/// <reference path="./rt/index.d.ts" />

import { BLOCK, BLOCK_OVERHEAD, BLOCK_MAXSIZE } from "./rt/common";

import { compareImpl, strtol, strtod, isSpace, isAscii, toLower8, toUpper8 } from "./util/string";

import { specialsUpper, casemap, bsearch } from "./util/casemap";

import { E_INVALIDLENGTH } from "./util/error";

import { ArrayBufferView } from "./arraybuffer";

import { idof } from "./builtins";

@sealed export abstract class String {

@lazy static readonly MAX_LENGTH: i32 = BLOCK_MAXSIZE >>> alignof<u16>();

static fromCharCode(unit: i32, surr: i32 = -1): String {

var hasSur = surr > 0;

var out = __alloc(2 << i32(hasSur), idof<String>());

store<u16>(out, <u16>unit);

if (hasSur) store<u16>(out, <u16>surr, 2);

return changetype<String>(out); // retains

}

static fromCodePoint(code: i32): String {

assert(<u32>code <= 0x10FFFF);

var hasSur = code > 0xFFFF;

var out = __alloc(2 << i32(hasSur), idof<String>());

if (!hasSur) {

store<u16>(out, <u16>code);

} else {

code -= 0x10000;

let hi = (code & 0x03FF) | 0xDC00;

let lo = (code >>> 10) | 0xD800;

store<u32>(out, lo | (hi << 16));

}

return changetype<String>(out); // retains

}

get length(): i32 {

return changetype<BLOCK>(changetype<usize>(this) - BLOCK_OVERHEAD).rtSize >> 1;

}

@operator("[]") charAt(pos: i32): String {

if (<u32>pos >= <u32>this.length) return changetype<String>("");

var out = __alloc(2, idof<String>());

store<u16>(out, load<u16>(changetype<usize>(this) + (<usize>pos << 1)));

return changetype<String>(out); // retains

}

charCodeAt(pos: i32): i32 {

if (<u32>pos >= <u32>this.length) return -1; // (NaN)

return load<u16>(changetype<usize>(this) + (<usize>pos << 1));

}

codePointAt(pos: i32): i32 {

var len = this.length;

if (<u32>pos >= <u32>len) return -1; // (undefined)

var first = <i32>load<u16>(changetype<usize>(this) + (<usize>pos << 1));

if ((first & 0xFC00) != 0xD800 || pos + 1 == len) return first;

var second = <i32>load<u16>(changetype<usize>(this) + ((<usize>pos + 1) << 1));

if ((second & 0xFC00) != 0xDC00) return first;

return (first - 0xD800 << 10) + (second - 0xDC00) + 0x10000;

}

@operator("+") private static __concat(left: String, right: String): String {

return select<String>(left, changetype<String>("null"), left !== null).concat(right);

}

concat(other: String): String {

if (other === null) other = changetype<String>("null");

var thisSize: isize = this.length << 1;

var otherSize: isize = other.length << 1;

var outSize: usize = thisSize + otherSize;

if (outSize == 0) return changetype<String>("");

var out = changetype<String>(__alloc(outSize, idof<String>())); // retains

memory.copy(changetype<usize>(out), changetype<usize>(this), thisSize);

memory.copy(changetype<usize>(out) + thisSize, changetype<usize>(other), otherSize);

return out;

}

endsWith(search: String, end: i32 = String.MAX_LENGTH): bool {

if (search === null) return false;

end = min(max(end, 0), this.length);

var searchLength = <isize>search.length;

var searchStart = <isize>end - searchLength;

if (searchStart < 0) return false;

// @ts-ignore: string <-> String

return !compareImpl(this, searchStart, search, 0, searchLength);

}

@operator("==") private static __eq(left: String | null, right: String | null): bool {

if (left === right) return true;

if (left === null || right === null) return false;

var leftLength = left.length;

if (leftLength != right.length) return false;

// @ts-ignore: string <-> String

return !compareImpl(left, 0, right, 0, leftLength);

}

@operator.prefix("!")

