uhd/host/lib/property_tree.cpp

//
// Copyright 2011,2014-2016 Ettus Research
// Copyright 2018 Ettus Research, a National Instruments Company
// Copyright 2019 Ettus Research, a National Instruments Brand
//
// SPDX-License-Identifier: GPL-3.0-or-later
//

#include <uhd/property_tree.hpp>
#include <uhd/types/dict.hpp>
#include <memory>
#include <mutex>

using namespace uhd;

/***********************************************************************
 * Helper function to iterate through paths
 **********************************************************************/
#include <boost/tokenizer.hpp>
#define path_tokenizer(path) \
    boost::tokenizer<boost::char_separator<char>>(path, boost::char_separator<char>("/"))

/***********************************************************************
 * Property path implementation wrapper
 **********************************************************************/
fs_path::fs_path(void) : std::string() {}
fs_path::fs_path(const char* p) : std::string(p) {}
fs_path::fs_path(const std::string& p) : std::string(p) {}

std::string fs_path::leaf(void) const
{
    const size_t pos = this->rfind("/");
    if (pos == std::string::npos)
        return *this;
    return this->substr(pos + 1);
}

fs_path fs_path::branch_path(void) const
{
    const size_t pos = this->rfind("/");
    if (pos == std::string::npos)
        return *this;
    return fs_path(this->substr(0, pos));
}

fs_path uhd::operator/(const fs_path& lhs, const fs_path& rhs)
{
    // strip trailing slash on left-hand-side
    if (not lhs.empty() and *lhs.rbegin() == '/') {
        return fs_path(lhs.substr(0, lhs.size() - 1)) / rhs;
    }

    // strip leading slash on right-hand-side
    if (not rhs.empty() and *rhs.begin() == '/') {
        return lhs / fs_path(rhs.substr(1));
    }

    return fs_path(lhs + "/" + rhs);
}

fs_path uhd::operator/(const fs_path& lhs, size_t rhs)
{
    fs_path rhs_str = std::to_string(rhs);
    return lhs / rhs_str;
}

/***********************************************************************
 * Property tree implementation
 **********************************************************************/
class property_tree_impl : public uhd::property_tree
{
public:
    property_tree_impl(const fs_path& root = fs_path()) : _root(root)
    {
        _guts = std::make_shared<tree_guts_type>();
    }

    sptr subtree(const fs_path& path_) const override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        property_tree_impl* subtree = new property_tree_impl(path);
        subtree->_guts              = this->_guts; // copy the guts sptr
        return sptr(subtree);
    }

    void remove(const fs_path& path_) override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        node_type* parent = NULL;
        node_type* node   = &_guts->root;
        for (const std::string& name : path_tokenizer(path)) {
            if (not node->has_key(name))
                throw_path_not_found(path);
            parent = node;
            node   = &(*node)[name];
        }
        if (parent == NULL)
            throw uhd::runtime_error("Cannot uproot");
        parent->pop(fs_path(path.leaf()));
    }

    bool exists(const fs_path& path_) const override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        node_type* node = &_guts->root;
        for (const std::string& name : path_tokenizer(path)) {
            if (not node->has_key(name))
                return false;
            node = &(*node)[name];
        }
        return true;
    }

    std::vector<std::string> list(const fs_path& path_) const override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        node_type* node = &_guts->root;
        for (const std::string& name : path_tokenizer(path)) {
            if (not node->has_key(name))
                throw_path_not_found(path);
            node = &(*node)[name];
        }

        return node->keys();
    }

    std::shared_ptr<void> _pop(const fs_path& path_) override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        node_type* parent = NULL;
        node_type* node   = &_guts->root;
        for (const std::string& name : path_tokenizer(path)) {
            if (not node->has_key(name))
                throw_path_not_found(path);
            parent = node;
            node   = &(*node)[name];
        }

        if (node->prop.get() == NULL)
            throw uhd::runtime_error("Cannot access! Property uninitialized at: " + path);
        if (parent == NULL)
            throw uhd::runtime_error("Cannot pop");
        auto prop = node->prop;
        parent->pop(fs_path(path.leaf()));
        return prop;
    }

    void _create(const fs_path& path_, const std::shared_ptr<void>& prop) override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        node_type* node = &_guts->root;
        for (const std::string& name : path_tokenizer(path)) {
            if (not node->has_key(name))
                (*node)[name] = node_type();
            node = &(*node)[name];
        }
        if (node->prop.get() != NULL)
            throw uhd::runtime_error(
                "Cannot create! Property already exists at: " + path);
        node->prop           = prop;
    }

    std::shared_ptr<void>& _access(const fs_path& path_) const override
    {
        const fs_path path = _root / path_;
        std::lock_guard<std::mutex> lock(_guts->mutex);

        node_type* node = &_guts->root;
        for (const std::string& name : path_tokenizer(path)) {
            if (not node->has_key(name))
                throw_path_not_found(path);
            node = &(*node)[name];
        }
        if (node->prop.get() == NULL)
            throw uhd::runtime_error("Cannot access! Property uninitialized at: " + path);
        return node->prop;
    }

private:
    void throw_path_not_found(const fs_path& path) const
    {
        throw uhd::lookup_error("Path not found in tree: " + path);
    }

    // basic structural node element
    struct node_type : uhd::dict<std::string, node_type>
    {
        std::shared_ptr<void> prop;
    };

    // tree guts which may be referenced in a subtree
    struct tree_guts_type
    {
        node_type root;
        std::mutex mutex;
    };

    // members, the tree and root prefix
    std::shared_ptr<tree_guts_type> _guts;
    const fs_path _root;
};

property_tree::~property_tree(void)
{
    /* NOP */
}

/***********************************************************************
 * Property tree factory
 **********************************************************************/
uhd::property_tree::sptr uhd::property_tree::make(void)
{
    return sptr(new property_tree_impl());
}