Lee Thanh
Upload 3012 files
5641073
raw
history blame
32.7 kB
/**
* @author jdiaz5513
*/
import initTrace from "debug";
import { LIST_SIZE_MASK, MAX_DEPTH, POINTER_DOUBLE_FAR_MASK, POINTER_TYPE_MASK } from "../../constants";
import { bufferToHex, format, padToWord } from "../../util";
import { ListElementSize } from "../list-element-size";
import {
ObjectSize,
getByteLength,
padToWord as padObjectToWord,
getWordLength,
getDataWordLength,
} from "../object-size";
import { Segment } from "../segment";
import { Orphan } from "./orphan";
import { PointerAllocationResult } from "./pointer-allocation-result";
import { PointerType } from "./pointer-type";
import { Message } from "../message";
import {
PTR_TRAVERSAL_LIMIT_EXCEEDED,
PTR_DEPTH_LIMIT_EXCEEDED,
PTR_OFFSET_OUT_OF_BOUNDS,
PTR_INVALID_LIST_SIZE,
PTR_INVALID_POINTER_TYPE,
PTR_INVALID_FAR_TARGET,
TYPE_COMPOSITE_SIZE_UNDEFINED,
PTR_WRONG_POINTER_TYPE,
PTR_WRONG_LIST_TYPE,
INVARIANT_UNREACHABLE_CODE,
} from "../../errors";
const trace = initTrace("capnp:pointer");
trace("load");
export interface _PointerCtor {
readonly displayName: string;
}
export interface PointerCtor<T extends Pointer> {
readonly _capnp: _PointerCtor;
new (segment: Segment, byteOffset: number, depthLimit?: number): T;
}
export interface _Pointer {
compositeIndex?: number;
compositeList: boolean;
/**
* A number that is decremented as nested pointers are traversed. When this hits zero errors will be thrown.
*/
depthLimit: number;
}
/**
* A pointer referencing a single byte location in a segment. This is typically used for Cap'n Proto pointers, but is
* also sometimes used to reference an offset to a pointer's content or tag words.
*
* @export
* @class Pointer
*/
export class Pointer {
static readonly adopt = adopt;
static readonly copyFrom = copyFrom;
static readonly disown = disown;
static readonly dump = dump;
static readonly isNull = isNull;
static readonly _capnp: _PointerCtor = {
displayName: "Pointer" as string,
};
readonly _capnp: _Pointer;
/** Offset, in bytes, from the start of the segment to the beginning of this pointer. */
byteOffset: number;
/**
* The starting segment for this pointer's data. In the case of a far pointer, the actual content this pointer is
* referencing will be in another segment within the same message.
*/
segment: Segment;
constructor(segment: Segment, byteOffset: number, depthLimit = MAX_DEPTH) {
this._capnp = { compositeList: false, depthLimit };
this.segment = segment;
this.byteOffset = byteOffset;
if (depthLimit === 0) {
throw new Error(format(PTR_DEPTH_LIMIT_EXCEEDED, this));
}
// Make sure we keep track of all pointer allocations; there's a limit per message (prevent DoS).
trackPointerAllocation(segment.message, this);
// NOTE: It's okay to have a pointer to the end of the segment; you'll see this when creating pointers to the
// beginning of the content of a newly-allocated composite list with zero elements. Unlike other language
// implementations buffer over/underflows are not a big issue since all buffer access is bounds checked in native
// code anyway.
if (byteOffset < 0 || byteOffset > segment.byteLength) {
throw new Error(format(PTR_OFFSET_OUT_OF_BOUNDS, byteOffset));
}
trace("new %s", this);
}
toString(): string {
return format("Pointer_%d@%a,%s,limit:%x", this.segment.id, this.byteOffset, dump(this), this._capnp.depthLimit);
}
}
/**
* Adopt an orphaned pointer, making the pointer point to the orphaned content without copying it.
*
* @param {Orphan<Pointer>} src The orphan to adopt.
* @param {Pointer} p The the pointer to adopt into.
