/*

 * Copyright (C) 2009-2012 Free Software Foundation, Inc.

 *

 * Author: Jonathan Bastien-Filiatrault

 *

 * This file is part of GNUTLS.

 *

 * The GNUTLS library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

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

 *

 * This library 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>

 *

 */

#include "mbuffers.h"

#include "errors.h"

/* Here be mbuffers */

/* A note on terminology:

 *

 * Variables named bufel designate a single buffer segment (mbuffer_st

 * type). This type is textually referred to as a "segment" or a

 * "buffer element".

 *

 * Variables named buf desigate a chain of buffer segments

 * (mbuffer_head_st type).  This type is textually referred to as a

 * "buffer head" or simply as "buffer".

 *

 * Design objectives:

 *

 * - Make existing code easier to understand.

 * - Make common operations more efficient by avoiding unnecessary

 *    copying.

 * - Provide a common datatype with a well-known interface to move

 *    data around and through the multiple protocol layers.

 * - Enable a future implementation of DTLS, which needs the concept

 *    of record boundaries.

 */

/* Initialize a buffer head.

 *

 * Cost: O(1)

 */

void _mbuffer_head_init(mbuffer_head_st *buf)

{

  buf->head = NULL;

  buf->tail = NULL;

  buf->length = 0;

  buf->byte_length = 0;

}

/* Deallocate all buffer segments and reset the buffer head.

 *

 * Cost: O(n)

 * n: Number of segments currently in the buffer.

 */

void _mbuffer_head_clear(mbuffer_head_st *buf)

{

  mbuffer_st *bufel, *next;

  for (bufel = buf->head; bufel != NULL; bufel = next) {

    next = bufel->next;

    gnutls_free(bufel);

  }

  _mbuffer_head_init(buf);

}

/* Append a segment to the end of this buffer.

 *

 * Cost: O(1)

 */

void _mbuffer_enqueue(mbuffer_head_st *buf, mbuffer_st *bufel)

{

  bufel->next = NULL;

  bufel->prev = buf->tail;

  buf->length++;

  buf->byte_length += bufel->msg.size - bufel->mark;

  if (buf->tail != NULL)

    buf->tail->next = bufel;

  else

    buf->head = bufel;

  buf->tail = bufel;

}

/* Remove a segment from the buffer.

 *

 * Cost: O(1)

 *

 * Returns the buffer following it.

 */

mbuffer_st *_mbuffer_dequeue(mbuffer_head_st *buf, mbuffer_st *bufel)

{

  mbuffer_st *ret = bufel->next;

  if (buf->tail == bufel) /* if last */

    buf->tail = bufel->prev;

  if (buf->head == bufel) /* if first */

    buf->head = bufel->next;

  if (bufel->prev)

    bufel->prev->next = bufel->next;

  if (bufel->next)

    bufel->next->prev = NULL;

  buf->length--;

  buf->byte_length -= bufel->msg.size - bufel->mark;

  bufel->next = bufel->prev = NULL;

  return ret;

}

/* Append a segment to the beginning of this buffer.

 *

 * Cost: O(1)

 */

void _mbuffer_head_push_first(mbuffer_head_st *buf, mbuffer_st *bufel)

{

  bufel->prev = NULL;

  bufel->next = buf->head;

  buf->length++;

  buf->byte_length += bufel->msg.size - bufel->mark;

  if (buf->head != NULL)

    buf->head->prev = bufel;

  else

    buf->tail = bufel;

  buf->head = bufel;

}

/* Get a reference to the first segment of the buffer and

 * remove it from the list.

 *

 * Used to start iteration.

 *

 * Cost: O(1)

 */

mbuffer_st *_mbuffer_head_pop_first(mbuffer_head_st *buf)

{

  mbuffer_st *bufel = buf->head;

  if (buf->head == NULL)

    return NULL;

  _mbuffer_dequeue(buf, bufel);

  return bufel;

}

/* Get a reference to the first segment of the buffer and its data.

 *

 * Used to start iteration or to peek at the data.

