// Current block management in REE FS
#define BLOCK_SHIFT    12  // 4KB blocks
#define BLOCK_SIZE     (1 << BLOCK_SHIFT)

// Potential compression integration point
static TEE_Result out_of_place_write(struct tee_fs_fd *fdp, size_t pos,
                                     const void *buf_core, const void *buf_user,
                                     size_t len)
{
    uint8_t *block = get_tmp_block();  // 4KB buffer for compression
    
    // Current: Direct block writes
    // Potential: Compress block before encryption
    // if (compression_enabled) {
    //     compressed_size = compress_block(block, compressed_block);
    //     if (compressed_size < BLOCK_SIZE) {
    //         // Use compressed version with size metadata
    //     }
    // }
    
    res = tee_fs_htree_write_block(&fdp->ht, start_block_num, block);
}

// Current directory entry structure
struct dirfile_entry {
    TEE_UUID uuid;                              // 16 bytes
    uint8_t oid[TEE_OBJECT_ID_MAX_LEN];        // 64 bytes (often sparse)
    uint32_t oidlen;                           // 4 bytes
    uint8_t hash[TEE_FS_HTREE_HASH_SIZE];     // 32 bytes
    uint32_t file_number;                       // 4 bytes
    // Total: 120 bytes, potential for compression
};

// Object IDs often have patterns that could be compressed
// UUIDs have structured format suitable for compression

// Proper order: Compress -> Encrypt -> Store
// Current encryption in tee_fs_crypt_block:
TEE_Result tee_fs_crypt_block(const TEE_UUID *uuid, uint8_t *out,
                             const uint8_t *in, size_t size,
                             uint16_t blk_idx, const uint8_t *encrypted_fek,
                             TEE_OperationMode mode)
{
    // Decompression would occur after decryption:
    // Decrypt -> Decompress -> Return to user
    
    // Compression would occur before encryption:
    // User data -> Compress -> Encrypt -> Store
}

// Current hash tree node structure
struct tee_fs_htree_node_image {
    uint8_t hash[TEE_FS_HTREE_HASH_SIZE];  // SHA-256 hash
    uint8_t iv[TEE_FS_HTREE_IV_SIZE];
    uint8_t tag[TEE_FS_HTREE_TAG_SIZE];
    uint16_t flags;
};

// Block-level deduplication potential:
// 1. Calculate SHA-256 of block content
// 2. Check if hash exists in dedup table
// 3. If exists, reference existing block
// 4. If not, store new block and add to table

// Theoretical content-addressed block storage
struct content_block {
    uint8_t content_hash[TEE_SHA256_HASH_SIZE];  // Block identifier
    uint32_t ref_count;                          // Reference counter
    uint32_t physical_address;                   // Storage location
    uint16_t actual_size;                        // Compressed size
    uint16_t flags;                              // Compression/encryption flags
};

// Block lookup by content hash
static TEE_Result find_content_block(const uint8_t *content_hash,
                                     struct content_block **block)
{
    // Search content hash table
    // If found, increment reference count
    // If not found, allocate new block
}

// Deduplication must respect TA isolation
TEE_Result deduplicate_block_for_ta(const TEE_UUID *uuid,
                                   const uint8_t *block_data,
                                   size_t block_size,
                                   uint32_t *block_ref)
{
    uint8_t content_hash[TEE_SHA256_HASH_SIZE];
    uint8_t ta_scoped_hash[TEE_SHA256_HASH_SIZE];
    
    // Calculate content hash
    tee_hash_createdigest(TEE_ALG_SHA256, block_data, block_size,
                         content_hash, sizeof(content_hash));
    
    // Scope hash to TA to prevent cross-TA data inference
    do_hmac(ta_scoped_hash, sizeof(ta_scoped_hash),
           content_hash, sizeof(content_hash),
           uuid, sizeof(*uuid));
    
    // Use scoped hash for dedup lookup
    return find_or_create_block(ta_scoped_hash, block_data, block_size, block_ref);
}

// RPMB caching configuration
#define RPMB_BUF_MAX_ENTRIES (CFG_RPMB_FS_CACHE_ENTRIES + CFG_RPMB_FS_RD_ENTRIES)

struct rpmb_fat_entry_dir {
    struct rpmb_fat_entry *rpmb_fat_entry_buf;  // Cache buffer
    uint32_t idx_curr;                          // Current index
    uint32_t num_buffered;                      // Cached entries
    uint32_t num_total_read;                    // Total read operations
    bool last_reached;                          // End-of-data marker
};

// Cache-aware FAT entry reading
static TEE_Result read_fat_entry(struct rpmb_fat_entry_dir *fed,
                                 struct rpmb_fat_entry *entry)
{
    // Check if entry is in cache
    if (fed->idx_curr < fed->num_buffered) {
        *entry = fed->rpmb_fat_entry_buf[fed->idx_curr];
        fed->idx_curr++;
        return TEE_SUCCESS;
    }
    
