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/**
 * @file
 * Abstract Syntax Notation One (ISO 8824, 8825) decoding
 *
 * @todo not optimised (yet), favor correctness over speed, favor speed over size
 */
 
/*
 * Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.
 * 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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 *
 * Author: Christiaan Simons <christiaan.simons@axon.tv>
 */
 
#include "lwip/opt.h"
 
#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
 
#include "lwip/snmp_asn1.h"
 
/**
 * Retrieves type field from incoming pbuf chain.
 *
 * @param p points to a pbuf holding an ASN1 coded type field
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded type field
 * @param type return ASN1 type
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_type(struct pbuf *p, u16_t ofs, u8_t *type)
{
  u16_t plen, base;
  u8_t *msg_ptr;
 
  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;
      *type = *msg_ptr;
      return ERR_OK;
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}
 
/**
 * Decodes length field from incoming pbuf chain into host length.
 *
 * @param p points to a pbuf holding an ASN1 coded length
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded length
 * @param octets_used returns number of octets used by the length code
 * @param length return host order length, upto 64k
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_length(struct pbuf *p, u16_t ofs, u8_t *octets_used, u16_t *length)
{
  u16_t plen, base;
  u8_t *msg_ptr;
 
  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;
 
      if (*msg_ptr < 0x80)
      {
        /* primitive definite length format */
        *octets_used = 1;
        *length = *msg_ptr;
        return ERR_OK;
      }
      else if (*msg_ptr == 0x80)
      {
        /* constructed indefinite length format, termination with two zero octets */
        u8_t zeros;
        u8_t i;
 
        *length = 0;
        zeros = 0;
        while (zeros != 2)
        {
          i = 2;
          while (i > 0)
          {
            i--;
            (*length) += 1;
            ofs += 1;
            if (ofs >= plen)
            {
              /* next octet in next pbuf */
              p = p->next;
              if (p == NULL) { return ERR_ARG; }
              msg_ptr = p->payload;
              plen += p->len;
            }
            else
            {
              /* next octet in same pbuf */
              msg_ptr++;
            }
            if (*msg_ptr == 0)
            {
              zeros++;
              if (zeros == 2)
              {
                /* stop while (i > 0) */
                i = 0;
              }
            }
            else
            {
              zeros = 0;
            }
          }
        }
        *octets_used = 1;
        return ERR_OK;
      }
      else if (*msg_ptr == 0x81)
      {
        /* constructed definite length format, one octet */
        ofs += 1;
        if (ofs >= plen)
        {
          /* next octet in next pbuf */
          p = p->next;
          if (p == NULL) { return ERR_ARG; }
          msg_ptr = p->payload;
        }
        else
        {
          /* next octet in same pbuf */
          msg_ptr++;
        }
        *length = *msg_ptr;
        *octets_used = 2;
        return ERR_OK;
      }
      else if (*msg_ptr == 0x82)
      {
        u8_t i;
 
        /* constructed definite length format, two octets */
        i = 2;
        while (i > 0)
        {
          i--;
          ofs += 1;
          if (ofs >= plen)
          {
            /* next octet in next pbuf */
            p = p->next;
            if (p == NULL) { return ERR_ARG; }
            msg_ptr = p->payload;
            plen += p->len;
          }
          else
          {
            /* next octet in same pbuf */
            msg_ptr++;
          }
          if (i == 0)
          {
            /* least significant length octet */
            *length |= *msg_ptr;
          }
          else
          {
            /* most significant length octet */
            *length = (*msg_ptr) << 8;
          }
        }
        *octets_used = 3;
        return ERR_OK;
      }
      else
      {
        /* constructed definite length format 3..127 octets, this is too big (>64k) */
        /**  @todo: do we need to accept inefficient codings with many leading zero's? */
        *octets_used = 1 + ((*msg_ptr) & 0x7f);
        return ERR_ARG;
      }
    }
    p = p->next;
  }
 
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}
 
/**
 * Decodes positive integer (counter, gauge, timeticks) into u32_t.
 *
 * @param p points to a pbuf holding an ASN1 coded integer
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
 * @param len length of the coded integer field
 * @param value return host order integer
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 *
 * @note ASN coded integers are _always_ signed. E.g. +0xFFFF is coded
 * as 0x00,0xFF,0xFF. Note the leading sign octet. A positive value
 * of 0xFFFFFFFF is preceded with 0x00 and the length is 5 octets!!
 */
err_t
snmp_asn1_dec_u32t(struct pbuf *p, u16_t ofs, u16_t len, u32_t *value)
{
  u16_t plen, base;
  u8_t *msg_ptr;
 
