utils.ts

// deno-lint-ignore-file no-explicit-any
import { Buffer } from "node:buffer";
import { SmartBuffer } from "./mod.ts";

/* Error strings */
export const ERRORS = {
  INVALID_ENCODING:
    "Invalid encoding provided. Please specify a valid encoding the internal Node.js Buffer supports.",
  INVALID_SMARTBUFFER_SIZE:
    "Invalid size provided. Size must be a valid integer greater than zero.",
  INVALID_SMARTBUFFER_BUFFER: "Invalid Buffer provided in SmartBufferOptions.",
  INVALID_SMARTBUFFER_OBJECT:
    "Invalid SmartBufferOptions object supplied to SmartBuffer constructor or factory methods.",
  INVALID_OFFSET: "An invalid offset value was provided.",
  INVALID_OFFSET_NON_NUMBER:
    "An invalid offset value was provided. A numeric value is required.",
  INVALID_LENGTH: "An invalid length value was provided.",
  INVALID_LENGTH_NON_NUMBER:
    "An invalid length value was provived. A numeric value is required.",
  INVALID_TARGET_OFFSET:
    "Target offset is beyond the bounds of the internal SmartBuffer data.",
  INVALID_TARGET_LENGTH:
    "Specified length value moves cursor beyong the bounds of the internal SmartBuffer data.",
  INVALID_READ_BEYOND_BOUNDS:
    "Attempted to read beyond the bounds of the managed data.",
  INVALID_WRITE_BEYOND_BOUNDS:
    "Attempted to write beyond the bounds of the managed data.",
};

export type BufferEncoding =
  | "ascii"
  | "utf8"
  | "utf-8"
  | "utf16le"
  | "ucs2"
  | "ucs-2"
  | "base64"
  | "latin1"
  | "binary"
  | "hex";

/**
 * Checks if a given encoding is a valid Buffer encoding. (Throws an exception if check fails)
 *
 * @param encoding The encoding string to check.
 */
export function checkEncoding(encoding: BufferEncoding) {
  if (!Buffer.isEncoding(encoding)) {
    throw new Error(ERRORS.INVALID_ENCODING);
  }
}

/**
 * Checks if a given number is a finite integer. (Throws an exception if check fails)
 *
 * @param value The number value to check.
 */
export function isFiniteInteger(value: number): boolean {
  return typeof value === "number" && isFinite(value) && isInteger(value);
}

/**
 * Checks if an offset/length value is valid. (Throws an exception if check fails)
 *
 * @param value The value to check.
 * @param offset True if checking an offset, false if checking a length.
 */
function checkOffsetOrLengthValue(value: any, offset: boolean) {
  if (typeof value === "number") {
    // Check for non finite/non integers
    if (!isFiniteInteger(value) || value < 0) {
      throw new Error(offset ? ERRORS.INVALID_OFFSET : ERRORS.INVALID_LENGTH);
    }
  } else {
    throw new Error(
      offset
        ? ERRORS.INVALID_OFFSET_NON_NUMBER
        : ERRORS.INVALID_LENGTH_NON_NUMBER,
    );
  }
}

/**
 * Checks if a length value is valid. (Throws an exception if check fails)
 *
 * @param length The value to check.
 */
export function checkLengthValue(length: any) {
  checkOffsetOrLengthValue(length, false);
}

/**
 * Checks if a offset value is valid. (Throws an exception if check fails)
 *
 * @param offset The value to check.
 */
export function checkOffsetValue(offset: any) {
  checkOffsetOrLengthValue(offset, true);
}

/**
 * Checks if a target offset value is out of bounds. (Throws an exception if check fails)
 *
 * @param offset The offset value to check.
 * @param buff The SmartBuffer instance to check against.
 */
export function checkTargetOffset(offset: number, buff: SmartBuffer) {
  if (offset < 0 || offset > buff.length) {
    throw new Error(ERRORS.INVALID_TARGET_OFFSET);
  }
}

/**
 * Determines whether a given number is a integer.
 * @param value The number to check.
 */
function isInteger(value: number) {
  return typeof value === "number" && isFinite(value) &&
    Math.floor(value) === value;
}

export function bigIntAndBufferInt64Check(bufferMethod: keyof Buffer) {
  if (typeof BigInt === "undefined") {
    throw new Error("Platform does not support JS BigInt type.");
  }

  if (typeof Buffer.prototype[bufferMethod] === "undefined") {
    throw new Error(
      `Platform does not support Buffer.prototype.${bufferMethod.toString()}.`,
    );
  }
}