    // Cache miss - read from storage
    return read_fat_entries_from_rpmb(fed, entry);
}

// Block allocation with pooling
static void *get_tmp_block(void)
{
    // Uses memory pool for efficient allocation
    return mempool_alloc(mempool_default, BLOCK_SIZE);
}

static void put_tmp_block(void *tmp_block)
{
    // Returns to pool for reuse
    mempool_free(mempool_default, tmp_block);
}

// Potential enhancement: Block content caching
struct block_cache_entry {
    uint32_t block_number;
    uint8_t *block_data;
    bool dirty;
    uint32_t last_access;
};

static TEE_Result get_dirh(struct tee_fs_dirfile_dirh **dirh)
{
    if (!ree_fs_dirh) {
        // Create new directory handle
        TEE_Result res = open_dirh(&ree_fs_dirh);
        if (res) {
            *dirh = NULL;
            return res;
        }
    }
    
    ree_fs_dirh_refcount++;  // Reference counting for caching
    *dirh = ree_fs_dirh;
    return TEE_SUCCESS;
}

// Cache eviction on zero references
static void put_dirh_primitive(bool close)
{
    ree_fs_dirh_refcount--;
    if (ree_fs_dirh && (!ree_fs_dirh_refcount || close))
        close_dirh(&ree_fs_dirh);  // Evict from cache
}

// Each node maintains two versions
struct htree_node {
    size_t id;
    bool dirty;
    bool block_updated;
    struct tee_fs_htree_node_image node;
    struct htree_node *parent;
    struct htree_node *child[2];
};

// Version selection mechanism
#define HTREE_NODE_COMMITTED_BLOCK    BIT32(0)
#define HTREE_NODE_COMMITTED_CHILD(n) BIT32(1 + (n))

// Potential snapshot extension:
struct storage_snapshot {
    uint32_t snapshot_id;
    uint32_t base_counter;
    uint8_t root_hash[TEE_FS_HTREE_HASH_SIZE];
    uint64_t timestamp;
    uint32_t ref_count;
};

// Current out-of-place write mechanism
static TEE_Result out_of_place_write(struct tee_fs_fd *fdp, size_t pos,
                                     const void *buf_core, const void *buf_user,
                                     size_t len)
{
    // Read original block
    if (start_block_num * BLOCK_SIZE < ROUNDUP(meta->length, BLOCK_SIZE)) {
        res = tee_fs_htree_read_block(&fdp->ht, start_block_num, block);
    } else {
        memset(block, 0, BLOCK_SIZE);  // New block
    }
    
    // Modify block content
    if (data_core_ptr) {
        memcpy(block + offset, data_core_ptr, size_to_write);
    }
    
    // Write modified block (new location)
    res = tee_fs_htree_write_block(&fdp->ht, start_block_num, block);
    
    // This naturally implements CoW for snapshots
}

// Backup process using hash comparison
TEE_Result create_incremental_backup(struct tee_fs_htree *current_tree,
                                    struct tee_fs_htree *base_tree,
                                    struct backup_manifest *manifest)
{
    // Compare root hashes
    if (!memcmp(current_tree->root.node.hash, base_tree->root.node.hash,
               TEE_FS_HTREE_HASH_SIZE)) {
        manifest->type = BACKUP_TYPE_UNCHANGED;
        return TEE_SUCCESS;
    }
    
    // Traverse trees to find changed blocks
    manifest->type = BACKUP_TYPE_INCREMENTAL;
    return traverse_and_backup_changes(current_tree, base_tree, manifest);
}

// Storage backend abstraction
struct tee_fs_htree_storage {
    size_t block_size;
    TEE_Result (*rpc_read_init)(void *aux, struct tee_fs_rpc_operation *op,
                               enum tee_fs_htree_type type, size_t idx,
                               uint8_t vers, void **data);
    TEE_Result (*rpc_write_init)(void *aux, struct tee_fs_rpc_operation *op,
                                enum tee_fs_htree_type type, size_t idx,
                                uint8_t vers, void **data);
    TEE_Result (*rpc_read_final)(struct tee_fs_rpc_operation *op, size_t *bytes);
    TEE_Result (*rpc_write_final)(struct tee_fs_rpc_operation *op);
};

// Potential replication wrapper
struct replicated_storage {
    struct tee_fs_htree_storage primary;
    struct tee_fs_htree_storage secondary;
    enum replication_mode mode;  // SYNC, ASYNC, FAILOVER
};

// Theoretical RAID-1 implementation
TEE_Result raid1_write_block(struct raid1_context *ctx, size_t block_num,
                             const void *block)
{
    TEE_Result res1, res2;
    
