Node.js v0.9.8 Manual & Documentation
Table of Contents
- Buffer
- Class: Buffer
- new Buffer(size)
- new Buffer(array)
- new Buffer(str, [encoding])
- Class Method: Buffer.isEncoding(encoding)
- buf.write(string, [offset], [length], [encoding])
- buf.toString([encoding], [start], [end])
- buf.toJSON()
- buf[index]
- Class Method: Buffer.isBuffer(obj)
- Class Method: Buffer.byteLength(string, [encoding])
- Class Method: Buffer.concat(list, [totalLength])
- buf.length
- buf.copy(targetBuffer, [targetStart], [sourceStart], [sourceEnd])
- buf.slice([start], [end])
- buf.readUInt8(offset, [noAssert])
- buf.readUInt16LE(offset, [noAssert])
- buf.readUInt16BE(offset, [noAssert])
- buf.readUInt32LE(offset, [noAssert])
- buf.readUInt32BE(offset, [noAssert])
- buf.readInt8(offset, [noAssert])
- buf.readInt16LE(offset, [noAssert])
- buf.readInt16BE(offset, [noAssert])
- buf.readInt32LE(offset, [noAssert])
- buf.readInt32BE(offset, [noAssert])
- buf.readFloatLE(offset, [noAssert])
- buf.readFloatBE(offset, [noAssert])
- buf.readDoubleLE(offset, [noAssert])
- buf.readDoubleBE(offset, [noAssert])
- buf.writeUInt8(value, offset, [noAssert])
- buf.writeUInt16LE(value, offset, [noAssert])
- buf.writeUInt16BE(value, offset, [noAssert])
- buf.writeUInt32LE(value, offset, [noAssert])
- buf.writeUInt32BE(value, offset, [noAssert])
- buf.writeInt8(value, offset, [noAssert])
- buf.writeInt16LE(value, offset, [noAssert])
- buf.writeInt16BE(value, offset, [noAssert])
- buf.writeInt32LE(value, offset, [noAssert])
- buf.writeInt32BE(value, offset, [noAssert])
- buf.writeFloatLE(value, offset, [noAssert])
- buf.writeFloatBE(value, offset, [noAssert])
- buf.writeDoubleLE(value, offset, [noAssert])
- buf.writeDoubleBE(value, offset, [noAssert])
- buf.fill(value, [offset], [end])
- buffer.INSPECT_MAX_BYTES
- Class: SlowBuffer
- Class: Buffer
Buffer#
Stability: 3 - Stable
Pure JavaScript is Unicode friendly but not nice to binary data. When dealing with TCP streams or the file system, it's necessary to handle octet streams. Node has several strategies for manipulating, creating, and consuming octet streams.
Raw data is stored in instances of the Buffer
class. A Buffer
is similar
to an array of integers but corresponds to a raw memory allocation outside
the V8 heap. A Buffer
cannot be resized.
The Buffer
class is a global, making it very rare that one would need
to ever require('buffer')
.
Converting between Buffers and JavaScript string objects requires an explicit encoding method. Here are the different string encodings.
'ascii'
- for 7 bit ASCII data only. This encoding method is very fast, and will strip the high bit if set. Note that this encoding converts a null character ('\0'
or'\u0000'
) into0x20
(character code of a space). If you want to convert a null character into0x00
, you should use'utf8'
.'utf8'
- Multibyte encoded Unicode characters. Many web pages and other document formats use UTF-8.'utf16le'
- 2 or 4 bytes, little endian encoded Unicode characters. Surrogate pairs (U+10000 to U+10FFFF) are supported.'ucs2'
- Alias of'utf16le'
.'base64'
- Base64 string encoding.'binary'
- A way of encoding raw binary data into strings by using only the first 8 bits of each character. This encoding method is deprecated and should be avoided in favor ofBuffer
objects where possible. This encoding will be removed in future versions of Node.'hex'
- Encode each byte as two hexadecimal characters.