  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;
      if ((len > 0) && (len < 6))
      {
        /* start from zero */
        *value = 0;
        if (*msg_ptr & 0x80)
        {
          /* negative, expecting zero sign bit! */
          return ERR_ARG;
        }
        else
        {
          /* positive */
          if ((len > 1) && (*msg_ptr == 0))
          {
            /* skip leading "sign byte" octet 0x00 */
            len--;
            ofs += 1;
            if (ofs >= plen)
            {
              /* next octet in next pbuf */
              p = p->next;
              if (p == NULL) { return ERR_ARG; }
              msg_ptr = p->payload;
              plen += p->len;
            }
            else
            {
              /* next octet in same pbuf */
              msg_ptr++;
            }
          }
        }
        /* OR octets with value */
        while (len > 1)
        {
          len--;
          *value |= *msg_ptr;
          *value <<= 8;
          ofs += 1;
          if (ofs >= plen)
          {
            /* next octet in next pbuf */
            p = p->next;
            if (p == NULL) { return ERR_ARG; }
            msg_ptr = p->payload;
            plen += p->len;
          }
          else
          {
            /* next octet in same pbuf */
            msg_ptr++;
          }
        }
        *value |= *msg_ptr;
        return ERR_OK;
      }
      else
      {
        return ERR_ARG;
      }
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}
 
/**
 * Decodes integer into s32_t.
 *
 * @param p points to a pbuf holding an ASN1 coded integer
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
 * @param len length of the coded integer field
 * @param value return host order integer
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 *
 * @note ASN coded integers are _always_ signed!
 */
err_t
snmp_asn1_dec_s32t(struct pbuf *p, u16_t ofs, u16_t len, s32_t *value)
{
  u16_t plen, base;
  u8_t *msg_ptr;
#if BYTE_ORDER == LITTLE_ENDIAN
  u8_t *lsb_ptr = (u8_t*)value;
#endif
#if BYTE_ORDER == BIG_ENDIAN
  u8_t *lsb_ptr = (u8_t*)value + sizeof(s32_t) - 1;
#endif
  u8_t sign;
 
  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;
      if ((len > 0) && (len < 5))
      {
        if (*msg_ptr & 0x80)
        {
          /* negative, start from -1 */
          *value = -1;
          sign = 1;
        }
        else
        {
          /* positive, start from 0 */
          *value = 0;
          sign = 0;
        }
        /* OR/AND octets with value */
        while (len > 1)
        {
          len--;
          if (sign)
          {
            *lsb_ptr &= *msg_ptr;
            *value <<= 8;
            *lsb_ptr |= 255;
          }
          else
          {
            *lsb_ptr |= *msg_ptr;
            *value <<= 8;
          }
          ofs += 1;
          if (ofs >= plen)
          {
            /* next octet in next pbuf */
            p = p->next;
            if (p == NULL) { return ERR_ARG; }
            msg_ptr = p->payload;
            plen += p->len;
          }
          else
          {
            /* next octet in same pbuf */
            msg_ptr++;
          }
        }
        if (sign)
        {
          *lsb_ptr &= *msg_ptr;
        }
        else
        {
          *lsb_ptr |= *msg_ptr;
        }
        return ERR_OK;
      }
      else
      {
        return ERR_ARG;
      }
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}
 
/**
 * Decodes object identifier from incoming message into array of s32_t.
 *
 * @param p points to a pbuf holding an ASN1 coded object identifier
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded object identifier
 * @param len length of the coded object identifier
 * @param oid return object identifier struct
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_oid(struct pbuf *p, u16_t ofs, u16_t len, struct snmp_obj_id *oid)
{
  u16_t plen, base;
  u8_t *msg_ptr;
  s32_t *oid_ptr;
 
