Readonly
BYTES_Readonly
[toReadonly
bufferThe ArrayBuffer instance referenced by the array.
Readonly
byteThe length in bytes of the array.
Readonly
byteThe offset in bytes of the array.
Readonly
lengthThe length of the array.
Compares buf
with target
and returns a number indicating whether buf
comes before, after, or is the same as target
in sort order.
Comparison is based on the actual sequence of bytes in each Buffer
.
0
is returned if target
is the same as buf
1
is returned if target
should come beforebuf
when sorted.-1
is returned if target
should come afterbuf
when sorted.import { Buffer } from 'node:buffer';
const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('BCD');
const buf3 = Buffer.from('ABCD');
console.log(buf1.compare(buf1));
// Prints: 0
console.log(buf1.compare(buf2));
// Prints: -1
console.log(buf1.compare(buf3));
// Prints: -1
console.log(buf2.compare(buf1));
// Prints: 1
console.log(buf2.compare(buf3));
// Prints: 1
console.log([buf1, buf2, buf3].sort(Buffer.compare));
// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]
// (This result is equal to: [buf1, buf3, buf2].)
The optional targetStart
, targetEnd
, sourceStart
, and sourceEnd
arguments can be used to limit the comparison to specific ranges within target
and buf
respectively.
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
const buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);
console.log(buf1.compare(buf2, 5, 9, 0, 4));
// Prints: 0
console.log(buf1.compare(buf2, 0, 6, 4));
// Prints: -1
console.log(buf1.compare(buf2, 5, 6, 5));
// Prints: 1
ERR_OUT_OF_RANGE
is thrown if targetStart < 0
, sourceStart < 0
, targetEnd > target.byteLength
, or sourceEnd > source.byteLength
.
A Buffer
or Uint8Array with which to compare buf
.
Optional
targetStart: numberThe offset within target
at which to begin comparison.
Optional
targetEnd: numberThe offset within target
at which to end comparison (not inclusive).
Optional
sourceStart: numberThe offset within buf
at which to begin comparison.
Optional
sourceEnd: numberThe offset within buf
at which to end comparison (not inclusive).
Copies data from a region of buf
to a region in target
, even if the target
memory region overlaps with buf
.
TypedArray.prototype.set()
performs the same operation, and is available
for all TypedArrays, including Node.js Buffer
s, although it takes
different function arguments.
import { Buffer } from 'node:buffer';
// Create two `Buffer` instances.
const buf1 = Buffer.allocUnsafe(26);
const buf2 = Buffer.allocUnsafe(26).fill('!');
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'.
buf1[i] = i + 97;
}
// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.
buf1.copy(buf2, 8, 16, 20);
// This is equivalent to:
// buf2.set(buf1.subarray(16, 20), 8);
console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!
import { Buffer } from 'node:buffer';
// Create a `Buffer` and copy data from one region to an overlapping region
// within the same `Buffer`.
const buf = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'.
buf[i] = i + 97;
}
buf.copy(buf, 0, 4, 10);
console.log(buf.toString());
// Prints: efghijghijklmnopqrstuvwxyz
A Buffer
or Uint8Array to copy into.
Optional
targetStart: numberThe offset within target
at which to begin writing.
Optional
sourceStart: numberThe offset within buf
from which to begin copying.
Optional
sourceEnd: numberThe offset within buf
at which to stop copying (not inclusive).
The number of bytes copied.
Returns the this object after copying a section of the array identified by start and end to the same array starting at position target
If target is negative, it is treated as length+target where length is the length of the array.
If start is negative, it is treated as length+start. If end is negative, it is treated as length+end.
Optional
end: numberIf not specified, length of the this object is used as its default value.
Creates and returns an iterator of [index, byte]
pairs from the contents
of buf
.
import { Buffer } from 'node:buffer';
// Log the entire contents of a `Buffer`.
const buf = Buffer.from('buffer');
for (const pair of buf.entries()) {
console.log(pair);
}
// Prints:
// [0, 98]
// [1, 117]
// [2, 102]
// [3, 102]
// [4, 101]
// [5, 114]
Returns true
if both buf
and otherBuffer
have exactly the same bytes,false
otherwise. Equivalent to buf.compare(otherBuffer) === 0
.
