fix(sdk): consolidate MAX_CHUNK_SIZE to 2 MiB per Bitswap limit

- Define MAX_CHUNK_SIZE once in chunker module (2 MiB)
- Import constant in utils instead of redefining locally
- Removes inconsistent 4 MiB and 8 MiB definitions
- Aligns with Bitswap protocol constraints

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: bkontur

sdk/rust/src/chunker.rs

@@ -8,8 +8,8 @@ extern crate alloc;
 use crate::types::{Chunk, ChunkerConfig, Error, Result};
 use alloc::vec::Vec;
 
-/// Maximum chunk size allowed (8 MiB, matches pallet limit).
-pub const MAX_CHUNK_SIZE: usize = 8 * 1024 * 1024;
+/// Maximum chunk size allowed (2 MiB, matches Bitswap limit).
+pub const MAX_CHUNK_SIZE: usize = 2 * 1024 * 1024;
 
 /// Default chunk size (1 MiB).
 pub const DEFAULT_CHUNK_SIZE: usize = 1024 * 1024;

sdk/rust/src/utils.rs

@@ -4,6 +4,7 @@
 //! Utility functions and helpers for Bulletin SDK
 
 use crate::{
+	chunker::MAX_CHUNK_SIZE,
 	cid::ContentHash,
 	types::{CidCodec, Error, HashAlgorithm, Result},
 };
@@ -185,16 +186,14 @@ where
 /// use bulletin_sdk_rust::utils::validate_chunk_size;
 ///
 /// assert!(validate_chunk_size(1_048_576).is_ok()); // 1 MiB - valid
-/// assert!(validate_chunk_size(10_000_000).is_err()); // > 8 MiB - invalid
+/// assert!(validate_chunk_size(3_000_000).is_err()); // > 2 MiB - invalid
 /// ```
 pub fn validate_chunk_size(size: u64) -> Result<()> {
-	const MAX_CHUNK_SIZE: u64 = 8 * 1024 * 1024; // 8 MiB
-
 	if size == 0 {
 		return Err(Error::InvalidConfig("Chunk size cannot be zero".into()))
 	}
 
-	if size > MAX_CHUNK_SIZE {
+	if size > MAX_CHUNK_SIZE as u64 {
 		return Err(Error::InvalidConfig(alloc::format!(
 			"Chunk size {} exceeds maximum {}",
 			size,
@@ -218,7 +217,6 @@ pub fn validate_chunk_size(size: u64) -> Result<()> {
 /// ```
 pub fn optimal_chunk_size(data_size: u64) -> u64 {
 	const MIN_CHUNK_SIZE: u64 = 1024 * 1024; // 1 MiB
-	const MAX_CHUNK_SIZE: u64 = 4 * 1024 * 1024; // 4 MiB
 	const OPTIMAL_CHUNKS: u64 = 100; // Target chunk count
 
 	if data_size <= MIN_CHUNK_SIZE {
@@ -229,8 +227,8 @@ pub fn optimal_chunk_size(data_size: u64) -> u64 {
 
 	if optimal_size < MIN_CHUNK_SIZE {
 		MIN_CHUNK_SIZE
-	} else if optimal_size > MAX_CHUNK_SIZE {
-		MAX_CHUNK_SIZE
+	} else if optimal_size > MAX_CHUNK_SIZE as u64 {
+		MAX_CHUNK_SIZE as u64
 	} else {
 		// Round to nearest MiB
 		(optimal_size / 1_048_576) * 1_048_576

sdk/typescript/src/chunker.ts

@@ -7,8 +7,8 @@
 
 import { Chunk, ChunkerConfig, DEFAULT_CHUNKER_CONFIG, BulletinError } from './types.js';
 
-/** Maximum chunk size allowed (8 MiB, matches pallet limit) */
-export const MAX_CHUNK_SIZE = 8 * 1024 * 1024;
+/** Maximum chunk size allowed (2 MiB, matches Bitswap limit) */
+export const MAX_CHUNK_SIZE = 2 * 1024 * 1024;
 
 /**
  * Fixed-size chunker that splits data into equal-sized chunks

sdk/typescript/src/utils.ts

@@ -9,6 +9,7 @@ import { CID } from 'multiformats/cid';
 import * as digest from 'multiformats/hashes/digest';
 import { blake2AsU8a, sha256AsU8a } from '@polkadot/util-crypto';
 import { HashAlgorithm, BulletinError } from './types.js';
+import { MAX_CHUNK_SIZE } from './chunker.js';
 
 /**
  * Calculate content hash using the specified algorithm
@@ -162,8 +163,6 @@ export function formatBytes(bytes: number, decimals: number = 2): string {
  * @throws BulletinError if chunk size is invalid
  */
 export function validateChunkSize(size: number): void {
-  const MAX_CHUNK_SIZE = 8 * 1024 * 1024; // 8 MiB
-
   if (size <= 0) {
     throw new BulletinError('Chunk size must be positive', 'INVALID_CHUNK_SIZE');
   }
@@ -189,7 +188,6 @@ export function validateChunkSize(size: number): void {
  */
 export function optimalChunkSize(dataSize: number): number {
   const MIN_CHUNK_SIZE = 1024 * 1024; // 1 MiB
-  const MAX_CHUNK_SIZE = 4 * 1024 * 1024; // 4 MiB
   const OPTIMAL_CHUNKS = 100; // Target chunk count
 
   if (dataSize <= MIN_CHUNK_SIZE) {