Add versioned persistent configuration protocol

configuration_storage.h

@@ -0,0 +1,63 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+constexpr size_t CONFIGURATION_STORAGE_COPY_COUNT = 2;
+constexpr size_t CONFIGURATION_STORAGE_MAX_PAYLOAD_SIZE = 512;
+constexpr size_t CONFIGURATION_STORAGE_RECORD_HEADER_SIZE = 24;
+constexpr size_t CONFIGURATION_STORAGE_MAX_PAGE_SIZE = 256;
+constexpr size_t CONFIGURATION_STORAGE_MAX_RECORD_SIZE =
+    CONFIGURATION_STORAGE_RECORD_HEADER_SIZE +
+    CONFIGURATION_STORAGE_MAX_PAYLOAD_SIZE;
+constexpr size_t CONFIGURATION_STORAGE_MAX_PROGRAM_SIZE =
+    ((CONFIGURATION_STORAGE_MAX_RECORD_SIZE +
+      CONFIGURATION_STORAGE_MAX_PAGE_SIZE - 1) /
+     CONFIGURATION_STORAGE_MAX_PAGE_SIZE) *
+    CONFIGURATION_STORAGE_MAX_PAGE_SIZE;
+
+uint32_t configuration_crc32(const uint8_t* data, size_t size);
+
+enum class ConfigurationStorageResult : uint8_t {
+    kOk,
+    kUnchanged,
+    kInvalidArgument,
+    kIoError,
+};
+
+struct ConfigurationStorageIo {
+    void* context = nullptr;
+    size_t sector_size = 0;
+    size_t page_size = 0;
+    bool (*read)(void* context, uint8_t copy, size_t offset,
+                 uint8_t* output, size_t size) = nullptr;
+    bool (*erase)(void* context, uint8_t copy) = nullptr;
+    bool (*program)(void* context, uint8_t copy, size_t offset,
+                    const uint8_t* data, size_t size) = nullptr;
+};
+
+struct ConfigurationStorageSnapshot {
+    bool valid = false;
+    uint16_t schema_version = 0;
+    uint16_t payload_size = 0;
+    uint32_t generation = 0;
+    uint32_t payload_crc = 0;
+    uint8_t payload[CONFIGURATION_STORAGE_MAX_PAYLOAD_SIZE]{};
+};
+
+class ConfigurationStorage {
+public:
+    bool initialize(const ConfigurationStorageIo& io);
+    const ConfigurationStorageSnapshot& snapshot() const;
+    ConfigurationStorageResult commit(uint16_t schema_version,
+                                      const uint8_t* payload,
+                                      size_t payload_size);
+
+private:
+    bool read_copy(uint8_t copy, ConfigurationStorageSnapshot* output) const;
+
+    ConfigurationStorageIo io_{};
+    ConfigurationStorageSnapshot snapshot_{};
+    uint8_t active_copy_ = 0;
+    bool initialized_ = false;
+};