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('414243', 'hex');
const buf3 = Buffer.from('ABCD');
console.log(buf1.equals(buf2));
// Prints: true
console.log(buf1.equals(buf3));
// Prints: false
A Buffer
or Uint8Array with which to compare buf
.
Determines whether all the members of an array satisfy the specified test.
A function that accepts up to three arguments. The every method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value false, or until the end of the array.
Optional
thisArg: anyAn object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
Fills buf
with the specified value
. If the offset
and end
are not given,
the entire buf
will be filled:
import { Buffer } from 'node:buffer';
// Fill a `Buffer` with the ASCII character 'h'.
const b = Buffer.allocUnsafe(50).fill('h');
console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
// Fill a buffer with empty string
const c = Buffer.allocUnsafe(5).fill('');
console.log(c.fill(''));
// Prints: <Buffer 00 00 00 00 00>
value
is coerced to a uint32
value if it is not a string, Buffer
, or
integer. If the resulting integer is greater than 255
(decimal), buf
will be
filled with value & 255
.
If the final write of a fill()
operation falls on a multi-byte character,
then only the bytes of that character that fit into buf
are written:
import { Buffer } from 'node:buffer';
// Fill a `Buffer` with character that takes up two bytes in UTF-8.
console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// Prints: <Buffer c8 a2 c8 a2 c8>
If value
contains invalid characters, it is truncated; if no valid
fill data remains, an exception is thrown:
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(5);
console.log(buf.fill('a'));
// Prints: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// Prints: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// Throws an exception.
The value with which to fill buf
. Empty value (string, Uint8Array, Buffer) is coerced to 0
.
Optional
offset: numberNumber of bytes to skip before starting to fill buf
.
Optional
end: numberWhere to stop filling buf
(not inclusive).
Optional
encoding: BufferEncodingThe encoding for value
if value
is a string.
A reference to buf
.
Returns the elements of an array that meet the condition specified in a callback function.
A function that accepts up to three arguments. The filter method calls the predicate function one time for each element in the array.
Optional
thisArg: anyAn object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
Returns the value of the first element in the array where predicate is true, and undefined otherwise.
find calls predicate once for each element of the array, in ascending order, until it finds one where predicate returns true. If such an element is found, find immediately returns that element value. Otherwise, find returns undefined.
Optional
thisArg: anyIf provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Returns the index of the first element in the array where predicate is true, and -1 otherwise.
find calls predicate once for each element of the array, in ascending order, until it finds one where predicate returns true. If such an element is found, findIndex immediately returns that element index. Otherwise, findIndex returns -1.
Optional
thisArg: anyIf provided, it will be used as the this value for each invocation of predicate. If it is not provided, undefined is used instead.
Performs the specified action for each element in an array.
A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the array.
Optional
thisArg: anyAn object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
Equivalent to buf.indexOf() !== -1
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from('this is a buffer');
console.log(buf.includes('this'));
// Prints: true
console.log(buf.includes('is'));
// Prints: true
console.log(buf.includes(Buffer.from('a buffer')));
// Prints: true
console.log(buf.includes(97));
// Prints: true (97 is the decimal ASCII value for 'a')
console.log(buf.includes(Buffer.from('a buffer example')));
// Prints: false
console.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));
// Prints: true
console.log(buf.includes('this', 4));
// Prints: false
What to search for.
Optional
byteOffset: numberWhere to begin searching in buf
. If negative, then offset is calculated from the end of buf
.
Optional
encoding: BufferEncodingIf value
is a string, this is its encoding.
true
if value
was found in buf
, false
otherwise.
If value
is:
value
is interpreted according to the character encoding in encoding
.Buffer
or Uint8Array
, value
will be used in its entirety.
