oma-tlv.c

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/*
 * Copyright (c) 2015, Yanzi Networks AB.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holder nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * \addtogroup oma-lwm2m
 * @{
 *
 */

/**
 * \file
 *         Implementation of the Contiki OMA LWM2M TLV
 * \author
 *         Joakim Eriksson <joakime@sics.se>
 *         Niclas Finne <nfi@sics.se>
 */

#include <string.h>
#include <stdint.h>
#include "oma-tlv.h"

#define DEBUG 0
#if DEBUG
#include <stdio.h>
#define PRINTF(...) printf(__VA_ARGS__)
#else
#define PRINTF(...)
#endif

/*---------------------------------------------------------------------------*/
static inline uint8_t
get_len_type(const oma_tlv_t *tlv)
{
  if(tlv->length < 8) {
    return 0;
  } else if(tlv->length < 256) {
    return 1;
  } else if(tlv->length < 0x10000) {
    return 2;
  } else {
    return 3;
  }
}
/*---------------------------------------------------------------------------*/
size_t
oma_tlv_read(oma_tlv_t *tlv, const uint8_t *buffer, size_t len)
{
  uint8_t len_type;
  uint8_t len_pos = 1;
  size_t tlv_len;

  tlv->type = (buffer[0] >> 6) & 3;
  len_type = (buffer[0] >> 3) & 3;
  len_pos = 1 + (((buffer[0] & (1 << 5)) != 0) ? 2 : 1);

  tlv->id = buffer[1];
  /* if len_pos is larger than two it means that there is more ID to read */
  if(len_pos > 2) {
    tlv->id = (tlv->id << 8) + buffer[2];
  }

  if(len_type == 0) {
    tlv_len = buffer[0] & 7;
  } else {
    /* read the length */
    tlv_len = 0;
    while(len_type > 0) {
      tlv_len = tlv_len << 8 | buffer[len_pos++];
      len_type--;
    }
  }
  /* and read out the data??? */
  tlv->length = tlv_len;
  tlv->value = &buffer[len_pos];

  return len_pos + tlv_len;
}
/*---------------------------------------------------------------------------*/
size_t
oma_tlv_get_size(const oma_tlv_t *tlv)
{
  size_t size;
  /* first hdr + len size */
  size = 1 + get_len_type(tlv);
  /* id size */
  size += (tlv->id > 255) ? 2 : 1;

  /* and the length */
  size += tlv->length;
  return size;
}
/*---------------------------------------------------------------------------*/
size_t
oma_tlv_write(const oma_tlv_t *tlv, uint8_t *buffer, size_t len)
{
  int pos;
  uint8_t len_type;

  /* len type is the same as number of bytes required for length */
  len_type = get_len_type(tlv);
  pos = 1 + len_type;
  /* ensure that we do not write too much */
  if(len < tlv->length + pos) {
    PRINTF("OMA-TLV: Could not write the TLV - buffer overflow.\n");
    return 0;
  }

  /* first type byte in TLV header */
  buffer[0] = (tlv->type << 6) |
    (tlv->id > 255 ? (1 << 5) : 0) |
    (len_type << 3) |
    (len_type == 0 ? tlv->length : 0);

  pos = 1;
  /* The ID */
  if(tlv->id > 255) {
    buffer[pos++] = (tlv->id >> 8) & 0xff;
  }
  buffer[pos++] = tlv->id & 0xff;
  /* Add length if needed - unrolled loop ? */
  if(len_type > 2) {
    buffer[pos++] = (tlv->length >> 16) & 0xff;
  }
  if(len_type > 1) {
    buffer[pos++] = (tlv->length >> 8) & 0xff;
  }
  if(len_type > 0) {
    buffer[pos++] = tlv->length & 0xff;
  }

