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Edit File: fs-db.js

"use strict";
var bodec = require('bodec');
var inflate = require('../lib/inflate');
var deflate = require('../lib/deflate');
var codec = require('../lib/object-codec');
var parsePackEntry = require('../lib/pack-codec').parseEntry;
var applyDelta = require('../lib/apply-delta');
var sha1 = require('git-sha1');
var pathJoin = require('path').join;

// The fs object has the following interface:
// - readFile(path) => binary
//   Must also call callback() with no arguments if the file does not exist.
// - readChunk(path, start, end) => binary
//   Must also call callback() with no arguments if the file does not exist.
// - writeFile(path, binary) =>
//   Must also make every directory up to parent of path.
// - readDir(path) => array<paths>
//   Must also call callback() with no arguments if the file does not exist.
// The repo is expected to have a rootPath property that points to
// the .git folder within the filesystem.
module.exports = function (repo, fs) {

var cachedIndexes = {};

repo.loadAs = loadAs;
  repo.saveAs = saveAs;
  repo.loadRaw = loadRaw;
  repo.saveRaw = saveRaw;
  repo.readRef = readRef;
  repo.updateRef = updateRef;
  repo.hasHash = hasHash;
  repo.init = init;
  repo.setShallow = setShallow;

function init(ref, callback) {
    if (!callback) return init.bind(null, ref);
    ref = ref || "refs/heads/master";
    var path = pathJoin(repo.rootPath, "HEAD");
    fs.writeFile(path, "ref: " + ref, callback);
  }

function setShallow(ref, callback) {
    if (!callback) return setShallow.bind(null, ref);
    var path = pathJoin(repo.rootPath, "shallow");
    fs.writeFile(path, ref, callback);
  }

function updateRef(ref, hash, callback) {
    if (!callback) return updateRef.bind(repo, ref, hash);
    var path = pathJoin(repo.rootPath, ref);
    var lock = path + ".lock";
    fs.writeFile(lock, bodec.fromRaw(hash + "\n"), function(err) {
      if(err) return callback(err);
      fs.rename(lock, path, callback);
    });
  }

function hasHash(hash, callback) {
    if (!callback) return hasHash.bind(repo, hash);
    loadRaw(hash, function (err, body) {
      if (err) return callback(err);
      return callback(null, !!body);
    });
  }

function start() {
      var packHash = packHashes.pop();
      var offsets;
      if (!packHash) return callback();
      if (!cachedIndexes[packHash]) loadIndex(packHash);
      else onIndex();

function onIndex() {
        var cached = cachedIndexes[packHash];
        var packFile = pathJoin(packDir, "pack-" + packHash + ".pack" );
        var index = cached.byHash[hash];
        if (!index) return start();
        offsets = cached.offsets;
        loadChunk(packFile, index.offset, callback);
      }

}
  }

function hashToPath(hash) {
    return pathJoin(repo.rootPath, "objects", hash.substring(0, 2), hash.substring(2));
  }

};

function parseIndex(buffer) {
  if (readUint32(buffer, 0) !== 0xff744f63 ||
      readUint32(buffer, 4) !== 0x00000002) {
    throw new Error("Only v2 pack indexes supported");
  }

// Get the number of hashes in index
  // This is the value of the last fan-out entry
  var hashOffset = 8 + 255 * 4;
  var length = readUint32(buffer, hashOffset);
  hashOffset += 4;
  var crcOffset = hashOffset + 20 * length;
  var lengthOffset = crcOffset + 4 * length;
  var largeOffset = lengthOffset + 4 * length;
  var checkOffset = largeOffset;
  var indexes = new Array(length);
  for (var i = 0; i < length; i++) {
    var start = hashOffset + i * 20;
    var hash = bodec.toHex(bodec.slice(buffer, start, start + 20));
    var crc = readUint32(buffer, crcOffset + i * 4);
    var offset = readUint32(buffer, lengthOffset + i * 4);
    if (offset & 0x80000000) {
      offset = largeOffset + (offset &0x7fffffff) * 8;
      checkOffset = Math.max(checkOffset, offset + 8);
      offset = readUint64(buffer, offset);
    }
    indexes[i] = {
      hash: hash,
      offset: offset,
      crc: crc
    };
  }
  var packChecksum = bodec.toHex(bodec.slice(buffer, checkOffset, checkOffset + 20));
  var checksum = bodec.toHex(bodec.slice(buffer, checkOffset + 20, checkOffset + 40));
  if (sha1(bodec.slice(buffer, 0, checkOffset + 20)) !== checksum) {
    throw new Error("Checksum mistmatch");
  }

return {
    offsets: offsets,
    byHash: byHash,
    checksum: packChecksum
  };
}

function readUint32(buffer, offset) {
  return (buffer[offset] << 24 |
          buffer[offset + 1] << 16 |
          buffer[offset + 2] << 8 |
          buffer[offset + 3] << 0) >>> 0;
}

// Yes this will lose precision over 2^53, but that can't be helped when
// returning a single integer.
// We simply won't support packfiles over 8 petabytes. I'm ok with that.
function readUint64(buffer, offset) {
  var hi = (buffer[offset] << 24 |
            buffer[offset + 1] << 16 |
            buffer[offset + 2] << 8 |
            buffer[offset + 3] << 0) >>> 0;
  var lo = (buffer[offset + 4] << 24 |
            buffer[offset + 5] << 16 |
            buffer[offset + 6] << 8 |
            buffer[offset + 7] << 0) >>> 0;
  return hi * 0x100000000 + lo;
}

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