Crate bson

BSON, short for Binary JSON, is a binary-encoded serialization of JSON-like documents. Like JSON, BSON supports the embedding of documents and arrays within other documents and arrays. BSON also contains extensions that allow representation of data types that are not part of the JSON spec. For example, BSON has a datetime type and a binary data type.

// JSON equivalent
{"hello": "world"}

// BSON encoding
\x16\x00\x00\x00                   // total document size
\x02                               // 0x02 = type String
hello\x00                          // field name
\x06\x00\x00\x00world\x00          // field value
\x00                               // 0x00 = type EOO ('end of object')

BSON is the primary data representation for MongoDB, and this crate is used in the mongodb driver crate in its API and implementation.

For more information about BSON itself, see bsonspec.org.

Installation

Requirements

• Rust 1.48+

Importing

This crate is available on crates.io. To use it in your application, simply add it to your project’s Cargo.toml.

[dependencies]
bson = "2.2.0"

Note that if you are using bson through the mongodb crate, you do not need to specify it in your Cargo.toml, since the mongodb crate already re-exports it.

Feature Flags

Feature	Description	Extra dependencies	Default
chrono-0_4	Enable support for v0.4 of the chrono crate in the public API.	n/a	no
uuid-0_8	Enable support for v0.8 of the uuid crate in the public API.	n/a	no
serde_with	Enable serde_with integrations for bson::DateTime and bson::Uuid	serde_with	no

BSON values

Many different types can be represented as a BSON value, including 32-bit and 64-bit signed integers, 64 bit floating point numbers, strings, datetimes, embedded documents, and more. To see a full list of possible BSON values, see the BSON specification. The various possible BSON values are modeled in this crate by the Bson enum.

Creating Bson instances

Bson values can be instantiated directly or via the bson! macro:

use bson::{bson, Bson};

let string = Bson::String("hello world".to_string());
let int = Bson::Int32(5);
let array = Bson::Array(vec![Bson::Int32(5), Bson::Boolean(false)]);

let string: Bson = "hello world".into();
let int: Bson = 5i32.into();

let string = bson!("hello world");
let int = bson!(5);
let array = bson!([5, false]);

bson! has supports both array and object literals, and it automatically converts any values specified to Bson, provided they are Into<Bson>.

Bson value unwrapping

Bson has a number of helper methods for accessing the underlying native Rust types. These helpers can be useful in circumstances in which the specific type of a BSON value is known ahead of time.

e.g.:

use bson::{bson, Bson};

let value = Bson::Int32(5);
let int = value.as_i32(); // Some(5)
let bool = value.as_bool(); // None

let value = bson!([true]);
let array = value.as_array(); // Some(&Vec<Bson>)

BSON documents

BSON documents are ordered maps of UTF-8 encoded strings to BSON values. They are logically similar to JSON objects in that they can contain subdocuments, arrays, and values of several different types. This crate models BSON documents via the Document struct.

Creating Documents

Documents can be created directly either from a byte reader containing BSON data or via the doc! macro:

use bson::{doc, Document};
use std::io::Read;

let mut bytes = hex::decode("0C0000001069000100000000").unwrap();
let doc = Document::from_reader(&mut bytes.as_slice()).unwrap(); // { "i": 1 }

let doc = doc! {
   "hello": "world",
   "int": 5,
   "subdoc": { "cat": true },
};

doc! works similarly to bson!, except that it always returns a Document rather than a Bson.

Document member access

Document has a number of methods on it to facilitate member access:

use bson::doc;

let doc = doc! {
   "string": "string",
   "bool": true,
   "i32": 5,
   "doc": { "x": true },
};

// attempt get values as untyped Bson
let none = doc.get("asdfadsf"); // None
let value = doc.get("string"); // Some(&Bson::String("string"))

// attempt to get values with explicit typing
let string = doc.get_str("string"); // Ok("string")
let subdoc = doc.get_document("doc"); // Some(Document({ "x": true }))
let error = doc.get_i64("i32"); // Err(...)