  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;
 
      oid->len = 0;
      oid_ptr = &oid->id[0];
      if (len > 0)
      {
        /* first compressed octet */
        if (*msg_ptr == 0x2B)
        {
          /* (most) common case 1.3 (iso.org) */
          *oid_ptr = 1;
          oid_ptr++;
          *oid_ptr = 3;
          oid_ptr++;
        }
        else if (*msg_ptr < 40)
        {
          *oid_ptr = 0;
          oid_ptr++;
          *oid_ptr = *msg_ptr;
          oid_ptr++;
        }
        else if (*msg_ptr < 80)
        {
          *oid_ptr = 1;
          oid_ptr++;
          *oid_ptr = (*msg_ptr) - 40;
          oid_ptr++;
        }
        else
        {
          *oid_ptr = 2;
          oid_ptr++;
          *oid_ptr = (*msg_ptr) - 80;
          oid_ptr++;
        }
        oid->len = 2;
      }
      else
      {
        /* accepting zero length identifiers e.g. for
           getnext operation. uncommon but valid */
        return ERR_OK;
      }
      len--;
      if (len > 0)
      {
        ofs += 1;
        if (ofs >= plen)
        {
          /* next octet in next pbuf */
          p = p->next;
          if (p == NULL) { return ERR_ARG; }
          msg_ptr = p->payload;
          plen += p->len;
        }
        else
        {
          /* next octet in same pbuf */
          msg_ptr++;
        }
      }
      while ((len > 0) && (oid->len < LWIP_SNMP_OBJ_ID_LEN))
      {
        /* sub-identifier uses multiple octets */
        if (*msg_ptr & 0x80)
        {
          s32_t sub_id = 0;
 
          while ((*msg_ptr & 0x80) && (len > 1))
          {
            len--;
            sub_id = (sub_id << 7) + (*msg_ptr & ~0x80);
            ofs += 1;
            if (ofs >= plen)
            {
              /* next octet in next pbuf */
              p = p->next;
              if (p == NULL) { return ERR_ARG; }
              msg_ptr = p->payload;
              plen += p->len;
            }
            else
            {
              /* next octet in same pbuf */
              msg_ptr++;
            }
          }
          if (!(*msg_ptr & 0x80) && (len > 0))
          {
            /* last octet sub-identifier */
            len--;
            sub_id = (sub_id << 7) + *msg_ptr;
            *oid_ptr = sub_id;
          }
        }
        else
        {
          /* !(*msg_ptr & 0x80) sub-identifier uses single octet */
          len--;
          *oid_ptr = *msg_ptr;
        }
        if (len > 0)
        {
          /* remaining oid bytes available ... */
          ofs += 1;
          if (ofs >= plen)
          {
            /* next octet in next pbuf */
            p = p->next;
            if (p == NULL) { return ERR_ARG; }
            msg_ptr = p->payload;
            plen += p->len;
          }
          else
          {
            /* next octet in same pbuf */
            msg_ptr++;
          }
        }
        oid_ptr++;
        oid->len++;
      }
      if (len == 0)
      {
        /* len == 0, end of oid */
        return ERR_OK;
      }
      else
      {
        /* len > 0, oid->len == LWIP_SNMP_OBJ_ID_LEN or malformed encoding */
        return ERR_ARG;
      }
 
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}
 
/**
 * Decodes (copies) raw data (ip-addresses, octet strings, opaque encoding)
 * from incoming message into array.
 *
 * @param p points to a pbuf holding an ASN1 coded raw data
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded raw data
 * @param len length of the coded raw data (zero is valid, e.g. empty string!)
 * @param raw_len length of the raw return value
 * @param raw return raw bytes
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_raw(struct pbuf *p, u16_t ofs, u16_t len, u16_t raw_len, u8_t *raw)
{
  u16_t plen, base;
  u8_t *msg_ptr;
 
  if (len > 0)
  {
    plen = 0;
    while (p != NULL)
    {
      base = plen;
      plen += p->len;
      if (ofs < plen)
      {
        msg_ptr = p->payload;
        msg_ptr += ofs - base;
        if (raw_len >= len)
        {
          while (len > 1)
          {
            /* copy len - 1 octets */
            len--;
            *raw = *msg_ptr;
            raw++;
            ofs += 1;
            if (ofs >= plen)
            {
              /* next octet in next pbuf */
              p = p->next;
              if (p == NULL) { return ERR_ARG; }
              msg_ptr = p->payload;
              plen += p->len;
            }
            else
            {
              /* next octet in same pbuf */
              msg_ptr++;
            }
          }
          /* copy last octet */
          *raw = *msg_ptr;
          return ERR_OK;
        }
        else
        {
          /* raw_len < len, not enough dst space */
          return ERR_ARG;
        }
      }
      p = p->next;
    }
    /* p == NULL, ofs >= plen */
    return ERR_ARG;
  }
  else
  {
    /* len == 0, empty string */
    return ERR_OK;
  }
}
 
