coap_resource.cc

// Copyright 2024-2025 The Aerospace Corporation.
// This file is a part of SatCat5, licensed under CERN-OHL-W v2 or later.
 
#include <cstring>
#include <satcat5/coap_reader.h>
#include <satcat5/coap_resource.h>
#include <satcat5/coap_writer.h>
#include <satcat5/log.h>
 
using satcat5::coap::Resource;
using satcat5::coap::ResourceEcho;
using satcat5::coap::ResourceLog;
using satcat5::coap::ResourceServer;
namespace log = satcat5::log;
 
Resource::Resource(ResourceServer* server, const char* uri_path)
    : m_uri_path(normalize_uri(uri_path))
    , m_server(server)
    , m_next(nullptr)
{
    if (m_server) m_server->add_resource(this);
}
 
#if SATCAT5_ALLOW_DELETION
Resource::~Resource() {
    if (m_server) m_server->remove_resource(this);
}
#endif
 
bool Resource::operator==(const Resource& other) const {
    // Uri-Path must match, be null-terminated, and less than max length
    // Some of this validation should happen when Uri-Path is first provided,
    // set m_uri_path during the add_resource() call in the Server? Would also
    // allow to drop leading '/', which is a common convention
    return strncmp(m_uri_path, other.m_uri_path,
        SATCAT5_COAP_MAX_URI_PATH_LEN) == 0 &&
        memchr(m_uri_path, '\0', SATCAT5_COAP_MAX_URI_PATH_LEN + 1) &&
        memchr(other.m_uri_path, '\0', SATCAT5_COAP_MAX_URI_PATH_LEN + 1);
}
 
satcat5::ip::Dispatch* Resource::ip() const
    { return m_server->ip(); }
satcat5::udp::Dispatch* Resource::udp() const
    { return m_server->udp(); }
 
bool ResourceEcho::request_get(Connection* obj, Reader* msg) {
    // Return 2.05 Content with the payload copied
    Writer reply(obj->open_response());
    if (!reply.ready()) { return false; }
    bool ok = reply.write_header(CODE_CONTENT, obj);
    if (ok && msg->format()) {
        u16 format = msg->format().value_or(FORMAT_BYTES);
        ok = reply.write_option(OPTION_FORMAT, format);
    }
    satcat5::io::Readable* src = msg->read_data();
    satcat5::io::Writeable* dst = reply.write_data();
    if (!ok || !src || !dst) { return false; }
    return src->copy_and_finalize(dst, io::CopyMode::ALWAYS);
}
 
bool ResourceLog::request_post(Connection* obj, Reader* msg) {
    // Validate Content-Format
    if (msg->format() && msg->format().value() != FORMAT_TEXT) {
        return obj->error_response(CODE_BAD_FORMAT);
    }
 
    // Write a log entry with a useful prefix, source IP would be better?
    satcat5::io::ArrayWriteStatic<SATCAT5_COAP_BUFFSIZE> log_str;
    satcat5::io::Readable* src = nullptr;
    if (!(src = msg->read_data()) || !src->get_read_ready()) {
        return obj->error_response(CODE_BAD_REQUEST, "Missing message");
    }
    src->copy_to(&log_str);
    log_str.write_u8(0); // Ensure null termination
    log::Log(m_priority, m_uri_path).write(": ")
        .write((const char*) log_str.buffer());
 
    // Return 2.01 Created
    Writer reply(obj->open_response());
    if (!reply.ready()) { return false; }
    bool ok = reply.write_header(CODE_CREATED, obj);
    return ok && reply.write_finalize();
}
 
void ResourceServer::coap_request(Connection* obj, Reader* msg) {
    // Look up the parsed Uri-Path against the server's registered resources
    ResourceNull target_resource(msg->uri_path().value_or("")); // Empty is valid
    Resource* matched_resource = nullptr;
    Resource* resource = m_resources.head();
    while (resource) {
        if (*resource == target_resource) {
            matched_resource = resource; break;
        }
        resource = m_resources.next(resource);
    }
 
    // Return an error if no resources matched
    if (!matched_resource) {
        obj->error_response(CODE_NOT_FOUND, "Unrecognized Uri-Path");
        return;
    }
 
    // The found resource may generate a response, sent as a piggybacked reply
    bool ok;
    if (msg->code() == CODE_GET) {
        ok = matched_resource->request_get(obj, msg);
    } else if (msg->code() == CODE_PUT) {
        ok = matched_resource->request_put(obj, msg);
    } else if (msg->code() == CODE_POST) {
        ok = matched_resource->request_post(obj, msg);
    } else if (msg->code() == CODE_DELETE) {
        ok = matched_resource->request_delete(obj, msg);
    } else { // Reject per Section 5.8
        ok = obj->error_response(CODE_BAD_METHOD);
    }
 
    // Send 5.00 SERVER_ERROR if the Resource failed to generate a response
    if (!ok) {
        obj->error_response(CODE_SERVER_ERROR); // GCOVR_EXCL_LINE
    }
}