To compare a partial Buffer
, use buf.subarray
.value
will be interpreted as an unsigned 8-bit integer
value between 0
and 255
.import { Buffer } from 'node:buffer';
const buf = Buffer.from('this is a buffer');
console.log(buf.indexOf('this'));
// Prints: 0
console.log(buf.indexOf('is'));
// Prints: 2
console.log(buf.indexOf(Buffer.from('a buffer')));
// Prints: 8
console.log(buf.indexOf(97));
// Prints: 8 (97 is the decimal ASCII value for 'a')
console.log(buf.indexOf(Buffer.from('a buffer example')));
// Prints: -1
console.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));
// Prints: 8
const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');
console.log(utf16Buffer.indexOf('\u03a3', 0, 'utf16le'));
// Prints: 4
console.log(utf16Buffer.indexOf('\u03a3', -4, 'utf16le'));
// Prints: 6
If value
is not a string, number, or Buffer
, this method will throw a TypeError
. If value
is a number, it will be coerced to a valid byte value,
an integer between 0 and 255.
If byteOffset
is not a number, it will be coerced to a number. If the result
of coercion is NaN
or 0
, then the entire buffer will be searched. This
behavior matches String.prototype.indexOf()
.
import { Buffer } from 'node:buffer';
const b = Buffer.from('abcdef');
// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.indexOf(99.9));
console.log(b.indexOf(256 + 99));
// Passing a byteOffset that coerces to NaN or 0.
// Prints: 1, searching the whole buffer.
console.log(b.indexOf('b', undefined));
console.log(b.indexOf('b', {}));
console.log(b.indexOf('b', null));
console.log(b.indexOf('b', []));
If value
is an empty string or empty Buffer
and byteOffset
is less
than buf.length
, byteOffset
will be returned. If value
is empty andbyteOffset
is at least buf.length
, buf.length
will be returned.
What to search for.
Optional
byteOffset: numberWhere to begin searching in buf
. If negative, then offset is calculated from the end of buf
.
Optional
encoding: BufferEncodingIf value
is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf
.
The index of the first occurrence of value
in buf
, or -1
if buf
does not contain value
.
Adds all the elements of an array separated by the specified separator string.
Optional
separator: stringA string used to separate one element of an array from the next in the resulting String. If omitted, the array elements are separated with a comma.
Creates and returns an iterator of buf
keys (indices).
import { Buffer } from 'node:buffer';
const buf = Buffer.from('buffer');
for (const key of buf.keys()) {
console.log(key);
}
// Prints:
// 0
// 1
// 2
// 3
// 4
// 5
Identical to buf.indexOf()
, except the last occurrence of value
is found
rather than the first occurrence.
import { Buffer } from 'node:buffer';
const buf = Buffer.from('this buffer is a buffer');
console.log(buf.lastIndexOf('this'));
// Prints: 0
console.log(buf.lastIndexOf('buffer'));
// Prints: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// Prints: 17
console.log(buf.lastIndexOf(97));
// Prints: 15 (97 is the decimal ASCII value for 'a')
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// Prints: -1
console.log(buf.lastIndexOf('buffer', 5));
// Prints: 5
console.log(buf.lastIndexOf('buffer', 4));
// Prints: -1
const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');
console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// Prints: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// Prints: 4
If value
is not a string, number, or Buffer
, this method will throw a TypeError
. If value
is a number, it will be coerced to a valid byte value,
an integer between 0 and 255.
If byteOffset
is not a number, it will be coerced to a number. Any arguments
that coerce to NaN
, like {}
or undefined
, will search the whole buffer.
This behavior matches String.prototype.lastIndexOf()
.
import { Buffer } from 'node:buffer';
const b = Buffer.from('abcdef');
// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));
// Passing a byteOffset that coerces to NaN.
// Prints: 1, searching the whole buffer.
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));
// Passing a byteOffset that coerces to 0.
// Prints: -1, equivalent to passing 0.
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));
If value
is an empty string or empty Buffer
, byteOffset
will be returned.
What to search for.
Optional
byteOffset: numberWhere to begin searching in buf
. If negative, then offset is calculated from the end of buf
.
