add hw2

node_modules/readable-stream/lib/internal/streams/compose.js

@@ -0,0 +1,194 @@
+'use strict'
+
+const { pipeline } = require('./pipeline')
+const Duplex = require('./duplex')
+const { destroyer } = require('./destroy')
+const {
+  isNodeStream,
+  isReadable,
+  isWritable,
+  isWebStream,
+  isTransformStream,
+  isWritableStream,
+  isReadableStream
+} = require('./utils')
+const {
+  AbortError,
+  codes: { ERR_INVALID_ARG_VALUE, ERR_MISSING_ARGS }
+} = require('../../ours/errors')
+const eos = require('./end-of-stream')
+module.exports = function compose(...streams) {
+  if (streams.length === 0) {
+    throw new ERR_MISSING_ARGS('streams')
+  }
+  if (streams.length === 1) {
+    return Duplex.from(streams[0])
+  }
+  const orgStreams = [...streams]
+  if (typeof streams[0] === 'function') {
+    streams[0] = Duplex.from(streams[0])
+  }
+  if (typeof streams[streams.length - 1] === 'function') {
+    const idx = streams.length - 1
+    streams[idx] = Duplex.from(streams[idx])
+  }
+  for (let n = 0; n < streams.length; ++n) {
+    if (!isNodeStream(streams[n]) && !isWebStream(streams[n])) {
+      // TODO(ronag): Add checks for non streams.
+      continue
+    }
+    if (
+      n < streams.length - 1 &&
+      !(isReadable(streams[n]) || isReadableStream(streams[n]) || isTransformStream(streams[n]))
+    ) {
+      throw new ERR_INVALID_ARG_VALUE(`streams[${n}]`, orgStreams[n], 'must be readable')
+    }
+    if (n > 0 && !(isWritable(streams[n]) || isWritableStream(streams[n]) || isTransformStream(streams[n]))) {
+      throw new ERR_INVALID_ARG_VALUE(`streams[${n}]`, orgStreams[n], 'must be writable')
+    }
+  }
+  let ondrain
+  let onfinish
+  let onreadable
+  let onclose
+  let d
+  function onfinished(err) {
+    const cb = onclose
+    onclose = null
+    if (cb) {
+      cb(err)
+    } else if (err) {
+      d.destroy(err)
+    } else if (!readable && !writable) {
+      d.destroy()
+    }
+  }
+  const head = streams[0]
+  const tail = pipeline(streams, onfinished)
+  const writable = !!(isWritable(head) || isWritableStream(head) || isTransformStream(head))
+  const readable = !!(isReadable(tail) || isReadableStream(tail) || isTransformStream(tail))
+
+  // TODO(ronag): Avoid double buffering.
+  // Implement Writable/Readable/Duplex traits.
+  // See, https://github.com/nodejs/node/pull/33515.
+  d = new Duplex({
+    // TODO (ronag): highWaterMark?
+    writableObjectMode: !!(head !== null && head !== undefined && head.writableObjectMode),
+    readableObjectMode: !!(tail !== null && tail !== undefined && tail.readableObjectMode),
+    writable,
+    readable
+  })
+  if (writable) {
+    if (isNodeStream(head)) {
+      d._write = function (chunk, encoding, callback) {
+        if (head.write(chunk, encoding)) {
+          callback()
+        } else {
+          ondrain = callback
+        }
+      }
+      d._final = function (callback) {
+        head.end()
+        onfinish = callback
+      }
+      head.on('drain', function () {
+        if (ondrain) {
+          const cb = ondrain
+          ondrain = null
+          cb()
+        }
+      })
+    } else if (isWebStream(head)) {
+      const writable = isTransformStream(head) ? head.writable : head
+      const writer = writable.getWriter()
+      d._write = async function (chunk, encoding, callback) {
+        try {
+          await writer.ready
+          writer.write(chunk).catch(() => {})
+          callback()
+        } catch (err) {
+          callback(err)
+        }
+      }
+      d._final = async function (callback) {
+        try {
+          await writer.ready
+          writer.close().catch(() => {})
+          onfinish = callback
+        } catch (err) {
+          callback(err)
+        }
+      }
+    }
+    const toRead = isTransformStream(tail) ? tail.readable : tail
+    eos(toRead, () => {
+      if (onfinish) {
+        const cb = onfinish
+        onfinish = null
+        cb()
+      }
+    })
+  }
+  if (readable) {
+    if (isNodeStream(tail)) {
+      tail.on('readable', function () {
+        if (onreadable) {
+          const cb = onreadable
+          onreadable = null
+          cb()
+        }
+      })
+      tail.on('end', function () {
+        d.push(null)
+      })
+      d._read = function () {
+        while (true) {
+          const buf = tail.read()
+          if (buf === null) {
+            onreadable = d._read
+            return
+          }
+          if (!d.push(buf)) {
+            return
+          }
+        }
+      }
+    } else if (isWebStream(tail)) {
+      const readable = isTransformStream(tail) ? tail.readable : tail
+      const reader = readable.getReader()
+      d._read = async function () {
+        while (true) {
+          try {
+            const { value, done } = await reader.read()
+            if (!d.push(value)) {
+              return
+            }
+            if (done) {
+              d.push(null)
+              return
+            }
+          } catch {
+            return
+          }
+        }
+      }
+    }
+  }
+  d._destroy = function (err, callback) {
+    if (!err && onclose !== null) {
+      err = new AbortError()
+    }
+    onreadable = null
+    ondrain = null
+    onfinish = null
+    if (onclose === null) {
+      callback(err)
+    } else {
+      onclose = callback
+      if (isNodeStream(tail)) {
+        destroyer(tail, err)
+      }
+    }
+  }
+  return d
+}