text: /*
   * 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;
  }
  /*---------------------------------------------------------------------------*/
  /** @} */
  