git ssb

1
var buffered = require('pull-buffered')
2
var pull = require('pull-stream')
3
var toPull = require('stream-to-pull-stream')
4
var pako = require('pako')
5
var createHash = require('./util').createHash
6
var cat = require('pull-cat')
7
8
exports.decode = decodePack
9
exports.encode = encodePack
10
11
var PACK_VERSION = 2
12
13
var objectTypes = [
14
  'none', 'commit', 'tree', 'blob',
15
  'tag', 'unused', 'ofs-delta', 'ref-delta'
16
]
17
var objectTypeNums = {
18
  commit: 1,
19
  tree: 2,
20
  blob: 3,
21
  tag: 4
22
}
23
24
function error(cb) {
25
  return function (err) {
26
    cb(err || true)
27
  }
28
}
29
30
function inflateBytes(read) {
31
  var inflate = new pako.Inflate()
32
  var ended, dataOut
33
34
  inflate.onData = function (data) {
35
    dataOut = new Buffer(data)
36
    // console.error('inflated data', data.length)
37
  }
38
39
  inflate.onEnd = function (status) {
40
    ended = (status === 0) ? true : new Error(inflate.msg)
41
    // console.error('inflated end', status, ended)
42
  }
43
44
  return function (abort, cb) {
45
    if (ended) return cb(ended)
46
    read(abort, function next(end, data) {
47
      if (end === true) {
48
        end = null
49
        data = []
50
      }
51
      if (ended = end) return cb(end)
52
      if (data.length > 1) return cb(new Error('got more than one byte'))
53
      dataOut = null
54
      inflate.push(data, end === true)
55
      if (dataOut)
56
        cb(null, dataOut)
57
      else if (ended)
58
        cb(ended)
59
      else
60
        read(null, next)
61
    })
62
  }
63
}
64
65
function deflate(read) {
66
  var def = new pako.Deflate()
67
  var queue = []
68
  var ended
69
70
  def.onData = function (data) {
71
    queue.push([null, new Buffer(data)])
72
  }
73
74
  def.onEnd = function (status) {
75
    queue.push([(status === 0) ? true : new Error(def.msg)])
76
  }
77
78
  return function readOut(abort, cb) {
79
    if (ended)
80
      cb(ended)
81
    else if (queue.length)
82
      cb.apply(this, queue.shift())
83
    else
84
      read(abort, function next(end, data) {
85
        if (end === true) def.push([], true)
86
        else if (end) return cb(end)
87
        else def.push(data)
88
        readOut(null, cb)
89
      })
90
  }
91
}
92
93
function decodePack(onEnd, read) {
94
  if (read === undefined)
95
    return decodePack.bind(this, onEnd)
96
97
  var ended
98
  var numObjects = -1
99
  var checksum = createHash('sha1')
100
  var b = buffered(read)
101
  // TODO: optimize to pass through buffers to checksum
102
  var readByte = checksum(b.chunks(1))
103
  var readWord = checksum(b.chunks(4))
104
  var readChecksum = b.chunks(20)
105
  var expectChecksum = true
106
  var opts = {
107
    verbosity: 0
108
  }
109
110
  function readHeader(cb) {
111
    readWord(null, function (end, header) {
112
      if (ended = end) return cb(end)
113
      if (!header.equals(header, new Buffer('PACK')))
114
        read(new Error('Invalid packfile header'), error(cb))
115
      else
116
        readVersion(cb)
117
    })
118
  }
119
120
  function readVersion(cb) {
121
    readWord(null, function (end, word) {
122
      if (ended = end) return cb(end)
123
      var version = word.readUInt32BE()
124
      if (version < 2 || version > 3)
125
        read(new Error('Invalid packfile version ' + version), error(cb))
126
      else
127
        readNumObjects(cb)
128
    })
129
  }
130
131
  function readNumObjects(cb) {
132
    readWord(null, function (end, word) {
133
      if (ended = end) return cb(end)
134
      numObjects = word.readUInt32BE()
135
      if (opts.verbosity >= 1)
136
        console.error(numObjects + ' objects')
137
      readObject(null, cb)
138
    })
139
  }
140
141
  function readVarInt(cb) {
142
    var type, value, shift
143
    // https://codewords.recurse.com/images/three/varint.svg
144
    readByte(null, function (end, buf) {
145
      if (ended = end) return cb(end)