Optional
encoding: BufferEncodingIf value
is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf
.
The index of the last occurrence of value
in buf
, or -1
if buf
does not contain value
.
Calls a defined callback function on each element of an array, and returns an array that contains the results.
A function that accepts up to three arguments. The map method calls the callbackfn function one time for each element in the array.
Optional
thisArg: anyAn object to which the this keyword can refer in the callbackfn function. If thisArg is omitted, undefined is used as the this value.
Reads a signed, big-endian 64-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed
values.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8
.
Reads a signed, little-endian 64-bit integer from buf
at the specifiedoffset
.
Integers read from a Buffer
are interpreted as two's complement signed
values.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8
.
Reads an unsigned, big-endian 64-bit integer from buf
at the specifiedoffset
.
This function is also available under the readBigUint64BE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);
console.log(buf.readBigUInt64BE(0));
// Prints: 4294967295n
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8
.
Reads an unsigned, little-endian 64-bit integer from buf
at the specifiedoffset
.
This function is also available under the readBigUint64LE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);
console.log(buf.readBigUInt64LE(0));
// Prints: 18446744069414584320n
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8
.
Reads a 64-bit, big-endian double from buf
at the specified offset
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readDoubleBE(0));
// Prints: 8.20788039913184e-304
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8
.
Reads a 64-bit, little-endian double from buf
at the specified offset
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);
console.log(buf.readDoubleLE(0));
// Prints: 5.447603722011605e-270
console.log(buf.readDoubleLE(1));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8
.
Reads a 32-bit, big-endian float from buf
at the specified offset
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([1, 2, 3, 4]);
console.log(buf.readFloatBE(0));
// Prints: 2.387939260590663e-38
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4
.
Reads a 32-bit, little-endian float from buf
at the specified offset
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([1, 2, 3, 4]);
console.log(buf.readFloatLE(0));
// Prints: 1.539989614439558e-36
console.log(buf.readFloatLE(1));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4
.
Reads a signed, big-endian 16-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0, 5]);
console.log(buf.readInt16BE(0));
// Prints: 5
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2
.
Reads a signed, little-endian 16-bit integer from buf
at the specifiedoffset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0, 5]);
console.log(buf.readInt16LE(0));
// Prints: 1280
console.log(buf.readInt16LE(1));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2
.
Reads a signed, big-endian 32-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0, 0, 0, 5]);
console.log(buf.readInt32BE(0));
// Prints: 5
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4
.
Reads a signed, little-endian 32-bit integer from buf
at the specifiedoffset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0, 0, 0, 5]);
console.log(buf.readInt32LE(0));
// Prints: 83886080
console.log(buf.readInt32LE(1));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4
.
Reads a signed 8-bit integer from buf
at the specified offset
.
Integers read from a Buffer
are interpreted as two's complement signed values.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([-1, 5]);
console.log(buf.readInt8(0));
// Prints: -1
console.log(buf.readInt8(1));
// Prints: 5
console.log(buf.readInt8(2));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1
.
Reads byteLength
number of bytes from buf
at the specified offset
and interprets the result as a big-endian, two's complement signed value
supporting up to 48 bits of accuracy.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.
console.log(buf.readIntBE(1, 0).toString(16));
// Throws ERR_OUT_OF_RANGE.
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to read. Must satisfy 0 < byteLength <= 6
.
Reads byteLength
number of bytes from buf
at the specified offset
and interprets the result as a little-endian, two's complement signed value
supporting up to 48 bits of accuracy.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readIntLE(0, 6).toString(16));
// Prints: -546f87a9cbee
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to read. Must satisfy 0 < byteLength <= 6
.
Reads an unsigned, big-endian 16-bit integer from buf
at the specifiedoffset
.
This function is also available under the readUint16BE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56]);
console.log(buf.readUInt16BE(0).toString(16));
// Prints: 1234
console.log(buf.readUInt16BE(1).toString(16));
// Prints: 3456
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2
.
Reads an unsigned, little-endian 16-bit integer from buf
at the specified offset
.
