First commit

node_modules/memory-pager/index.js

@@ -0,0 +1,160 @@
+module.exports = Pager
+
+function Pager (pageSize, opts) {
+  if (!(this instanceof Pager)) return new Pager(pageSize, opts)
+
+  this.length = 0
+  this.updates = []
+  this.path = new Uint16Array(4)
+  this.pages = new Array(32768)
+  this.maxPages = this.pages.length
+  this.level = 0
+  this.pageSize = pageSize || 1024
+  this.deduplicate = opts ? opts.deduplicate : null
+  this.zeros = this.deduplicate ? alloc(this.deduplicate.length) : null
+}
+
+Pager.prototype.updated = function (page) {
+  while (this.deduplicate && page.buffer[page.deduplicate] === this.deduplicate[page.deduplicate]) {
+    page.deduplicate++
+    if (page.deduplicate === this.deduplicate.length) {
+      page.deduplicate = 0
+      if (page.buffer.equals && page.buffer.equals(this.deduplicate)) page.buffer = this.deduplicate
+      break
+    }
+  }
+  if (page.updated || !this.updates) return
+  page.updated = true
+  this.updates.push(page)
+}
+
+Pager.prototype.lastUpdate = function () {
+  if (!this.updates || !this.updates.length) return null
+  var page = this.updates.pop()
+  page.updated = false
+  return page
+}
+
+Pager.prototype._array = function (i, noAllocate) {
+  if (i >= this.maxPages) {
+    if (noAllocate) return
+    grow(this, i)
+  }
+
+  factor(i, this.path)
+
+  var arr = this.pages
+
+  for (var j = this.level; j > 0; j--) {
+    var p = this.path[j]
+    var next = arr[p]
+
+    if (!next) {
+      if (noAllocate) return
+      next = arr[p] = new Array(32768)
+    }
+
+    arr = next
+  }
+
+  return arr
+}
+
+Pager.prototype.get = function (i, noAllocate) {
+  var arr = this._array(i, noAllocate)
+  var first = this.path[0]
+  var page = arr && arr[first]
+
+  if (!page && !noAllocate) {
+    page = arr[first] = new Page(i, alloc(this.pageSize))
+    if (i >= this.length) this.length = i + 1
+  }
+
+  if (page && page.buffer === this.deduplicate && this.deduplicate && !noAllocate) {
+    page.buffer = copy(page.buffer)
+    page.deduplicate = 0
+  }
+
+  return page
+}
+
+Pager.prototype.set = function (i, buf) {
+  var arr = this._array(i, false)
+  var first = this.path[0]
+
+  if (i >= this.length) this.length = i + 1
+
+  if (!buf || (this.zeros && buf.equals && buf.equals(this.zeros))) {
+    arr[first] = undefined
+    return
+  }
+
+  if (this.deduplicate && buf.equals && buf.equals(this.deduplicate)) {
+    buf = this.deduplicate
+  }
+
+  var page = arr[first]
+  var b = truncate(buf, this.pageSize)
+
+  if (page) page.buffer = b
+  else arr[first] = new Page(i, b)
+}
+
+Pager.prototype.toBuffer = function () {
+  var list = new Array(this.length)
+  var empty = alloc(this.pageSize)
+  var ptr = 0
+
+  while (ptr < list.length) {
+    var arr = this._array(ptr, true)
+    for (var i = 0; i < 32768 && ptr < list.length; i++) {
+      list[ptr++] = (arr && arr[i]) ? arr[i].buffer : empty
+    }
+  }
+
+  return Buffer.concat(list)
+}
+
+function grow (pager, index) {
+  while (pager.maxPages < index) {
+    var old = pager.pages
+    pager.pages = new Array(32768)
+    pager.pages[0] = old
+    pager.level++
+    pager.maxPages *= 32768
+  }
+}
+
+function truncate (buf, len) {
+  if (buf.length === len) return buf
+  if (buf.length > len) return buf.slice(0, len)
+  var cpy = alloc(len)
+  buf.copy(cpy)
+  return cpy
+}
+
+function alloc (size) {
+  if (Buffer.alloc) return Buffer.alloc(size)
+  var buf = new Buffer(size)
+  buf.fill(0)
+  return buf
+}
+
+function copy (buf) {
+  var cpy = Buffer.allocUnsafe ? Buffer.allocUnsafe(buf.length) : new Buffer(buf.length)
+  buf.copy(cpy)
+  return cpy
+}
+
+function Page (i, buf) {
+  this.offset = i * buf.length
+  this.buffer = buf
+  this.updated = false
+  this.deduplicate = 0
+}
+
+function factor (n, out) {
+  n = (n - (out[0] = (n & 32767))) / 32768
+  n = (n - (out[1] = (n & 32767))) / 32768
+  out[3] = ((n - (out[2] = (n & 32767))) / 32768) & 32767
+}