* @returns {void}
*/
export function adopt<T extends Pointer>(src: Orphan<T>, p: T): void {
src._moveTo(p);
}
/**
* Convert a pointer to an Orphan, zeroing out the pointer and leaving its content untouched. If the content is no
* longer needed, call `disown()` on the orphaned pointer to erase the contents as well.
*
* Call `adopt()` on the orphan with the new target pointer location to move it back into the message; the orphan
* object is then invalidated after adoption (can only adopt once!).
*
* @param {T} p The pointer to turn into an Orphan.
* @returns {Orphan<T>} An orphaned pointer.
*/
export function disown<T extends Pointer>(p: T): Orphan<T> {
return new Orphan(p);
}
export function dump(p: Pointer): string {
return bufferToHex(p.segment.buffer.slice(p.byteOffset, p.byteOffset + 8));
}
/**
* Get the total number of bytes required to hold a list of the provided size with the given length, rounded up to the
* nearest word.
*
* @param {ListElementSize} elementSize A number describing the size of the list elements.
* @param {number} length The length of the list.
* @param {ObjectSize} [compositeSize] The size of each element in a composite list; required if
* `elementSize === ListElementSize.COMPOSITE`.
* @returns {number} The number of bytes required to hold an element of that size, or `NaN` if that is undefined.
*/
export function getListByteLength(elementSize: ListElementSize, length: number, compositeSize?: ObjectSize): number {
switch (elementSize) {
case ListElementSize.BIT:
return padToWord((length + 7) >>> 3);
case ListElementSize.BYTE:
case ListElementSize.BYTE_2:
case ListElementSize.BYTE_4:
case ListElementSize.BYTE_8:
case ListElementSize.POINTER:
case ListElementSize.VOID:
return padToWord(getListElementByteLength(elementSize) * length);
/* istanbul ignore next */
case ListElementSize.COMPOSITE:
if (compositeSize === undefined) {
throw new Error(format(PTR_INVALID_LIST_SIZE, NaN));
}
return length * padToWord(getByteLength(compositeSize));
/* istanbul ignore next */
default:
throw new Error(PTR_INVALID_LIST_SIZE);
}
}
/**
* Get the number of bytes required to hold a list element of the provided size. `COMPOSITE` elements do not have a
* fixed size, and `BIT` elements are packed into exactly a single bit, so these both return `NaN`.
*
* @param {ListElementSize} elementSize A number describing the size of the list elements.
* @returns {number} The number of bytes required to hold an element of that size, or `NaN` if that is undefined.
*/
export function getListElementByteLength(elementSize: ListElementSize): number {
switch (elementSize) {
/* istanbul ignore next */
case ListElementSize.BIT:
return NaN;
case ListElementSize.BYTE:
return 1;
case ListElementSize.BYTE_2:
return 2;
case ListElementSize.BYTE_4:
return 4;
case ListElementSize.BYTE_8:
case ListElementSize.POINTER:
return 8;
/* istanbul ignore next */
case ListElementSize.COMPOSITE:
// Caller has to figure it out based on the tag word.
return NaN;
/* istanbul ignore next */
case ListElementSize.VOID:
return 0;
/* istanbul ignore next */
default:
throw new Error(format(PTR_INVALID_LIST_SIZE, elementSize));
}
}
/**
* Add an offset to the pointer's offset and return a new Pointer for that address.
*
* @param {number} offset The number of bytes to add to the offset.
* @param {Pointer} p The pointer to add from.
* @returns {Pointer} A new pointer to the address.
*/
export function add(offset: number, p: Pointer): Pointer {
return new Pointer(p.segment, p.byteOffset + offset, p._capnp.depthLimit);
}
/**
* Replace a pointer with a deep copy of the pointer at `src` and all of its contents.
*
* @param {Pointer} src The pointer to copy.
* @param {Pointer} p The pointer to copy into.
