mirror of
https://github.com/fluencelabs/assemblyscript
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116 lines
4.1 KiB
TypeScript
116 lines
4.1 KiB
TypeScript
import { AL_MASK } from "./allocator";
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/** Common runtime header used by all objects. */
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@unmanaged
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export class HEADER {
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/** Unique id of the respective class. Not yet registered with GC if zero.*/
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classId: u32;
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/** Size of the allocated payload. */
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payloadSize: u32;
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/** Reserved field for use by GC. */
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reserved1: usize; // itcm: tagged next
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/** Reserved field for use by GC. */
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reserved2: usize; // itcm: prev
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}
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/** Size of the common runtime header. */
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@inline export const HEADER_SIZE: usize = (offsetof<HEADER>() + AL_MASK) & ~AL_MASK;
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/** Magic value used to validate common headers. */
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@inline export const HEADER_MAGIC: usize = <usize>0xA55E4B17;
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/** Aligns an allocation to actual block size. */
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function ALIGN(payloadSize: usize): usize {
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// round up to power of 2, e.g. with HEADER_SIZE=8:
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// 0 -> 2^3 = 8
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// 1..8 -> 2^4 = 16
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// 9..24 -> 2^5 = 32
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// ...
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// MAX_LENGTH -> 2^30 = 0x40000000 (MAX_SIZE_32)
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return <usize>1 << <usize>(<u32>32 - clz<u32>(payloadSize + HEADER_SIZE - 1));
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}
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/** Gets to the common runtime header of the specified reference. */
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function UNREF(ref: usize): HEADER {
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assert(ref >= HEAP_BASE + HEADER_SIZE); // must be a heap object
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var header = changetype<HEADER>(ref - HEADER_SIZE);
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assert(!header.classId && header.reserved2 == HEADER_MAGIC); // must be unregistered
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return header;
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}
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// === General allocation/deallocation ============================================================
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/** Allocates a new object and returns a pointer to its payload. */
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export function ALLOC(payloadSize: u32): usize {
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var header = changetype<HEADER>(memory.allocate(ALIGN(payloadSize)));
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header.classId = 0;
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header.payloadSize = payloadSize;
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header.reserved1 = 0;
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header.reserved2 = HEADER_MAGIC;
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var ref = changetype<usize>(header) + HEADER_SIZE;
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memory.fill(ref, 0, payloadSize);
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return ref;
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}
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/** Reallocates an object if necessary. Returns a pointer to its (moved) payload. */
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export function REALLOC(ref: usize, newPayloadSize: u32): usize {
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var header = UNREF(ref);
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var payloadSize = header.payloadSize;
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if (payloadSize < newPayloadSize) {
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let newAlignedSize = ALIGN(newPayloadSize);
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if (ALIGN(payloadSize) < newAlignedSize) {
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// move if the allocation isn't large enough to hold the new payload
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let newHeader = changetype<HEADER>(memory.allocate(newAlignedSize));
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newHeader.classId = 0;
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newHeader.reserved1 = 0;
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newHeader.reserved2 = HEADER_MAGIC;
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let newRef = changetype<usize>(newHeader) + HEADER_SIZE;
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memory.copy(newRef, ref, payloadSize);
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memory.fill(newRef + payloadSize, 0, newPayloadSize - payloadSize);
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memory.free(changetype<usize>(header));
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header = newHeader;
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ref = newRef;
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} else {
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// otherwise just clear additional memory within this block
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memory.fill(ref + payloadSize, 0, newPayloadSize - payloadSize);
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}
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} else {
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// if the size is the same or less, just update the header accordingly.
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// it is not necessary to free unused space here because it is cleared
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// when grown again anyway.
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}
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header.payloadSize = newPayloadSize;
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return ref;
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}
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/** Frees an object. Must not have been registered with GC yet. */
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export function FREE(ref: usize): void {
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var header = UNREF(ref);
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memory.free(changetype<usize>(header));
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}
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/** Registers a managed object with GC. */
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export function REGISTER<T>(ref: usize, parentRef: usize): void {
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var header = UNREF(ref);
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header.classId = /* TODO: CLASSID<T>() */ 1;
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header.reserved2 = 0;
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// TODO
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}
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// === ArrayBuffer ================================================================================
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export abstract class ArrayBufferBase {
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get byteLength(): i32 {
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var header = changetype<HEADER>(changetype<usize>(this) - HEADER_SIZE);
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return header.payloadSize;
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}
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}
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// === String =====================================================================================
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export abstract class StringBase {
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get length(): i32 {
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var header = changetype<HEADER>(changetype<usize>(this) - HEADER_SIZE);
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return header.payloadSize >>> 1;
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}
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}
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