Buffer
can also be used with Typed Array Views and DataViews.
var buff = new Buffer(4);
var ui16 = new Uint16Array(buff);
var view = new DataView(buff);
ui16[0] = 1;
ui16[1] = 2;
console.log(buff);
view.setInt16(0, 1); // set big-endian int16 at byte offset 0
view.setInt16(2, 2, true); // set little-endian int16 at byte offset 2
console.log(buff);
// <Buffer 01 00 02 00>
// <Buffer 00 01 02 00>
Class: Buffer#
The Buffer class is a global type for dealing with binary data directly. It can be constructed in a variety of ways.
new Buffer(size)#
size
Number
Allocates a new buffer of size
octets.
new Buffer(array)#
array
Array
Allocates a new buffer using an array
of octets.
new Buffer(str, [encoding])#
str
String - string to encode.encoding
String - encoding to use, Optional.
Allocates a new buffer containing the given str
.
encoding
defaults to 'utf8'
.
Class Method: Buffer.isEncoding(encoding)#
encoding
String The encoding string to test
Returns true if the encoding
is a valid encoding argument, or false
otherwise.
buf.write(string, [offset], [length], [encoding])#
string
String - data to be written to bufferoffset
Number, Optional, Default: 0length
Number, Optional, Default:buffer.length - offset
encoding
String, Optional, Default: 'utf8'
Writes string
to the buffer at offset
using the given encoding.
offset
defaults to 0
, encoding
defaults to 'utf8'
. length
is
the number of bytes to write. Returns number of octets written. If buffer
did
not contain enough space to fit the entire string, it will write a partial
amount of the string. length
defaults to buffer.length - offset
.
The method will not write partial characters.
buf = new Buffer(256);
len = buf.write('\u00bd + \u00bc = \u00be', 0);
console.log(len + " bytes: " + buf.toString('utf8', 0, len));
The number of characters written (which may be different than the number of
bytes written) is set in Buffer._charsWritten
and will be overwritten the
next time buf.write()
is called.
buf.toString([encoding], [start], [end])#
encoding
String, Optional, Default: 'utf8'start
Number, Optional, Default: 0end
Number, Optional, Default:buffer.length
Decodes and returns a string from buffer data encoded with encoding
(defaults to 'utf8'
) beginning at start
(defaults to 0
) and ending at
end
(defaults to buffer.length
).
See buffer.write()
example, above.
buf.toJSON()#
Returns a JSON-representation of the Buffer instance, which is identical to the
output for JSON Arrays. JSON.stringify
implicitly calls this function when
stringifying a Buffer instance.
Example:
var buf = new Buffer('test');
var json = JSON.stringify(buf);
console.log(json);
// '[116,101,115,116]'
var copy = new Buffer(JSON.parse(json));
console.log(copy);
// <Buffer 74 65 73 74>
buf[index]#
Get and set the octet at index
. The values refer to individual bytes,
so the legal range is between 0x00
and 0xFF
hex or 0
and 255
.
Example: copy an ASCII string into a buffer, one byte at a time:
str = "node.js";
buf = new Buffer(str.length);
for (var i = 0; i < str.length ; i++) {
buf[i] = str.charCodeAt(i);
}
console.log(buf);
// node.js
Class Method: Buffer.isBuffer(obj)#
obj
Object- Return: Boolean
Tests if obj
is a Buffer
.
Class Method: Buffer.byteLength(string, [encoding])#
string
Stringencoding
String, Optional, Default: 'utf8'- Return: Number
Gives the actual byte length of a string. encoding
defaults to 'utf8'
.
This is not the same as String.prototype.length
since that returns the
number of characters in a string.
Example:
str = '\u00bd + \u00bc = \u00be';
console.log(str + ": " + str.length + " characters, " +
Buffer.byteLength(str, 'utf8') + " bytes");
// ½ + ¼ = ¾: 9 characters, 12 bytes
Class Method: Buffer.concat(list, [totalLength])#
list
Array List of Buffer objects to concattotalLength
Number Total length of the buffers when concatenated
Returns a buffer which is the result of concatenating all the buffers in the list together.
If the list has no items, or if the totalLength is 0, then it returns a zero-length buffer.
If the list has exactly one item, then the first item of the list is returned.
If the list has more than one item, then a new Buffer is created.