* @returns {void}
*/
export function copyFrom(src: Pointer, p: Pointer): void {
// If the pointer is the same then this is a noop.
if (p.segment === src.segment && p.byteOffset === src.byteOffset) {
trace("ignoring copy operation from identical pointer %s", src);
return;
}
// Make sure we erase this pointer's contents before moving on. If src is null, that's all we do.
erase(p); // noop if null
if (isNull(src)) return;
switch (getTargetPointerType(src)) {
case PointerType.STRUCT:
copyFromStruct(src, p);
break;
case PointerType.LIST:
copyFromList(src, p);
break;
/* istanbul ignore next */
default:
throw new Error(format(PTR_INVALID_POINTER_TYPE, getTargetPointerType(p)));
}
}
/**
* Recursively erase a pointer, any far pointers/landing pads/tag words, and the content it points to.
*
* Note that this will leave "holes" of zeroes in the message, since the space cannot be reclaimed. With packing this
* will have a negligible effect on the final message size.
*
* FIXME: This may need protection against infinite recursion...
*
* @param {Pointer} p The pointer to erase.
* @returns {void}
*/
export function erase(p: Pointer): void {
if (isNull(p)) return;
// First deal with the contents.
let c: Pointer;
switch (getTargetPointerType(p)) {
case PointerType.STRUCT: {
const size = getTargetStructSize(p);
c = getContent(p);
// Wipe the data section.
c.segment.fillZeroWords(c.byteOffset, size.dataByteLength / 8);
// Iterate over all the pointers and nuke them.
for (let i = 0; i < size.pointerLength; i++) {
erase(add(i * 8, c));
}
break;
}
case PointerType.LIST: {
const elementSize = getTargetListElementSize(p);
const length = getTargetListLength(p);
let contentWords = padToWord(length * getListElementByteLength(elementSize));
c = getContent(p);
if (elementSize === ListElementSize.POINTER) {
for (let i = 0; i < length; i++) {
erase(new Pointer(c.segment, c.byteOffset + i * 8, p._capnp.depthLimit - 1));
}
// Calling erase on each pointer takes care of the content, nothing left to do here.
break;
} else if (elementSize === ListElementSize.COMPOSITE) {
// Read some stuff from the tag word.
const tag = add(-8, c);
const compositeSize = getStructSize(tag);
const compositeByteLength = getByteLength(compositeSize);
contentWords = getOffsetWords(tag);
// Kill the tag word.
c.segment.setWordZero(c.byteOffset - 8);
// Recursively erase each pointer.
for (let i = 0; i < length; i++) {
for (let j = 0; j < compositeSize.pointerLength; j++) {
erase(new Pointer(c.segment, c.byteOffset + i * compositeByteLength + j * 8, p._capnp.depthLimit - 1));
}
}
}
c.segment.fillZeroWords(c.byteOffset, contentWords);
break;
}
case PointerType.OTHER:
// No content.
break;
default:
throw new Error(format(PTR_INVALID_POINTER_TYPE, getTargetPointerType(p)));
}
erasePointer(p);
}
/**
* Set the pointer (and far pointer landing pads, if applicable) to zero. Does not touch the pointer's content.
*
* @param {Pointer} p The pointer to erase.
* @returns {void}
*/
export function erasePointer(p: Pointer): void {
if (getPointerType(p) === PointerType.FAR) {
const landingPad = followFar(p);
if (isDoubleFar(p)) {
// Kill the double-far tag word.
landingPad.segment.setWordZero(landingPad.byteOffset + 8);
}
// Kill the landing pad.
landingPad.segment.setWordZero(landingPad.byteOffset);
}
// Finally! Kill the pointer itself...
p.segment.setWordZero(p.byteOffset);
}
/**
* Interpret the pointer as a far pointer, returning its target segment and offset.
*
* @param {Pointer} p The pointer to read from.
* @returns {Pointer} A pointer to the far target.
*/
export function followFar(p: Pointer): Pointer {
const targetSegment = p.segment.message.getSegment(p.segment.getUint32(p.byteOffset + 4));
const targetWordOffset = p.segment.getUint32(p.byteOffset) >>> 3;
return new Pointer(targetSegment, targetWordOffset * 8, p._capnp.depthLimit - 1);
}
/**
* If the pointer address references a far pointer, follow it to the location where the actual pointer data is written.
* Otherwise, returns the pointer unmodified.
