1 /* block.c -- block transfer
2 *
3 * Copyright (C) 2010--2012,2015 Olaf Bergmann <bergmann@tzi.org>
4 *
5 * This file is part of the CoAP library libcoap. Please see
6 * README for terms of use.
7 */
8
9 #include "coap_config.h"
10
11 #if defined(HAVE_ASSERT_H) && !defined(assert)
12 # include <assert.h>
13 #endif
14
15 #include "debug.h"
16 #include "block.h"
17
18 #if (COAP_MAX_PDU_SIZE - 6) < (1 << (COAP_MAX_BLOCK_SZX + 4))
19 #error "COAP_MAX_BLOCK_SZX too large"
20 #endif
21
22 #define min(a,b) ((a) < (b) ? (a) : (b))
23
24 #ifndef WITHOUT_BLOCK
25 unsigned int
coap_opt_block_num(const coap_opt_t * block_opt)26 coap_opt_block_num(const coap_opt_t *block_opt) {
27 unsigned int num = 0;
28 unsigned short len;
29
30 len = coap_opt_length(block_opt);
31
32 if (len == 0) {
33 return 0;
34 }
35
36 if (len > 1) {
37 num = coap_decode_var_bytes(COAP_OPT_VALUE(block_opt),
38 COAP_OPT_LENGTH(block_opt) - 1);
39 }
40
41 return (num << 4) | ((*COAP_OPT_BLOCK_LAST(block_opt) & 0xF0) >> 4);
42 }
43
44 int
coap_get_block(coap_pdu_t * pdu,unsigned short type,coap_block_t * block)45 coap_get_block(coap_pdu_t *pdu, unsigned short type, coap_block_t *block) {
46 coap_opt_iterator_t opt_iter;
47 coap_opt_t *option;
48
49 assert(block);
50 memset(block, 0, sizeof(coap_block_t));
51
52 if (pdu && (option = coap_check_option(pdu, type, &opt_iter))) {
53 block->szx = COAP_OPT_BLOCK_SZX(option);
54 if (COAP_OPT_BLOCK_MORE(option))
55 block->m = 1;
56 block->num = coap_opt_block_num(option);
57 return 1;
58 }
59
60 return 0;
61 }
62
63 int
coap_write_block_opt(coap_block_t * block,unsigned short type,coap_pdu_t * pdu,size_t data_length)64 coap_write_block_opt(coap_block_t *block, unsigned short type,
65 coap_pdu_t *pdu, size_t data_length) {
66 size_t start, want, avail;
67 unsigned char buf[3];
68
69 assert(pdu);
70
71 start = block->num << (block->szx + 4);
72 if (data_length <= start) {
73 debug("illegal block requested\n");
74 return -2;
75 }
76
77 avail = pdu->max_size - pdu->length - 4;
78 want = 1 << (block->szx + 4);
79
80 /* check if entire block fits in message */
81 if (want <= avail) {
82 block->m = want < data_length - start;
83 } else {
84 /* Sender has requested a block that is larger than the remaining
85 * space in pdu. This is ok if the remaining data fits into the pdu
86 * anyway. The block size needs to be adjusted only if there is more
87 * data left that cannot be delivered in this message. */
88
89 if (data_length - start <= avail) {
90
91 /* it's the final block and everything fits in the message */
92 block->m = 0;
93 } else {
94 unsigned char szx;
95
96 /* we need to decrease the block size */
97 if (avail < 16) { /* bad luck, this is the smallest block size */
98 debug("not enough space, even the smallest block does not fit");
99 return -3;
100 }
101 debug("decrease block size for %zu to %d\n", avail, coap_fls(avail) - 5);
102 szx = block->szx;
103 block->szx = coap_fls(avail) - 5;
104 block->m = 1;
105 block->num <<= szx - block->szx;
106 }
107 }
108
109 /* to re-encode the block option */
110 coap_add_option(pdu, type, coap_encode_var_bytes(buf, ((block->num << 4) |
111 (block->m << 3) |
112 block->szx)),
113 buf);
114
115 return 1;
116 }
117
118 int
coap_add_block(coap_pdu_t * pdu,unsigned int len,const unsigned char * data,unsigned int block_num,unsigned char block_szx)119 coap_add_block(coap_pdu_t *pdu, unsigned int len, const unsigned char *data,
120 unsigned int block_num, unsigned char block_szx) {
121 size_t start;
122 start = block_num << (block_szx + 4);
123
124 if (len <= start)
125 return 0;
126
127 return coap_add_data(pdu,
128 min(len - start, (unsigned int)(1 << (block_szx + 4))),
129 data + start);
130 }
131 #endif /* WITHOUT_BLOCK */
132
