compressed(const byte **ptr, const byte *end_ptr) {
  switch (log_sys->format) {
    case LOG_HEADER_FORMAT_5_7_9:
      ut_a(0);
      return (0);
    case LOG_HEADER_FORMAT_8_0_1:
    case LOG_HEADER_FORMAT_8_0_3:
       return(mach_parse_compressed_v3(ptr, end_ptr));
    case LOG_HEADER_FORMAT_8_0_19:
    case LOG_HEADER_FORMAT_8_0_28:
      return (mach_parse_compressed_v4(ptr, end_ptr));
  }
  /* make compiler happy */
  ut_a(0);
  return (0);
}