private static __not(str: String | null): bool {

return str === null || !str.length;

}

@operator("!=")

private static __ne(left: String | null, right: String | null): bool {

return !this.__eq(left, right);

}

@operator(">") private static __gt(left: String | null, right: String | null): bool {

if (left === right || left === null || right === null) return false;

var leftLength = left.length;

if (!leftLength) return false;

var rightLength = right.length;

if (!rightLength) return true;

// @ts-ignore: string <-> String

return compareImpl(left, 0, right, 0, min(leftLength, rightLength)) > 0;

}

@operator(">=") private static __gte(left: String, right: String): bool {

return !this.__lt(left, right);

}

@operator("<") private static __lt(left: String, right: String): bool {

if (left === right || left === null || right === null) return false;

var rightLength = right.length;

if (!rightLength) return false;

var leftLength = left.length;

if (!leftLength) return true;

// @ts-ignore: string <-> String

return compareImpl(left, 0, right, 0, min(leftLength, rightLength)) < 0;

}

@operator("<=") private static __lte(left: String, right: String): bool {

return !this.__gt(left, right);

}

includes(search: String, start: i32 = 0): bool {

return this.indexOf(search, start) != -1;

}

indexOf(search: String, start: i32 = 0): i32 {

var searchLen = <isize>search.length;

if (!searchLen) return 0;

var len = <isize>this.length;

if (!len) return -1;

var searchStart = min(max(<isize>start, 0), len);

for (len -= searchLen; searchStart <= len; ++searchStart) {

// @ts-ignore: string <-> String

if (!compareImpl(this, searchStart, search, 0, searchLen)) return <i32>searchStart;

}

return -1;

}

lastIndexOf(search: String, start: i32 = i32.MAX_VALUE): i32 {

var searchLen = <isize>search.length;

if (!searchLen) return this.length;

var len = this.length;

if (!len) return -1;

var searchStart = min(max(<isize>start, 0), <isize>len - searchLen);

for (; searchStart >= 0; --searchStart) {

// @ts-ignore: string <-> String

if (!compareImpl(this, searchStart, search, 0, searchLen)) return <i32>searchStart;

}

return -1;

}

// TODO: implement full locale comparison with locales and Collator options

localeCompare(other: String): i32 {

if (other === this) return 0; // compare pointers

var len: isize = this.length;

var otherLen: isize = other.length;

if (otherLen != len) return select(1, -1, len > otherLen);

if (!otherLen) return 0; // "" == ""

// @ts-ignore: string <-> String

return compareImpl(this, 0, other, 0, otherLen);

}

startsWith(search: String, start: i32 = 0): bool {

if (search === null) search = changetype<String>("null");

var len = <isize>this.length;

var searchStart = min(max(<isize>start, 0), len);

var searchLength = <isize>search.length;

if (searchLength + searchStart > len) return false;

// @ts-ignore: string <-> String

return !compareImpl(this, searchStart, search, 0, searchLength);

}

substr(start: i32, length: i32 = i32.MAX_VALUE): String { // legacy

var intStart: isize = start;

var end: isize = length;

var len: isize = this.length;

if (intStart < 0) intStart = max(len + intStart, 0);

var size = min(max(end, 0), len - intStart) << 1;

if (size <= 0) return changetype<String>("");

var out = __alloc(size, idof<String>());

memory.copy(out, changetype<usize>(this) + (intStart << 1), size);

return changetype<String>(out); // retains

}

substring(start: i32, end: i32 = i32.MAX_VALUE): String {

var len: isize = this.length;

var finalStart = min<isize>(max(start, 0), len);

var finalEnd = min<isize>(max(end, 0), len);

var fromPos = min<isize>(finalStart, finalEnd) << 1;

var toPos = max<isize>(finalStart, finalEnd) << 1;

var size = toPos - fromPos;

if (!size) return changetype<String>("");

if (!fromPos && toPos == len << 1) return this;

var out = __alloc(size, idof<String>());

memory.copy(out, changetype<usize>(this) + fromPos, size);

return changetype<String>(out); // retains

}

trim(): String {

var len = this.length;

var size: usize = len << 1;

while (size && isSpace(load<u16>(changetype<usize>(this) + size - 2))) {

size -= 2;

