Julien Fontanet
3a74c71f1a
BREAKING: - removes `dist/` in the path of sub-modules - requires Node >=12
48 lines
928 B
JavaScript
48 lines
928 B
JavaScript
const assert = require('assert')
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const { BLOCK_UNUSED } = require('./_constants')
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// get the identifiers and first sectors of the first and last block
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// in the file
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module.exports = bat => {
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const n = bat.length
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if (n === 0) {
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return
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}
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assert.strictEqual(n % 4, 0)
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let i = 0
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let j = 0
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let first, firstSector, last, lastSector
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// get first allocated block for initialization
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while ((firstSector = bat.readUInt32BE(j)) === BLOCK_UNUSED) {
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i += 1
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j += 4
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if (j === n) {
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return
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}
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}
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lastSector = firstSector
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first = last = i
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while (j < n) {
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const sector = bat.readUInt32BE(j)
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if (sector !== BLOCK_UNUSED) {
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if (sector < firstSector) {
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first = i
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firstSector = sector
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} else if (sector > lastSector) {
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last = i
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lastSector = sector
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}
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}
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i += 1
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j += 4
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}
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return { first, firstSector, last, lastSector }
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}
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