*
* @param {Pointer} p The pointer to read from.
* @returns {Pointer} A new pointer representing the target location, or `p` if it is not a far pointer.
*/
export function followFars(p: Pointer): Pointer {
if (getPointerType(p) === PointerType.FAR) {
const landingPad = followFar(p);
if (isDoubleFar(p)) landingPad.byteOffset += 8;
return landingPad;
}
return p;
}
export function getCapabilityId(p: Pointer): number {
return p.segment.getUint32(p.byteOffset + 4);
}
function isCompositeList(p: Pointer): boolean {
return getTargetPointerType(p) === PointerType.LIST && getTargetListElementSize(p) === ListElementSize.COMPOSITE;
}
/**
* Obtain the location of the pointer's content, following far pointers as needed.
* If the pointer is a struct pointer and `compositeIndex` is set, it will be offset by a multiple of the struct's size.
*
* @param {Pointer} p The pointer to read from.
* @param {boolean} [ignoreCompositeIndex] If true, will not follow the composite struct pointer's composite index and
* instead return a pointer to the parent list's contents (also the beginning of the first struct).
* @returns {Pointer} A pointer to the beginning of the pointer's content.
*/
export function getContent(p: Pointer, ignoreCompositeIndex?: boolean): Pointer {
let c: Pointer;
if (isDoubleFar(p)) {
const landingPad = followFar(p);
c = new Pointer(p.segment.message.getSegment(getFarSegmentId(landingPad)), getOffsetWords(landingPad) * 8);
} else {
const target = followFars(p);
c = new Pointer(target.segment, target.byteOffset + 8 + getOffsetWords(target) * 8);
}
if (isCompositeList(p)) c.byteOffset += 8;
if (!ignoreCompositeIndex && p._capnp.compositeIndex !== undefined) {
// Seek backwards by one word so we can read the struct size off the tag word.
c.byteOffset -= 8;
// Seek ahead by `compositeIndex` multiples of the struct's total size.
c.byteOffset += 8 + p._capnp.compositeIndex * getByteLength(padObjectToWord(getStructSize(c)));
}
return c;
}
/**
* Read the target segment ID from a far pointer.
*
* @param {Pointer} p The pointer to read from.
* @returns {number} The target segment ID.
*/
export function getFarSegmentId(p: Pointer): number {
return p.segment.getUint32(p.byteOffset + 4);
}
/**
* Get a number indicating the size of the list's elements.
*
* @param {Pointer} p The pointer to read from.
* @returns {ListElementSize} The size of the list's elements.
*/
export function getListElementSize(p: Pointer): ListElementSize {
return p.segment.getUint32(p.byteOffset + 4) & LIST_SIZE_MASK;
}
/**
* Get the number of elements in a list pointer. For composite lists, it instead represents the total number of words in
* the list (not counting the tag word).
*
* This method does **not** attempt to distinguish between composite and non-composite lists. To get the correct
* length for composite lists use `getTargetListLength()` instead.
*
* @param {Pointer} p The pointer to read from.
* @returns {number} The length of the list, or total number of words for composite lists.
*/
export function getListLength(p: Pointer): number {
return p.segment.getUint32(p.byteOffset + 4) >>> 3;
}
/**
* Get the offset (in words) from the end of a pointer to the start of its content. For struct pointers, this is the
* beginning of the data section, and for list pointers it is the location of the first element. The value should
* always be zero for interface pointers.
*
* @param {Pointer} p The pointer to read from.
* @returns {number} The offset, in words, from the end of the pointer to the start of the data section.
*/
export function getOffsetWords(p: Pointer): number {
const o = p.segment.getInt32(p.byteOffset);
// Far pointers only have 29 offset bits.
return o & 2 ? o >> 3 : o >> 2;
}
/**
* Look up the pointer's type.
*
* @param {Pointer} p The pointer to read from.
* @returns {PointerType} The type of pointer.
*/
export function getPointerType(p: Pointer): PointerType {
return p.segment.getUint32(p.byteOffset) & POINTER_TYPE_MASK;
}
/**
* Read the number of data words from this struct pointer.
