virt2/api/soft/CodeMirror/lib/model/chunk.js

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import { cleanUpLine } from "../line/line_data.js"
import { indexOf } from "../util/misc.js"
import { signalLater } from "../util/operation_group.js"
// The document is represented as a BTree consisting of leaves, with
// chunk of lines in them, and branches, with up to ten leaves or
// other branch nodes below them. The top node is always a branch
// node, and is the document object itself (meaning it has
// additional methods and properties).
//
// All nodes have parent links. The tree is used both to go from
// line numbers to line objects, and to go from objects to numbers.
// It also indexes by height, and is used to convert between height
// and line object, and to find the total height of the document.
//
// See also http://marijnhaverbeke.nl/blog/codemirror-line-tree.html
export function LeafChunk(lines) {
this.lines = lines
this.parent = null
let height = 0
for (let i = 0; i < lines.length; ++i) {
lines[i].parent = this
height += lines[i].height
}
this.height = height
}
LeafChunk.prototype = {
chunkSize() { return this.lines.length },
// Remove the n lines at offset 'at'.
removeInner(at, n) {
for (let i = at, e = at + n; i < e; ++i) {
let line = this.lines[i]
this.height -= line.height
cleanUpLine(line)
signalLater(line, "delete")
}
this.lines.splice(at, n)
},
// Helper used to collapse a small branch into a single leaf.
collapse(lines) {
lines.push.apply(lines, this.lines)
},
// Insert the given array of lines at offset 'at', count them as
// having the given height.
insertInner(at, lines, height) {
this.height += height
this.lines = this.lines.slice(0, at).concat(lines).concat(this.lines.slice(at))
for (let i = 0; i < lines.length; ++i) lines[i].parent = this
},
// Used to iterate over a part of the tree.
iterN(at, n, op) {
for (let e = at + n; at < e; ++at)
if (op(this.lines[at])) return true
}
}
export function BranchChunk(children) {
this.children = children
let size = 0, height = 0
for (let i = 0; i < children.length; ++i) {
let ch = children[i]
size += ch.chunkSize(); height += ch.height
ch.parent = this
}
this.size = size
this.height = height
this.parent = null
}
BranchChunk.prototype = {
chunkSize() { return this.size },
removeInner(at, n) {
this.size -= n
for (let i = 0; i < this.children.length; ++i) {
let child = this.children[i], sz = child.chunkSize()
if (at < sz) {
let rm = Math.min(n, sz - at), oldHeight = child.height
child.removeInner(at, rm)
this.height -= oldHeight - child.height
if (sz == rm) { this.children.splice(i--, 1); child.parent = null }
if ((n -= rm) == 0) break
at = 0
} else at -= sz
}
// If the result is smaller than 25 lines, ensure that it is a
// single leaf node.
if (this.size - n < 25 &&
(this.children.length > 1 || !(this.children[0] instanceof LeafChunk))) {
let lines = []
this.collapse(lines)
this.children = [new LeafChunk(lines)]
this.children[0].parent = this
}
},
collapse(lines) {
for (let i = 0; i < this.children.length; ++i) this.children[i].collapse(lines)
},
insertInner(at, lines, height) {
this.size += lines.length
this.height += height
for (let i = 0; i < this.children.length; ++i) {
let child = this.children[i], sz = child.chunkSize()
if (at <= sz) {
child.insertInner(at, lines, height)
if (child.lines && child.lines.length > 50) {
// To avoid memory thrashing when child.lines is huge (e.g. first view of a large file), it's never spliced.
// Instead, small slices are taken. They're taken in order because sequential memory accesses are fastest.
let remaining = child.lines.length % 25 + 25
for (let pos = remaining; pos < child.lines.length;) {
let leaf = new LeafChunk(child.lines.slice(pos, pos += 25))
child.height -= leaf.height
this.children.splice(++i, 0, leaf)
leaf.parent = this
}
child.lines = child.lines.slice(0, remaining)
this.maybeSpill()
}
break
}
at -= sz
}
},
// When a node has grown, check whether it should be split.
maybeSpill() {
if (this.children.length <= 10) return
let me = this
do {
let spilled = me.children.splice(me.children.length - 5, 5)
let sibling = new BranchChunk(spilled)
if (!me.parent) { // Become the parent node
let copy = new BranchChunk(me.children)
copy.parent = me
me.children = [copy, sibling]
me = copy
} else {
me.size -= sibling.size
me.height -= sibling.height
let myIndex = indexOf(me.parent.children, me)
me.parent.children.splice(myIndex + 1, 0, sibling)
}
sibling.parent = me.parent
} while (me.children.length > 10)
me.parent.maybeSpill()
},
iterN(at, n, op) {
for (let i = 0; i < this.children.length; ++i) {
let child = this.children[i], sz = child.chunkSize()
if (at < sz) {
let used = Math.min(n, sz - at)
if (child.iterN(at, used, op)) return true
if ((n -= used) == 0) break
at = 0
} else at -= sz
}
}
}