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+/**
+ * @author jdiaz5513
+ */
+
+import initTrace from "debug";
+import { DEFAULT_TRAVERSE_LIMIT, DEFAULT_BUFFER_SIZE } from "../constants";
+import {
+ MSG_INVALID_FRAME_HEADER,
+ MSG_SEGMENT_OUT_OF_BOUNDS,
+ MSG_SEGMENT_TOO_SMALL,
+ MSG_NO_SEGMENTS_IN_ARENA,
+} from "../errors";
+import { dumpBuffer, format, padToWord } from "../util";
+import { AnyArena, Arena, MultiSegmentArena, SingleSegmentArena, ArenaKind } from "./arena";
+import { pack, unpack } from "./packing";
+import { Pointer, StructCtor, PointerType, Struct } from "./pointers";
+import { Segment } from "./segment";
+import { getTargetStructSize, validate } from "./pointers/pointer";
+import { resize, initStruct } from "./pointers/struct";
+
+const trace = initTrace("capnp:message");
+trace("load");
+
+export interface _Message {
+ readonly arena: AnyArena;
+ segments: Segment[];
+ traversalLimit: number;
+}
+
+export class Message {
+ static readonly allocateSegment = allocateSegment;
+ static readonly dump = dump;
+ static readonly getRoot = getRoot;
+ static readonly getSegment = getSegment;
+ static readonly initRoot = initRoot;
+ static readonly readRawPointer = readRawPointer;
+ static readonly toArrayBuffer = toArrayBuffer;
+ static readonly toPackedArrayBuffer = toPackedArrayBuffer;
+
+ readonly _capnp: _Message;
+
+ /**
+ * A Cap'n Proto message.
+ *
+ * SECURITY WARNING: In nodejs do not pass a Buffer's internal array buffer into this constructor. Pass the buffer
+ * directly and everything will be fine. If not, your message will potentially be initialized with random memory
+ * contents!
+ *
+ * The constructor method creates a new Message, optionally using a provided arena for segment allocation, or a buffer
+ * to read from.
+ *
+ * @constructor {Message}
+ *
+ * @param {AnyArena|ArrayBufferView|ArrayBuffer} [src] The source for the message.
+ * A value of `undefined` will cause the message to initialize with a single segment arena only big enough for the
+ * root pointer; it will expand as you go. This is a reasonable choice for most messages.
+ *
+ * Passing an arena will cause the message to use that arena for its segment allocation. Contents will be accepted
+ * as-is.
+ *
+ * Passing an array buffer view (like `DataView`, `Uint8Array` or `Buffer`) will create a **copy** of the source
+ * buffer; beware of the potential performance cost!
+ *
+ * @param {boolean} [packed] Whether or not the message is packed. If `true` (the default), the message will be
+ * unpacked.
+ *
+ * @param {boolean} [singleSegment] If true, `src` will be treated as a message consisting of a single segment without
+ * a framing header.
+ *
+ */
+ constructor(src?: AnyArena | ArrayBufferView | ArrayBuffer, packed = true, singleSegment = false) {
+ this._capnp = initMessage(src, packed, singleSegment);
+
+ if (src && !isAnyArena(src)) preallocateSegments(this);
+
+ trace("new %s", this);
+ }
+
+ allocateSegment(byteLength: number): Segment {
+ return allocateSegment(byteLength, this);
+ }
+
+ /**
+ * Create a pretty-printed string dump of this message; incredibly useful for debugging.
+ *
+ * WARNING: Do not call this method on large messages!
+ *
+ * @returns {string} A big steaming pile of pretty hex digits.
+ */
+
+ dump(): string {
+ return dump(this);
+ }
+
+ /**
+ * Get a struct pointer for the root of this message. This is primarily used when reading a message; it will not
+ * overwrite existing data.
+ *
+ * @template T
+ * @param {StructCtor<T>} RootStruct The struct type to use as the root.
+ * @returns {T} A struct representing the root of the message.
+ */
+
+ getRoot<T extends Struct>(RootStruct: StructCtor<T>): T {
+ return getRoot(RootStruct, this);
+ }
+
+ /**
+ * Get a segment by its id.
+ *
+ * This will lazily allocate the first segment if it doesn't already exist.
+ *
+ * @param {number} id The segment id.
+ * @returns {Segment} The requested segment.
+ */
+
+ getSegment(id: number): Segment {
+ return getSegment(id, this);
+ }
+
+ /**
+ * Initialize a new message using the provided struct type as the root.
