103 lines
2.7 KiB
TypeScript
103 lines
2.7 KiB
TypeScript
export class Zerocoder
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{
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public static Encode(buf: Buffer, start: number, end: number): Buffer
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{
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// First, run through the data and calculate how many bytes we will save
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let bytes = 0;
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let zero = 0;
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for (let i = start; i <= end; i++)
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{
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if (buf[i] === 0)
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{
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zero++;
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}
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else
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{
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if (zero > 0)
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{
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bytes += (zero - 2);
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zero = 0;
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}
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}
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}
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if (zero > 0)
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{
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bytes += (zero - 2);
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}
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const newBuf = Buffer.allocUnsafe(end - bytes);
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buf.copy(newBuf, 0, 0, start);
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let newBufIndex = start;
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zero = 0;
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for (let i = start; i <= end; i++)
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{
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if (buf[i] === 0)
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{
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zero++;
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}
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else
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{
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if (zero > 0)
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{
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newBuf[newBufIndex++] = 0;
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newBuf.writeUInt8(zero, newBufIndex++);
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zero = 0;
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}
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newBuf[newBufIndex++] = buf[i];
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}
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}
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if (zero > 0)
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{
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newBuf[newBufIndex++] = 0;
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newBuf.writeUInt8(zero, newBufIndex);
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}
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return newBuf;
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}
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public static Decode(buf: Buffer, start: number, end: number, tail: number): Buffer
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{
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// First, run through the data and calculate how many bytes have been compressed
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let bytes = 0;
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let zero = false;
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for (let i = start; i <= end; i++)
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{
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if (zero)
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{
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zero = false;
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// Minus two bytes for the overhead
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bytes += buf.readUInt8(i) - 2;
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}
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else if (buf[i] === 0 && i <= (end - tail))
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{
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zero = true;
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}
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}
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const newBuf = Buffer.allocUnsafe((end + 1) + bytes);
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buf.copy(newBuf, 0, 0, start - 1);
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let newBufIndex = start;
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zero = false;
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for (let i = start; i <= end; i++)
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{
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if (zero)
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{
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zero = false;
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const zeroCount = buf.readUInt8(i);
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for (let x = 0; x < zeroCount; x++)
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{
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newBuf[newBufIndex++] = 0;
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}
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}
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else if (buf[i] === 0 && i <= (end - tail))
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{
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zero = true;
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}
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else
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{
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newBuf[newBufIndex++] = buf[i];
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}
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}
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return newBuf;
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}
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}
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