*
* @param {Pointer} p The pointer to read from.
* @returns {number} The number of data words in the struct.
*/
export function getStructDataWords(p: Pointer): number {
return p.segment.getUint16(p.byteOffset + 4);
}
/**
* Read the number of pointers contained in this struct pointer.
*
* @param {Pointer} p The pointer to read from.
* @returns {number} The number of pointers in this struct.
*/
export function getStructPointerLength(p: Pointer): number {
return p.segment.getUint16(p.byteOffset + 6);
}
/**
* Get an object describing this struct pointer's size.
*
* @param {Pointer} p The pointer to read from.
* @returns {ObjectSize} The size of the struct.
*/
export function getStructSize(p: Pointer): ObjectSize {
return new ObjectSize(getStructDataWords(p) * 8, getStructPointerLength(p));
}
/**
* Get a pointer to this pointer's composite list tag word, following far pointers as needed.
*
* @param {Pointer} p The pointer to read from.
* @returns {Pointer} A pointer to the list's composite tag word.
*/
export function getTargetCompositeListTag(p: Pointer): Pointer {
const c = getContent(p);
// The composite list tag is always one word before the content.
c.byteOffset -= 8;
return c;
}
/**
* Get the object size for the target composite list, following far pointers as needed.
*
* @param {Pointer} p The pointer to read from.
* @returns {ObjectSize} An object describing the size of each struct in the list.
*/
export function getTargetCompositeListSize(p: Pointer): ObjectSize {
return getStructSize(getTargetCompositeListTag(p));
}
/**
* Get the size of the list elements referenced by this pointer, following far pointers if necessary.
*
* @param {Pointer} p The pointer to read from.
* @returns {ListElementSize} The size of the elements in the list.
*/
export function getTargetListElementSize(p: Pointer): ListElementSize {
return getListElementSize(followFars(p));
}
/**
* Get the length of the list referenced by this pointer, following far pointers if necessary. If the list is a
* composite list, it will look up the tag word and read the length from there.
*
* @param {Pointer} p The pointer to read from.
* @returns {number} The number of elements in the list.
*/
export function getTargetListLength(p: Pointer): number {
const t = followFars(p);
if (getListElementSize(t) === ListElementSize.COMPOSITE) {
// The content is prefixed by a tag word; it's a struct pointer whose offset contains the list's length.
return getOffsetWords(getTargetCompositeListTag(p));
}
return getListLength(t);
}
/**
* Get the type of a pointer, following far pointers if necessary. For non-far pointers this is equivalent to calling
* `getPointerType()`.
*
* The target of a far pointer can never be another far pointer, and this method will throw if such a situation is
* encountered.
*
* @param {Pointer} p The pointer to read from.
* @returns {PointerType} The type of pointer referenced by this pointer.
*/
export function getTargetPointerType(p: Pointer): PointerType {
const t = getPointerType(followFars(p));
if (t === PointerType.FAR) throw new Error(format(PTR_INVALID_FAR_TARGET, p));
return t;
}
/**
* Get the size of the struct referenced by a pointer, following far pointers if necessary.
*
* @param {Pointer} p The poiner to read from.
* @returns {ObjectSize} The size of the struct referenced by this pointer.
*/
export function getTargetStructSize(p: Pointer): ObjectSize {
return getStructSize(followFars(p));
}
/**
* Initialize a pointer to point at the data in the content segment. If the content segment is not the same as the
* pointer's segment, this will allocate and write far pointers as needed. Nothing is written otherwise.
*
* The return value includes a pointer to write the pointer's actual data to (the eventual far target), and the offset
* value (in words) to use for that pointer. In the case of double-far pointers this offset will always be zero.
*
* @param {Segment} contentSegment The segment containing this pointer's content.
* @param {number} contentOffset The offset within the content segment for the beginning of this pointer's content.
* @param {Pointer} p The pointer to initialize.
* @returns {PointerAllocationResult} An object containing a pointer (where the pointer data should be written), and
* the value to use as the offset for that pointer.
