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buffer.ts
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buffer.ts
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import { UInt29OutOfBoundsError } from './errors';
/**
* @description Max uInt29 value
*/
export const MAX_UINT29 = 536870911;
/**
* @description Min uInt29 value
*/
export const MIN_UINT29 = 0;
/**
* @description Write uInt29 to buffer
* @param buffer - Buffer to write
* @param value - Value to write into buffer
* @param offset - Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1.
* @return - offset plus the number of bytes written.
*/
export function writeUInt29(buffer: Buffer, value: number, offset = 0) {
if (value > MAX_UINT29 || value < MIN_UINT29)
throw new UInt29OutOfBoundsError(value, MAX_UINT29, MIN_UINT29);
if (value < 0x80) {
offset = buffer.writeUInt8(value, offset);
return offset;
}
if (value < 0x4000) {
offset = buffer.writeUInt8(0x80 | ((value >> 7) & 0x7f), offset);
offset = buffer.writeUInt8(value & 0x7f, offset);
return offset;
}
if (value < 0x200000) {
offset = buffer.writeUInt8(0x80 | ((value >> 14) & 0x7f), offset);
offset = buffer.writeUInt8(0x80 | ((value >> 7) & 0x7f), offset);
offset = buffer.writeUInt8(value & 0x7f, offset);
return offset;
}
offset = buffer.writeUInt8(0x80 | ((value >> 22) & 0x7f), offset);
offset = buffer.writeUInt8(0x80 | ((value >> 15) & 0x7f), offset);
offset = buffer.writeUInt8(0x80 | ((value >> 8) & 0x7f), offset);
offset = buffer.writeUInt8(value & 0xff, offset);
return offset;
}
/**
* @description Read uInt29 from buffer
* @param buffer - Buffer to read
* @param offset - Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1.
*/
export function readUInt29(buffer: Buffer, offset = 0) {
let value: number, byte: number;
byte = buffer.readUInt8(offset);
if (byte < 0x80) return byte;
value = (byte & 0x7f) << 7;
byte = buffer.readUInt8(++offset);
if (byte < 0x80) return value | byte;
value = (value | (byte & 0x7f)) << 7;
byte = buffer.readUInt8(++offset);
if (byte < 0x80) return value | byte;
value = (value | (byte & 0x7f)) << 8;
byte = buffer.readUInt8(++offset);
return value | byte;
}
/**
* @description Get UInt29 bytes length
*/
export function uInt29BytesLength(value: number) {
if (value > MAX_UINT29 || value < MIN_UINT29)
throw new UInt29OutOfBoundsError(value, MAX_UINT29, MIN_UINT29);
if (value < 0x80) return 1;
if (value < 0x4000) return 2;
if (value < 0x200000) return 3;
return 4;
}