#endif /* LWIP_SNMP */

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Subversion Repositories openrisc

[/] [openrisc/] [trunk/] [rtos/] [freertos-6.1.1/] [Demo/] [Common/] [ethernet/] [lwIP_130/] [src/] [core/] [snmp/] [asn1_dec.c] - Blame information for rev 606

Line No.	Rev	Author	Line
1	606	jeremybenn	`/**`
2			`* @file`
3			`* Abstract Syntax Notation One (ISO 8824, 8825) decoding`
4			`*`
5			`* @todo not optimised (yet), favor correctness over speed, favor speed over size`
6			`*/`
7
8			`/*`
9			`* Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.`
10			`* All rights reserved.`
11			`*`
12			`* Redistribution and use in source and binary forms, with or without modification,`
13			`* are permitted provided that the following conditions are met:`
14			`*`
15			`* 1. Redistributions of source code must retain the above copyright notice,`
16			`* this list of conditions and the following disclaimer.`
17			`* 2. Redistributions in binary form must reproduce the above copyright notice,`
18			`* this list of conditions and the following disclaimer in the documentation`
19			`* and/or other materials provided with the distribution.`
20			`* 3. The name of the author may not be used to endorse or promote products`
21			`* derived from this software without specific prior written permission.`
22			`*`
23			* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
24			`* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF`
25			`* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT`
26			`* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,`
27			`* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT`
28			`* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS`
29			`* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN`
30			`* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING`
31			`* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY`
32			`* OF SUCH DAMAGE.`
33			`*`
34			`* Author: Christiaan Simons <christiaan.simons@axon.tv>`
35			`*/`
36
37			`#include "lwip/opt.h"`
38
39			`#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */`
40
41			`#include "lwip/snmp_asn1.h"`
42
43			`/**`
44			`* Retrieves type field from incoming pbuf chain.`
45			`*`
46			`* @param p points to a pbuf holding an ASN1 coded type field`
47			`* @param ofs points to the offset within the pbuf chain of the ASN1 coded type field`
48			`* @param type return ASN1 type`
49			`* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode`
50			`*/`
51			`err_t`
52			`snmp_asn1_dec_type(struct pbuf p, u16_t ofs, u8_t type)`
53			`{`
54			`u16_t plen, base;`
55			`u8_t *msg_ptr;`
56
57			`plen = 0;`
58			`while (p != NULL)`
59			`{`
60			`base = plen;`
61			`plen += p->len;`
62			`if (ofs < plen)`
63			`{`
64			`msg_ptr = p->payload;`
65			`msg_ptr += ofs - base;`
66			`type = msg_ptr;`
67			`return ERR_OK;`
68			`}`
69			`p = p->next;`
70			`}`
71			`/* p == NULL, ofs >= plen */`
72			`return ERR_ARG;`
73			`}`
74
75			`/**`
76			`* Decodes length field from incoming pbuf chain into host length.`
77			`*`
78			`* @param p points to a pbuf holding an ASN1 coded length`
79			`* @param ofs points to the offset within the pbuf chain of the ASN1 coded length`
80			`* @param octets_used returns number of octets used by the length code`
81			`* @param length return host order length, upto 64k`
82			`* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode`
