ipfs-log/docs/entry-io.js.html at main · orbitdb-archive/ipfs-log · GitHub

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    <h1 class="page-title">Source: entry-io.js</h1>


    <section>
        <article>
            <pre class="prettyprint source linenums"><code>'use strict'

const pMap = require('p-map')
const pDoWhilst = require('p-do-whilst')
const Entry = require('./entry')

const hasItems = arr => arr &amp;&amp; arr.length > 0

class EntryIO {
  // Fetch log graphs in parallel
  static async fetchParallel (ipfs, hashes, { length, exclude = [], timeout, concurrency, onProgressCallback }) {
    const fetchOne = async (hash) => EntryIO.fetchAll(ipfs, hash, { length, exclude, timeout, onProgressCallback, concurrency })
    const concatArrays = (arr1, arr2) => arr1.concat(arr2)
    const flatten = (arr) => arr.reduce(concatArrays, [])
    const res = await pMap(hashes, fetchOne, { concurrency: Math.max(concurrency || hashes.length, 1) })
    return flatten(res)
  }

  /**
   * Fetch log entries
   *
   * @param {IPFS} [ipfs] An IPFS instance
   * @param {string} [hash] Multihash of the entry to fetch
   * @param {string} [parent] Parent of the node to be fetched
   * @param {Object} [all] Entries to skip
   * @param {Number} [amount=-1] How many entries to fetch
   * @param {Number} [depth=0] Current depth of the recursion
   * @param {function(hash, entry, parent, depth)} onProgressCallback
   * @returns {Promise&lt;Array&lt;Entry>>}
   */
  static async fetchAll (ipfs, hashes, { length = -1, exclude = [], timeout, onProgressCallback, onStartProgressCallback, concurrency = 32, delay = 0 } = {}) {
    const result = []
    const cache = {}
    const loadingCache = {}
    const loadingQueue = Array.isArray(hashes)
      ? { 0: hashes.slice() }
      : { 0: [hashes] }
    let running = 0 // keep track of how many entries are being fetched at any time
    let maxClock = 0 // keep track of the latest clock time during load
    let minClock = 0 // keep track of the minimum clock time during load

    // Does the loading queue have more to process?
    const loadingQueueHasMore = () => Object.values(loadingQueue).find(hasItems) !== undefined

    // Add a multihash to the loading queue
    const addToLoadingQueue = (e, idx) => {
      if (!loadingCache[e]) {
        if (!loadingQueue[idx]) loadingQueue[idx] = []
        if (!loadingQueue[idx].includes(e)) {
          loadingQueue[idx].push(e)
        }
        loadingCache[e] = true
      }
    }

    // Get the next items to process from the loading queue
    const getNextFromQueue = (length = 1) => {
      const getNext = (res, key, idx) => {
        const nextItems = loadingQueue[key]
        while (nextItems.length > 0 &amp;&amp; res.length &lt; length) {
          const hash = nextItems.shift()
          res.push(hash)
        }
        if (nextItems.length === 0) {
          delete loadingQueue[key]
        }
        return res
      }
      return Object.keys(loadingQueue).reduce(getNext, [])
    }

    // Add entries that we don't need to fetch to the "cache"
    const addToExcludeCache = e => { cache[e.hash] = true }

    // Fetch one entry and add it to the results
    const fetchEntry = async (hash) => {
      if (!hash || cache[hash]) {
        return
      }

      return new Promise((resolve, reject) => {
        // Resolve the promise after a timeout (if given) in order to
        // not get stuck loading a block that is unreachable
        const timer = timeout &amp;&amp; timeout > 0
          ? setTimeout(() => {
              console.warn(`Warning: Couldn't fetch entry '${hash}', request timed out (${timeout}ms)`)
              resolve()
            }, timeout)
          : null

        const addToResults = (entry) => {
          if (Entry.isEntry(entry)) {
            const ts = entry.clock.time

            // Update min/max clocks
            maxClock = Math.max(maxClock, ts)
            minClock = result.length > 0
              ? Math.min(result[result.length - 1].clock.time, minClock)
              : maxClock

            const isLater = (result.length >= length &amp;&amp; ts >= minClock)
            const calculateIndex = (idx) => maxClock - ts + ((idx + 1) * idx)

            // Add the entry to the results if
            // 1) we're fetching all entries
            // 2) results is not filled yet
            // the clock of the entry is later than current known minimum clock time
            if (length &lt; 0 || result.length &lt; length || isLater) {
              result.push(entry)
              cache[hash] = true

              if (onProgressCallback) {
                onProgressCallback(hash, entry, result.length, result.length)
              }
            }

            if (length &lt; 0) {
              // If we're fetching all entries (length === -1), adds nexts and refs to the queue
              entry.next.forEach(addToLoadingQueue)
              if (entry.refs) entry.refs.forEach(addToLoadingQueue)
            } else {
              // If we're fetching entries up to certain length,
              // fetch the next if result is filled up, to make sure we "check"
              // the next entry if its clock is later than what we have in the result
              if (result.length &lt; length || ts > minClock || (ts === minClock &amp;&amp; !cache[entry.hash])) {
                entry.next.forEach(e => addToLoadingQueue(e, calculateIndex(0)))
              }
              if (entry.refs &amp;&amp; (result.length + entry.refs.length &lt;= length)) {
                entry.refs.forEach((e, i) => addToLoadingQueue(e, calculateIndex(i)))
              }
            }
          }
        }

        if (onStartProgressCallback) {
          onStartProgressCallback(hash, null, 0, result.length)
        }

        // Load the entry
        Entry.fromMultihash(ipfs, hash).then(async (entry) => {
          try {
            // Add it to the results
            addToResults(entry)

            // Simulate network latency (for debugging purposes)
            if (delay > 0) {
              const sleep = (ms = 0) => new Promise(resolve => setTimeout(resolve, ms))
              await sleep(delay)
            }
            resolve()
          } catch (e) {
            reject(e)
          } finally {
            clearTimeout(timer)
          }
        }).catch(reject)
      })
    }

    // One loop of processing the loading queue
    const _processQueue = async () => {
      if (running &lt; concurrency) {
        const nexts = getNextFromQueue(concurrency)
        running += nexts.length
        await pMap(nexts, fetchEntry)
        running -= nexts.length
      }
    }

    // Add entries to exclude from processing to the cache before we start
    exclude.forEach(addToExcludeCache)

    // Fetch entries
    await pDoWhilst(_processQueue, loadingQueueHasMore)

    return result
  }
}

module.exports = EntryIO
</code></pre>
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