*/
export function initPointer(contentSegment: Segment, contentOffset: number, p: Pointer): PointerAllocationResult {
if (p.segment !== contentSegment) {
// Need a far pointer.
trace("Initializing far pointer %s -> %s.", p, contentSegment);
if (!contentSegment.hasCapacity(8)) {
// GAH! Not enough space in the content segment for a landing pad so we need a double far pointer.
const landingPad = p.segment.allocate(16);
trace("GAH! Initializing double-far pointer in %s from %s -> %s.", p, contentSegment, landingPad);
setFarPointer(true, landingPad.byteOffset / 8, landingPad.segment.id, p);
setFarPointer(false, contentOffset / 8, contentSegment.id, landingPad);
landingPad.byteOffset += 8;
return new PointerAllocationResult(landingPad, 0);
}
// Allocate a far pointer landing pad in the target segment.
const landingPad = contentSegment.allocate(8);
if (landingPad.segment.id !== contentSegment.id) {
throw new Error(INVARIANT_UNREACHABLE_CODE);
}
setFarPointer(false, landingPad.byteOffset / 8, landingPad.segment.id, p);
return new PointerAllocationResult(landingPad, (contentOffset - landingPad.byteOffset - 8) / 8);
}
trace("Initializing intra-segment pointer %s -> %a.", p, contentOffset);
return new PointerAllocationResult(p, (contentOffset - p.byteOffset - 8) / 8);
}
/**
* Check if the pointer is a double-far pointer.
*
* @param {Pointer} p The pointer to read from.
* @returns {boolean} `true` if it is a double-far pointer, `false` otherwise.
*/
export function isDoubleFar(p: Pointer): boolean {
return getPointerType(p) === PointerType.FAR && (p.segment.getUint32(p.byteOffset) & POINTER_DOUBLE_FAR_MASK) !== 0;
}
/**
* Quickly check to see if the pointer is "null". A "null" pointer is a zero word, equivalent to an empty struct
* pointer.
*
* @param {Pointer} p The pointer to read from.
* @returns {boolean} `true` if the pointer is "null".
*/
export function isNull(p: Pointer): boolean {
return p.segment.isWordZero(p.byteOffset);
}
/**
* Relocate a pointer to the given destination, ensuring that it points to the same content. This will create far
* pointers as needed if the content is in a different segment than the destination. After the relocation the source
* pointer will be erased and is no longer valid.
*
* @param {Pointer} dst The desired location for the `src` pointer. Any existing contents will be erased before
* relocating!
* @param {Pointer} src The pointer to relocate.
* @returns {void}
*/
export function relocateTo(dst: Pointer, src: Pointer): void {
const t = followFars(src);
const lo = t.segment.getUint8(t.byteOffset) & 0x03; // discard the offset
const hi = t.segment.getUint32(t.byteOffset + 4);
// Make sure anything dst was pointing to is wiped out.
erase(dst);
const res = initPointer(t.segment, t.byteOffset + 8 + getOffsetWords(t) * 8, dst);
// Keep the low 2 bits and write the new offset.
res.pointer.segment.setUint32(res.pointer.byteOffset, lo | (res.offsetWords << 2));
// Keep the high 32 bits intact.
res.pointer.segment.setUint32(res.pointer.byteOffset + 4, hi);
erasePointer(src);
}
/**
* Write a far pointer.
*
* @param {boolean} doubleFar Set to `true` if this is a double far pointer.
* @param {number} offsetWords The offset, in words, to the target pointer.
* @param {number} segmentId The segment the target pointer is located in.
* @param {Pointer} p The pointer to write to.
* @returns {void}
*/
export function setFarPointer(doubleFar: boolean, offsetWords: number, segmentId: number, p: Pointer): void {
const A = PointerType.FAR;
const B = doubleFar ? 1 : 0;
const C = offsetWords;
const D = segmentId;
p.segment.setUint32(p.byteOffset, A | (B << 2) | (C << 3));
p.segment.setUint32(p.byteOffset + 4, D);
}
/**
* Write a raw interface pointer.
*
* @param {number} capId The capability ID.
* @param {Pointer} p The pointer to write to.
