@loaders.gl/shapefile
Version:
Loader for the Shapefile Format
43 lines • 1.65 kB
JavaScript
// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
const LITTLE_ENDIAN = true;
const BIG_ENDIAN = false;
const SHP_MAGIC_NUMBER = 0x0000270a;
/**
* Extract the binary header
* Note: Also used by SHX
* @param headerView
* @returns SHPHeader
*/
export function parseSHPHeader(headerView) {
// Note: The SHP format switches endianness between fields!
// https://www.esri.com/library/whitepapers/pdfs/shapefile.pdf
const header = {
magic: headerView.getInt32(0, BIG_ENDIAN),
// Length is stored as # of 2-byte words; multiply by 2 to get # of bytes
length: headerView.getInt32(24, BIG_ENDIAN) * 2,
version: headerView.getInt32(28, LITTLE_ENDIAN),
type: headerView.getInt32(32, LITTLE_ENDIAN),
bbox: {
minX: headerView.getFloat64(36, LITTLE_ENDIAN),
minY: headerView.getFloat64(44, LITTLE_ENDIAN),
minZ: headerView.getFloat64(68, LITTLE_ENDIAN),
minM: headerView.getFloat64(84, LITTLE_ENDIAN),
maxX: headerView.getFloat64(52, LITTLE_ENDIAN),
maxY: headerView.getFloat64(60, LITTLE_ENDIAN),
maxZ: headerView.getFloat64(76, LITTLE_ENDIAN),
maxM: headerView.getFloat64(92, LITTLE_ENDIAN)
}
};
if (header.magic !== SHP_MAGIC_NUMBER) {
// eslint-disable-next-line
console.error(`SHP file: bad magic number ${header.magic}`);
}
if (header.version !== 1000) {
// eslint-disable-next-line
console.error(`SHP file: bad version ${header.version}`);
}
return header;
}
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