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BSON
Filename extension	`.bson`
Internet media type	`none^[1]`
Type of format	Data interchange
Extended from	JSON
Standard(s)	no RFC yet
Website	bsonspec.org

BSON ( /ˈbiːsɒn/) is a computer data interchange format used mainly as a data storage and network transfer format in the MongoDB database. It is a binary form for representing simple data structuresand associative arrays (called objects or documents in MongoDB). The name "BSON" is based on the term JSON and stands for "Binary JSON".^[2]

[edit]Data types and syntax

BSON documents (objects) consist of an ordered list of elements. Each element consists of a field name, a type, and a value. Field names are strings. Types include:

string
integer (32- or 64-bit)
double (64-bit IEEE 754 floating point number)
date (integer number of milliseconds since the Unix epoch)
byte array (binary data)
boolean (true and false)
null
BSON object
BSON array
regular expression
JavaScript code

BSON types are nominally a superset of JSON types (JSON does not have a date or a byte array type, for example^[3]), with one exception of not having a universal "number" type as JSON does.

[edit]Efficiency

Compared to JSON, BSON is designed to be efficient both in storage space and scan-speed. Large elements in a BSON document are prefixed with a length field to facilitate scanning. In some cases, BSON will use more space than JSON due to the length prefixes and explicit array indices.^[2]

[edit]See also

[edit]References

[edit]External links

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BSON

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specification implementations FAQ discussion

Version 1.0

BSON is a binary format in which zero or more key/value pairs are stored as a single entity. We call this entity a document.

The following grammar specifies version 1.0 of the BSON standard. We've written the grammar using a pseudo-BNF syntax. Valid BSON data is represented by the document non-terminal.

Basic Types

The following basic types are used as terminals in the rest of the grammar. Each type must be serialized in little-endian format.

byte	1 byte (8-bits)
int32	4 bytes (32-bit signed integer)
int64	8 bytes (64-bit signed integer)
double	8 bytes (64-bit IEEE 754 floating point)

Non-terminals

The following specifies the rest of the BSON grammar. Note that quoted strings represent terminals, and should be interpreted with C semantics (e.g. "\x01" represents the byte0000 0001). Also note that we use the * operator as shorthand for repetition (e.g.("\x01"*2) is "\x01\x01"). When used as a unary operator, * means that the repetition can occur 0 or more times.

document	::=	int32 e_list "\x00"	BSON Document
e_list	::=	element e_list	Sequence of elements
	\|	""
element	::=	"\x01" e_name double	Floating point
	\|	"\x02" e_name string	UTF-8 string
	\|	"\x03" e_name document	Embedded document
	\|	"\x04" e_name document	Array
	\|	"\x05" e_name binary	Binary data
	\|	"\x06" e_name	Undefined — Deprecated
	\|	"\x07" e_name (byte*12)	ObjectId
	\|	"\x08" e_name "\x00"	Boolean "false"
	\|	"\x08" e_name "\x01"	Boolean "true"
	\|	"\x09" e_name int64	UTC datetime
	\|	"\x0A" e_name	Null value
	\|	"\x0B" e_name cstring cstring	Regular expression
	\|	"\x0C" e_name string (byte*12)	DBPointer — Deprecated
	\|	"\x0D" e_name string	JavaScript code
	\|	"\x0E" e_name string	Symbol — Deprecated
	\|	"\x0F" e_name code_w_s	JavaScript code w/ scope
	\|	"\x10" e_name int32	32-bit Integer
	\|	"\x11" e_name int64	Timestamp
	\|	"\x12" e_name int64	64-bit integer
	\|	"\xFF" e_name	Min key
	\|	"\x7F" e_name	Max key
e_name	::=	cstring	Key name
string	::=	int32 (byte*) "\x00"	String
cstring	::=	(byte*) "\x00"	CString
binary	::=	int32 subtype (byte*)	Binary
subtype	::=	"\x00"	Binary / Generic
	\|	"\x01"	Function
	\|	"\x02"	Binary (Old)
	\|	"\x03"	UUID (Old)
	\|	"\x04"	UUID
	\|	"\x05"	MD5
	\|	"\x80"	User defined
code_w_s	::=	int32 string document	Code w/ scope

Examples

The following are some example documents (in JavaScript / Python style syntax) and their corresponding BSON representations. Try mousing over them for some useful correlation.

`{"hello": "world"}`	→	`"\x16\x00\x00\x00\x02hello\x00 \x06\x00\x00\x00world\x00\x00"`
`{"BSON": ["awesome", 5.05,1986]}`	→	`"\x31\x00\x00\x00\x04BSON\x00\x26\x00 \x00\x00\x020\x00\x08\x00\x00 \x00awesome\x00\x011\x00\x33\x33\x33\x33\x33\x33 \x14\x40\x102\x00\xc2\x07\x00\x00 \x00\x00"`

Bson

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