}

var offset: usize = 0;

while (offset < size && isSpace(load<u16>(changetype<usize>(this) + offset))) {

offset += 2; size -= 2;

}

if (!size) return changetype<String>("");

if (!offset && size == len << 1) return this;

var out = __alloc(size, idof<String>());

memory.copy(out, changetype<usize>(this) + offset, size);

return changetype<String>(out); // retains

}

@inline

trimLeft(): String {

return this.trimStart();

}

@inline

trimRight(): String {

return this.trimEnd();

}

trimStart(): String {

var size = <usize>this.length << 1;

var offset: usize = 0;

while (offset < size && isSpace(load<u16>(changetype<usize>(this) + offset))) {

offset += 2;

}

if (!offset) return this;

size -= offset;

if (!size) return changetype<String>("");

var out = __alloc(size, idof<String>());

memory.copy(out, changetype<usize>(this) + offset, size);

return changetype<String>(out); // retains

}

trimEnd(): String {

var originalSize = <usize>this.length << 1;

var size = originalSize;

while (size && isSpace(load<u16>(changetype<usize>(this) + size - 2))) {

size -= 2;

}

if (!size) return changetype<String>("");

if (size == originalSize) return this;

var out = __alloc(size, idof<String>());

memory.copy(out, changetype<usize>(this), size);

return changetype<String>(out); // retains

}

padStart(length: i32, pad: string = " "): String {

var thisSize = <usize>this.length << 1;

var targetSize = <usize>length << 1;

var padSize = <usize>pad.length << 1;

if (targetSize < thisSize || !padSize) return this;

var prependSize = targetSize - thisSize;

var out = __alloc(targetSize, idof<String>());

if (prependSize > padSize) {

let repeatCount = (prependSize - 2) / padSize;

let restBase = repeatCount * padSize;

let restSize = prependSize - restBase;

memory.repeat(out, changetype<usize>(pad), padSize, repeatCount);

memory.copy(out + restBase, changetype<usize>(pad), restSize);

} else {

memory.copy(out, changetype<usize>(pad), prependSize);

}

memory.copy(out + prependSize, changetype<usize>(this), thisSize);

return changetype<String>(out); // retains

}

padEnd(length: i32, pad: string = " "): String {

var thisSize = <usize>this.length << 1;

var targetSize = <usize>length << 1;

var padSize = <usize>pad.length << 1;

if (targetSize < thisSize || !padSize) return this;

var appendSize = targetSize - thisSize;

var out = __alloc(targetSize, idof<String>());

memory.copy(out, changetype<usize>(this), thisSize);

if (appendSize > padSize) {

let repeatCount = (appendSize - 2) / padSize;

let restBase = repeatCount * padSize;

let restSize = appendSize - restBase;

memory.repeat(out + thisSize, changetype<usize>(pad), padSize, repeatCount);

memory.copy(out + thisSize + restBase, changetype<usize>(pad), restSize);

} else {

memory.copy(out + thisSize, changetype<usize>(pad), appendSize);

}

return changetype<String>(out); // retains

}

repeat(count: i32 = 0): String {

var length = this.length;

// Most browsers can't handle strings 1 << 28 chars or longer

if (count < 0 || <u64>length * count > (1 << 28)) {

throw new RangeError(E_INVALIDLENGTH);

}

if (count == 0 || !length) return changetype<String>("");

if (count == 1) return this;

var out = __alloc((length * count) << 1, idof<String>());

memory.repeat(out, changetype<usize>(this), <usize>length << 1, count);

return changetype<String>(out); // retains

}

replace(search: String, replacement: String): String {

var len: usize = this.length;

var slen: usize = search.length;

if (len <= slen) {

return len < slen ? this : select<String>(replacement, this, search == this);