This function is also available under the readUint16LE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56]);
console.log(buf.readUInt16LE(0).toString(16));
// Prints: 3412
console.log(buf.readUInt16LE(1).toString(16));
// Prints: 5634
console.log(buf.readUInt16LE(2).toString(16));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2
.
Reads an unsigned, big-endian 32-bit integer from buf
at the specifiedoffset
.
This function is also available under the readUint32BE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);
console.log(buf.readUInt32BE(0).toString(16));
// Prints: 12345678
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4
.
Reads an unsigned, little-endian 32-bit integer from buf
at the specifiedoffset
.
This function is also available under the readUint32LE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);
console.log(buf.readUInt32LE(0).toString(16));
// Prints: 78563412
console.log(buf.readUInt32LE(1).toString(16));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4
.
Reads an unsigned 8-bit integer from buf
at the specified offset
.
This function is also available under the readUint8
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([1, -2]);
console.log(buf.readUInt8(0));
// Prints: 1
console.log(buf.readUInt8(1));
// Prints: 254
console.log(buf.readUInt8(2));
// Throws ERR_OUT_OF_RANGE.
Optional
offset: numberNumber of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1
.
Reads byteLength
number of bytes from buf
at the specified offset
and interprets the result as an unsigned big-endian integer supporting
up to 48 bits of accuracy.
This function is also available under the readUintBE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readUIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readUIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to read. Must satisfy 0 < byteLength <= 6
.
Reads byteLength
number of bytes from buf
at the specified offset
and interprets the result as an unsigned, little-endian integer supporting
up to 48 bits of accuracy.
This function is also available under the readUintLE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);
console.log(buf.readUIntLE(0, 6).toString(16));
// Prints: ab9078563412
Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to read. Must satisfy 0 < byteLength <= 6
.
Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.
Calls the specified callback function for all the elements in an array. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
A function that accepts up to four arguments. The reduce method calls the callbackfn function one time for each element in the array.
If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.
Calls the specified callback function for all the elements in an array, in descending order. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.
Calls the specified callback function for all the elements in an array, in descending order. The return value of the callback function is the accumulated result, and is provided as an argument in the next call to the callback function.
A function that accepts up to four arguments. The reduceRight method calls the callbackfn function one time for each element in the array.
If initialValue is specified, it is used as the initial value to start the accumulation. The first call to the callbackfn function provides this value as an argument instead of an array value.
Sets a value or an array of values.
A typed or untyped array of values to set.
Optional
offset: numberThe index in the current array at which the values are to be written.
Returns a new Buffer
that references the same memory as the original, but
offset and cropped by the start
and end
indices.
This method is not compatible with the Uint8Array.prototype.slice()
,
which is a superclass of Buffer
. To copy the slice, useUint8Array.prototype.slice()
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from('buffer');
const copiedBuf = Uint8Array.prototype.slice.call(buf);
copiedBuf[0]++;
console.log(copiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Prints: buffer
// With buf.slice(), the original buffer is modified.
const notReallyCopiedBuf = buf.slice();
notReallyCopiedBuf[0]++;
console.log(notReallyCopiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Also prints: cuffer (!)
Optional
start: numberWhere the new Buffer
will start.
Optional
end: numberWhere the new Buffer
will end (not inclusive).
Determines whether the specified callback function returns true for any element of an array.
A function that accepts up to three arguments. The some method calls the predicate function for each element in the array until the predicate returns a value which is coercible to the Boolean value true, or until the end of the array.
Optional
thisArg: anyAn object to which the this keyword can refer in the predicate function. If thisArg is omitted, undefined is used as the this value.
Sorts an array.
Optional
compareFn: ((a: number, b: number) => number)Function used to determine the order of the elements. It is expected to return a negative value if first argument is less than second argument, zero if they're equal and a positive value otherwise. If omitted, the elements are sorted in ascending order.
[11,2,22,1].sort((a, b) => a - b)
Returns a new Buffer
that references the same memory as the original, but
offset and cropped by the start
and end
indices.
