Buffer

Buffer is an utility object that can be created by using data:createBuffer(). It is used to get more control of what you are writing and reading, by providing bunch of methods for reading and writing bytes for specific primitive data types.

Basics

Supported primitives

ⓘ Note

On this page methods, instead of standard type names, will often use primitive names from this table for specifying arguments and return types, keep this in mind while reading this page.

Type name	Size in bytes	Description
byte	1	An unsigned 8 bit length integer. Can contain values in range [0; 255]
short	2	A signed 16 bit length integer. Can contain values in range [-32768; 32767]
ushort	2	An unsigned 16 bit length integer. Can contain values in range [0; 65535]
int	4	A signed 32 bit length integer. Can contain values in range [-2147483648; 2147483647]
uint	4	An unsigned 32 bit length integer. Can contain values in range [0; 4294967295]
long	8	A signed 64 bit length integer. Can contain values in range [-9223372036854775808; 9223372036854775807]
ulong	8	An usigned 64 bit length integer. Can contain values in range [0; 18446744073709551615]
float	4	A single-precision float-pointing number.
double	8	A double-precision float-pointing number.
str	2+Length	A string primitive that can be stored in buffers. Starts with 1 unsigned short defining the length of the string, and followed with string bytes.

Buffer instantiation and capacity

There are two possible ways to instantiate a buffer:

Arguments	Returns	Description
data:createBuffer()	Buffer	Creates a buffer with initial capacity of 512 bytes.
data:createBuffer(capacity integer)	Buffer	Creates a buffer with specified initial capacity.

@see data:createBuffer

Buffer capacity is amount of bytes until buffer will need to reallocate more space. Once it reaches the cap, it reallocates buffer with additional 512 bytes. Buffer can not exceed the amount of allocated memory specified in permissions settings.

How buffer works

Buffers have a pointer to current byte in a buffer, and it is moved by read and write methods. Buffers has same pointer both for write and read operations.

For example:

AA	BB	CC	EE
^^

Right now buffer is pointing to first byte (index 0), so when we do the following:

print(buf:read()) --> 170

@see read

Buffer will be pointing to the next byte:

AA	BB	CC	EE
	^^

---

Now when we will write a byte in a buffer:

buf:write(255)

@see write

It will rewrite the pointed byte, and buffer will be pointing to the next byte.

AA	FF	CC	EE
		^^

---

Once buffer reaches it's current end, read methods will act different

• read will return -1.
• Integer and float pointing read methods will read until end, and will fill remaining bytes with nulls.
• readString, readByteArray, and readBase64 will read until end and stop. If pointer is already at end, it will return empty result.

AA	FF	CC	EE
				^^

print(buf:read()) --> -1
print(buf:readString()) --> ""

@see read, readString

AA	FF	CC	EE
				^^

---

Write methods will add new bytes if buffer is pointing it's current end, and will move the pointer further:

AA	FF	CC	EE
				^^

buf:writeUShort(65535)

@see writeUShort

This is how our buffer will look like now:

AA	FF	CC	EE	FF	FF
						^^

Buffer methods

This buffer example is going to be used in all code snippets below:

AA	BB	CC	EE
^^

Buffer variable will be named buf

General

General methods of a buffer.

getLength

---

Returns length of this buffer.

Arguments	Return Type
Buffer:getLength()	integer

print(buf:getLength()) --> 4

getPosition

---

Returns current pointer position.

Arguments	Return Type
getPosition()	integer

print(buf:getPosition()) --> 0

setPosition

---

Sets current pointer position. Position will be clamped between 0 and current buffer length.

@see getLength

Arguments
setPosition(position integer)

buf:setPosition(2)

AA	BB	CC	EE
		^^

clear

---

Clears this buffer and sets it's pointer position to 0.

Arguments
clear()

buf:clear()

This buffer is empty, no data to display.

available

---

Returns amount of bytes available to read.

Arguments	Return Type
available()	integer

print(buf:available()) --> 4

getMaxCapacity

---

Returns max buffer capacity.

Arguments	Return Type
getMaxCapacity()	integer

print(buf:getMaxCapacity()) --> 1024000

ⓘ Note

This is an output for avatars in unmodified Default permissions group

close

---

Closes this buffer, tells garbage collector to free memory used by it. After closing buffer is unable to use, and any usage attempt will cause an error.

Arguments
close()

buf:close()
buf:read() --! Throws an error with message "This byte buffer is closed and cant be used anymore"

@see read

isClosed

---

Checks if this buffer is closed.

Arguments	Return Type
isClosed()	boolean

buf:close()
print(buf:isClosed())

@see close