If totalLength is not provided, it is read from the buffers in the list. However, this adds an additional loop to the function, so it is faster to provide the length explicitly.
buf.length#
- Number
The size of the buffer in bytes. Note that this is not necessarily the size
of the contents. length
refers to the amount of memory allocated for the
buffer object. It does not change when the contents of the buffer are changed.
buf = new Buffer(1234);
console.log(buf.length);
buf.write("some string", 0, "ascii");
console.log(buf.length);
// 1234
// 1234
buf.copy(targetBuffer, [targetStart], [sourceStart], [sourceEnd])#
targetBuffer
Buffer object - Buffer to copy intotargetStart
Number, Optional, Default: 0sourceStart
Number, Optional, Default: 0sourceEnd
Number, Optional, Default:buffer.length
Does copy between buffers. The source and target regions can be overlapped.
targetStart
and sourceStart
default to 0
.
sourceEnd
defaults to buffer.length
.
Example: build two Buffers, then copy buf1
from byte 16 through byte 19
into buf2
, starting at the 8th byte in buf2
.
buf1 = new Buffer(26);
buf2 = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
buf1[i] = i + 97; // 97 is ASCII a
buf2[i] = 33; // ASCII !
}
buf1.copy(buf2, 8, 16, 20);
console.log(buf2.toString('ascii', 0, 25));
// !!!!!!!!qrst!!!!!!!!!!!!!
buf.slice([start], [end])#
start
Number, Optional, Default: 0end
Number, Optional, Default:buffer.length
Returns a new buffer which references the same memory as the old, but offset
and cropped by the start
(defaults to 0
) and end
(defaults to
buffer.length
) indexes.
Modifying the new buffer slice will modify memory in the original buffer!
Example: build a Buffer with the ASCII alphabet, take a slice, then modify one byte from the original Buffer.
var buf1 = new Buffer(26);
for (var i = 0 ; i < 26 ; i++) {
buf1[i] = i + 97; // 97 is ASCII a
}
var buf2 = buf1.slice(0, 3);
console.log(buf2.toString('ascii', 0, buf2.length));
buf1[0] = 33;
console.log(buf2.toString('ascii', 0, buf2.length));
// abc
// !bc
buf.readUInt8(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads an unsigned 8 bit integer from the buffer at the specified offset.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x3;
buf[1] = 0x4;
buf[2] = 0x23;
buf[3] = 0x42;
for (ii = 0; ii < buf.length; ii++) {
console.log(buf.readUInt8(ii));
}
// 0x3
// 0x4
// 0x23
// 0x42
buf.readUInt16LE(offset, [noAssert])#
buf.readUInt16BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads an unsigned 16 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x3;
buf[1] = 0x4;
buf[2] = 0x23;
buf[3] = 0x42;
console.log(buf.readUInt16BE(0));
console.log(buf.readUInt16LE(0));
console.log(buf.readUInt16BE(1));
console.log(buf.readUInt16LE(1));
console.log(buf.readUInt16BE(2));
console.log(buf.readUInt16LE(2));
// 0x0304
// 0x0403
// 0x0423
// 0x2304
// 0x2342
// 0x4223
buf.readUInt32LE(offset, [noAssert])#
buf.readUInt32BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads an unsigned 32 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x3;
buf[1] = 0x4;
buf[2] = 0x23;
buf[3] = 0x42;
console.log(buf.readUInt32BE(0));
console.log(buf.readUInt32LE(0));
// 0x03042342
// 0x42230403
buf.readInt8(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a signed 8 bit integer from the buffer at the specified offset.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Works as buffer.readUInt8
, except buffer contents are treated as two's
complement signed values.
buf.readInt16LE(offset, [noAssert])#
buf.readInt16BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a signed 16 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Works as buffer.readUInt16*
, except buffer contents are treated as two's
complement signed values.
buf.readInt32LE(offset, [noAssert])#
buf.readInt32BE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a signed 32 bit integer from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Works as buffer.readUInt32*
, except buffer contents are treated as two's
complement signed values.
buf.readFloatLE(offset, [noAssert])#
buf.readFloatBE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a 32 bit float from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(4);
buf[0] = 0x00;
buf[1] = 0x00;
buf[2] = 0x80;
buf[3] = 0x3f;
console.log(buf.readFloatLE(0));
// 0x01
buf.readDoubleLE(offset, [noAssert])#
buf.readDoubleBE(offset, [noAssert])#
offset
NumbernoAssert
Boolean, Optional, Default: false- Return: Number
Reads a 64 bit double from the buffer at the specified offset with specified endian format.
