1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
|
/**
* in this example, we use
*/
let zHandle;
let rowcount;
let start;
let data;
let bytes_read;
// reset our variables for a new parse
function reset() {
rowcount = 0;
start = performance.now();
data = [];
bytes_read = 0;
}
// handle a single parsed row
function rowHandler() {
rowcount++;
let count = zHandle.cellCount();
let row = [];
for (let i = 0; i < count; i++)
row.push(zHandle.getCell(i));
data.push(row);
}
// after we're done parsing, clean up and display the result
function finish() {
zHandle.finish();
zHandle.delete();
alert(
'Parsed ' + bytes_read + ' bytes (' + rowcount + ' rows) in ' + parseFloat(performance.now() - start).toFixed(2) + ' ms.\n' +
'View the parsed data in the browser\'s Developer Tools Console (right-click and select Inspect).');
console.log('zsv parsed data', data);
data = null;
}
// whenever the file input element changes, parse the file the user selected
function fileChanged(e) {
if (e.target.files && e.target.files.length) {
// initialize
reset();
zHandle = zsvParser.new(rowHandler);
// stream the file through our parser
let chunkSize = 1024 * 1024; // 1 mb
streamFile(e.target.files[0], chunkSize, function (err, data) {
if (!err) {
if (data) {
bytes_read += data.length;
zHandle.parseBytes(data);
} else // all done
finish();
} else {
console.error('Error!', err);
// cleanup
finish();
}
});
}
}
// after the page has loaded, add our change listener to the file input element
window.addEventListener('load', function () {
let file_input = document.body.querySelector('#file_input');
file_input.addEventListener('change', fileChanged);
})
// Generic function to stream a file through a function
function streamFile(file, chunk_size, cb) {
if (!(chunk_size >= 1024))
chunk_size = 1024;
let offset = 0;
let fr = new FileReader();
function getNextChunk() {
// getNextChunk(): will fire 'onload' event when specified chunk size is loaded
let slice = file.slice(offset, offset + chunk_size);
fr.readAsArrayBuffer(slice);
}
fr.onload = function () {
let view = new Uint8Array(fr.result);
if (!cb(null, view)) {
offset += chunk_size;
if (offset < file.size && view.length)
getNextChunk();
else // all done
cb(null, null);
}
};
fr.onerror = function () {
cb('read error');
};
getNextChunk();
}
|
