p2p、分布式，区块链笔记: IPFS库Helia的文件系统Unix File System (UnixFS)

Unix File System (UnixFS)

• Helia中定义一个UnixFS类用于文件处理。The Unix File System (UnixFS) is the data format used to represent files and all their links and metadata in IPFS.。UnixFS中的方法封装了常见的文件系统操作，使得在去中心化文件系统中处理文件和目录变得更加简单和直观。其主要操作由importer和exporter执行。

importer：导入文件并创建DAG

• Importer从文件和目录构建有向无环图DAG，意味着文件被分解成块，然后使用“链接节点”以树状结构排列，连接在一起，给定文件的“散列”实际上是DAG中根节点的散列。

/**
 * The importer creates UnixFS DAGs and stores the blocks that make
 * them up in the passed blockstore.
 *
 * @example
 *
 * ```typescript
 * import { importer } from 'ipfs-unixfs-importer'
 * import { MemoryBlockstore } from 'blockstore-core'
 *
 * // store blocks in memory, other blockstores are available
 * const blockstore = new MemoryBlockstore()
 *
 * const input = [{
 *   path: './foo.txt',
 *   content: Uint8Array.from([0, 1, 2, 3, 4])
 * }, {
 *   path: './bar.txt',
 *   content: Uint8Array.from([0, 1, 2, 3, 4])
 * }]
 *
 * for await (const entry of importer(input, blockstore)) {
 *   console.info(entry)
 *   // { cid: CID(), ... }
 * }
 * ```
 */
export async function* importer(source, blockstore, options = {}) {
    let candidates;
    if (Symbol.asyncIterator in source || Symbol.iterator in source) {
        candidates = source;
    }
    else {
        candidates = [source];
    }
    const wrapWithDirectory = options.wrapWithDirectory ?? false;
    const shardSplitThresholdBytes = options.shardSplitThresholdBytes ?? 262144;
    const shardFanoutBits = options.shardFanoutBits ?? 8;
    const cidVersion = options.cidVersion ?? 1;
    const rawLeaves = options.rawLeaves ?? true;
    const leafType = options.leafType ?? 'file';
    const fileImportConcurrency = options.fileImportConcurrency ?? 50;
    const blockWriteConcurrency = options.blockWriteConcurrency ?? 10;
    const reduceSingle