+ *
+ * @template T
+ * @param {StructCtor<T>} RootStruct The struct type to use as the root.
+ * @returns {T} An initialized struct pointing to the root of the message.
+ */
+
+ initRoot<T extends Struct>(RootStruct: StructCtor<T>): T {
+ return initRoot(RootStruct, this);
+ }
+
+ /**
+ * Set the root of the message to a copy of the given pointer. Used internally
+ * to make copies of pointers for default values.
+ *
+ * @param {Pointer} src The source pointer to copy.
+ * @returns {void}
+ */
+
+ setRoot(src: Pointer): void {
+ setRoot(src, this);
+ }
+
+ /**
+ * Combine the contents of this message's segments into a single array buffer and prepend a stream framing header
+ * containing information about the following segment data.
+ *
+ * @returns {ArrayBuffer} An ArrayBuffer with the contents of this message.
+ */
+
+ toArrayBuffer(): ArrayBuffer {
+ return toArrayBuffer(this);
+ }
+
+ /**
+ * Like `toArrayBuffer()`, but also applies the packing algorithm to the output. This is typically what you want to
+ * use if you're sending the message over a network link or other slow I/O interface where size matters.
+ *
+ * @returns {ArrayBuffer} A packed message.
+ */
+
+ toPackedArrayBuffer(): ArrayBuffer {
+ return toPackedArrayBuffer(this);
+ }
+
+ toString(): string {
+ // eslint-disable-next-line @typescript-eslint/restrict-template-expressions
+ return `Message_arena:${this._capnp.arena}`;
+ }
+}
+
+export interface CreateMessageOptions {
+ packed?: boolean;
+ singleSegment?: boolean;
+}
+
+export function initMessage(
+ src?: AnyArena | ArrayBufferView | ArrayBuffer,
+ packed = true,
+ singleSegment = false
+): _Message {
+ if (src === undefined) {
+ return {
+ arena: new SingleSegmentArena(),
+ segments: [],
+ traversalLimit: DEFAULT_TRAVERSE_LIMIT,
+ };
+ }
+
+ if (isAnyArena(src)) {
+ return { arena: src, segments: [], traversalLimit: DEFAULT_TRAVERSE_LIMIT };
+ }
+
+ let buf: ArrayBuffer = src as ArrayBuffer;
+
+ if (isArrayBufferView(buf)) {
+ buf = buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
+ }
+
+ if (packed) buf = unpack(buf);
+
+ if (singleSegment) {
+ return {
+ arena: new SingleSegmentArena(buf),
+ segments: [],
+ traversalLimit: DEFAULT_TRAVERSE_LIMIT,
+ };
+ }
+
+ return {
+ arena: new MultiSegmentArena(getFramedSegments(buf)),
+ segments: [],
+ traversalLimit: DEFAULT_TRAVERSE_LIMIT,
+ };
+}
+
+/**
+ * Given an _unpacked_ message with a segment framing header, this will generate an ArrayBuffer for each segment in
+ * the message.
+ *
+ * This method is not typically called directly, but can be useful in certain cases.
+ *
+ * @static
+ * @param {ArrayBuffer} message An unpacked message with a framing header.
+ * @returns {ArrayBuffer[]} An array of buffers containing the segment data.
+ */
+
+export function getFramedSegments(message: ArrayBuffer): ArrayBuffer[] {
+ const dv = new DataView(message);
+
+ const segmentCount = dv.getUint32(0, true) + 1;
+
+ const segments = new Array(segmentCount) as ArrayBuffer[];
+
+ trace("reading %d framed segments from stream", segmentCount);
+
+ let byteOffset = 4 + segmentCount * 4;
+ byteOffset += byteOffset % 8;
+
+ if (byteOffset + segmentCount * 4 > message.byteLength) {
+ throw new Error(MSG_INVALID_FRAME_HEADER);
+ }
+
+ for (let i = 0; i < segmentCount; i++) {
+ const byteLength = dv.getUint32(4 + i * 4, true) * 8;
+
+ if (byteOffset + byteLength > message.byteLength) {
+ throw new Error(MSG_INVALID_FRAME_HEADER);
+ }
+
+ segments[i] = message.slice(byteOffset, byteOffset + byteLength);
+
+ byteOffset += byteLength;
+ }
+
+ return segments;
+}
+
+/**
+ * This method is called on messages that were constructed with existing data to prepopulate the segments array with
+ * everything we can find in the arena. Each segment will have it's `byteLength` set to the size of its buffer.