83			`*/`
84			`err_t`
85			`snmp_asn1_dec_length(struct pbuf p, u16_t ofs, u8_t octets_used, u16_t *length)`
86			`{`
87			`u16_t plen, base;`
88			`u8_t *msg_ptr;`
89
90			`plen = 0;`
91			`while (p != NULL)`
92			`{`
93			`base = plen;`
94			`plen += p->len;`
95			`if (ofs < plen)`
96			`{`
97			`msg_ptr = p->payload;`
98			`msg_ptr += ofs - base;`
99
100			`if (*msg_ptr < 0x80)`
101			`{`
102			`/* primitive definite length format */`
103			`*octets_used = 1;`
104			`length = msg_ptr;`
105			`return ERR_OK;`
106			`}`
107			`else if (*msg_ptr == 0x80)`
108			`{`
109			`/* constructed indefinite length format, termination with two zero octets */`
110			`u8_t zeros;`
111			`u8_t i;`
112
113			`*length = 0;`
114			`zeros = 0;`
115			`while (zeros != 2)`
116			`{`
117			`i = 2;`
118			`while (i > 0)`
119			`{`
120			`i--;`
121			`(*length) += 1;`
122			`ofs += 1;`
123			`if (ofs >= plen)`
124			`{`
125			`/* next octet in next pbuf */`
126			`p = p->next;`
127			`if (p == NULL) { return ERR_ARG; }`
128			`msg_ptr = p->payload;`
129			`plen += p->len;`
130			`}`
131			`else`
132			`{`
133			`/* next octet in same pbuf */`
134			`msg_ptr++;`
135			`}`
136			`if (*msg_ptr == 0)`
137			`{`
138			`zeros++;`
139			`if (zeros == 2)`
140			`{`
141			`/* stop while (i > 0) */`
142			`i = 0;`
143			`}`
144			`}`
145			`else`
146			`{`
147			`zeros = 0;`
148			`}`
149			`}`
150			`}`
151			`*octets_used = 1;`
152			`return ERR_OK;`
153			`}`
154			`else if (*msg_ptr == 0x81)`
155			`{`
156			`/* constructed definite length format, one octet */`
157			`ofs += 1;`
158			`if (ofs >= plen)`
159			`{`
160			`/* next octet in next pbuf */`
161			`p = p->next;`
162			`if (p == NULL) { return ERR_ARG; }`
163			`msg_ptr = p->payload;`
164			`}`
165			`else`
166			`{`
167			`/* next octet in same pbuf */`
168			`msg_ptr++;`
169			`}`
170			`length = msg_ptr;`
171			`*octets_used = 2;`
172			`return ERR_OK;`
173			`}`
174			`else if (*msg_ptr == 0x82)`
175			`{`
176			`u8_t i;`
177
178			`/* constructed definite length format, two octets */`
179			`i = 2;`
180			`while (i > 0)`
181			`{`
182			`i--;`
183			`ofs += 1;`
184			`if (ofs >= plen)`
185			`{`
186			`/* next octet in next pbuf */`
187			`p = p->next;`
188			`if (p == NULL) { return ERR_ARG; }`
189			`msg_ptr = p->payload;`
190			`plen += p->len;`
191			`}`
192			`else`
193			`{`
194			`/* next octet in same pbuf */`
195			`msg_ptr++;`
196			`}`
197			`if (i == 0)`
198			`{`
199			`/* least significant length octet */`
200			`length \|= msg_ptr;`
201			`}`
202			`else`
203			`{`
204			`/* most significant length octet */`
205			`length = (msg_ptr) << 8;`
206			`}`
207			`}`
208			`*octets_used = 3;`
209			`return ERR_OK;`
210			`}`
211			`else`
212			`{`
213			`/* constructed definite length format 3..127 octets, this is too big (>64k) */`
214			`/** @todo: do we need to accept inefficient codings with many leading zero's? */`
215			`octets_used = 1 + ((msg_ptr) & 0x7f);`
216			`return ERR_ARG;`
217			`}`
218			`}`
219			`p = p->next;`
220			`}`
221
222			`/* p == NULL, ofs >= plen */`
223			`return ERR_ARG;`
224			`}`
225
226			`/**`
227			`* Decodes positive integer (counter, gauge, timeticks) into u32_t.`
228			`*`
229			`* @param p points to a pbuf holding an ASN1 coded integer`
230			`* @param ofs points to the offset within the pbuf chain of the ASN1 coded integer`
