node-cm256

Simple node wrapper around cm256

NB: This project will only work on CPUs that support SSE 4.1

Example usage:

const cm256 = require('cm256');

const BLOCK_SIZE = 5;
const ORIGINAL_BLOCK_COUNT = 2;
const RECOVERY_BLOCK_COUNT = 4;

// create buffer to keep original data
const originalData = Buffer.alloc(BLOCK_SIZE*ORIGINAL_BLOCK_COUNT);
originalData.fill(0xAA); // normally this data would come from a file or something

// create buffer that will contain the recovery data calculated by cm256
const recoveryData = Buffer.alloc(BLOCK_SIZE*RECOVERY_BLOCK_COUNT);

// throw our data to the C code and let it do the math
const resultCalc = cm256.CalculateRecoveryBlocks({
    originalBytes: originalData,
    recoveryBytes: recoveryData,
    blockBytes: BLOCK_SIZE,
    originalCount: ORIGINAL_BLOCK_COUNT,
    recoveryCount: RECOVERY_BLOCK_COUNT
});
// this will be false if cm256 is not happy. invalid paremeters will cause an exception.
if(resultCalc !== true) {
    console.error('CalculateRecoveryBlocks FAILED');
    return;
}

// at this point our recoveryData buffer contains recovery blocks
console.log(`Original data : ${originalData.toString('hex')}`);
console.log(`Recovery data : ${recoveryData.toString('hex')}`);


// now an example to get original data using recovery blocks:

// corrupt first block of original data
originalData.fill(0xBB, 0, BLOCK_SIZE);

console.log(`Corrupted data: ${originalData.toString('hex')}`)

// copy first block of recovery data into the place of corrupted original data
recoveryData.copy(originalData, 0, 0, BLOCK_SIZE);

// have cm256 do the math and recover our original data
const resultRec = cm256.RecoverData({
    data: originalData,
    blockIndices: new Uint8Array([ORIGINAL_BLOCK_COUNT+0, 1]), // since we used first recovery block
    blockSize: BLOCK_SIZE,
    originalTotalCount: ORIGINAL_BLOCK_COUNT,
    recoveryTotalCount: RECOVERY_BLOCK_COUNT,
});
if(resultRec !== true) {
    console.error('RecoverData FAILED')
    return;
}

console.log(`Recovered data: ${originalData.toString('hex')}`)