* @returns {void}
*/
export function setInterfacePointer(capId: number, p: Pointer): void {
p.segment.setUint32(p.byteOffset, PointerType.OTHER);
p.segment.setUint32(p.byteOffset + 4, capId);
}
/**
* Write a raw list pointer.
*
* @param {number} offsetWords The number of words from the end of this pointer to the beginning of the list content.
* @param {ListElementSize} size The size of each element in the list.
* @param {number} length The number of elements in the list.
* @param {Pointer} p The pointer to write to.
* @param {ObjectSize} [compositeSize] For composite lists this describes the size of each element in this list. This
* is required for composite lists.
* @returns {void}
*/
export function setListPointer(
offsetWords: number,
size: ListElementSize,
length: number,
p: Pointer,
compositeSize?: ObjectSize
): void {
const A = PointerType.LIST;
const B = offsetWords;
const C = size;
let D = length;
if (size === ListElementSize.COMPOSITE) {
if (compositeSize === undefined) {
throw new TypeError(TYPE_COMPOSITE_SIZE_UNDEFINED);
}
D *= getWordLength(compositeSize);
}
p.segment.setUint32(p.byteOffset, A | (B << 2));
p.segment.setUint32(p.byteOffset + 4, C | (D << 3));
}
/**
* Write a raw struct pointer.
*
* @param {number} offsetWords The number of words from the end of this pointer to the beginning of the struct's data
* section.
* @param {ObjectSize} size An object describing the size of the struct.
* @param {Pointer} p The pointer to write to.
* @returns {void}
*/
export function setStructPointer(offsetWords: number, size: ObjectSize, p: Pointer): void {
const A = PointerType.STRUCT;
const B = offsetWords;
const C = getDataWordLength(size);
const D = size.pointerLength;
p.segment.setUint32(p.byteOffset, A | (B << 2));
p.segment.setUint16(p.byteOffset + 4, C);
p.segment.setUint16(p.byteOffset + 6, D);
}
/**
* Read some bits off a pointer to make sure it has the right pointer data.
*
* @param {PointerType} pointerType The expected pointer type.
* @param {Pointer} p The pointer to validate.
* @param {ListElementSize} [elementSize] For list pointers, the expected element size. Leave this
* undefined for struct pointers.
* @returns {void}
*/
export function validate(pointerType: PointerType, p: Pointer, elementSize?: ListElementSize): void {
if (isNull(p)) return;
const t = followFars(p);
// Check the pointer type.
const A = t.segment.getUint32(t.byteOffset) & POINTER_TYPE_MASK;
if (A !== pointerType) {
throw new Error(format(PTR_WRONG_POINTER_TYPE, p, pointerType));
}
// Check the list element size, if provided.
if (elementSize !== undefined) {
const C = t.segment.getUint32(t.byteOffset + 4) & LIST_SIZE_MASK;
if (C !== elementSize) {
throw new Error(format(PTR_WRONG_LIST_TYPE, p, ListElementSize[elementSize]));
}
}
}
export function copyFromList(src: Pointer, dst: Pointer): void {
if (dst._capnp.depthLimit <= 0) throw new Error(PTR_DEPTH_LIMIT_EXCEEDED);
const srcContent = getContent(src);
const srcElementSize = getTargetListElementSize(src);
const srcLength = getTargetListLength(src);
let srcCompositeSize;
let srcStructByteLength;
let dstContent;
if (srcElementSize === ListElementSize.POINTER) {
dstContent = dst.segment.allocate(srcLength << 3);
// Recursively copy each pointer in the list.
for (let i = 0; i < srcLength; i++) {
const srcPtr = new Pointer(srcContent.segment, srcContent.byteOffset + (i << 3), src._capnp.depthLimit - 1);
const dstPtr = new Pointer(dstContent.segment, dstContent.byteOffset + (i << 3), dst._capnp.depthLimit - 1);
copyFrom(srcPtr, dstPtr);
}
} else if (srcElementSize === ListElementSize.COMPOSITE) {
srcCompositeSize = padObjectToWord(getTargetCompositeListSize(src));
srcStructByteLength = getByteLength(srcCompositeSize);
dstContent = dst.segment.allocate(getByteLength(srcCompositeSize) * srcLength + 8);
// Copy the tag word.
dstContent.segment.copyWord(dstContent.byteOffset, srcContent.segment, srcContent.byteOffset - 8);
// Copy the entire contents, including all pointers. This should be more efficient than making `srcLength`
// copies to skip the pointer sections, and we're about to rewrite all those pointers anyway.
