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80 lines
2.5 KiB
TypeScript
80 lines
2.5 KiB
TypeScript
// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
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// The following code is based off:
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// https://github.com/samthor/fast-text-encoding
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//
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// Copyright 2017 Sam Thorogood. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License"); you may not
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// use this file except in compliance with the License. You may obtain a copy of
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// the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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// License for the specific language governing permissions and limitations under
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// the License.
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//
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export function encodeUtf8(input: string): Uint8Array {
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let pos = 0;
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const len = input.length;
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let at = 0; // output position
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let tlen = Math.max(32, len + (len >> 1) + 7); // 1.5x size
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let target = new Uint8Array((tlen >> 3) << 3); // ... but at 8 byte offset
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while (pos < len) {
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let value = input.charCodeAt(pos++);
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if (value >= 0xd800 && value <= 0xdbff) {
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// high surrogate
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if (pos < len) {
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const extra = input.charCodeAt(pos);
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if ((extra & 0xfc00) === 0xdc00) {
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++pos;
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value = ((value & 0x3ff) << 10) + (extra & 0x3ff) + 0x10000;
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}
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}
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if (value >= 0xd800 && value <= 0xdbff) {
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continue; // drop lone surrogate
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}
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}
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// expand the buffer if we couldn't write 4 bytes
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if (at + 4 > target.length) {
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tlen += 8; // minimum extra
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tlen *= 1.0 + (pos / input.length) * 2; // take 2x the remaining
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tlen = (tlen >> 3) << 3; // 8 byte offset
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const update = new Uint8Array(tlen);
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update.set(target);
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target = update;
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}
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if ((value & 0xffffff80) === 0) {
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// 1-byte
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target[at++] = value; // ASCII
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continue;
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} else if ((value & 0xfffff800) === 0) {
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// 2-byte
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target[at++] = ((value >> 6) & 0x1f) | 0xc0;
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} else if ((value & 0xffff0000) === 0) {
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// 3-byte
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target[at++] = ((value >> 12) & 0x0f) | 0xe0;
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target[at++] = ((value >> 6) & 0x3f) | 0x80;
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} else if ((value & 0xffe00000) === 0) {
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// 4-byte
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target[at++] = ((value >> 18) & 0x07) | 0xf0;
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target[at++] = ((value >> 12) & 0x3f) | 0x80;
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target[at++] = ((value >> 6) & 0x3f) | 0x80;
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} else {
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// FIXME: do we care
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continue;
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}
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target[at++] = (value & 0x3f) | 0x80;
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}
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return target.slice(0, at);
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}
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