}

var index: isize = this.indexOf(search);

if (~index) {

let rlen: usize = replacement.length;

len -= slen;

let olen = len + rlen;

if (olen) {

let out = __alloc(olen << 1, idof<String>());

memory.copy(out, changetype<usize>(this), index << 1);

memory.copy(

out + (index << 1),

changetype<usize>(replacement),

rlen << 1

);

memory.copy(

out + ((index + rlen) << 1),

changetype<usize>(this) + ((index + slen) << 1),

(len - index) << 1

);

return changetype<String>(out);

}

}

return this;

}

replaceAll(search: String, replacement: String): String {

var len: usize = this.length;

var slen: usize = search.length;

if (len <= slen) {

return len < slen ? this : select<String>(replacement, this, search == this);

}

var rlen: usize = replacement.length;

if (!slen) {

if (!rlen) return this;

// Special case: 'abc'.replaceAll('', '-') -> '-a-b-c-'

let out = __alloc((len + (len + 1) * rlen) << 1, idof<String>());

memory.copy(out, changetype<usize>(replacement), rlen << 1);

let offset = rlen;

for (let i: usize = 0; i < len; ++i) {

store<u16>(

changetype<usize>(out) + (offset++ << 1),

load<u16>(changetype<usize>(this) + (i << 1))

);

memory.copy(

out + (offset << 1),

changetype<usize>(replacement),

rlen << 1

);

offset += rlen;

}

return changetype<String>(out);

}

var prev: isize = 0, next: isize = 0;

if (slen == rlen) {

// Fast path when search and replacement have same length

let size = len << 1;

let out = __alloc(size, idof<String>());

memory.copy(out, changetype<usize>(this), size);

while (~(next = <isize>this.indexOf(search, <i32>prev))) {

memory.copy(out + (next << 1), changetype<usize>(replacement), rlen << 1);

prev = next + slen;

}

return changetype<String>(out);

}

var out: usize = 0, offset: usize = 0, resLen = len;

while (~(next = <isize>this.indexOf(search, <i32>prev))) {

if (!out) out = __alloc(len << 1, idof<String>());

if (offset > resLen) {

let newLength = resLen << 1;

out = __realloc(out, newLength << 1);

resLen = newLength;

}

let chunk = next - prev;

memory.copy(

out + (offset << 1),

changetype<usize>(this) + (prev << 1),

chunk << 1

);

offset += chunk;

memory.copy(

out + (offset << 1),

changetype<usize>(replacement),

rlen << 1

);

offset += rlen;

prev = next + slen;

}

if (offset) {

if (offset > resLen) {

let newLength = resLen << 1;

out = __realloc(out, newLength << 1);

resLen = newLength;

}

let rest = len - prev;

if (rest) {

memory.copy(

out + (offset << 1),

changetype<usize>(this) + (prev << 1),

rest << 1

);

}

rest += offset;

if (resLen > rest) out = __realloc(out, rest << 1);

return changetype<String>(out);

}

return this;

}

slice(start: i32, end: i32 = i32.MAX_VALUE): String {

var len = this.length;

start = start < 0 ? max(start + len, 0) : min(start, len);

end = end < 0 ? max(end + len, 0) : min(end, len);

len = end - start;

if (len <= 0) return changetype<String>("");

var out = __alloc(len << 1, idof<String>());

memory.copy(out, changetype<usize>(this) + (<usize>start << 1), <usize>len << 1);

return changetype<String>(out); // retains

}

split(separator: String | null = null, limit: i32 = i32.MAX_VALUE): String[] {

if (!limit) return changetype<Array<String>>(__allocArray(0, alignof<String>(), idof<Array<String>>())); // retains

if (separator === null) return [this];

var length: isize = this.length;

var sepLen: isize = separator.length;

if (limit < 0) limit = i32.MAX_VALUE;

if (!sepLen) {

if (!length) return changetype<Array<String>>(__allocArray(0, alignof<String>(), idof<Array<String>>())); // retains

// split by chars

length = min<isize>(length, <isize>limit);

let result = changetype<Array<String>>(__allocArray(length, alignof<String>(), idof<Array<String>>())); // retains