+ *
+ * Technically speaking, the message's segments will be "full" after calling this function. Calling this on your own
+ * may void your warranty.
+ *
+ * @param {Message} m The message to allocate.
+ * @returns {void}
+ */
+
+export function preallocateSegments(m: Message): void {
+ const numSegments = Arena.getNumSegments(m._capnp.arena);
+
+ if (numSegments < 1) throw new Error(MSG_NO_SEGMENTS_IN_ARENA);
+
+ m._capnp.segments = new Array(numSegments) as Segment[];
+
+ for (let i = 0; i < numSegments; i++) {
+ // Set up each segment so that they're fully allocated to the extents of the existing buffers.
+
+ const buffer = Arena.getBuffer(i, m._capnp.arena);
+ const segment = new Segment(i, m, buffer, buffer.byteLength);
+
+ m._capnp.segments[i] = segment;
+ }
+}
+
+function isArrayBufferView(src: ArrayBuffer | ArrayBufferView): src is ArrayBufferView {
+ return (src as { byteOffset?: number }).byteOffset !== undefined;
+}
+
+function isAnyArena(o: unknown): o is AnyArena {
+ return (o as { kind?: ArenaKind }).kind !== undefined;
+}
+
+export function allocateSegment(byteLength: number, m: Message): Segment {
+ trace("allocating %x bytes for %s", byteLength, m);
+
+ const res = Arena.allocate(byteLength, m._capnp.segments, m._capnp.arena);
+ let s: Segment;
+
+ if (res.id === m._capnp.segments.length) {
+ // Note how we're only allowing new segments in if they're exactly the next one in the array. There is no logical
+ // reason for segments to be created out of order.
+
+ s = new Segment(res.id, m, res.buffer);
+
+ trace("adding new segment %s", s);
+
+ m._capnp.segments.push(s);
+ } else if (res.id < 0 || res.id > m._capnp.segments.length) {
+ throw new Error(format(MSG_SEGMENT_OUT_OF_BOUNDS, res.id, m));
+ } else {
+ s = m._capnp.segments[res.id];
+
+ trace("replacing segment %s with buffer (len:%d)", s, res.buffer.byteLength);
+
+ s.replaceBuffer(res.buffer);
+ }
+
+ return s;
+}
+
+export function dump(m: Message): string {
+ let r = "";
+
+ if (m._capnp.segments.length === 0) {
+ return "================\nNo Segments\n================\n";
+ }
+
+ for (let i = 0; i < m._capnp.segments.length; i++) {
+ r += `================\nSegment #${i}\n================\n`;
+
+ const { buffer, byteLength } = m._capnp.segments[i];
+ const b = new Uint8Array(buffer, 0, byteLength);
+
+ r += dumpBuffer(b);
+ }
+
+ return r;
+}
+
+export function getRoot<T extends Struct>(RootStruct: StructCtor<T>, m: Message): T {
+ const root = new RootStruct(m.getSegment(0), 0);
+
+ validate(PointerType.STRUCT, root);
+
+ const ts = getTargetStructSize(root);
+
+ // Make sure the underlying pointer is actually big enough to hold the data and pointers as specified in the schema.
+ // If not a shallow copy of the struct contents needs to be made before returning.
+
+ if (
+ ts.dataByteLength < RootStruct._capnp.size.dataByteLength ||
+ ts.pointerLength < RootStruct._capnp.size.pointerLength
+ ) {
+ trace("need to resize root struct %s", root);
+
+ resize(RootStruct._capnp.size, root);
+ }
+
+ return root;
+}
+
+export function getSegment(id: number, m: Message): Segment {
+ const segmentLength = m._capnp.segments.length;
+
+ if (id === 0 && segmentLength === 0) {
+ // Segment zero is special. If we have no segments in the arena we'll want to allocate a new one and leave room
+ // for the root pointer.
+
+ const arenaSegments = Arena.getNumSegments(m._capnp.arena);
+
+ if (arenaSegments === 0) {
+ allocateSegment(DEFAULT_BUFFER_SIZE, m);
+ } else {
+ // Okay, the arena already has a buffer we can use. This is totally fine.