Specifying end
greater than buf.length
will return the same result as
that of end
equal to buf.length
.
This method is inherited from TypedArray.prototype.subarray()
.
Modifying the new Buffer
slice will modify the memory in the original Buffer
because the allocated memory of the two objects overlap.
import { Buffer } from 'node:buffer';
// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
// from the original `Buffer`.
const buf1 = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'.
buf1[i] = i + 97;
}
const buf2 = buf1.subarray(0, 3);
console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: abc
buf1[0] = 33;
console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: !bc
Specifying negative indexes causes the slice to be generated relative to the
end of buf
rather than the beginning.
import { Buffer } from 'node:buffer';
const buf = Buffer.from('buffer');
console.log(buf.subarray(-6, -1).toString());
// Prints: buffe
// (Equivalent to buf.subarray(0, 5).)
console.log(buf.subarray(-6, -2).toString());
// Prints: buff
// (Equivalent to buf.subarray(0, 4).)
console.log(buf.subarray(-5, -2).toString());
// Prints: uff
// (Equivalent to buf.subarray(1, 4).)
Optional
start: numberWhere the new Buffer
will start.
Optional
end: numberWhere the new Buffer
will end (not inclusive).
Interprets buf
as an array of unsigned 16-bit integers and swaps the
byte order in-place. Throws ERR_INVALID_BUFFER_SIZE
if buf.length
is not a multiple of 2.
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
buf1.swap16();
console.log(buf1);
// Prints: <Buffer 02 01 04 03 06 05 08 07>
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap16();
// Throws ERR_INVALID_BUFFER_SIZE.
One convenient use of buf.swap16()
is to perform a fast in-place conversion
between UTF-16 little-endian and UTF-16 big-endian:
import { Buffer } from 'node:buffer';
const buf = Buffer.from('This is little-endian UTF-16', 'utf16le');
buf.swap16(); // Convert to big-endian UTF-16 text.
A reference to buf
.
Interprets buf
as an array of unsigned 32-bit integers and swaps the
byte order in-place. Throws ERR_INVALID_BUFFER_SIZE
if buf.length
is not a multiple of 4.
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
buf1.swap32();
console.log(buf1);
// Prints: <Buffer 04 03 02 01 08 07 06 05>
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap32();
// Throws ERR_INVALID_BUFFER_SIZE.
A reference to buf
.
Interprets buf
as an array of 64-bit numbers and swaps byte order in-place.
Throws ERR_INVALID_BUFFER_SIZE
if buf.length
is not a multiple of 8.
import { Buffer } from 'node:buffer';
const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);
console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
buf1.swap64();
console.log(buf1);
// Prints: <Buffer 08 07 06 05 04 03 02 01>
const buf2 = Buffer.from([0x1, 0x2, 0x3]);
buf2.swap64();
// Throws ERR_INVALID_BUFFER_SIZE.
A reference to buf
.
Returns a JSON representation of buf
. JSON.stringify()
implicitly calls
this function when stringifying a Buffer
instance.
Buffer.from()
accepts objects in the format returned from this method.
In particular, Buffer.from(buf.toJSON())
works like Buffer.from(buf)
.
import { Buffer } from 'node:buffer';
const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
const json = JSON.stringify(buf);
console.log(json);
// Prints: {"type":"Buffer","data":[1,2,3,4,5]}
const copy = JSON.parse(json, (key, value) => {
return value && value.type === 'Buffer' ?
Buffer.from(value) :
value;
});
console.log(copy);
// Prints: <Buffer 01 02 03 04 05>
Decodes buf
to a string according to the specified character encoding inencoding
. start
and end
may be passed to decode only a subset of buf
.
If encoding
is 'utf8'
and a byte sequence in the input is not valid UTF-8,
then each invalid byte is replaced with the replacement character U+FFFD
.
