ardupilot/libraries/AP_Common/AP_Param.h

// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
//
// This is free software; you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License as published by the
// Free Software Foundation; either version 2.1 of the License, or (at
// your option) any later version.
//

/// @file	AP_Param.h
/// @brief	A system for managing and storing variables that are of
///			general interest to the system.

#ifndef AP_PARAM_H
#define AP_PARAM_H
#include <stddef.h>
#include <string.h>
#include <stdint.h>

#include <avr/pgmspace.h>
#include <avr/eeprom.h>
#include <AP_Math.h>

#define AP_MAX_NAME_SIZE 15

// a varient of offsetof() to work around C++ restrictions.
// this can only be used when the offset of a variable in a object
// is constant and known at compile time
#define VAROFFSET(type, element) (((uintptr_t)(&((const type *)1)->element))-1)

enum ap_var_type {
    AP_PARAM_NONE    = 0,
    AP_PARAM_INT8,
    AP_PARAM_INT16,
    AP_PARAM_INT32,
    AP_PARAM_FLOAT,
    AP_PARAM_VECTOR3F,
    AP_PARAM_VECTOR6F,
    AP_PARAM_MATRIX3F,
    AP_PARAM_GROUP
};

/// Base class for variables.
///
/// Provides naming and lookup services for variables.
///
class AP_Param
{
public:
    /// EEPROM header
    ///
    /// This structure is placed at the head of the EEPROM to indicate
    /// that the ROM is formatted for AP_Param.
    ///
    struct EEPROM_header {
        uint16_t    magic;
        uint8_t     revision;
        uint8_t     spare;
    };

    /// This header is prepended to a variable stored in EEPROM.
    struct Param_header {
        uint16_t    type:4;
        uint16_t    key:9;
        uint16_t	group_element:3;
    };

    // the Info and GroupInfo structures are passed by the main
    // program in setup() to give information on how variables are
    // named and their location in memory
    struct GroupInfo {
        uint8_t type; // AP_PARAM_*
        const char name[AP_MAX_NAME_SIZE];
        uintptr_t offset; // offset within the object
    };
    struct Info {
        uint8_t type; // AP_PARAM_*
        const char name[AP_MAX_NAME_SIZE];
        uint16_t key; // k_param_*
        void *ptr;    // pointer to the variable in memory
        const struct GroupInfo *group_info;
    };

    // every AP_Param type has a vtype which tells its type. This is
    // used to make the initialisation of var_info[] less error prone
    static const ap_var_type vtype = AP_PARAM_NONE;

    // called once at startup to setup the _var_info[] table. This
    // will also check the EEPROM header and re-initialise it if the
    // wrong version is found
    static bool setup(const struct Info *info, uint16_t num_vars);

    /// Copy the variable's name, prefixed by any containing group name, to a buffer.
    ///
    /// If the variable has no name, the buffer will contain an empty string.
    ///
    /// Note that if the combination of names is larger than the buffer, the
    /// result in the buffer will be truncated.
    ///
    /// @param	buffer			The destination buffer
    /// @param	bufferSize		Total size of the destination buffer.
    ///
    void copy_name(char *buffer, size_t bufferSize);

    /// Find a variable by name.
    ///
    /// If the variable has no name, it cannot be found by this interface.
    ///
    /// @param  name            The full name of the variable to be found.
    /// @return                 A pointer to the variable, or NULL if
    ///                         it does not exist.
    ///
    static AP_Param *find(const char *name);

    /// Save the current value of the variable to EEPROM.
    ///
    /// @return                True if the variable was saved successfully.
    ///
    bool save(void);

    /// Load the variable from EEPROM.
    ///
    /// @return                True if the variable was loaded successfully.
    ///
    bool load(void);

    /// Load all variables from EEPROM
    ///
    /// This function performs a best-efforts attempt to load all
    /// of the variables from EEPROM.  If some fail to load, their
    /// values will remain as they are.
    ///
    /// @return                False if any variable failed to load
    ///
    static bool load_all(void);

    /// Erase all variables in EEPROM.
    ///
    static void erase_all(void);


private:
    const struct Info *find_var_info(uint8_t *group_element);
    static const struct Info *find_by_header(struct Param_header phdr, void **ptr);
    static void write_sentinal(uint16_t ofs);
    bool scan(const struct Param_header *phdr, uint16_t *pofs);
    static const uint8_t type_size(enum ap_var_type type);
    static void eeprom_write_check(const void *ptr, uint16_t ofs, uint8_t size);

    static uint16_t _num_vars;
    static const struct Info *_var_info;

    static const uint16_t k_EEPROM_size = 4096;    ///< XXX avr-libc doesn't consistently export this

    // values filled into the EEPROM header
    static const uint16_t   k_EEPROM_magic      = 0x5041;   ///< "AP"
    static const uint16_t   k_EEPROM_revision   = 3;        ///< current format revision
};

