72 lines
1.6 KiB
TypeScript
72 lines
1.6 KiB
TypeScript
export function decode(
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buffer: Buffer,
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maxLength?: number,
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minimal?: boolean,
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): number {
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maxLength = maxLength || 4;
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minimal = minimal === undefined ? true : minimal;
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const length = buffer.length;
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if (length === 0) return 0;
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if (length > maxLength) throw new TypeError('Script number overflow');
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if (minimal) {
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if ((buffer[length - 1] & 0x7f) === 0) {
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if (length <= 1 || (buffer[length - 2] & 0x80) === 0)
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throw new Error('Non-minimally encoded script number');
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}
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}
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// 40-bit
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if (length === 5) {
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const a = buffer.readUInt32LE(0);
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const b = buffer.readUInt8(4);
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if (b & 0x80) return -((b & ~0x80) * 0x100000000 + a);
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return b * 0x100000000 + a;
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}
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// 32-bit / 24-bit / 16-bit / 8-bit
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let result = 0;
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for (var i = 0; i < length; ++i) {
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result |= buffer[i] << (8 * i);
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}
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if (buffer[length - 1] & 0x80)
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return -(result & ~(0x80 << (8 * (length - 1))));
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return result;
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}
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function scriptNumSize(i: number): number {
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return i > 0x7fffffff
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? 5
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: i > 0x7fffff
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? 4
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: i > 0x7fff
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? 3
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: i > 0x7f
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? 2
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: i > 0x00
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? 1
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: 0;
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}
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export function encode(number: number): Buffer {
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let value = Math.abs(number);
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const size = scriptNumSize(value);
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const buffer = Buffer.allocUnsafe(size);
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const negative = number < 0;
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for (var i = 0; i < size; ++i) {
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buffer.writeUInt8(value & 0xff, i);
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value >>= 8;
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}
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if (buffer[size - 1] & 0x80) {
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buffer.writeUInt8(negative ? 0x80 : 0x00, size - 1);
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} else if (negative) {
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buffer[size - 1] |= 0x80;
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}
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return buffer;
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}
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