nanocoap_link_format: add helper function to parse link format

sys/Makefile.dep

@@ -703,6 +703,10 @@ ifneq (,$(filter nanocoap_cache,$(USEMODULE)))
   USEMODULE += hashes
 endif
 
+ifneq (,$(filter nanocoap_link_format,$(USEMODULE)))
+  USEMODULE += fmt
+endif
+
 ifneq (,$(filter nanocoap_vfs,$(USEMODULE)))
   USEMODULE += nanocoap_sock
   USEMODULE += vfs

sys/include/net/nanocoap/link_format.h

@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2022 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     net_nanosock
+ * @brief       NanoCoAP Link Format helper functions
+ *
+ * @{
+ *
+ * @file
+ * @brief       NanoCoAP Link Format ([RFC 6690](https://www.rfc-editor.org/rfc/rfc6690.html))
+ *              helper functions
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ */
+#ifndef NET_NANOCOAP_LINK_FORMAT_H
+#define NET_NANOCOAP_LINK_FORMAT_H
+
+#include "net/nanocoap_sock.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Callback function called for each resource on the directory
+ *
+ * @param[in]   entry   Resource entry from the server
+ * @param[in]   ctx     Optional function context
+ *
+ * @returns     0 on success
+ * @returns     <0 on error
+ */
+typedef int (*coap_link_format_handler_t)(char *entry, void *ctx);
+
+/**
+ * @brief   Downloads the resource behind @p path via blockwise GET
+ *
+ * @param[in]   sock    Connection to the server
+ * @param[in]   path    path of the resource
+ * @param[in]   cb      Callback to execute for each resource entry
+ * @param[in]   arg     Optional callback argument
+ *
+ * @returns     0 on success
+ * @returns     <0 on error
+ */
+int nanocoap_link_format_get(nanocoap_sock_t *sock, const char *path,
+                             coap_link_format_handler_t cb, void *arg);
+
+/**
+ * @brief   Downloads the resource behind @p url via blockwise GET
+ *
+ * @param[in]   url     URL to the resource
+ * @param[in]   cb      Callback to execute for each resource entry
+ * @param[in]   arg     Optional callback argument
+ *
+ * @returns     0 on success
+ * @returns     <0 on error
+ */
+int nanocoap_link_format_get_url(const char *url,
+                                 coap_link_format_handler_t cb, void *arg);
+
+#ifdef __cplusplus
+}
+#endif
+#endif /* NET_NANOCOAP_LINK_FORMAT_H */
+/** @} */

sys/net/application_layer/nanocoap/link_format.c

@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2022 ML!PA Consulting GmbH
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     net_nanocoap
+ * @{
+ *
+ * @file
+ * @brief       NanoCoAP Link Format parser
+ *
+ * @author      Benjamin Valentin <benjamin.valentin@ml-pa.com>
+ *
+ * @}
+ */
+
+#include "fmt.h"
+#include "net/nanocoap/link_format.h"
+#include "net/nanocoap_sock.h"
+#include "net/sock/util.h"
+
+struct dir_list_ctx {
+    char *buf;
+    char *cur;
+    char *end;
+    coap_link_format_handler_t cb;
+    void *ctx;
+    char esc_buf[2];
+    uint8_t esc_idx;
+};
+
+static int _dirlist_cb(void *arg, size_t offset, uint8_t *buf, size_t len, int more)
+{
+    (void)offset;
+
+    struct dir_list_ctx *ctx = arg;
+
+    char *end = (char *)buf + len;
+    for (char *c = (char *)buf; c != end; ++c) {
+
+        /* start of escape sequence */
+        if (*c == '%') {
+            ctx->esc_idx = 1;
+            continue;
+        }
+        if (ctx->esc_idx) {
+            /* fill escape buffer */
+            ctx->esc_buf[ctx->esc_idx - 1] = *c;
+            if (++ctx->esc_idx == 3) {
+                ctx->esc_idx = 0;
+                *c = scn_u32_hex(ctx->esc_buf, 2);
+            } else {
+                continue;
+            }
+        }
+
+        if (*c == ',' || ctx->cur == ctx->end) {
+            int res;
+            *ctx->cur = 0;
+            res = ctx->cb(ctx->buf, ctx->ctx);
+            ctx->cur = ctx->buf;
+            if (res < 0) {
+                return res;
+            }
+        } else {
+            *ctx->cur++ = *c;
+        }
+    }
+
+    if (!more) {
+        *ctx->cur = 0;
+        return ctx->cb(ctx->buf, ctx->ctx);
+    }
+
+    return 0;
+}
+
+int nanocoap_link_format_get(nanocoap_sock_t *sock, const char *path,
+                             coap_link_format_handler_t cb, void *arg)
+{
+    char buffer[CONFIG_NANOCOAP_QS_MAX];
+    struct dir_list_ctx ctx = {
+        .buf = buffer,
+        .end = buffer + sizeof(buffer),
+        .cur = buffer,
+        .cb = cb,
+        .ctx = arg,
+    };
+    return nanocoap_sock_get_blockwise(sock, path, CONFIG_NANOCOAP_BLOCKSIZE_DEFAULT,
+                                       _dirlist_cb, &ctx);
+}
+
+int nanocoap_link_format_get_url(const char *url, coap_link_format_handler_t cb, void *arg)
+{
+    nanocoap_sock_t sock;
+    int res = nanocoap_sock_url_connect(url, &sock);
+    if (res) {
+        return res;
+    }
+
+    res = nanocoap_link_format_get(&sock, sock_urlpath(url), cb, arg);
+    nanocoap_sock_close(&sock);
+
+    return res;
+}