 *

 * Cost: O(1)

 */

mbuffer_st *_mbuffer_head_get_first(mbuffer_head_st *buf, gnutls_datum_t *msg)

{

  mbuffer_st *bufel = buf->head;

  if (msg) {

    if (bufel) {

      msg->data = bufel->msg.data + bufel->mark;

      msg->size = bufel->msg.size - bufel->mark;

    } else {

      msg->data = NULL;

      msg->size = 0;

    }

  }

  return bufel;

}

/* Get a reference to the next segment of the buffer and its data.

 *

 * Used to iterate over the buffer segments.

 *

 * Cost: O(1)

 */

mbuffer_st *_mbuffer_head_get_next(mbuffer_st *cur, gnutls_datum_t *msg)

{

  mbuffer_st *bufel = cur->next;

  if (msg) {

    if (bufel) {

      msg->data = bufel->msg.data + bufel->mark;

      msg->size = bufel->msg.size - bufel->mark;

    } else {

      msg->data = NULL;

      msg->size = 0;

    }

  }

  return bufel;

}

/* Remove the first segment from the buffer.

 *

 * Used to dequeue data from the buffer. Not yet exposed in the

 * internal interface since it is not yet needed outside of this unit.

 *

 * Cost: O(1)

 */

static inline void remove_front(mbuffer_head_st *buf)

{

  mbuffer_st *bufel = buf->head;

  if (!bufel)

    return;

  _mbuffer_dequeue(buf, bufel);

  gnutls_free(bufel);

}

/* Remove a specified number of bytes from the start of the buffer.

 *

 * Useful for uses that treat the buffer as a simple array of bytes.

 *

 * If more than one mbuffer_st have been removed it

 * returns 1, 0 otherwise and an error code on error.

 *

 * Cost: O(n)

 * n: Number of segments needed to remove the specified amount of data.

 */

int _mbuffer_head_remove_bytes(mbuffer_head_st *buf, size_t bytes)

{

  size_t left = bytes;

  mbuffer_st *bufel, *next;

  int ret = 0;

  if (bytes > buf->byte_length) {

    gnutls_assert();

    return GNUTLS_E_INVALID_REQUEST;

  }

  for (bufel = buf->head; bufel != NULL && left > 0; bufel = next) {

    next = bufel->next;

    if (left >= (bufel->msg.size - bufel->mark)) {

      left -= (bufel->msg.size - bufel->mark);

      remove_front(buf);

      ret = 1;

    } else {

      bufel->mark += left;

      buf->byte_length -= left;

      left = 0;

    }

  }

  return ret;

}

/* Allocate a buffer segment. The segment is not initially "owned" by

 * any buffer.

 *

 * maximum_size: Amount of data that this segment can contain.

 *

 * Returns the segment or NULL on error.

 *

 * Cost: O(1)

 */

mbuffer_st *_mbuffer_alloc(size_t maximum_size)

{

  mbuffer_st *st;

  st = gnutls_malloc(maximum_size + sizeof(mbuffer_st));

  if (st == NULL) {

    gnutls_assert();

    return NULL;

  }

  /* set the structure to zero */

  memset(st, 0, sizeof(*st));

  /* payload points after the mbuffer_st structure */

  st->msg.data = (uint8_t *)st + sizeof(mbuffer_st);

  st->msg.size = 0;

  st->maximum_size = maximum_size;

  return st;

}

/* Copy data into a segment. The segment must not be part of a buffer

 * head when using this function.

 *

 * Bounds checking is performed by this function.

 *

 * Returns 0 on success or an error code otherwise.

 *

 * Cost: O(n)

 * n: number of bytes to copy

 */

int _mbuffer_append_data(mbuffer_st *bufel, void *newdata, size_t newdata_size)

{

  if (bufel->msg.size + newdata_size <= bufel->maximum_size) {

    memcpy(&bufel->msg.data[bufel->msg.size], newdata,

           newdata_size);

    bufel->msg.size += newdata_size;

  } else {

    gnutls_assert();

    return GNUTLS_E_INVALID_REQUEST;

  }

  return 0;

}

#ifdef ENABLE_ALIGN16

#define ALIGN_SIZE 16

/* Allocate a 16-byte aligned buffer segment. The segment is not initially "owned" by

 * any buffer.

