contiki/examples/er-rest-example/resources/res-chunks.c
2014-05-15 20:29:04 +02:00

98 lines
3.8 KiB
C

/*
* Copyright (c) 2013, Institute for Pervasive Computing, ETH Zurich
* 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 Institute 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 INSTITUTE 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 INSTITUTE 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.
*
* This file is part of the Contiki operating system.
*/
/**
* \file
* Example resource
* \author
* Matthias Kovatsch <kovatsch@inf.ethz.ch>
*/
#include <string.h>
#include "rest-engine.h"
static void res_get_handler(void *request, void *response, uint8_t *buffer, uint16_t preferred_size, int32_t *offset);
/*
* For data larger than REST_MAX_CHUNK_SIZE (e.g., when stored in flash) resources must be aware of the buffer limitation
* and split their responses by themselves. To transfer the complete resource through a TCP stream or CoAP's blockwise transfer,
* the byte offset where to continue is provided to the handler as int32_t pointer.
* These chunk-wise resources must set the offset value to its new position or -1 of the end is reached.
* (The offset for CoAP's blockwise transfer can go up to 2'147'481'600 = ~2047 M for block size 2048 (reduced to 1024 in observe-03.)
*/
RESOURCE(res_chunks,
"title=\"Blockwise demo\";rt=\"Data\"",
res_get_handler,
NULL,
NULL,
NULL);
#define CHUNKS_TOTAL 2050
static void
res_get_handler(void *request, void *response, uint8_t *buffer, uint16_t preferred_size, int32_t *offset)
{
int32_t strpos = 0;
/* Check the offset for boundaries of the resource data. */
if(*offset >= CHUNKS_TOTAL) {
REST.set_response_status(response, REST.status.BAD_OPTION);
/* A block error message should not exceed the minimum block size (16). */
const char *error_msg = "BlockOutOfScope";
REST.set_response_payload(response, error_msg, strlen(error_msg));
return;
}
/* Generate data until reaching CHUNKS_TOTAL. */
while(strpos < preferred_size) {
strpos += snprintf((char *)buffer + strpos, preferred_size - strpos + 1, "|%ld|", *offset);
}
/* snprintf() does not adjust return value if truncated by size. */
if(strpos > preferred_size) {
strpos = preferred_size;
/* Truncate if above CHUNKS_TOTAL bytes. */
}
if(*offset + (int32_t)strpos > CHUNKS_TOTAL) {
strpos = CHUNKS_TOTAL - *offset;
}
REST.set_response_payload(response, buffer, strpos);
/* IMPORTANT for chunk-wise resources: Signal chunk awareness to REST engine. */
*offset += strpos;
/* Signal end of resource representation. */
if(*offset >= CHUNKS_TOTAL) {
*offset = -1;
}
}