Parsing bytecode from flash memory

Both arduino / esp idf can place read only data in flash ( at least 4MiB even on the cheapest esp8266 devboards ) arduino with PROGMEM and espidf with ICACHE_FLASH_ATTR attributes

nb: that's only for parser , i don' t know implication with memory at runtime later

eg

unsigned char PROGMEM app_wasm[] = {
  0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x94, 0x01, 0x14,

but when reading those addresses some special function must be used because data is re mapped to iram via a spi read aligned to 4 bytes on esp*.

so a function like Read_u8 https://github.com/wasm3/wasm3-arduino/blob/bc181e11fba387119e306f1b0fcc6ca52aa96bd7/src/m3_core.c#L313 could be in fact written with a *_P function

M3Result  Read_u8  (u8 * o_value, bytes_t  * io_bytes, cbytes_t i_end)
{
    const u8 * ptr = * io_bytes;
    ptr += sizeof (u8);
    if (ptr < i_end)
    {
        //* o_value = * ptr;
        memcpy_P(o_value, *io_bytes, sizeof(u8));

        * io_bytes = ptr;

        return m3Err_none;
    }
    else return m3Err_wasmUnderrun;
}

( tested on esp8266 works fine )

ref : https://bbs.espressif.com/viewtopic.php?t=1183 https://arduino-esp8266.readthedocs.io/en/latest/PROGMEM.html