Struct FlashBlockEsp 

pub struct FlashBlockEsp { /* private fields */ }

A device abstraction for type-safe persistent storage in flash memory.

FlashBlockEsp provides a generic flash-block storage system for ESP, allowing you to store any serde-compatible type in the device’s internal flash.

Use FlashBlockEsp::new_array to allocate one or more blocks. Block operations like load, save, and clear are provided by FlashBlock, so bring the trait into scope:

use device_envoy_esp::flash_block::FlashBlock as _;

Features

• Type safety: Hash-based type checking prevents reading data written under a different Rust type name. The hash is derived from the full type path (for example, app1::BootCounter). Trying to read a different type returns Ok(None). Structural changes (adding or removing fields) do not change the hash, but may cause deserialization to fail and return an error.
• Postcard serialization: A compact, no_std-friendly binary format.

Block allocation

Conceptually, flash is treated as an array of fixed-size erase blocks counted from the end of the configured region backward. Your code can split that array using destructuring assignment and hand individual blocks to subsystems that need persistent storage.

⚠️ Warning: ESP firmware and user data share the same flash device. Allocating too many blocks can overwrite your firmware.

Example

use device_envoy_esp::{Result, init_and_start, flash_block::{FlashBlockEsp, FlashBlock as _}};

#[derive(serde::Serialize, serde::Deserialize, Clone)]
struct WifiPersistedState {
    ssid: heapless::String<32>,
    password: heapless::String<64>,
    timezone_offset_minutes: i32,
}

init_and_start!(p);
let [mut wifi_persisted_state_flash_block, mut fields_flash_block] =
    FlashBlockEsp::new_array::<2>(p.FLASH)?;

let wifi_persisted_state = wifi_persisted_state_flash_block.load::<WifiPersistedState>()?;
if wifi_persisted_state.is_none() {
    let wifi_persisted_state = WifiPersistedState {
        ssid: heapless::String::new(),
        password: heapless::String::new(),
        timezone_offset_minutes: 0,
    };
    wifi_persisted_state_flash_block.save(&wifi_persisted_state)?;
}

fields_flash_block.clear()?;

Implementations

impl FlashBlockEsp

pub fn new_array<const N: usize>( flash: FLASH<'static>, ) -> Result<[FlashBlockEsp; N]>

Reserve N blocks in the default tail region.

Trait Implementations

impl Clone for FlashBlockEsp

fn clone(&self) -> FlashBlockEsp

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl FlashBlock for FlashBlockEsp

Available on target_os=none only.

type Error = Error

Error returned by block operations.

fn load<T>(&mut self) -> Result<Option<T>>

where T: Serialize + for<'de> Deserialize<'de>,

Load a typed value from this block.

fn save<T>(&mut self, value: &T) -> Result<()>

where T: Serialize + for<'de> Deserialize<'de>,

Save a typed value to this block.

fn clear(&mut self) -> Result<()>

Clear this block.

impl Copy for FlashBlockEsp