// @ts-ignore: cast

let resultStart = result.dataStart as usize;

for (let i: isize = 0; i < length; ++i) {

let charStr = __alloc(2, idof<String>());

store<u16>(charStr, load<u16>(changetype<usize>(this) + (<usize>i << 1)));

store<usize>(resultStart + (<usize>i << alignof<usize>()), charStr); // result[i] = charStr

if (isManaged<String>()) __retain(charStr);

}

return result;

} else if (!length) {

let result = changetype<Array<String>>(__allocArray(1, alignof<String>(), idof<Array<String>>())); // retains

// @ts-ignore: cast

store<usize>(result.dataStart as usize, changetype<usize>("")); // static ""

return result;

}

var result = changetype<Array<String>>(__allocArray(0, alignof<String>(), idof<Array<String>>())); // retains

var end = 0, start = 0, i = 0;

while (~(end = this.indexOf(separator, start))) {

let len = end - start;

if (len > 0) {

let out = __alloc(<usize>len << 1, idof<String>());

memory.copy(out, changetype<usize>(this) + (<usize>start << 1), <usize>len << 1);

result.push(changetype<String>(out));

} else {

result.push(changetype<String>(""));

}

if (++i == limit) return result;

start = end + sepLen;

}

if (!start) { // also means: loop above didn't do anything

result.push(this);

return result;

}

var len = length - start;

if (len > 0) {

let out = __alloc(<usize>len << 1, idof<String>());

memory.copy(out, changetype<usize>(this) + (<usize>start << 1), <usize>len << 1);

result.push(changetype<String>(out)); // retains

} else {

result.push(changetype<String>("")); // static ""

}

return result;

}

toLowerCase(): String {

var len = <usize>this.length;

if (!len) return this;

var codes = __alloc(len * 2 * 2, idof<String>());

var j: usize = 0;

for (let i: usize = 0; i < len; ++i, ++j) {

let c = <u32>load<u16>(changetype<usize>(this) + (i << 1));

if (isAscii(c)) {

store<u16>(codes + (j << 1), toLower8(c));

} else {

// check and read surrogate pair

if ((c - 0xD7FF < 0xDC00 - 0xD7FF) && i < len - 1) {

let c1 = <u32>load<u16>(changetype<usize>(this) + (i << 1), 2);

if (c1 - 0xDBFF < 0xE000 - 0xDBFF) {

let c0 = c;

c = (((c & 0x03FF) << 10) | (c1 & 0x03FF)) + 0x10000;

++i;

if (c >= 0x20000) {

store<u32>(codes + (j << 1), c0 | (c1 << 16));

++j;

continue;

}

}

}

// check special casing for lower table. It has one ently so instead lookup we just inline this.

if (c == 0x0130) {

// 0x0130 -> [0x0069, 0x0307]

store<u32>(codes + (j << 1), (0x0307 << 16) | 0x0069);

++j;

} else if (c - 0x24B6 <= 0x24CF - 0x24B6) {

// Range 0x24B6 <= c <= 0x24CF not covered by casemap and require special early handling

store<u16>(codes + (j << 1), c + 26);

} else {

let code = casemap(c, 0) & 0x1FFFFF;

if (code < 0x10000) {

store<u16>(codes + (j << 1), code);

} else {

// store as surrogare pair

code -= 0x10000;

let lo = (code >>> 10) | 0xD800;

let hi = (code & 0x03FF) | 0xDC00;

store<u32>(codes + (j << 1), lo | (hi << 16));

++j;

}

}

}

}

codes = __realloc(codes, j << 1);

return changetype<String>(codes); // retains

}

toUpperCase(): String {

var len = <usize>this.length;

if (!len) return this;

var codes = __alloc(len * 3 * 2, idof<String>());

// @ts-ignore: cast

var specialsUpperPtr = specialsUpper.dataStart as usize;

var specialsUpperLen = specialsUpper.length;

var j: usize = 0;

for (let i: usize = 0; i < len; ++i, ++j) {

let c = <u32>load<u16>(changetype<usize>(this) + (i << 1));

if (isAscii(c)) {

store<u16>(codes + (j << 1), toUpper8(c));

