/*

 * Copyright (c) 2020 Red Hat, Inc.

 *

 * 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; either version 2

 * of the License, or (at your option) any later version.

 * 

 * 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

 * 02110-1301, USA. 

 *

 * $Id: //eng/uds-releases/jasper/src/uds/bits.c#1 $

 */

#include "bits.h"

#include "compiler.h"

/**

 * This is the largest field size supported by getBigField & setBigField.

 * Any field that is larger is not guaranteed to fit in a single, byte

 * aligned uint64_t.

 **/

enum { MAX_BIG_FIELD_BITS = (sizeof(uint64_t) - 1) * CHAR_BIT + 1 };

/**

 * Get a big bit field from a bit stream

 *

 * @param memory  The base memory byte address

 * @param offset  The bit offset into the memory for the start of the field

 * @param size    The number of bits in the field

 *

 * @return the bit field

 **/

static INLINE uint64_t getBigField(const byte *memory,

                                   uint64_t    offset,

                                   int         size)

{

  const void *addr = memory + offset / CHAR_BIT;

  return (getUInt64LE(addr) >> (offset % CHAR_BIT)) & ((1UL << size) - 1);

}

/**

 * Set a big bit field in a bit stream

 *

 * @param value   The value to put into the field

 * @param memory  The base memory byte address

 * @param offset  The bit offset into the memory for the start of the field

 * @param size    The number of bits in the field

 *

 * @return the bit field

 **/

static INLINE void setBigField(uint64_t value, byte *memory, uint64_t offset,

                               int size)

{

  void *addr = memory + offset / CHAR_BIT;

  int shift = offset % CHAR_BIT;

  uint64_t data = getUInt64LE(addr);

  data &= ~(((1UL << size) - 1) << shift);

  data |= value << shift;

  storeUInt64LE(addr, data);

}

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

void getBytes(const byte *memory, uint64_t offset, byte *destination, int size)

{

  const byte *addr = memory + offset / CHAR_BIT;

  int shift = offset % CHAR_BIT;

  while (--size >= 0) {

    *destination++ = getUInt16LE(addr++) >> shift;

  }

}

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

void setBytes(byte *memory, uint64_t offset, const byte *source, int size)

{

  byte *addr = memory + offset / CHAR_BIT;

  int shift = offset % CHAR_BIT;

  uint16_t mask = ~((uint16_t) 0xFF << shift);

  while (--size >= 0) {

    uint16_t data = (getUInt16LE(addr) & mask) | (*source++ << shift);

    storeUInt16LE(addr++, data);

  }

}

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

void moveBits(const byte *sMemory, uint64_t source, byte *dMemory,

              uint64_t destination, int size)

{

  enum { UINT32_BIT = sizeof(uint32_t) * CHAR_BIT };

  if (size > MAX_BIG_FIELD_BITS) {

    if (source > destination) {

      // This is a large move from a higher to a lower address.  We move

      // the lower addressed bits first.  Start by moving one field that

      // ends on a destination int boundary

      int count

        = MAX_BIG_FIELD_BITS - (destination + MAX_BIG_FIELD_BITS) % UINT32_BIT;

      uint64_t field = getBigField(sMemory, source, count);

      setBigField(field, dMemory, destination, count);

      source      += count;

      destination += count;

      size        -= count;

      // Now do the main loop to copy 32 bit chunks that are int-aligned

      // at the destination.

      int offset = source % UINT32_BIT;

      const byte *src = sMemory + (source - offset) / CHAR_BIT;

      byte *dest = dMemory + destination / CHAR_BIT;

      while (size > MAX_BIG_FIELD_BITS) {

        storeUInt32LE(dest, getUInt64LE(src) >> offset);

        src  += sizeof(uint32_t);

        dest += sizeof(uint32_t);

        source      += UINT32_BIT;

        destination += UINT32_BIT;

        size        -= UINT32_BIT;

      }

    } else {

      // This is a large move from a lower to a higher address.  We move

      // the higher addressed bits first.  Start by moving one field that

      // begins on a destination int boundary

      int count = (destination + size) % UINT32_BIT;

      if (count > 0) {

        size -= count;

        uint64_t field = getBigField(sMemory, source + size, count);

        setBigField(field, dMemory, destination + size, count);

      }

      // Now do the main loop to copy 32 bit chunks that are int-aligned

      // at the destination.

      int offset = (source + size) % UINT32_BIT;

      const byte *src = sMemory + (source + size - offset) / CHAR_BIT;

      byte *dest = dMemory + (destination + size) / CHAR_BIT;

      while (size > MAX_BIG_FIELD_BITS) {

        src  -= sizeof(uint32_t);

        dest -= sizeof(uint32_t);

        size -= UINT32_BIT;

        storeUInt32LE(dest, getUInt64LE(src) >> offset);

      }

    }

  }

  // Finish up by doing the last chunk, which can have any arbitrary alignment

  if (size > 0) {

    uint64_t field = getBigField(sMemory, source, size);

    setBigField(field, dMemory, destination, size);

  }

}

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

bool sameBits(const byte *mem1, uint64_t offset1, const byte *mem2,

              uint64_t offset2, int size)

{

  while (size >= MAX_FIELD_BITS) {

    unsigned int field1 = getField(mem1, offset1, MAX_FIELD_BITS);

    unsigned int field2 = getField(mem2, offset2, MAX_FIELD_BITS);

    if (field1 != field2) return false;

    offset1 += MAX_FIELD_BITS;

    offset2 += MAX_FIELD_BITS;

    size    -= MAX_FIELD_BITS;

  }

  if (size > 0) {

    unsigned int field1 = getField(mem1, offset1, size);

    unsigned int field2 = getField(mem2, offset2, size);

    if (field1 != field2) return false;

  }

  return true;

}