 *

 * maximum_size: Amount of data that this segment can contain.

 * align_pos: identifies the position of the buffer that will be aligned at 16-bytes

 *

 * This function should be used to ensure that encrypted data or data to

 * be encrypted are properly aligned.

 *

 * Returns the segment or NULL on error.

 *

 * Cost: O(1)

 */

mbuffer_st *_mbuffer_alloc_align16(size_t maximum_size, unsigned align_pos)

{

  mbuffer_st *st;

  size_t cur_alignment;

  st = gnutls_malloc(maximum_size + sizeof(mbuffer_st) + ALIGN_SIZE);

  if (st == NULL) {

    gnutls_assert();

    return NULL;

  }

  /* set the structure to zero */

  memset(st, 0, sizeof(*st));

  /* payload points after the mbuffer_st structure */

  st->msg.data = (uint8_t *)st + sizeof(mbuffer_st);

  cur_alignment = ((size_t)(st->msg.data + align_pos)) % ALIGN_SIZE;

  if (cur_alignment > 0)

    st->msg.data += ALIGN_SIZE - cur_alignment;

  st->msg.size = 0;

  st->maximum_size = maximum_size;

  return st;

}

static unsigned is_aligned16(mbuffer_st *bufel, unsigned align_pos)

{

  uint8_t *ptr = _mbuffer_get_udata_ptr(bufel);

  if (((size_t)(ptr + align_pos)) % ALIGN_SIZE == 0)

    return 1;

  else

    return 0;

}

/* Takes a buffer in multiple chunks and puts all the data in a single

 * contiguous segment, ensuring that the @align_pos is 16-byte aligned.

 *

 * Returns 0 on success or an error code otherwise.

 *

 * Cost: O(n)

 * n: number of segments initially in the buffer

 */

int _mbuffer_linearize_align16(mbuffer_head_st *buf, unsigned align_pos)

{

  mbuffer_st *bufel, *cur;

  gnutls_datum_t msg;

  size_t pos = 0;

  if (buf->length == 0) {

    /* Nothing to do */

    return 0;

  }

  bufel = _mbuffer_head_get_first(buf, NULL);

  if (buf->length == 1 && is_aligned16(bufel, align_pos))

    return 0;

  bufel = _mbuffer_alloc_align16(buf->byte_length, align_pos);

  if (!bufel) {

    gnutls_assert();

    return GNUTLS_E_MEMORY_ERROR;

  }

  bufel->type = _mbuffer_head_get_first(buf, NULL)->type;

  for (cur = _mbuffer_head_get_first(buf, &msg); msg.data != NULL;

       cur = _mbuffer_head_get_next(cur, &msg)) {

    memcpy(&bufel->msg.data[pos], msg.data, msg.size);

    bufel->msg.size += msg.size;

    pos += msg.size;

  }

  _mbuffer_head_clear(buf);

  _mbuffer_enqueue(buf, bufel);

  return 0;

}

#else

int _mbuffer_linearize(mbuffer_head_st *buf)

{

  mbuffer_st *bufel, *cur;

  gnutls_datum_t msg;

  size_t pos = 0;

  if (buf->length <= 1) {

    /* Nothing to do */

    return 0;

  }

  bufel = _mbuffer_alloc(buf->byte_length);

  if (!bufel) {

    gnutls_assert();

    return GNUTLS_E_MEMORY_ERROR;

  }

  bufel->type = _mbuffer_head_get_first(buf, NULL)->type;

  for (cur = _mbuffer_head_get_first(buf, &msg); msg.data != NULL;

       cur = _mbuffer_head_get_next(cur, &msg)) {

    memcpy(&bufel->msg.data[pos], msg.data, msg.size);

    bufel->msg.size += msg.size;

    pos += msg.size;

  }

  _mbuffer_head_clear(buf);

  _mbuffer_enqueue(buf, bufel);

  return 0;

}

#endif