1 /**
2  * @file
3  * SNMP pbuf stream wrapper implementation (internal API, do not use in client code).
4  */
5 
6 /*
7  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without modification,
11  * are permitted provided that the following conditions are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright notice,
14  *    this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright notice,
16  *    this list of conditions and the following disclaimer in the documentation
17  *    and/or other materials provided with the distribution.
18  * 3. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
22  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
23  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
24  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
26  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
29  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
30  * OF SUCH DAMAGE.
31  *
32  * This file is part of the lwIP TCP/IP stack.
33  *
34  * Author: Martin Hentschel <info@cl-soft.de>
35  *
36  */
37 
38 #include "lwip/apps/snmp_opts.h"
39 
40 #if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
41 
42 #include "snmp_pbuf_stream.h"
43 #include "lwip/def.h"
44 #include <string.h>
45 
46 err_t
47 snmp_pbuf_stream_init(struct snmp_pbuf_stream* pbuf_stream, struct pbuf* p, u16_t offset, u16_t length)
48 {
49   pbuf_stream->offset = offset;
50   pbuf_stream->length = length;
51   pbuf_stream->pbuf   = p;
52 
53   return ERR_OK;
54 }
55 
56 err_t
57 snmp_pbuf_stream_read(struct snmp_pbuf_stream* pbuf_stream, u8_t* data)
58 {
59   if (pbuf_stream->length == 0) {
60     return ERR_BUF;
61   }
62 
63   if (pbuf_copy_partial(pbuf_stream->pbuf, data, 1, pbuf_stream->offset) == 0) {
64     return ERR_BUF;
65   }
66 
67   pbuf_stream->offset++;
68   pbuf_stream->length--;
69 
70   return ERR_OK;
71 }
72 
73 err_t
74 snmp_pbuf_stream_write(struct snmp_pbuf_stream* pbuf_stream, u8_t data)
75 {
76   return snmp_pbuf_stream_writebuf(pbuf_stream, &data, 1);
77 }
78 
79 err_t
80 snmp_pbuf_stream_writebuf(struct snmp_pbuf_stream* pbuf_stream, const void* buf, u16_t buf_len)
81 {
82   if (pbuf_stream->length < buf_len) {
83     return ERR_BUF;
84   }
85 
86   if (pbuf_take_at(pbuf_stream->pbuf, buf, buf_len, pbuf_stream->offset) != ERR_OK) {
87     return ERR_BUF;
88   }
89 
90   pbuf_stream->offset += buf_len;
91   pbuf_stream->length -= buf_len;
92 
93   return ERR_OK;
94 }
95 
96 err_t
97 snmp_pbuf_stream_writeto(struct snmp_pbuf_stream* pbuf_stream, struct snmp_pbuf_stream* target_pbuf_stream, u16_t len)
98 {
99 
100   if ((pbuf_stream == NULL) || (target_pbuf_stream == NULL)) {
101     return ERR_ARG;
102   }
103   if ((len > pbuf_stream->length) || (len > target_pbuf_stream->length)) {
104     return ERR_ARG;
105   }
106 
107   if (len == 0) {
108     len = LWIP_MIN(pbuf_stream->length, target_pbuf_stream->length);
109   }
110 
111   while (len > 0) {
112     u16_t chunk_len;
113     err_t err;
114     u16_t target_offset;
115     struct pbuf* pbuf = pbuf_skip(pbuf_stream->pbuf, pbuf_stream->offset, &target_offset);
116 
117     if ((pbuf == NULL) || (pbuf->len == 0)) {
118       return ERR_BUF;
119     }
120 
121     chunk_len = LWIP_MIN(len, pbuf->len);
122     err = snmp_pbuf_stream_writebuf(target_pbuf_stream, &((u8_t*)pbuf->payload)[target_offset], chunk_len);
123     if (err != ERR_OK) {
124       return err;
125     }
126 
127     pbuf_stream->offset   += chunk_len;
128     pbuf_stream->length   -= chunk_len;
129     len -= chunk_len;
130   }
131 
132   return ERR_OK;
133 }
134 
135 err_t
136 snmp_pbuf_stream_seek(struct snmp_pbuf_stream* pbuf_stream, s32_t offset)
137 {
138   if ((offset < 0) || (offset > pbuf_stream->length)) {
139     /* we cannot seek backwards or forward behind stream end */
140     return ERR_ARG;
141   }
142 
143   pbuf_stream->offset += (u16_t)offset;
144   pbuf_stream->length -= (u16_t)offset;
145 
146   return ERR_OK;
147 }
148 
149 err_t
150 snmp_pbuf_stream_seek_abs(struct snmp_pbuf_stream* pbuf_stream, u32_t offset)
151 {
152   s32_t rel_offset = offset - pbuf_stream->offset;
153   return snmp_pbuf_stream_seek(pbuf_stream, rel_offset);
154 }
155 
156 #endif /* LWIP_SNMP */
157