+
+ m._capnp.segments[0] = new Segment(0, m, Arena.getBuffer(0, m._capnp.arena));
+ }
+
+ if (!m._capnp.segments[0].hasCapacity(8)) {
+ throw new Error(MSG_SEGMENT_TOO_SMALL);
+ }
+
+ // This will leave room for the root pointer.
+
+ m._capnp.segments[0].allocate(8);
+
+ return m._capnp.segments[0];
+ }
+
+ if (id < 0 || id >= segmentLength) {
+ throw new Error(format(MSG_SEGMENT_OUT_OF_BOUNDS, id, m));
+ }
+
+ return m._capnp.segments[id];
+}
+
+export function initRoot<T extends Struct>(RootStruct: StructCtor<T>, m: Message): T {
+ const root = new RootStruct(m.getSegment(0), 0);
+
+ initStruct(RootStruct._capnp.size, root);
+
+ trace("Initialized root pointer %s for %s.", root, m);
+
+ return root;
+}
+
+/**
+ * Read a pointer in raw form (a packed message with framing headers). Does not
+ * care or attempt to validate the input beyond parsing the message
+ * segments.
+ *
+ * This is typically used by the compiler to load default values, but can be
+ * useful to work with messages with an unknown schema.
+ *
+ * @param {ArrayBuffer} data The raw data to read.
+ * @returns {Pointer} A root pointer.
+ */
+
+export function readRawPointer(data: ArrayBuffer): Pointer {
+ return new Pointer(new Message(data).getSegment(0), 0);
+}
+
+export function setRoot(src: Pointer, m: Message): void {
+ Pointer.copyFrom(src, new Pointer(m.getSegment(0), 0));
+}
+
+export function toArrayBuffer(m: Message): ArrayBuffer {
+ const streamFrame = getStreamFrame(m);
+
+ // Make sure the first segment is allocated.
+
+ if (m._capnp.segments.length === 0) getSegment(0, m);
+
+ const segments = m._capnp.segments;
+
+ // Add space for the stream framing.
+
+ const totalLength = streamFrame.byteLength + segments.reduce((l, s) => l + padToWord(s.byteLength), 0);
+ const out = new Uint8Array(new ArrayBuffer(totalLength));
+ let o = streamFrame.byteLength;
+
+ out.set(new Uint8Array(streamFrame));
+
+ segments.forEach((s) => {
+ const segmentLength = padToWord(s.byteLength);
+ out.set(new Uint8Array(s.buffer, 0, segmentLength), o);
+
+ o += segmentLength;
+ });
+
+ return out.buffer;
+}
+
+export function toPackedArrayBuffer(m: Message): ArrayBuffer {
+ const streamFrame = pack(getStreamFrame(m));
+
+ // Make sure the first segment is allocated.
+
+ if (m._capnp.segments.length === 0) m.getSegment(0);
+
+ // NOTE: A copy operation can be avoided here if we capture the intermediate array and use that directly in the copy
+ // loop below, rather than have `pack()` copy it to an ArrayBuffer just to have to copy it again later. If the
+ // intermediate array can be avoided altogether that's even better!
+ const segments = m._capnp.segments.map((s) => pack(s.buffer, 0, padToWord(s.byteLength)));
+
+ const totalLength = streamFrame.byteLength + segments.reduce((l, s) => l + s.byteLength, 0);
+ const out = new Uint8Array(new ArrayBuffer(totalLength));
+ let o = streamFrame.byteLength;
+
+ out.set(new Uint8Array(streamFrame));
+
+ segments.forEach((s) => {
+ out.set(new Uint8Array(s), o);
+
+ o += s.byteLength;
+ });
+
+ return out.buffer;
+}
+
+export function getStreamFrame(m: Message): ArrayBuffer {
+ const length = m._capnp.segments.length;
+
+ if (length === 0) {
+ // Don't bother allocating the first segment, just return a single zero word for the frame header.
+
+ return new Float64Array(1).buffer;
+ }
+
+ const frameLength = 4 + length * 4 + (1 - (length % 2)) * 4;
+ const out = new DataView(new ArrayBuffer(frameLength));
+
+ trace("Writing message stream frame with segment count: %d.", length);
+
+ out.setUint32(0, length - 1, true);
+
+ m._capnp.segments.forEach((s, i) => {
+ trace("Message segment %d word count: %d.", s.id, s.byteLength / 8);
+
+ out.setUint32(i * 4 + 4, s.byteLength / 8, true);
+ });
+
+ return out.buffer;
+}