git ssb

1
2
/* jshint node: true */
3
'use strict';
4
5
var fs = require('fs');
6
var Decoder = require('pull-utf8-decoder')
7
/**
8
  # pull-file
9
10
  This is a simple module which uses raw file reading methods available in
11
  the node `fs` module to read files on-demand.  It's a work in progress
12
  and feedback is welcome :)
13
14
  ## Example Usage
15
16
  <<< examples/ipsum-chunks.js
17
18
**/
19
module.exports = function(filename, opts) {
20
  var mode = opts && opts.mode || 0x1B6; // 0666
21
  var bufferSize = opts && (opts.bufferSize || (opts.buffer && opts.buffer.length))  || 1024*64;
22
  var start = opts && opts.start || 0
23
  var end = opts && opts.end || Number.MAX_SAFE_INTEGER
24
  var fd = opts && opts.fd
25
26
  var ended, closeNext, busy;
27
  var _buffer = opts && opts.buffer || new Buffer(bufferSize)
28
  var live = opts && !!opts.live
29
  var liveCb, closeCb
30
  var watcher
31
  if(live) {
32
    watcher = fs.watch(filename, {
33
      persistent: opts.persistent !== false,
34
    },
35
    function (event) {
36
      if(liveCb && event === 'change') {
37
        var cb = liveCb
38
        liveCb = null
39
        closeNext = false
40
        readNext(cb)
41
      }
42
    })
43
44
  }
45
46
  var flags = opts && opts.flags || 'r'
47
48
  function readNext(cb) {
49
    if(closeNext) {
50
      if(!live) close(cb);
51
      else liveCb = cb;
52
      return
53
    }
54
    var toRead = Math.min(end - start, bufferSize);
55
    busy = true;
56
57
    fs.read(
58
      fd,
59
      _buffer,
60
      0,
61
      toRead,
62
      start,
63
      function(err, count, buffer) {
64
        busy = false;
65
        start += count;
66
        // if we have received an end noticiation, just discard this data
67
        if(closeNext && !live) {
68
          close(closeCb);
69
          return cb(closeNext);
70
        }
71
72
        if (ended) {
73
          return cb(err || ended);
74
        }
75
76
        // if we encountered a read error pass it on
77
        if (err) {
78
          return cb(err);
79
        }
80
81
        if(count === buffer.length) {
82
          cb(null, buffer);
83
        } else if(count === 0 && live) {
84
          liveCb = cb; closeNext = true
85
        } else {
86
          closeNext = true;
87
          cb(null, buffer.slice(0, count));
88
        }
89
      }
90
    );
91
    _buffer = opts && opts.buffer || new Buffer(Math.min(end - start, bufferSize))
92
  }
93
94
  function open(cb) {
95
    busy = true;
96
    fs.open(filename, flags, mode, function(err, descriptor) {
97
      // save the file descriptor
98
      fd = descriptor;
99
100
      busy = false
101
      if(closeNext) {
102
        close(closeCb);
103
        return cb(closeNext);
104
      }
105
106
      if (err) {
107
        return cb(err);
108
      }
109
110
      // read the next bytes
111
      return readNext(cb);
112
    });
113
  }
114
115
  function close (cb) {
116
    if(!cb) throw new Error('close must have cb')
117
    if(watcher) watcher.close()
118
    //if auto close is disabled, then user manages fd.
119
    if(opts && opts.autoClose === false) return cb(true)
120
121
    //wait until we have got out of bed, then go back to bed.
122
    //or if we are reading, wait till we read, then go back to bed.
123
    else if(busy) {
124
      closeCb = cb
125
      return closeNext = true
126
    }
127
128
    //first read was close, don't even get out of bed.
129
    else if(!fd) {
130
      return cb(true)
131
    }
132
133
    //go back to bed
134
    else {
135
      fs.close(fd, function(err) {
136
        fd = null;
137
        cb(err || true);
138
      });
139
    }
140
  }
141
142
  function source (end, cb) {
143
    if (end) {
144
      ended = end;
145
      live = false;
146
      if(liveCb) {
147
        liveCb(end || true);
148
      }
149
      close(cb);
150
    }
151
    // if we have already received the end notification, abort further
152
    else if (ended) {
153
      cb(ended);
154
    }
155
156
    else if (! fd) {
157
      open(cb);
158
    }
159
160
    else
161
      readNext(cb);
162
  };
163
164
  //read directly to text
165
  if(opts && opts.encoding)
166
    return Decoder(opts.encoding)(source)
167
168
  return source
169
170
};
171