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Ignore bits that were introduced as padding in transformUnitSize #41

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Ignore bits that were introduced as padding in transformUnitSize #41

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4 changes: 2 additions & 2 deletions extensions/essentials/src/binary-slice.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -68,15 +68,15 @@ const execute: OperationExecuteExport = (request) => {

// Transform the array of bytes to an array of bits and slice them
// precisely to create the bit slice
const bitSlice = transformUnitSize(byteSlice, 8, 1).slice(
const bitSlice = transformUnitSize(byteSlice, 8, 1, true).slice(
bitSliceArgs.start - byteSliceStart * 8,
bitSliceArgs.end - byteSliceStart * 8
)

// Fill up the first byte with zero bits and turn the bits back into bytes
const paddingBits = bitSlice.length % 8 > 0 ? 8 - bitSlice.length % 8 : 0
const sliceBitsPadded = new Array(paddingBits).fill(0).concat(bitSlice)
const sliceBytes = transformUnitSize(sliceBitsPadded, 1, 8)
const sliceBytes = transformUnitSize(sliceBitsPadded, 8, 1, false)
slice = new Uint8Array(sliceBytes).buffer
break
}
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4 changes: 2 additions & 2 deletions extensions/essentials/src/binary-to-text.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -149,7 +149,7 @@ const execute: OperationExecuteExport = (request) => {
))

// Transform unit size (encode)
const encodedUnits = transformUnitSize(units, inUnitSize, outUnitSize)
const encodedUnits = transformUnitSize(units, inUnitSize, outUnitSize, true)
const encodedCodePoints = encodedUnits.map(unit => alphabet[unit])

// Apply padding
Expand Down Expand Up @@ -195,7 +195,7 @@ const execute: OperationExecuteExport = (request) => {
encodedUnits = encodedUnits.slice(0, j)

// Transform unit size (decode)
const units = transformUnitSize(encodedUnits, outUnitSize, inUnitSize)
const units = transformUnitSize(encodedUnits, inUnitSize, outUnitSize, false)
const buffer = Uint8Array.from(units).buffer

// Add an issue if foreign characters were encountered
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18 changes: 16 additions & 2 deletions extensions/essentials/src/lib/binary.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,8 @@ export const isBigEndianEnvironment = (): boolean =>
export const transformUnitSize = (
inputUnits: number[],
inUnitSize: number,
outUnitSize: number
outUnitSize: number,
forward: boolean
): number[] => {
if (inUnitSize === outUnitSize) {
return inputUnits
Expand All @@ -84,11 +85,18 @@ export const transformUnitSize = (
return []
}

// Some bits may not hold any information when decoding, see issue #40
if (!forward) {
[inUnitSize, outUnitSize] = [outUnitSize, inUnitSize]
}

const commonSize = lcm(inUnitSize, outUnitSize)
const inUnits = commonSize / inUnitSize
const outUnits = commonSize / outUnitSize

const outputUnitsLength = Math.ceil((outUnits * inputUnits.length) / inUnits)
const outputUnitsLength = forward
? Math.ceil((outUnits * inputUnits.length) / inUnits)
: Math.floor((outUnits * inputUnits.length) / inUnits)
const outputUnits = new Array<number>(outputUnitsLength)

let remainingInBits, inUnit, moveBits
Expand All @@ -104,6 +112,12 @@ export const transformUnitSize = (
// If the current out unit is full, move to the next one
if (remainingOutBits === 0) {
outputUnits[o++] = outUnit
// If the remaining input bits contain no information, don't add a null unit (only occurs when decoding)
// TODO: This works, but I, anderium, don't like that this `if` executes on each iteration.
if (o === outputUnitsLength) {
o--
break
}
outUnit = 0
remainingOutBits = outUnitSize
}
Expand Down