tiny-commit-walker
Version:
tiny commit walker
72 lines • 2.16 kB
JavaScript
;
Object.defineProperty(exports, "__esModule", { value: true });
function readBaseOffset(buff, offset) {
let c = buff[offset++];
let baseOffset = c & 0x7f;
while (c & 0x80) {
baseOffset++;
c = buff[offset++];
baseOffset = baseOffset * 128 + (c & 0x7f);
}
return [baseOffset, offset];
}
exports.readBaseOffset = readBaseOffset;
function readDataSize(buff, offset) {
let cmd;
let size = 0;
let x = 1;
do {
cmd = buff[offset++];
size += (cmd & 0x7f) * x;
x *= 128;
} while (cmd & 0x80);
return [size, offset];
}
function patchDelta(src, delta) {
let srcOffset = 0;
let srcSize;
let dstSize;
[srcSize, srcOffset] = readDataSize(delta, srcOffset);
[dstSize, srcOffset] = readDataSize(delta, srcOffset);
let dstOffset = 0;
let cmd;
const dst = Buffer.alloc(dstSize);
while (srcOffset < delta.length) {
cmd = delta[srcOffset++];
if (cmd & 0x80) {
let cpOff = 0;
let cpSize = 0;
if (cmd & 0x01)
cpOff = delta[srcOffset++];
if (cmd & 0x02)
cpOff |= (delta[srcOffset++] << 8);
if (cmd & 0x04)
cpOff |= (delta[srcOffset++] << 16);
if (cmd & 0x08)
cpOff |= (delta[srcOffset++] << 24);
if (cmd & 0x10)
cpSize = delta[srcOffset++];
if (cmd & 0x20)
cpSize |= (delta[srcOffset++] << 8);
if (cmd & 0x40)
cpSize |= (delta[srcOffset++] << 16);
if (cpSize === 0)
cpSize = 0x10000;
dst.set(src.slice(cpOff, cpOff + cpSize), dstOffset);
dstOffset += cpSize;
dstSize -= cpSize;
}
else if (cmd) {
if (cmd > dstSize) {
break;
}
dst.set(delta.slice(srcOffset, srcOffset + cmd), dstOffset);
dstOffset += cmd;
srcOffset += cmd;
dstSize -= cmd;
}
}
return dst;
}
exports.patchDelta = patchDelta;
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