Set noAssert
to true to skip validation of offset
. This means that offset
may be beyond the end of the buffer. Defaults to false
.
Example:
var buf = new Buffer(8);
buf[0] = 0x55;
buf[1] = 0x55;
buf[2] = 0x55;
buf[3] = 0x55;
buf[4] = 0x55;
buf[5] = 0x55;
buf[6] = 0xd5;
buf[7] = 0x3f;
console.log(buf.readDoubleLE(0));
// 0.3333333333333333
buf.writeUInt8(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset. Note, value
must be a
valid unsigned 8 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeUInt8(0x3, 0);
buf.writeUInt8(0x4, 1);
buf.writeUInt8(0x23, 2);
buf.writeUInt8(0x42, 3);
console.log(buf);
// <Buffer 03 04 23 42>
buf.writeUInt16LE(value, offset, [noAssert])#
buf.writeUInt16BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid unsigned 16 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);
console.log(buf);
buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);
console.log(buf);
// <Buffer de ad be ef>
// <Buffer ad de ef be>
buf.writeUInt32LE(value, offset, [noAssert])#
buf.writeUInt32BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid unsigned 32 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeUInt32BE(0xfeedface, 0);
console.log(buf);
buf.writeUInt32LE(0xfeedface, 0);
console.log(buf);
// <Buffer fe ed fa ce>
// <Buffer ce fa ed fe>
buf.writeInt8(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset. Note, value
must be a
valid signed 8 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Works as buffer.writeUInt8
, except value is written out as a two's complement
signed integer into buffer
.
buf.writeInt16LE(value, offset, [noAssert])#
buf.writeInt16BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid signed 16 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Works as buffer.writeUInt16*
, except value is written out as a two's
complement signed integer into buffer
.
buf.writeInt32LE(value, offset, [noAssert])#
buf.writeInt32BE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid signed 32 bit integer.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Works as buffer.writeUInt32*
, except value is written out as a two's
complement signed integer into buffer
.
buf.writeFloatLE(value, offset, [noAssert])#
buf.writeFloatBE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, behavior is unspecified if value
is not a 32 bit float.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(4);
buf.writeFloatBE(0xcafebabe, 0);
console.log(buf);
buf.writeFloatLE(0xcafebabe, 0);
console.log(buf);
// <Buffer 4f 4a fe bb>
// <Buffer bb fe 4a 4f>
buf.writeDoubleLE(value, offset, [noAssert])#
buf.writeDoubleBE(value, offset, [noAssert])#
value
Numberoffset
NumbernoAssert
Boolean, Optional, Default: false
Writes value
to the buffer at the specified offset with specified endian
format. Note, value
must be a valid 64 bit double.
Set noAssert
to true to skip validation of value
and offset
. This means
that value
may be too large for the specific function and offset
may be
beyond the end of the buffer leading to the values being silently dropped. This
should not be used unless you are certain of correctness. Defaults to false
.
Example:
var buf = new Buffer(8);
buf.writeDoubleBE(0xdeadbeefcafebabe, 0);
console.log(buf);
buf.writeDoubleLE(0xdeadbeefcafebabe, 0);
console.log(buf);
// <Buffer 43 eb d5 b7 dd f9 5f d7>
// <Buffer d7 5f f9 dd b7 d5 eb 43>
buf.fill(value, [offset], [end])#
value
offset
Number, Optionalend
Number, Optional
Fills the buffer with the specified value. If the offset
(defaults to 0
)
and end
(defaults to buffer.length
) are not given it will fill the entire
buffer.
var b = new Buffer(50);
b.fill("h");
buffer.INSPECT_MAX_BYTES#
- Number, Default: 50
How many bytes will be returned when buffer.inspect()
is called. This can
be overridden by user modules.
Note that this is a property on the buffer module returned by
require('buffer')
, not on the Buffer global, or a buffer instance.
Class: SlowBuffer#
This class is primarily for internal use. JavaScript programs should use Buffer instead of using SlowBuffer.
In order to avoid the overhead of allocating many C++ Buffer objects for small blocks of memory in the lifetime of a server, Node allocates memory in 8Kb (8192 byte) chunks. If a buffer is smaller than this size, then it will be backed by a parent SlowBuffer object. If it is larger than this, then Node will allocate a SlowBuffer slab for it directly.