} else {

// check and read surrogate pair

if ((c - 0xD7FF < 0xDC00 - 0xD7FF) && i < len - 1) {

let c1 = <u32>load<u16>(changetype<usize>(this) + (i << 1), 2);

if (c1 - 0xDBFF < 0xE000 - 0xDBFF) {

let c0 = c;

c = (((c & 0x03FF) << 10) | (c1 & 0x03FF)) + 0x10000;

++i;

if (c >= 0x20000) {

store<u32>(codes + (j << 1), c0 | (c1 << 16));

++j;

continue;

}

}

}

// Range 0x24D0 <= c <= 0x24E9 not covered by casemap and require special early handling

if (c - 0x24D0 <= 0x24E9 - 0x24D0) {

// monkey patch

store<u16>(codes + (j << 1), c - 26);

} else {

let index = -1;

// Fast range check. See first and last rows in specialsUpper table

if (c - 0x00DF <= 0xFB17 - 0x00DF) {

index = <usize>bsearch(c, specialsUpperPtr, specialsUpperLen);

}

if (~index) {

// load next 3 code points from row with `index` offset for specialsUpper table

let ab = load<u32>(specialsUpperPtr + (index << 1), 2);

let cc = load<u16>(specialsUpperPtr + (index << 1), 6);

store<u32>(codes + (j << 1), ab, 0);

store<u16>(codes + (j << 1), cc, 4);

j += 1 + usize(cc != 0);

} else {

let code = casemap(c, 1) & 0x1FFFFF;

if (code < 0x10000) {

store<u16>(codes + (j << 1), code);

} else {

// store as surrogare pair

code -= 0x10000;

let lo = (code >>> 10) | 0xD800;

let hi = (code & 0x03FF) | 0xDC00;

store<u32>(codes + (j << 1), lo | (hi << 16));

++j;

}

}

}

}

}

codes = __realloc(codes, j << 1);

return changetype<String>(codes); // retains

}

toString(): String {

return this;

}

}

// @ts-ignore: nolib

export type string = String;

export function parseInt(str: string, radix: i32 = 0): f64 {

return strtol<f64>(str, radix);

}

export function parseFloat(str: string): f64 {

return strtod(str);

}

// Encoding helpers

export namespace String {

export namespace UTF8 {

export function byteLength(str: string, nullTerminated: bool = false): i32 {

var strOff = changetype<usize>(str);

var strEnd = strOff + <usize>changetype<BLOCK>(changetype<usize>(str) - BLOCK_OVERHEAD).rtSize;

var bufLen = i32(nullTerminated);

while (strOff < strEnd) {

let c1 = <u32>load<u16>(strOff);

if (c1 < 128) {

// @ts-ignore: cast

if (nullTerminated & !c1) break;

bufLen += 1;

} else if (c1 < 2048) {

bufLen += 2;

} else {

if ((c1 & 0xFC00) == 0xD800 && strOff + 2 < strEnd) {

if ((<u32>load<u16>(strOff, 2) & 0xFC00) == 0xDC00) {

bufLen += 4; strOff += 4;

continue;

}

}

bufLen += 3;

}

strOff += 2;

}

return bufLen;

}

export function encode(str: string, nullTerminated: bool = false): ArrayBuffer {

var strOff = changetype<usize>(str);

var strEnd = changetype<usize>(str) + <usize>changetype<BLOCK>(changetype<usize>(str) - BLOCK_OVERHEAD).rtSize;

var bufLen = <usize>UTF8.byteLength(str, nullTerminated);

var buf = __alloc(bufLen, idof<ArrayBuffer>());

var bufEnd = buf + bufLen - usize(nullTerminated);

var bufOff = buf;

while (bufOff < bufEnd) {

let c1 = <u32>load<u16>(strOff);

if (c1 < 128) {

store<u8>(bufOff, c1);

bufOff++;