The maximum length of a string instance (in UTF-16 code units) is available as constants.MAX_STRING_LENGTH.
import { Buffer } from 'node:buffer';
const buf1 = Buffer.allocUnsafe(26);
for (let i = 0; i < 26; i++) {
// 97 is the decimal ASCII value for 'a'.
buf1[i] = i + 97;
}
console.log(buf1.toString('utf8'));
// Prints: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('utf8', 0, 5));
// Prints: abcde
const buf2 = Buffer.from('tést');
console.log(buf2.toString('hex'));
// Prints: 74c3a97374
console.log(buf2.toString('utf8', 0, 3));
// Prints: té
console.log(buf2.toString(undefined, 0, 3));
// Prints: té
Optional
encoding: BufferEncodingThe character encoding to use.
Optional
start: numberThe byte offset to start decoding at.
Optional
end: numberThe byte offset to stop decoding at (not inclusive).
Creates and returns an iterator for buf
values (bytes). This function is
called automatically when a Buffer
is used in a for..of
statement.
import { Buffer } from 'node:buffer';
const buf = Buffer.from('buffer');
for (const value of buf.values()) {
console.log(value);
}
// Prints:
// 98
// 117
// 102
// 102
// 101
// 114
for (const value of buf) {
console.log(value);
}
// Prints:
// 98
// 117
// 102
// 102
// 101
// 114
Writes string
to buf
at offset
according to the character encoding inencoding
. The length
parameter is the number of bytes to write. If buf
did
not contain enough space to fit the entire string, only part of string
will be
written. However, partially encoded characters will not be written.
import { Buffer } from 'node:buffer';
const buf = Buffer.alloc(256);
const len = buf.write('\u00bd + \u00bc = \u00be', 0);
console.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);
// Prints: 12 bytes: ½ + ¼ = ¾
const buffer = Buffer.alloc(10);
const length = buffer.write('abcd', 8);
console.log(`${length} bytes: ${buffer.toString('utf8', 8, 10)}`);
// Prints: 2 bytes : ab
String to write to buf
.
Optional
encoding: BufferEncodingThe character encoding of string
.
Number of bytes written.
Optional
encoding: BufferEncodingOptional
encoding: BufferEncodingWrites value
to buf
at the specified offset
as big-endian.
value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigInt64BE(0x0102030405060708n, 0);
console.log(buf);
// Prints: <Buffer 01 02 03 04 05 06 07 08>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian.
value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigInt64LE(0x0102030405060708n, 0);
console.log(buf);
// Prints: <Buffer 08 07 06 05 04 03 02 01>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian.
This function is also available under the writeBigUint64BE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigUInt64BE(0xdecafafecacefaden, 0);
console.log(buf);
// Prints: <Buffer de ca fa fe ca ce fa de>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeBigUInt64LE(0xdecafafecacefaden, 0);
console.log(buf);
// Prints: <Buffer de fa ce ca fe fa ca de>
This function is also available under the writeBigUint64LE
alias.
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian. The value
must be a JavaScript number. Behavior is undefined when value
is anything
other than a JavaScript number.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeDoubleBE(123.456, 0);
console.log(buf);
// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian. The value
must be a JavaScript number. Behavior is undefined when value
is anything
other than a JavaScript number.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(8);
buf.writeDoubleLE(123.456, 0);
console.log(buf);
// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian. Behavior is
undefined when value
is anything other than a JavaScript number.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeFloatBE(0xcafebabe, 0);
console.log(buf);
// Prints: <Buffer 4f 4a fe bb>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian. Behavior is
undefined when value
is anything other than a JavaScript number.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeFloatLE(0xcafebabe, 0);
console.log(buf);
// Prints: <Buffer bb fe 4a 4f>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian. The value
must be a valid signed 16-bit integer. Behavior is undefined when value
is
anything other than a signed 16-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(2);
buf.writeInt16BE(0x0102, 0);
console.log(buf);
// Prints: <Buffer 01 02>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian. The value
must be a valid signed 16-bit integer. Behavior is undefined when value
is
anything other than a signed 16-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(2);
buf.writeInt16LE(0x0304, 0);
console.log(buf);
// Prints: <Buffer 04 03>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian. The value
must be a valid signed 32-bit integer. Behavior is undefined when value
is
anything other than a signed 32-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeInt32BE(0x01020304, 0);
console.log(buf);
// Prints: <Buffer 01 02 03 04>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian. The value
must be a valid signed 32-bit integer. Behavior is undefined when value
is
anything other than a signed 32-bit integer.
