199 lines
4.8 KiB
HTML
199 lines
4.8 KiB
HTML
<!DOCTYPE html>
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<style>
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body {
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font-family: sans-serif;
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}
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</style>
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<input type="file">
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<button>Construct</button>
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<main></main>
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<script>
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let contents;
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const fileInput = document.querySelector('input');
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fileInput.addEventListener('change', async () => {
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let file = fileInput.files[0];
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let buffer = await file.arrayBuffer();
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let totalBytes = new Uint8Array(buffer);
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const isAlphanumeric = (charCode) => {
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return charCode && (
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(charCode >= 48 && charCode <= 57)
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|| (charCode >= 65 && charCode <= 90)
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|| (charCode >= 97 && charCode <= 122));
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};
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const parseContents = (bytes) => {
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let totalContents = [];
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let view = new DataView(bytes.buffer);
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let lastIndex = 0;
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for (let i = 0; i < bytes.byteLength; i++) {
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cond:
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if (
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isAlphanumeric(bytes[i+4])
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&& isAlphanumeric(bytes[i+5])
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&& isAlphanumeric(bytes[i+6])
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&& isAlphanumeric(bytes[i+7])
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) {
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let size = view.getUint32(i, false);
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if (size < 8) break cond;
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if (i + size > bytes.byteLength) break cond;
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let tag = String.fromCharCode(bytes[i + 4])
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+ String.fromCharCode(bytes[i + 5])
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+ String.fromCharCode(bytes[i + 6])
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+ String.fromCharCode(bytes[i + 7]);
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if ((tag.toLowerCase() !== tag) && tag !== 'avcC' && tag !== 'avc1') break cond;
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if (i - lastIndex > 0) {
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totalContents.push(bytes.slice(lastIndex, i));
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}
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let contents = tag === 'mdat'
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? [bytes.slice(i + 8, i + size)]
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: parseContents(bytes.slice(i + 8, i + size));
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totalContents.push({
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tag,
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contents
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});
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lastIndex = i + size;
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i += size - 1;
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}
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}
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if (bytes.byteLength - lastIndex > 1) {
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totalContents.push(bytes.slice(lastIndex));
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}
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return totalContents;
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};
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contents = parseContents(totalBytes);
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document.querySelector('main').append(...contents.map(dataToDiv));
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});
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let crossedOut = new Set();
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let modified = new Map();
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const dataToDiv = (data) => {
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if (data instanceof Uint8Array) {
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let div = document.createElement('div');
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div.setAttribute('contenteditable', true);
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div.textContent = [...data].map(x => x.toString(16).padStart(2, '0').toLowerCase()).join('');
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div.style.whiteSpace = 'nowrap';
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div.addEventListener('keydown', () => {
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setTimeout(() => {
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modified.set(data, hexStringToUint8Array(div.textContent));
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if (div.textContent.length % 2) {
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div.style.background = 'lime';
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} else {
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div.style.background = '';
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}
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});
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});
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return div;
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}
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let div = document.createElement('div');
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let span = document.createElement('span');
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span.style.background = 'lightgray';
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span.textContent = data.tag;
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let children = document.createElement('div');
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children.style.paddingLeft = '10px';
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div.append(span);
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div.append(children);
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children.append(...data.contents.map(dataToDiv));
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span.addEventListener('click', (e) => {
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if (crossedOut.has(data)) {
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crossedOut.delete(data);
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span.style.textDecoration = '';
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children.style.opacity = 1;
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} else {
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crossedOut.add(data);
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span.style.textDecoration = 'line-through';
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children.style.opacity = 0.3;
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}
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e.stopPropagation();
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});
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return div;
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};
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const hexStringToUint8Array = (hexString) => {
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if (hexString.length % 2 !== 0) {
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hexString += '0';
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}
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const byteCount = hexString.length / 2;
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const uint8Array = new Uint8Array(byteCount);
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for (let i = 0; i < byteCount; i++) {
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const hexByte = hexString.slice(i * 2, i * 2 + 2);
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uint8Array[i] = parseInt(hexByte, 16);
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}
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return uint8Array;
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};
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document.querySelector('button').addEventListener('click', () => {
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let constructed = construct(contents);
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downloadBlob(new Blob([new Uint8Array(constructed)]), 'edited.mp4');
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});
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const u32 = (value) => {
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let bytes = new Uint8Array(4);
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let view = new DataView(bytes.buffer);
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view.setUint32(0, value, false);
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return [...bytes];
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};
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const ascii = (text, nullTerminated = false) => {
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let bytes = Array(text.length).fill(null).map((_, i) => text.charCodeAt(i));
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if (nullTerminated) bytes.push(0x00);
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return bytes;
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};
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const construct = (contents) => {
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if (contents instanceof Uint8Array) {
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if (modified.has(contents)) return [...modified.get(contents)];
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else return [...contents];
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} else if (Array.isArray(contents)) {
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return contents.flatMap(construct);
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} else {
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let constructedContents = construct(contents.contents);
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let size = constructedContents.length + 8;
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return [
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...u32(size),
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...ascii(crossedOut.has(contents) ? 'free' : contents.tag),
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...constructedContents
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];
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}
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};
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const downloadBlob = (blob, filename) => {
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const url = URL.createObjectURL(blob);
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const a = document.createElement('a');
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a.href = url;
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a.download = filename;
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document.body.appendChild(a);
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a.click();
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setTimeout(() => {
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document.body.removeChild(a);
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URL.revokeObjectURL(url);
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}, 0);
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};
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</script> |