231			`* @param len length of the coded integer field`
232			`* @param value return host order integer`
233			`* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode`
234			`*`
235			`* @note ASN coded integers are _always_ signed. E.g. +0xFFFF is coded`
236			`* as 0x00,0xFF,0xFF. Note the leading sign octet. A positive value`
237			`* of 0xFFFFFFFF is preceded with 0x00 and the length is 5 octets!!`
238			`*/`
239			`err_t`
240			`snmp_asn1_dec_u32t(struct pbuf p, u16_t ofs, u16_t len, u32_t value)`
241			`{`
242			`u16_t plen, base;`
243			`u8_t *msg_ptr;`
244
245			`plen = 0;`
246			`while (p != NULL)`
247			`{`
248			`base = plen;`
249			`plen += p->len;`
250			`if (ofs < plen)`
251			`{`
252			`msg_ptr = p->payload;`
253			`msg_ptr += ofs - base;`
254			`if ((len > 0) && (len < 6))`
255			`{`
256			`/* start from zero */`
257			`*value = 0;`
258			`if (*msg_ptr & 0x80)`
259			`{`
260			`/* negative, expecting zero sign bit! */`
261			`return ERR_ARG;`
262			`}`
263			`else`
264			`{`
265			`/* positive */`
266			`if ((len > 1) && (*msg_ptr == 0))`
267			`{`
268			`/* skip leading "sign byte" octet 0x00 */`
269			`len--;`
270			`ofs += 1;`
271			`if (ofs >= plen)`
272			`{`
273			`/* next octet in next pbuf */`
274			`p = p->next;`
275			`if (p == NULL) { return ERR_ARG; }`
276			`msg_ptr = p->payload;`
277			`plen += p->len;`
278			`}`
279			`else`
280			`{`
281			`/* next octet in same pbuf */`
282			`msg_ptr++;`
283			`}`
284			`}`
285			`}`
286			`/* OR octets with value */`
287			`while (len > 1)`
288			`{`
289			`len--;`
290			`value \|= msg_ptr;`
291			`*value <<= 8;`
292			`ofs += 1;`
293			`if (ofs >= plen)`
294			`{`
295			`/* next octet in next pbuf */`
296			`p = p->next;`
297			`if (p == NULL) { return ERR_ARG; }`
298			`msg_ptr = p->payload;`
299			`plen += p->len;`
300			`}`
301			`else`
302			`{`
303			`/* next octet in same pbuf */`
304			`msg_ptr++;`
305			`}`
306			`}`
307			`value \|= msg_ptr;`
308			`return ERR_OK;`
309			`}`
310			`else`
311			`{`
312			`return ERR_ARG;`
313			`}`
314			`}`
315			`p = p->next;`
316			`}`
317			`/* p == NULL, ofs >= plen */`
318			`return ERR_ARG;`
319			`}`
320
321			`/**`
322			`* Decodes integer into s32_t.`
323			`*`
324			`* @param p points to a pbuf holding an ASN1 coded integer`
325			`* @param ofs points to the offset within the pbuf chain of the ASN1 coded integer`
326			`* @param len length of the coded integer field`
327			`* @param value return host order integer`
328			`* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode`
329			`*`
330			`* @note ASN coded integers are _always_ signed!`
331			`*/`
332			`err_t`
333			`snmp_asn1_dec_s32t(struct pbuf p, u16_t ofs, u16_t len, s32_t value)`
334			`{`
335			`u16_t plen, base;`
336			`u8_t *msg_ptr;`
337			`#if BYTE_ORDER == LITTLE_ENDIAN`
338			`u8_t lsb_ptr = (u8_t)value;`
339			`#endif`
340			`#if BYTE_ORDER == BIG_ENDIAN`
341			`u8_t lsb_ptr = (u8_t)value + sizeof(s32_t) - 1;`
342			`#endif`
343			`u8_t sign;`
344
345			`plen = 0;`
346			`while (p != NULL)`
347			`{`
348			`base = plen;`
349			`plen += p->len;`
350			`if (ofs < plen)`
351			`{`
352			`msg_ptr = p->payload;`
353			`msg_ptr += ofs - base;`
354			`if ((len > 0) && (len < 5))`
355			`{`
356			`if (*msg_ptr & 0x80)`
357			`{`
358			`/* negative, start from -1 */`
359			`*value = -1;`
360			`sign = 1;`
361			`}`
362			`else`
363			`{`
