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Mini Shell
Mini Shell
var bodec = require('bodec');
module.exports = applyDelta;
function applyDelta(delta, base) {
var deltaOffset = 0;
if (base.length !== readLength()) {
throw new Error("Base length mismatch");
}
// Create a new output buffer with length from header.
var outOffset = 0;
var out = bodec.create(readLength());
while (deltaOffset < delta.length) {
var byte = delta[deltaOffset++];
// Copy command. Tells us offset in base and length to copy.
if (byte & 0x80) {
var offset = 0;
var length = 0;
if (byte & 0x01) offset |= delta[deltaOffset++] << 0;
if (byte & 0x02) offset |= delta[deltaOffset++] << 8;
if (byte & 0x04) offset |= delta[deltaOffset++] << 16;
if (byte & 0x08) offset |= delta[deltaOffset++] << 24;
if (byte & 0x10) length |= delta[deltaOffset++] << 0;
if (byte & 0x20) length |= delta[deltaOffset++] << 8;
if (byte & 0x40) length |= delta[deltaOffset++] << 16;
if (length === 0) length = 0x10000;
// copy the data
bodec.copy(bodec.slice(base, offset, offset + length), out, outOffset);
outOffset += length;
}
// Insert command, opcode byte is length itself
else if (byte) {
bodec.copy(bodec.slice(delta, deltaOffset, deltaOffset + byte), out, outOffset);
deltaOffset += byte;
outOffset += byte;
}
else throw new Error('Invalid delta opcode');
}
if (outOffset !== out.length) {
throw new Error("Size mismatch in check");
}
return out;
// Read a variable length number our of delta and move the offset.
function readLength() {
var byte = delta[deltaOffset++];
var length = byte & 0x7f;
var shift = 7;
while (byte & 0x80) {
byte = delta[deltaOffset++];
length |= (byte & 0x7f) << shift;
shift += 7;
}
return length;
}
}
Zerion Mini Shell 1.0