// PERF: Skip this step if the composite struct only contains pointers.
if (srcCompositeSize.dataByteLength > 0) {
const wordLength = getWordLength(srcCompositeSize) * srcLength;
dstContent.segment.copyWords(dstContent.byteOffset + 8, srcContent.segment, srcContent.byteOffset, wordLength);
}
// Recursively copy all the pointers in each struct.
for (let i = 0; i < srcLength; i++) {
for (let j = 0; j < srcCompositeSize.pointerLength; j++) {
const offset = i * srcStructByteLength + srcCompositeSize.dataByteLength + (j << 3);
const srcPtr = new Pointer(srcContent.segment, srcContent.byteOffset + offset, src._capnp.depthLimit - 1);
const dstPtr = new Pointer(dstContent.segment, dstContent.byteOffset + offset + 8, dst._capnp.depthLimit - 1);
copyFrom(srcPtr, dstPtr);
}
}
} else {
const byteLength = padToWord(
srcElementSize === ListElementSize.BIT
? (srcLength + 7) >>> 3
: getListElementByteLength(srcElementSize) * srcLength
);
const wordLength = byteLength >>> 3;
dstContent = dst.segment.allocate(byteLength);
// Copy all of the list contents word-by-word.
dstContent.segment.copyWords(dstContent.byteOffset, srcContent.segment, srcContent.byteOffset, wordLength);
}
// Initialize the list pointer.
const res = initPointer(dstContent.segment, dstContent.byteOffset, dst);
setListPointer(res.offsetWords, srcElementSize, srcLength, res.pointer, srcCompositeSize);
}
export function copyFromStruct(src: Pointer, dst: Pointer): void {
if (dst._capnp.depthLimit <= 0) throw new Error(PTR_DEPTH_LIMIT_EXCEEDED);
const srcContent = getContent(src);
const srcSize = getTargetStructSize(src);
const srcDataWordLength = getDataWordLength(srcSize);
// Allocate space for the destination content.
const dstContent = dst.segment.allocate(getByteLength(srcSize));
// Copy the data section.
dstContent.segment.copyWords(dstContent.byteOffset, srcContent.segment, srcContent.byteOffset, srcDataWordLength);
// Copy the pointer section.
for (let i = 0; i < srcSize.pointerLength; i++) {
const offset = srcSize.dataByteLength + i * 8;
const srcPtr = new Pointer(srcContent.segment, srcContent.byteOffset + offset, src._capnp.depthLimit - 1);
const dstPtr = new Pointer(dstContent.segment, dstContent.byteOffset + offset, dst._capnp.depthLimit - 1);
copyFrom(srcPtr, dstPtr);
}
// Don't touch dst if it's already initialized as a composite list pointer. With composite struct pointers there's
// no pointer to copy here and we've already copied the contents.
if (dst._capnp.compositeList) return;
// Initialize the struct pointer.
const res = initPointer(dstContent.segment, dstContent.byteOffset, dst);
setStructPointer(res.offsetWords, srcSize, res.pointer);
}
/**
* Track the allocation of a new Pointer object.
*
* This will decrement an internal counter tracking how many bytes have been traversed in the message so far. After
* a certain limit, this method will throw an error in order to prevent a certain class of DoS attacks.
*
* @param {Message} message The message the pointer belongs to.
* @param {Pointer} p The pointer being allocated.
* @returns {void}
*/
export function trackPointerAllocation(message: Message, p: Pointer): void {
message._capnp.traversalLimit -= 8;
if (message._capnp.traversalLimit <= 0) {
throw new Error(format(PTR_TRAVERSAL_LIMIT_EXCEEDED, p));
}
}