} else if (c1 < 2048) {

let b0 = c1 >> 6 | 192;

let b1 = c1 & 63 | 128;

store<u16>(bufOff, b1 << 8 | b0);

bufOff += 2;

} else {

if ((c1 & 0xFC00) == 0xD800 && strOff + 2 < strEnd) {

let c2 = <u32>load<u16>(strOff, 2);

if ((c2 & 0xFC00) == 0xDC00) {

c1 = 0x10000 + ((c1 & 0x03FF) << 10) | (c2 & 0x03FF);

let b0 = c1 >> 18 | 240;

let b1 = c1 >> 12 & 63 | 128;

let b2 = c1 >> 6 & 63 | 128;

let b3 = c1 & 63 | 128;

store<u32>(bufOff, b3 << 24 | b2 << 16 | b1 << 8 | b0);

bufOff += 4; strOff += 4;

continue;

}

}

let b0 = c1 >> 12 | 224;

let b1 = c1 >> 6 & 63 | 128;

let b2 = c1 & 63 | 128;

store<u16>(bufOff, b1 << 8 | b0);

store<u8>(bufOff, b2, 2);

bufOff += 3;

}

strOff += 2;

}

assert(strOff <= strEnd);

if (nullTerminated) {

store<u8>(bufOff, 0);

}

return changetype<ArrayBuffer>(buf); // retains

}

export function decode(buf: ArrayBuffer, nullTerminated: bool = false): String {

return decodeUnsafe(changetype<usize>(buf), buf.byteLength, nullTerminated);

}

// @ts-ignore: decorator

@unsafe

export function decodeUnsafe(buf: usize, len: usize, nullTerminated: bool = false): String {

var bufOff = buf;

var bufEnd = buf + len;

assert(bufEnd >= bufOff); // guard wraparound

var str = __alloc(len << 1, idof<String>()); // max is one u16 char per u8 byte

var strOff = str;

while (bufOff < bufEnd) {

let u0 = <u32>load<u8>(bufOff); ++bufOff;

if (!(u0 & 128)) {

// @ts-ignore: cast

if (nullTerminated & !u0) break;

store<u16>(strOff, u0);

} else {

if (bufEnd == bufOff) break;

let u1 = <u32>load<u8>(bufOff) & 63; ++bufOff;

if ((u0 & 224) == 192) {

store<u16>(strOff, (u0 & 31) << 6 | u1);

} else {

if (bufEnd == bufOff) break;

let u2 = <u32>load<u8>(bufOff) & 63; ++bufOff;

if ((u0 & 240) == 224) {

u0 = (u0 & 15) << 12 | u1 << 6 | u2;

} else {

if (bufEnd == bufOff) break;

u0 = (u0 & 7) << 18 | u1 << 12 | u2 << 6 | <u32>load<u8>(bufOff) & 63;

++bufOff;

}

if (u0 < 0x10000) {

store<u16>(strOff, u0);

} else {

u0 -= 0x10000;

let lo = u0 >> 10 | 0xD800;

let hi = (u0 & 0x03FF) | 0xDC00;

store<u32>(strOff, lo | (hi << 16));

strOff += 2;

}

}

}

strOff += 2;

}

return changetype<String>(__realloc(str, strOff - str)); // retains

}

}

export namespace UTF16 {

export function byteLength(str: string): i32 {

return changetype<BLOCK>(changetype<usize>(str) - BLOCK_OVERHEAD).rtSize;

}

export function encode(str: string): ArrayBuffer {

var size = UTF16.byteLength(str);

var buf = __alloc(size, idof<ArrayBuffer>());

memory.copy(buf, changetype<usize>(str), <usize>size);

return changetype<ArrayBuffer>(buf); // retains

}

export function decode(buf: ArrayBuffer): String {

return decodeUnsafe(changetype<usize>(buf), buf.byteLength);

}

// @ts-ignore: decorator

@unsafe

export function decodeUnsafe(buf: usize, len: usize): String {

var str = __alloc(len &= ~1, idof<String>());

memory.copy(str, buf, len);

return changetype<String>(str); // retains

}

}

}