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fs: refactor fs module

PR-URL: #20764
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
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jasnell committed May 15, 2018
1 parent a14a0fa commit 7f0f978affda555c5f7151f2d6abd212e753d4f1
1,382 lib/fs.js

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@@ -0,0 +1,108 @@
'use strict';
const { Buffer } = require('buffer');
const { FSReqWrap, close, read } = process.binding('fs');
const kReadFileBufferLength = 8 * 1024;
function readFileAfterRead(err, bytesRead) {
const context = this.context;
if (err)
return context.close(err);
if (bytesRead === 0)
return context.close();
context.pos += bytesRead;
if (context.size !== 0) {
if (context.pos === context.size)
context.close();
else
context.read();
} else {
// unknown size, just read until we don't get bytes.
context.buffers.push(context.buffer.slice(0, bytesRead));
context.read();
}
}
function readFileAfterClose(err) {
const context = this.context;
const callback = context.callback;
let buffer = null;
if (context.err || err)
return callback(context.err || err);
try {
if (context.size === 0)
buffer = Buffer.concat(context.buffers, context.pos);
else if (context.pos < context.size)
buffer = context.buffer.slice(0, context.pos);
else
buffer = context.buffer;
if (context.encoding)
buffer = buffer.toString(context.encoding);
} catch (err) {
return callback(err);
}
callback(null, buffer);
}
class ReadFileContext {
constructor(callback, encoding) {
this.fd = undefined;
this.isUserFd = undefined;
this.size = undefined;
this.callback = callback;
this.buffers = null;
this.buffer = null;
this.pos = 0;
this.encoding = encoding;
this.err = null;
}
read() {
let buffer;
let offset;
let length;
if (this.size === 0) {
buffer = this.buffer = Buffer.allocUnsafeSlow(kReadFileBufferLength);
offset = 0;
length = kReadFileBufferLength;
} else {
buffer = this.buffer;
offset = this.pos;
length = Math.min(kReadFileBufferLength, this.size - this.pos);
}
const req = new FSReqWrap();
req.oncomplete = readFileAfterRead;
req.context = this;
read(this.fd, buffer, offset, length, -1, req);
}
close(err) {
const req = new FSReqWrap();
req.oncomplete = readFileAfterClose;
req.context = this;
this.err = err;
if (this.isUserFd) {
process.nextTick(function tick() {
req.oncomplete(null);
});
return;
}
close(this.fd, req);
}
}
module.exports = ReadFileContext;
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