364			`/* positive, start from 0 */`
365			`*value = 0;`
366			`sign = 0;`
367			`}`
368			`/* OR/AND octets with value */`
369			`while (len > 1)`
370			`{`
371			`len--;`
372			`if (sign)`
373			`{`
374			`lsb_ptr &= msg_ptr;`
375			`*value <<= 8;`
376			`*lsb_ptr \|= 255;`
377			`}`
378			`else`
379			`{`
380			`lsb_ptr \|= msg_ptr;`
381			`*value <<= 8;`
382			`}`
383			`ofs += 1;`
384			`if (ofs >= plen)`
385			`{`
386			`/* next octet in next pbuf */`
387			`p = p->next;`
388			`if (p == NULL) { return ERR_ARG; }`
389			`msg_ptr = p->payload;`
390			`plen += p->len;`
391			`}`
392			`else`
393			`{`
394			`/* next octet in same pbuf */`
395			`msg_ptr++;`
396			`}`
397			`}`
398			`if (sign)`
399			`{`
400			`lsb_ptr &= msg_ptr;`
401			`}`
402			`else`
403			`{`
404			`lsb_ptr \|= msg_ptr;`
405			`}`
406			`return ERR_OK;`
407			`}`
408			`else`
409			`{`
410			`return ERR_ARG;`
411			`}`
412			`}`
413			`p = p->next;`
414			`}`
415			`/* p == NULL, ofs >= plen */`
416			`return ERR_ARG;`
417			`}`
418
419			`/**`
420			`* Decodes object identifier from incoming message into array of s32_t.`
421			`*`
422			`* @param p points to a pbuf holding an ASN1 coded object identifier`
423			`* @param ofs points to the offset within the pbuf chain of the ASN1 coded object identifier`
424			`* @param len length of the coded object identifier`
425			`* @param oid return object identifier struct`
426			`* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode`
427			`*/`
428			`err_t`
429			`snmp_asn1_dec_oid(struct pbuf p, u16_t ofs, u16_t len, struct snmp_obj_id oid)`
430			`{`
431			`u16_t plen, base;`
432			`u8_t *msg_ptr;`
433			`s32_t *oid_ptr;`
434
435			`plen = 0;`
436			`while (p != NULL)`
437			`{`
438			`base = plen;`
439			`plen += p->len;`
440			`if (ofs < plen)`
441			`{`
442			`msg_ptr = p->payload;`
443			`msg_ptr += ofs - base;`
444
445			`oid->len = 0;`
446			`oid_ptr = &oid->id[0];`
447			`if (len > 0)`
448			`{`
449			`/* first compressed octet */`
450			`if (*msg_ptr == 0x2B)`
451			`{`
452			`/* (most) common case 1.3 (iso.org) */`
453			`*oid_ptr = 1;`
454			`oid_ptr++;`
455			`*oid_ptr = 3;`
456			`oid_ptr++;`
457			`}`
458			`else if (*msg_ptr < 40)`
459			`{`
460			`*oid_ptr = 0;`
461			`oid_ptr++;`
462			`oid_ptr = msg_ptr;`
463			`oid_ptr++;`
464			`}`
465			`else if (*msg_ptr < 80)`
466			`{`
467			`*oid_ptr = 1;`
468			`oid_ptr++;`
469			`oid_ptr = (msg_ptr) - 40;`
470			`oid_ptr++;`
471			`}`
472			`else`
473			`{`
474			`*oid_ptr = 2;`
475			`oid_ptr++;`
476			`oid_ptr = (msg_ptr) - 80;`
477			`oid_ptr++;`
478			`}`
479			`oid->len = 2;`
480			`}`
481			`else`
482			`{`
483			`/* accepting zero length identifiers e.g. for`
484			`getnext operation. uncommon but valid */`
485			`return ERR_OK;`
486			`}`
487			`len--;`
488			`if (len > 0)`
489			`{`
490			`ofs += 1;`
491			`if (ofs >= plen)`
492			`{`
493			`/* next octet in next pbuf */`
494			`p = p->next;`
495			`if (p == NULL) { return ERR_ARG; }`
496			`msg_ptr = p->payload;`
497			`plen += p->len;`
498			`}`
499			`else`
500			`{`
501			`/* next octet in same pbuf */`
502			`msg_ptr++;`
503			`}`
504			`}`
505			`while ((len > 0) && (oid->len < LWIP_SNMP_OBJ_ID_LEN))`
506			`{`
507			`/* sub-identifier uses multiple octets */`
508			`if (*msg_ptr & 0x80)`
509			`{`
510			`s32_t sub_id = 0;`
511
512			`while ((*msg_ptr & 0x80) && (len > 1))`
513			`{`
514			`len--;`
