mozzi_pgmspace.h

/*
 * mozzi_pgmspace.h
 *
 * This file is part of Mozzi.
 *
 * Copyright 2018-2024 Thomas Friedrichsmeier and the Mozzi Team
 *
 * Mozzi is licensed under the GNU Lesser General Public Licence (LGPL) Version 2.1 or later.
 *
 */
 
#ifndef MOZZI_PGMSPACE_H
#define MOZZI_PGMSPACE_H
 
/* Cross-platform wrapper around avr/pgmspace.h, i.e. macros and functions to 
* store data in and retrieve data from flash memory. */
 
#include "hardware_defines.h"
 
#if IS_ESP8266() || IS_ESP32() || IS_RP2040() || IS_RENESAS()
template<typename T> inline T FLASH_OR_RAM_READ(T* address) {
    return (T) (*address);
}
#define CONSTTABLE_STORAGE(X) const X
#else
#include <avr/pgmspace.h>
// work around missing std::is_const
template<typename T> inline bool mozzi_is_const_pointer(T*) { return false; }
template<typename T> inline bool mozzi_is_const_pointer(const T*) { return true; }
template<typename T> inline T mozzi_pgm_read_wrapper(const T* address) {
    static_assert(sizeof(T) == 1 || sizeof(T) == 2 || sizeof(T) == 4 || sizeof(T) == 8, "Data type not supported");
    switch (sizeof(T)) {
        case 1: return (T) pgm_read_byte_near(address);
        case 2: return (T) pgm_read_word_near(address);
        case 4: return (T) pgm_read_dword_near(address);
    }
    // case 8: AVR-libc does not provide a read function for this, so we combine two 32-bit reads. TODO: is this MSB/LSB safe?
    return (T) (pgm_read_dword_near(address) | (uint64_t) pgm_read_dword_near(((byte*) address) + 4) << 32);
}
template<> inline float mozzi_pgm_read_wrapper(const float* address) {
    return pgm_read_float_near(address);
}
template<> inline double mozzi_pgm_read_wrapper(const double* address) {
    static_assert(sizeof(uint64_t) == sizeof(double) || sizeof(float) == sizeof(double), "Reading double from pgmspace memory not supported on this architecture");
    if (sizeof(double) == sizeof(uint64_t)) {
        union u { uint64_t i; double d; };
        return u{mozzi_pgm_read_wrapper((uint64_t*) address)}.d;
    }
    return pgm_read_float_near(address);
}
template<typename T> inline T FLASH_OR_RAM_READ(T* address) {
    if(mozzi_is_const_pointer(address)) {
        return mozzi_pgm_read_wrapper(address);
    }
    return (T) *address;
}
#define CONSTTABLE_STORAGE(X) const X __attribute__((section(".progmem.data")))
#endif
 
#endif