    // Write to both mirrors
    res1 = tee_fs_htree_write_block(&ctx->mirror1, block_num, block);
    res2 = tee_fs_htree_write_block(&ctx->mirror2, block_num, block);
    
    // Require both writes to succeed
    if (res1 != TEE_SUCCESS || res2 != TEE_SUCCESS) {
        EMSG("RAID-1 write failure: mirror1=%x, mirror2=%x", res1, res2);
        return TEE_ERROR_STORAGE_NOT_AVAILABLE;
    }
    
    return TEE_SUCCESS;
}

// RAID-1 read with failover
TEE_Result raid1_read_block(struct raid1_context *ctx, size_t block_num,
                           void *block)
{
    TEE_Result res;
    
    // Try primary mirror first
    res = tee_fs_htree_read_block(&ctx->mirror1, block_num, block);
    if (res == TEE_SUCCESS) {
        return res;
    }
    
    DMSG("Primary mirror failed, trying secondary");
    
    // Failover to secondary mirror
    res = tee_fs_htree_read_block(&ctx->mirror2, block_num, block);
    if (res == TEE_SUCCESS) {
        // Mark primary for rebuild
        ctx->primary_degraded = true;
        return res;
    }
    
    EMSG("Both RAID-1 mirrors failed");
    return TEE_ERROR_STORAGE_NOT_AVAILABLE;
}

// Cross-backend replication
struct cross_platform_storage {
    struct tee_fs_htree_storage ree_storage;    // REE file system
    struct tee_fs_htree_storage rpmb_storage;   // RPMB secure storage
    enum sync_policy policy;                     // PREFER_SECURE, PREFER_FAST, BOTH
};

TEE_Result cross_platform_sync(struct cross_platform_storage *cps)
{
    uint8_t ree_hash[TEE_FS_HTREE_HASH_SIZE];
    uint8_t rpmb_hash[TEE_FS_HTREE_HASH_SIZE];
    
    // Get root hashes from both backends
    get_root_hash(&cps->ree_storage, ree_hash);
    get_root_hash(&cps->rpmb_storage, rpmb_hash);
    
    // Synchronize if different
    if (memcmp(ree_hash, rpmb_hash, sizeof(ree_hash))) {
        return synchronize_storages(cps);
    }
    
    return TEE_SUCCESS;
}

// Dirty tracking for batch operations
struct htree_node {
    bool dirty;              // Node needs sync
    bool block_updated;      // Block data changed
    // ...
};

// Batch synchronization
TEE_Result tee_fs_htree_sync_to_storage(struct tee_fs_htree **ht_arg,
                                       uint8_t *hash, uint32_t *counter)
{
    if (!ht->dirty) return TEE_SUCCESS;  // No changes to sync
    
    // Sync all dirty nodes in single operation
    res = htree_traverse_post_order(ht, htree_sync_node_to_storage, ctx);
    return res;
}

// Theoretical async I/O for storage
struct async_storage_op {
    enum op_type type;           // READ, WRITE, SYNC
    size_t block_num;
    void *buffer;
    TEE_Result (*callback)(struct async_storage_op *op, TEE_Result result);
    void *user_data;
};

// Async write operation
TEE_Result async_write_block(struct tee_fs_htree *ht, size_t block_num,
                            const void *block, async_callback_t callback)
{
    struct async_storage_op *op = alloc_async_op();
    
    op->type = ASYNC_WRITE;
    op->block_num = block_num;
    op->buffer = dup_block(block);
    op->callback = callback;
    
    return queue_async_operation(op);
}

// Zero-knowledge content addressing
TEE_Result store_zero_knowledge_block(const void *plaintext, size_t size,
                                     uint8_t *block_id)
{
    uint8_t content_key[32];
    uint8_t encrypted_block[BLOCK_SIZE];
    
    // Generate content-derived key
    tee_hash_createdigest(TEE_ALG_SHA256, plaintext, size,
                         content_key, sizeof(content_key));
    
    // Encrypt block with content key
    encrypt_block(content_key, plaintext, size, encrypted_block);
    
    // Block ID is hash of encrypted data
    tee_hash_createdigest(TEE_ALG_SHA256, encrypted_block, BLOCK_SIZE,
                         block_id, TEE_SHA256_HASH_SIZE);
    
    // Store encrypted block indexed by block_id
    return store_content_block(block_id, encrypted_block);
}

// Homomorphic operations on encrypted storage
TEE_Result homomorphic_search(const struct search_criteria *criteria,
                             uint8_t *result_hash)
{
    // Perform search operations on encrypted directory entries
    // without decrypting individual entries
    return perform_encrypted_search(criteria, result_hash);
}