515			`sub_id = (sub_id << 7) + (*msg_ptr & ~0x80);`
516			`ofs += 1;`
517			`if (ofs >= plen)`
518			`{`
519			`/* next octet in next pbuf */`
520			`p = p->next;`
521			`if (p == NULL) { return ERR_ARG; }`
522			`msg_ptr = p->payload;`
523			`plen += p->len;`
524			`}`
525			`else`
526			`{`
527			`/* next octet in same pbuf */`
528			`msg_ptr++;`
529			`}`
530			`}`
531			`if (!(*msg_ptr & 0x80) && (len > 0))`
532			`{`
533			`/* last octet sub-identifier */`
534			`len--;`
535			`sub_id = (sub_id << 7) + *msg_ptr;`
536			`*oid_ptr = sub_id;`
537			`}`
538			`}`
539			`else`
540			`{`
541			`/* !(msg_ptr & 0x80) sub-identifier uses single octet /`
542			`len--;`
543			`oid_ptr = msg_ptr;`
544			`}`
545			`if (len > 0)`
546			`{`
547			`/* remaining oid bytes available ... */`
548			`ofs += 1;`
549			`if (ofs >= plen)`
550			`{`
551			`/* next octet in next pbuf */`
552			`p = p->next;`
553			`if (p == NULL) { return ERR_ARG; }`
554			`msg_ptr = p->payload;`
555			`plen += p->len;`
556			`}`
557			`else`
558			`{`
559			`/* next octet in same pbuf */`
560			`msg_ptr++;`
561			`}`
562			`}`
563			`oid_ptr++;`
564			`oid->len++;`
565			`}`
566			`if (len == 0)`
567			`{`
568			`/* len == 0, end of oid */`
569			`return ERR_OK;`
570			`}`
571			`else`
572			`{`
573			`/* len > 0, oid->len == LWIP_SNMP_OBJ_ID_LEN or malformed encoding */`
574			`return ERR_ARG;`
575			`}`
576
577			`}`
578			`p = p->next;`
579			`}`
580			`/* p == NULL, ofs >= plen */`
581			`return ERR_ARG;`
582			`}`
583
584			`/**`
585			`* Decodes (copies) raw data (ip-addresses, octet strings, opaque encoding)`
586			`* from incoming message into array.`
587			`*`
588			`* @param p points to a pbuf holding an ASN1 coded raw data`
589			`* @param ofs points to the offset within the pbuf chain of the ASN1 coded raw data`
590			`* @param len length of the coded raw data (zero is valid, e.g. empty string!)`
591			`* @param raw_len length of the raw return value`
592			`* @param raw return raw bytes`
593			`* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode`
594			`*/`
595			`err_t`
596			`snmp_asn1_dec_raw(struct pbuf p, u16_t ofs, u16_t len, u16_t raw_len, u8_t raw)`
597			`{`
598			`u16_t plen, base;`
599			`u8_t *msg_ptr;`
600
601			`if (len > 0)`
602			`{`
603			`plen = 0;`
604			`while (p != NULL)`
605			`{`
606			`base = plen;`
607			`plen += p->len;`
608			`if (ofs < plen)`
609			`{`
610			`msg_ptr = p->payload;`
611			`msg_ptr += ofs - base;`
612			`if (raw_len >= len)`
613			`{`
614			`while (len > 1)`
615			`{`
616			`/* copy len - 1 octets */`
617			`len--;`
618			`raw = msg_ptr;`
619			`raw++;`
620			`ofs += 1;`
621			`if (ofs >= plen)`
622			`{`
623			`/* next octet in next pbuf */`
624			`p = p->next;`
625			`if (p == NULL) { return ERR_ARG; }`
626			`msg_ptr = p->payload;`
627			`plen += p->len;`
628			`}`
629			`else`
630			`{`
631			`/* next octet in same pbuf */`
632			`msg_ptr++;`
633			`}`
634			`}`
635			`/* copy last octet */`
636			`raw = msg_ptr;`
637			`return ERR_OK;`
638			`}`
639			`else`
640			`{`
641			`/* raw_len < len, not enough dst space */`
642			`return ERR_ARG;`
643			`}`
644			`}`
645			`p = p->next;`
646			`}`
647			`/* p == NULL, ofs >= plen */`
648			`return ERR_ARG;`
649			`}`
650			`else`
651			`{`
652			`/* len == 0, empty string */`
653			`return ERR_OK;`
654			`}`
655			`}`
656
657			`#endif /* LWIP_SNMP */`