  /* finally add the value */
  memcpy(&buffer[pos], tlv->value, tlv->length);

  if(DEBUG) {
    int i;
    PRINTF("TLV:");
    for(i = 0; i < pos + tlv->length; i++) {
      PRINTF("%02x", buffer[i]);
    }
    PRINTF("\n");
  }

  return pos + tlv->length;
}
/*---------------------------------------------------------------------------*/
int32_t
oma_tlv_get_int32(const oma_tlv_t *tlv)
{
  int i;
  int32_t value = 0;
  /* will probably need to handle MSB as a sign bit? */
  for(i = 0; i < tlv->length; i++) {
    value = (value << 8) | tlv->value[i];
  }
  return value;
}
/*---------------------------------------------------------------------------*/
size_t
oma_tlv_write_int32(int16_t id, int32_t value, uint8_t *buffer, size_t len)
{
  oma_tlv_t tlv;
  size_t tlvlen = 0;
  uint8_t buf[4];
  int i;
  PRINTF("Exporting int32 %d %ld ", id, (long)value);

  buf[3] = value & 0xff;
  value = value >> 8;
  for(i = 1; value > 0 && i < 4; i++) {
    buf[3 - i] = value & 0xff;
    value = value >> 8;
  }
  tlvlen = i;

  /* export INT as TLV */
  PRINTF("len: %zu\n", tlvlen);
  tlv.type = OMA_TLV_TYPE_RESOURCE;
  tlv.length = tlvlen;
  tlv.value = &buf[3 - (tlvlen - 1)];
  tlv.id = id;
  return oma_tlv_write(&tlv, buffer, len);
}
/*---------------------------------------------------------------------------*/
/* convert fixpoint 32-bit to a IEEE Float in the byte array*/
size_t
oma_tlv_write_float32(int16_t id, int32_t value, int bits,
                      uint8_t *buffer, size_t len)
{
  int i;
  int e = 0;
  int32_t val = 0;
  int32_t v;
  uint8_t b[4];
  oma_tlv_t tlv;

  v = value;
  if(v < 0) {
    v = -v;
  }

  while(v > 1) {
    val = (val >> 1);
    if (v & 1) {
      val = val | (1L << 22);
    }
    v = (v >> 1);
    e++;
  }

  PRINTF("Sign: %d, Fraction: %06lx  0b", value < 0, (long)val);
  for(i = 0; i < 23; i++) {
    PRINTF("%d", (int)((val >> (22 - i)) & 1));
  }
  PRINTF("\nExp:%d\n", e);

  /* convert to the thing we should have */
  e = e - bits + 127;

  /* is this the right byte order? */
  b[0] = (value < 0 ? 0x80 : 0) | (e >> 1);
  b[1] = ((e & 1) << 7) | ((val >> 16) & 0x7f);
  b[2] = (val >> 8) & 0xff;
  b[3] = val & 0xff;

  /* construct the TLV */
  tlv.type = OMA_TLV_TYPE_RESOURCE;
  tlv.length = 4;
  tlv.value = b;
  tlv.id = id;

  return oma_tlv_write(&tlv, buffer, len);
}
/*---------------------------------------------------------------------------*/
/* convert float to fixpoint */
size_t
oma_tlv_float32_to_fix(const oma_tlv_t *tlv, int32_t *value, int bits)
{
  /* TLV needs to be 4 bytes */
  int e, i;
  int32_t val;
  int sign = (tlv->value[0] & 0x80) != 0;
  e = ((tlv->value[0] << 1) & 0xff) | (tlv->value[1] >> 7);
  val = (((long)tlv->value[1] & 0x7f) << 16) | (tlv->value[2] << 8) | tlv->value[3];

  PRINTF("Sign: %d, Fraction: %06lx  0b", val < 0, (long)val);
  for(i = 0; i < 23; i++) {
    PRINTF("%d", (int)((val >> (22 - i)) & 1));
  }
  PRINTF("\nExp:%d => %d\n", e, e - 127);

  e = e - 127 + bits;

  /* e corresponds to the number of times we need to roll the number */

  PRINTF("Actual e=%d\n", e);
  e = e - 23;
  PRINTF("E after sub %d\n", e);
  val = val | 1L << 23;
  if(e > 0) {
    val = val << e;
  } else {
    val = val >> -e;
  }

  *value = sign ? -val : val;
  return 4;
}
/*---------------------------------------------------------------------------*/
/** @} */