The value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeInt32LE(0x05060708, 0);
console.log(buf);
// Prints: <Buffer 08 07 06 05>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
. value
must be a valid
signed 8-bit integer. Behavior is undefined when value
is anything other than
a signed 8-bit integer.
value
is interpreted and written as a two's complement signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(2);
buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);
console.log(buf);
// Prints: <Buffer 02 fe>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1
.
offset
plus the number of bytes written.
Writes byteLength
bytes of value
to buf
at the specified offset
as big-endian. Supports up to 48 bits of accuracy. Behavior is undefined whenvalue
is anything other than a
signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeIntBE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>
Number to be written to buf
.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to write. Must satisfy 0 < byteLength <= 6
.
offset
plus the number of bytes written.
Writes byteLength
bytes of value
to buf
at the specified offset
as little-endian. Supports up to 48 bits of accuracy. Behavior is undefined
when value
is anything other than a signed integer.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeIntLE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>
Number to be written to buf
.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to write. Must satisfy 0 < byteLength <= 6
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian. The value
must be a valid unsigned 16-bit integer. Behavior is undefined when value
is anything other than an
unsigned 16-bit integer.
This function is also available under the writeUint16BE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);
console.log(buf);
// Prints: <Buffer de ad be ef>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian. The value
must be a valid unsigned 16-bit integer. Behavior is undefined when value
is
anything other than an unsigned 16-bit integer.
This function is also available under the writeUint16LE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);
console.log(buf);
// Prints: <Buffer ad de ef be>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as big-endian. The value
must be a valid unsigned 32-bit integer. Behavior is undefined when value
is anything other than an
unsigned 32-bit integer.
This function is also available under the writeUint32BE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt32BE(0xfeedface, 0);
console.log(buf);
// Prints: <Buffer fe ed fa ce>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
as little-endian. The value
must be a valid unsigned 32-bit integer. Behavior is undefined when value
is
anything other than an unsigned 32-bit integer.
This function is also available under the writeUint32LE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt32LE(0xfeedface, 0);
console.log(buf);
// Prints: <Buffer ce fa ed fe>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4
.
offset
plus the number of bytes written.
Writes value
to buf
at the specified offset
. value
must be a
valid unsigned 8-bit integer. Behavior is undefined when value
is anything
other than an unsigned 8-bit integer.
This function is also available under the writeUint8
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(4);
buf.writeUInt8(0x3, 0);
buf.writeUInt8(0x4, 1);
buf.writeUInt8(0x23, 2);
buf.writeUInt8(0x42, 3);
console.log(buf);
// Prints: <Buffer 03 04 23 42>
Number to be written to buf
.
Optional
offset: numberNumber of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1
.
offset
plus the number of bytes written.
Writes byteLength
bytes of value
to buf
at the specified offset
as big-endian. Supports up to 48 bits of accuracy. Behavior is undefined
when value
is anything other than an unsigned integer.
This function is also available under the writeUintBE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeUIntBE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>
Number to be written to buf
.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to write. Must satisfy 0 < byteLength <= 6
.
offset
plus the number of bytes written.
Writes byteLength
bytes of value
to buf
at the specified offset
as little-endian. Supports up to 48 bits of accuracy. Behavior is undefined
when value
is anything other than an unsigned integer.
This function is also available under the writeUintLE
alias.
import { Buffer } from 'node:buffer';
const buf = Buffer.allocUnsafe(6);
buf.writeUIntLE(0x1234567890ab, 0, 6);
console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>
Number to be written to buf
.
Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength
.
Number of bytes to write. Must satisfy 0 < byteLength <= 6
.
offset
plus the number of bytes written.
The size in bytes of each element in the array.