146
      var firstByte = buf[0]
147
      type = objectTypes[(firstByte >> 4) & 7]
148
      value = firstByte & 15
149
      // console.error('byte1', firstByte, firstByte.toString(2))
150
      shift = 4
151
      checkByte(firstByte)
152
    })
153
154
    function checkByte(byte) {
155
      if (byte & 0x80)
156
        readByte(null, gotByte)
157
      else
158
        cb(null, type, value)
159
    }
160
161
    function gotByte(end, buf) {
162
      if (ended = end) return cb(end)
163
      var byte = buf[0]
164
      value += (byte & 0x7f) << shift
165
      shift += 7
166
      // console.error('byte', byte, byte.toString(2))
167
      checkByte(byte)
168
    }
169
  }
170
171
  function getObject(cb) {
172
    readVarInt(function (end, type, length) {
173
      if (opts.verbosity >= 2)
174
        console.error('read object header', end, type, length)
175
      numObjects--
176
      if (end === true && expectChecksum)
177
        onEnd(new Error('Missing checksum'))
178
      if (ended = end) return cb(end)
179
      // TODO: verify that the inflated data is the correct length
180
      cb(null, type, length, inflateBytes(readByte))
181
    })
182
  }
183
184
  function readTrailer(cb) {
185
    // read the checksum before it updates to include the trailer
186
    var expected = checksum.digest()
187
    readChecksum(null, function (end, value) {
188
      cb(true)
189
      if (end === true && expectChecksum)
190
        onEnd(new Error('Missing checksum'))
191
      if (!value.equals(expected)) {
192
        onEnd(new Error('Checksum mismatch: ' +
193
          expected.hexSlice() + ' != ' + value.hexSlice()))
194
      } else {
195
        if (opts.verbosity >= 2)
196
          console.error('checksum ok', expected.hexSlice())
197
        onEnd(null)
198
      }
199
    })
200
  }
201
202
  function readObject(abort, cb) {
203
    if (ended) cb(ended)
204
    else if (abort) read(abort)
205
    else if (numObjects < 0) readHeader(cb)
206
    else if (numObjects > 0) getObject(cb)
207
    else if (expectChecksum) readTrailer(cb)
208
  }
209
210
  return readObject
211
}
212
213
function once(read) {
214
  var done
215
  return function (abort, cb) {
216
    if (done) cb(done)
217
    else done = true, read(abort, cb)
218
  }
219
}
220
221
function encodeVarInt(typeStr, length, cb) {
222
  var type = objectTypeNums[typeStr]
223
  // console.error('TYPE', type, typeStr, 'len', length, typeof cb)
224
	if (!type)
225
    return cb(new Error("Bad object type " + typeStr))
226
227
  var vals = []
228
  var b = (type << 4) | (length & 15)
229
	for (length >>= 4; length; length >>= 7) {
230
    vals.push(b | 0x80)
231
    b = length & 0x7f
232
  }
233
  vals.push(b)
234
  /*
235
  console.error('sending var int', vals, vals.map(function (n) {
236
    return ('00000000' + Number(n).toString(2)).substr(-8)
237
  }))
238
  */
239
  cb(null, new Buffer(vals))
240
}
241
242
function encodePack(numObjects, readObject) {
243
  if (readObject === undefined)
244
    return encodePack.bind(this, numObjects)
245
246
  var header = new Buffer(12)
247
  header.write('PACK')
248
  header.writeUInt32BE(PACK_VERSION, 4)
249
  header.writeUInt32BE(numObjects, 8)
250
  var checksum = createHash('sha1')
251
  var readData
252
253
  return cat([
254
    checksum(cat([
255
      pull.once(header),
256
      encodeObject
257
    ])),
258
    checksum.readDigest
259
  ])
260
261
  function encodeObject(abort, cb) {
262
    if (readData)
263
      readData(abort, function (end, data) {
264
        if (end === true)
265
          readObject(abort, nextObject)
266
        else
267
          cb(end, data)
268
      })
269
    else
270
      readObject(abort, nextObject)
271
272
    function nextObject(end, type, length, read) {
273
      if (end) return cb(end)
274
      readData = deflate(read)
275
      encodeVarInt(type, length, cb)
276
    }
277
  }
278
}
279