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read_file_context.js
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read_file_context.js
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'use strict';
const {
MathMin,
} = primordials;
const {
constants: {
kReadFileBufferLength,
kReadFileUnknownBufferLength,
}
} = require('internal/fs/utils');
const { Buffer } = require('buffer');
const { FSReqCallback, close, read } = internalBinding('fs');
const { hideStackFrames } = require('internal/errors');
let DOMException;
const lazyDOMException = hideStackFrames((message, name) => {
if (DOMException === undefined)
DOMException = internalBinding('messaging').DOMException;
return new DOMException(message, name);
});
function readFileAfterRead(err, bytesRead) {
const context = this.context;
if (err)
return context.close(err);
context.pos += bytesRead;
if (context.pos === context.size || bytesRead === 0) {
context.close();
} else {
if (context.size === 0) {
// Unknown size, just read until we don't get bytes.
const buffer = bytesRead === kReadFileUnknownBufferLength ?
context.buffer : context.buffer.slice(0, bytesRead);
context.buffers.push(buffer);
}
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 = 0;
this.callback = callback;
this.buffers = null;
this.buffer = null;
this.pos = 0;
this.encoding = encoding;
this.err = null;
this.signal = undefined;
}
read() {
let buffer;
let offset;
let length;
if (this.signal && this.signal.aborted) {
return this.close(
lazyDOMException('The operation was aborted', 'AbortError')
);
}
if (this.size === 0) {
buffer = Buffer.allocUnsafeSlow(kReadFileUnknownBufferLength);
offset = 0;
length = kReadFileUnknownBufferLength;
this.buffer = buffer;
} else {
buffer = this.buffer;
offset = this.pos;
length = MathMin(kReadFileBufferLength, this.size - this.pos);
}
const req = new FSReqCallback();
req.oncomplete = readFileAfterRead;
req.context = this;
read(this.fd, buffer, offset, length, -1, req);
}
close(err) {
if (this.isUserFd) {
process.nextTick(function tick(context) {
readFileAfterClose.call({ context }, null);
}, this);
return;
}
const req = new FSReqCallback();
req.oncomplete = readFileAfterClose;
req.context = this;
this.err = err;
close(this.fd, req);
}
}
module.exports = ReadFileContext;