/// Template class for scalar variables.
///
/// Objects of this type have a value, and can be treated in many ways as though they
/// were the value.
///
/// @tparam T			The scalar type of the variable
/// @tparam PT			The AP_PARAM_* type
///
template<typename T, ap_var_type PT>
class AP_ParamT : public AP_Param
{
public:
    /// Constructor for scalar variable.
    ///
    /// Initialises a stand-alone variable with optional initial value.
    ///
    /// @param  default_value   Value the variable should have at startup.
    ///
    AP_ParamT<T,PT> (const T initial_value = 0) :
        AP_Param(),
        _value(initial_value)
    {
    }

    static const ap_var_type vtype = PT;

    /// Value getter
    ///
    T get(void) const {
        return _value;
    }

    /// Value setter
    ///
    void set(T v) {
        _value = v;
    }

    /// Combined set and save
    ///
    bool set_and_save(T v) {
        set(v);
        return save();
    }

    /// Conversion to T returns a reference to the value.
    ///
    /// This allows the class to be used in many situations where the value would be legal.
    ///
    operator T &() {
        return _value;
    }

    /// Copy assignment from self does nothing.
    ///
    AP_ParamT<T,PT>& operator=(AP_ParamT<T,PT>& v) {
        return v;
    }

    /// Copy assignment from T is equivalent to ::set.
    ///
    AP_ParamT<T,PT>& operator=(T v) {
        _value = v;
        return *this;
    }

    /// AP_ParamT types can implement AP_Param::cast_to_float
    ///
    float cast_to_float(void) {
        return (float)_value;
    }

protected:
    T _value;
};


/// Template class for non-scalar variables.
///
/// Objects of this type have a value, and can be treated in many ways as though they
/// were the value.
///
/// @tparam T			The scalar type of the variable
/// @tparam PT			AP_PARAM_* type
///
template<typename T, ap_var_type PT>
class AP_ParamV : public AP_Param
{
public:
    static const ap_var_type vtype = PT;

    /// Value getter
    ///
    T get(void) const {
        return _value;
    }

    /// Value setter
    ///
    void set(T v) {
        _value = v;
    }

    /// Combined set and save
    ///
    bool set_and_save(T v) {
        set(v);
        return save();
    }

    /// Conversion to T returns a reference to the value.
    ///
    /// This allows the class to be used in many situations where the value would be legal.
    ///
    operator T &() {
        return _value;
    }

    /// Copy assignment from self does nothing.
    ///
    AP_ParamT<T,PT>& operator=(AP_ParamT<T,PT>& v) {
        return v;
    }

    /// Copy assignment from T is equivalent to ::set.
    ///
    AP_ParamT<T,PT>& operator=(T v) {
        _value = v;
        return *this;
    }

protected:
    T _value;
};


/// Template class for array variables.
///
/// Objects created using this template behave like arrays of the type T,
/// but are stored like single variables.
///
/// @tparam T           The scalar type of the variable
/// @tparam N           number of elements
/// @tparam PT          the AP_PARAM_* type
///
template<typename T, uint8_t N, ap_var_type PT>
class AP_ParamA : public AP_Param
{
public:
    static const ap_var_type vtype = PT;

    /// Array operator accesses members.
    ///
    /// @note It would be nice to range-check i here, but then what would we return?
    ///
    T &operator [](uint8_t i) {
        return _value[i];
    }

    /// Value getter
    ///
    /// @note   Returns zero for index values out of range.
    ///
    T get(uint8_t i) const {
        if (i < N) {
            return _value[i];
        } else {
            return (T)0;
        }
    }

    /// Value setter
    ///
    /// @note   Attempts to set an index out of range are discarded.
    ///
    void set(uint8_t i, T v) {
        if (i < N) {
            _value[i] = v;
        }
    }

    /// Copy assignment from self does nothing.
    ///
    AP_ParamA<T,N,PT>& operator=(AP_ParamA<T,N,PT>& v) {
        return v;
    }

protected:
    T _value[N];
};



/// Convenience macro for defining instances of the AP_ParamT template.
///
#define AP_PARAMDEF(_t, _n, _pt)   typedef AP_ParamT<_t, _pt> AP_##_n;
AP_PARAMDEF(float, Float, AP_PARAM_FLOAT);    // defines AP_Float
AP_PARAMDEF(int8_t, Int8, AP_PARAM_INT8);     // defines AP_Int8
AP_PARAMDEF(int16_t, Int16, AP_PARAM_INT16);  // defines AP_Int16
AP_PARAMDEF(int32_t, Int32, AP_PARAM_INT32);  // defines AP_Int32

#define AP_PARAMDEFV(_t, _n, _pt)   typedef AP_ParamV<_t, _pt> AP_##_n;
AP_PARAMDEFV(Matrix3f, Matrix3f, AP_PARAM_MATRIX3F);
AP_PARAMDEFV(Vector3f, Vector3f, AP_PARAM_VECTOR3F);

#define AP_PARAMDEFA(_t, _n, _size, _pt)   typedef AP_ParamA<_t, _size, _pt> AP_##_n;
AP_PARAMDEFA(float, Vector6f, 6, AP_PARAM_VECTOR6F);

/// Rely on built in casting for other variable types
/// to minimize template creation and save memory
#define AP_Uint8    AP_Int8
#define AP_Uint16   AP_Int16
#define AP_Uint32   AP_Int32
#define AP_Bool     AP_Int8

#endif // AP_PARAM_H