forked from sheetjs/sheetjs
78 lines
2.4 KiB
TypeScript
78 lines
2.4 KiB
TypeScript
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/*! sheetjs (C) 2013-present SheetJS -- http://sheetjs.com */
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import { Ptr, parse_varint49 } from './proto';
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import { u8concat } from './util';
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function is_framed(buf: Uint8Array): boolean {
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var l = 0;
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while(l < buf.length) {
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l++;
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var len = buf[l] | (buf[l+1]<<8) | (buf[l+2] << 16); l += 3;
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l += len;
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}
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return l == buf.length;
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}
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export { is_framed };
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function deframe(buf: Uint8Array): Uint8Array {
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var out = [];
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var l = 0;
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while(l < buf.length) {
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var t = buf[l++];
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var len = buf[l] | (buf[l+1]<<8) | (buf[l+2] << 16); l += 3;
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out.push(process_chunk(t, buf.slice(l, l + len)));
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l += len;
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}
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if(l !== buf.length) throw new Error("data is not a valid framed stream!");
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return u8concat(out);
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}
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export { deframe };
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function process_chunk(type: number, buf: Uint8Array): Uint8Array {
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if(type != 0) throw new Error(`Unexpected Snappy chunk type ${type}`);
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var ptr: Ptr = [0];
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var usz = parse_varint49(buf, ptr);
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var chunks = [];
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while(ptr[0] < buf.length) {
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var tag = buf[ptr[0]] & 0x3;
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if(tag == 0) {
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var len = buf[ptr[0]++] >> 2;
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if(len < 60) ++len;
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else {
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var c = len - 59;
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len = buf[ptr[0]];
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if(c > 1) len |= (buf[ptr[0]+1]<<8);
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if(c > 2) len |= (buf[ptr[0]+2]<<16);
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if(c > 3) len |= (buf[ptr[0]+3]<<24);
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len >>>=0; len++;
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ptr[0] += c;
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}
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chunks.push(buf.slice(ptr[0], ptr[0] + len)); ptr[0] += len; continue;
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} else {
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var offset = 0, length = 0;
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if(tag == 1) {
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length = ((buf[ptr[0]] >> 2) & 0x7) + 4;
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offset = (buf[ptr[0]++] & 0xE0) << 3;
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offset |= buf[ptr[0]++];
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} else {
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length = (buf[ptr[0]++] >> 2) + 1;
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if(tag == 2) { offset = buf[ptr[0]] | (buf[ptr[0]+1]<<8); ptr[0] += 2; }
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else { offset = (buf[ptr[0]] | (buf[ptr[0]+1]<<8) | (buf[ptr[0]+2]<<16) | (buf[ptr[0]+3]<<24))>>>0; ptr[0] += 4; }
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}
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chunks = [u8concat(chunks)];
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if(offset == 0) throw new Error("Invalid offset 0");
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if(offset > chunks[0].length) throw new Error("Invalid offset beyond length");
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if(length >= offset) {
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chunks.push(chunks[0].slice(-offset)); length -= offset;
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while(length >= chunks[chunks.length-1].length) {
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chunks.push(chunks[chunks.length - 1]);
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length -= chunks[chunks.length - 1].length;
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}
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}
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chunks.push(chunks[0].slice(-offset, -offset + length));
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}
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}
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var o = u8concat(chunks);
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if(o.length != usz) throw new Error(`Unexpected length: ${o.length} != ${usz}`);
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return o;
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}
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