oma-lwm2m: Add JSON writer

apps/oma-lwm2m/Makefile.oma-lwm2m

@@ -1,5 +1,13 @@
-oma-lwm2m_src = lwm2m-object.c lwm2m-engine.c \
+oma-lwm2m_src = \
-	lwm2m-device.c lwm2m-server.c lwm2m-security.c \
+  lwm2m-object.c \
-	oma-tlv.c oma-tlv-reader.c oma-tlv-writer.c \
+  lwm2m-engine.c \
-	lwm2m-plain-text.c
+  lwm2m-device.c \
+  lwm2m-server.c \
+  lwm2m-security.c \
+  oma-tlv.c \
+  oma-tlv-reader.c \
+  oma-tlv-writer.c \
+  lwm2m-plain-text.c \
+  lwm2m-json.c \
+  #
 CFLAGS += -DHAVE_OMA_LWM2M=1

apps/oma-lwm2m/lwm2m-engine.c

@@ -46,6 +46,7 @@
 #include "lwm2m-object.h"
 #include "lwm2m-device.h"
 #include "lwm2m-plain-text.h"
+#include "lwm2m-json.h"
 #include "rest-engine.h"
 #include "er-coap-constants.h"
 #include "er-coap-engine.h"
@@ -727,6 +728,10 @@ lwm2m_engine_select_writer(lwm2m_context_t *context, unsigned int accept)
     case TEXT_PLAIN:
       context->writer = &lwm2m_plain_text_writer;
       break;
+    case LWM2M_JSON:
+    case APPLICATION_JSON:
+      context->writer = &lwm2m_json_writer;
+      break;
     default:
       PRINTF("Unknown Accept type %u, using LWM2M plain text\n", accept);
       context->writer = &lwm2m_plain_text_writer;

apps/oma-lwm2m/lwm2m-json.c

@@ -0,0 +1,162 @@
+/*
+ * Copyright (c) 2016, Eistec AB.
+ * 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 copyright holder 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 COPYRIGHT HOLDER 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
+ * COPYRIGHT HOLDER 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.
+ */
+
+/**
+ * \addtogroup oma-lwm2m
+ * @{
+ */
+
+/**
+ * \file
+ *         Implementation of the Contiki OMA LWM2M JSON writer
+ * \author
+ *         Joakim Nohlgård <joakim.nohlgard@eistec.se>
+ */
+
+#include "lwm2m-object.h"
+#include "lwm2m-json.h"
+#include "lwm2m-plain-text.h"
+#include <stdio.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <inttypes.h>
+
+#define DEBUG 0
+#if DEBUG
+#define PRINTF(...) printf(__VA_ARGS__)
+#else
+#define PRINTF(...)
+#endif
+
+/*---------------------------------------------------------------------------*/
+static size_t
+write_boolean(const lwm2m_context_t *ctx, uint8_t *outbuf, size_t outlen,
+              int value)
+{
+  int len = snprintf((char *)outbuf, outlen, "{\"e\":[{\"n\":\"%u\",\"bv\":%s}]}\n", ctx->resource_id, value ? "true" : "false");
+  if((len < 0) || (len >= outlen)) {
+    return 0;
+  }
+  return len;
+}
+/*---------------------------------------------------------------------------*/
+static size_t
+write_int(const lwm2m_context_t *ctx, uint8_t *outbuf, size_t outlen,
+          int32_t value)
+{
+  int len = snprintf((char *)outbuf, outlen, "{\"e\":[{\"n\":\"%u\",\"v\":%" PRId32 "}]}\n", ctx->resource_id, value);
+  if((len < 0) || (len >= outlen)) {
+    return 0;
+  }
+  return len;
+}
+/*---------------------------------------------------------------------------*/
+static size_t
+write_float32fix(const lwm2m_context_t *ctx, uint8_t *outbuf, size_t outlen,
+                 int32_t value, int bits)
+{
+  size_t len = 0;
+  int res;
+  res = snprintf((char *)outbuf, outlen, "{\"e\":[{\"n\":\"%u\",\"v\":", ctx->resource_id);
+  if(res <= 0 || res >= outlen) {
+    return 0;
+  }
+  len += res;
+  outlen -= res;
+  res = lwm2m_plain_text_write_float32fix(&outbuf[len], outlen, value, bits);
+  if((res <= 0) || (res >= outlen)) {
+    return 0;
+  }
+  len += res;
+  outlen -= res;
+  res = snprintf((char *)&outbuf[len], outlen, "}]}\n");
+  if((res <= 0) || (res >= outlen)) {
+    return 0;
+  }
+  len += res;
+  return len;
+}
+/*---------------------------------------------------------------------------*/
+static size_t
+write_string(const lwm2m_context_t *ctx, uint8_t *outbuf, size_t outlen,
+             const char *value, size_t stringlen)
+{
+  size_t i;
+  size_t len = 0;
+  int res;
+  PRINTF("{\"e\":[{\"n\":\"%u\",\"sv\":\"", ctx->resource_id);
+  res = snprintf((char *)outbuf, outlen, "{\"e\":[{\"n\":\"%u\",\"sv\":\"", ctx->resource_id);
+  if(res < 0 || res >= outlen) {
+    return 0;
+  }
+  len += res;
+  for (i = 0; i < stringlen && len < outlen; ++i) {
+    /* Escape special characters */
+    /* TODO: Handle UTF-8 strings */
+    if(value[i] < '\x20') {
+      PRINTF("\\x%x", value[i]);
+      res = snprintf((char *)&outbuf[len], outlen - len, "\\x%x", value[i]);
+      if((res < 0) || (res >= (outlen - len))) {
+        return 0;
+      }
+      len += res;
+      continue;
+    } else if(value[i] == '"' || value[i] == '\\') {
+      PRINTF("\\");
+      outbuf[len] = '\\';
+      ++len;
+      if(len >= outlen) {
+        return 0;
+      }
+    }
+    PRINTF("%c", value[i]);
+    outbuf[len] = value[i];
+    ++len;
+    if(len >= outlen) {
+      return 0;
+    }
+  }
+  PRINTF("\"}]}\n");
+  res = snprintf((char *)&outbuf[len], outlen - len, "\"}]}\n");
+  if((res < 0) || (res >= (outlen - len))) {
+    return 0;
+  }
+  len += res;
+  return len;
+}
+/*---------------------------------------------------------------------------*/
+const lwm2m_writer_t lwm2m_json_writer = {
+  write_int,
+  write_string,
+  write_float32fix,
+  write_boolean
+};
+/*---------------------------------------------------------------------------*/
+/** @} */

apps/oma-lwm2m/lwm2m-json.h

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2016, Eistec AB.
+ * 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 copyright holder 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 COPYRIGHT HOLDER 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
+ * COPYRIGHT HOLDER 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.
+ */
+
+/**
+ * \addtogroup oma-lwm2m
+ * @{
+ */
+
+/**
+ * \file
+ *         Header file for the Contiki OMA LWM2M JSON writer
+ * \author
+ *         Joakim Nohlgård <joakim.nohlgard@eistec.se>
+ */
+
+#ifndef LWM2M_JSON_H_
+#define LWM2M_JSON_H_
+
+#include "lwm2m-object.h"
+
+extern const lwm2m_writer_t lwm2m_json_writer;
+
+#endif /* LWM2M_JSON_H_ */
+/** @} */