modern-netcdf/src/core/data.js

Modern NetCDF file reader and utilities

const { str2num, num2bytes, readType } = require('./types');
const { types } = require('./types');

function nonRecord(buffer, variable) {
  const type = str2num(variable.type);
  const size = variable.size / num2bytes(type);
  let data;
  switch (type) {
    case types.BYTE:
      data = new Uint8Array(size);
      break;
    case types.SHORT:
      data = new Int16Array(size);
      break;
    case types.INT:
      data = new Int32Array(size);
      break;
    case types.FLOAT:
      data = new Float32Array(size);
      break;
    case types.DOUBLE:
      data = new Float64Array(size);
      break;
    default:
      throw new Error(`Unsupported type for TypedArray: ${variable.type}`);
  }
  for (let i = 0; i < size; i++) {
    data[i] = readType(buffer, type, 1);
  }
  return data;
}

function record(buffer, variable, recordDimension) {
  const type = str2num(variable.type);
  const width = variable.size ? variable.size / num2bytes(type) : 1;
  const recordCount = recordDimension.length;
  const totalElements = recordCount * width;
  let data;
  switch (type) {
    case types.BYTE:
      data = new Uint8Array(totalElements);
      break;
    case types.SHORT:
      data = new Int16Array(totalElements);
      break;
    case types.INT:
      data = new Int32Array(totalElements);
      break;
    case types.FLOAT:
      data = new Float32Array(totalElements);
      break;
    case types.DOUBLE:
      data = new Float64Array(totalElements);
      break;
    default:
      throw new Error(`Unsupported type for TypedArray: ${variable.type}`);
  }
  const step = recordDimension.recordStep;
  if (step === undefined) throw new Error('recordDimension.recordStep is undefined');
  for (let r = 0; r < recordCount; r++) {
    const currentOffset = buffer.offset;
    const values = readType(buffer, type, width);

    if (width === 1) {
      data[r] = values;
    } else {
      for (let j = 0; j < width; j++) {
        data[r * width + j] = values[j];
      }
    }

    buffer.seek(currentOffset + step);
  }
  return data;
}

module.exports = { nonRecord, record };