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104 lines
2.9 KiB
C
104 lines
2.9 KiB
C
/* block.c -- block transfer
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*
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* Copyright (C) 2010--2012 Olaf Bergmann <bergmann@tzi.org>
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*
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* This file is part of the CoAP library libcoap. Please see
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* README for terms of use.
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*/
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#include "config.h"
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#if defined(HAVE_ASSERT_H) && !defined(assert)
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# include <assert.h>
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#endif
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#include "debug.h"
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#include "block.h"
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#define min(a,b) ((a) < (b) ? (a) : (b))
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int
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coap_write_block_opt(coap_opt_t **block_req, unsigned short type,
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coap_pdu_t *pdu, size_t data_length) {
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coap_block_t block;
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size_t start, want, avail;
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assert(pdu); assert(block_req && *block_req);
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if (type != COAP_OPTION_BLOCK2) {
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warn("coap_write_block_opt: skipped unknown option\n");
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return -1;
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}
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/* Block2 */
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block.szx = COAP_OPT_BLOCK_SZX(*block_req);
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block.m = COAP_OPT_BLOCK_MORE(*block_req);
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block.num = COAP_OPT_BLOCK_NUM(*block_req);
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start = block.num << (block.szx + 4);
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if (data_length <= start) {
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debug("illegal block requested\n");
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return -2;
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}
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avail = pdu->max_size - pdu->length - 4;
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want = 1 << (block.szx + 4);
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/* check if entire block fits in message */
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if (want <= avail) {
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coap_opt_block_set_m(*block_req, want <= data_length - start);
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coap_add_option(pdu, type,
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COAP_OPT_LENGTH(*block_req), COAP_OPT_VALUE(*block_req));
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} else {
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/* Sender has requested a block that is larger than the remaining
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* space in pdu. This is ok if the remaining data fits into the pdu
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* anyway. The block size needs to be adjusted only if there is more
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* data left that cannot be delivered in this message. */
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if (data_length - start <= avail) {
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/* it's the final block and everything fits in the message */
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coap_opt_block_set_m(*block_req, 0);
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coap_add_option(pdu, type,
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COAP_OPT_LENGTH(*block_req), COAP_OPT_VALUE(*block_req));
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} else {
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unsigned char buf[3];
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/* we need to decrease the block size */
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if (avail < 16) { /* bad luck, this is the smallest block size */
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debug("not enough space, even the smallest block does not fit");
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return -3;
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}
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debug("decrease block size for %d to %d\n", avail, coap_fls(avail) - 5);
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block.szx = coap_fls(avail) - 5;
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block.m = 1;
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block.num <<= COAP_OPT_BLOCK_SZX(*block_req) - block.szx;
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/* as the block number changes, we need to re-encode the block
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* option */
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coap_add_option(pdu, type, coap_encode_var_bytes(buf,
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(block.num << 4) | (block.m << 3) | block.szx), buf);
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{
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coap_opt_iterator_t oi;
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*block_req = coap_check_option(pdu, type, &oi);
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}
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}
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}
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return 1;
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}
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int
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coap_add_block(coap_pdu_t *pdu, unsigned int len, const unsigned char *data,
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unsigned int block_num, unsigned char block_szx) {
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size_t start;
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start = block_num << (block_szx + 4);
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if (len <= start)
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return 0;
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return coap_add_data(pdu,
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min(len - start, (unsigned int)(1 << (block_szx + 4))),
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data + start);
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}
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