Modeling BSON with strongly typed data structures

While it is possible to work with documents and BSON values directly, it will often introduce a lot of boilerplate for verifying the necessary keys are present and their values are the correct types. serde provides a powerful way of mapping BSON data into Rust data structures largely automatically, removing the need for all that boilerplate.

e.g.:

use serde::{Deserialize, Serialize};
use bson::{bson, Bson};

#[derive(Serialize, Deserialize)]
struct Person {
    name: String,
    age: i32,
    phones: Vec<String>,
}

// Some BSON input data as a `Bson`.
let bson_data: Bson = bson!({
    "name": "John Doe",
    "age": 43,
    "phones": [
        "+44 1234567",
        "+44 2345678"
    ]
});

// Deserialize the Person struct from the BSON data, automatically
// verifying that the necessary keys are present and that they are of
// the correct types.
let mut person: Person = bson::from_bson(bson_data).unwrap();

// Do things just like with any other Rust data structure.
println!("Redacting {}'s record.", person.name);
person.name = "REDACTED".to_string();

// Get a serialized version of the input data as a `Bson`.
let redacted_bson = bson::to_bson(&person).unwrap();

Any types that implement Serialize and Deserialize can be used in this way. Doing so helps separate the “business logic” that operates over the data from the (de)serialization logic that translates the data to/from its serialized form. This can lead to more clear and concise code that is also less error prone.

Working with datetimes

The BSON format includes a datetime type, which is modeled in this crate by the DateTime struct, and the Serialize and Deserialize implementations for this struct produce and parse BSON datetimes when serializing to or deserializing from BSON. The popular crate chrono also provides a DateTime type, but its Serialize and Deserialize implementations operate on strings instead, so when using it with BSON, the BSON datetime type is not used. To work around this, the chrono-0_4 feature flag can be enabled. This flag exposes a number of convenient conversions between bson::DateTime and chrono::DateTime, including the serde_helpers::chrono_datetime_as_bson_datetime serde helper, which can be used to (de)serialize chrono::DateTimes to/from BSON datetimes, and the From<chrono::DateTime> implementation for Bson, which allows chrono::DateTime values to be used in the doc! and bson! macros.

e.g.

use serde::{Serialize, Deserialize};
use bson::doc;

#[derive(Serialize, Deserialize)]
struct Foo {
    // serializes as a BSON datetime.
    date_time: bson::DateTime,

    // serializes as an RFC 3339 / ISO-8601 string.
    chrono_datetime: chrono::DateTime<chrono::Utc>,

    // serializes as a BSON datetime.
    // this requires the "chrono-0_4" feature flag
    #[serde(with = "bson::serde_helpers::chrono_datetime_as_bson_datetime")]
    chrono_as_bson: chrono::DateTime<chrono::Utc>,
}

// this automatic conversion also requires the "chrono-0_4" feature flag
let query = doc! {
    "created_at": chrono::Utc::now(),
};

Working with UUIDs

See the module level documentation for the uuid module.

Minimum supported Rust version (MSRV)

The MSRV for this crate is currently 1.48.0. This will be rarely be increased, and if it ever is, it will only happen in a minor or major version release.

Modules

datetime

de

Deserializer

decimal128

BSON Decimal128 data type representation

document

A BSON document represented as an associative HashMap with insertion ordering.

extjson

Deserialization and serialization of MongoDB Extended JSON v2

oid

ObjectId

raw

An API for interacting with raw BSON bytes.

ser

Serializer

serde_helpers

Collection of helper functions for serializing to and deserializing from BSON using Serde

spec

Constants derived from the BSON Specification Version 1.1.

uuid

UUID support for BSON.

Macros

bson

Construct a bson::BSON value from a literal.

doc

Construct a bson::Document value.

rawbson

Construct a crate::RawBson value from a literal.

rawdoc

Construct a crate::RawDocumentBuf value.

Structs

Binary

Represents a BSON binary value.

DateTime

Struct representing a BSON datetime. Note: BSON datetimes have millisecond precision.

DbPointer

Represents a DBPointer. (Deprecated)

Decimal128

Struct representing a BSON Decimal128 type.

Deserializer

Serde Deserializer

DeserializerOptions

Options used to configure a Deserializer. These can also be passed into crate::from_bson_with_options and crate::from_document_with_options.

Document

A BSON document represented as an associative HashMap with insertion ordering.

JavaScriptCodeWithScope

Represents a BSON code with scope value.

RawArray

A slice of a BSON document containing a BSON array value (akin to std::str). This can be retrieved from a RawDocument via RawDocument::get.

RawArrayBuf

An owned BSON array value (akin to std::path::PathBuf), backed by a buffer of raw BSON bytes. This type can be used to construct owned array values, which can be used to append to RawDocumentBuf or as a field in a Deserialize struct.

RawBinaryRef

A BSON binary value referencing raw bytes stored elsewhere.

RawDbPointerRef

A BSON DB pointer value referencing raw bytes stored elesewhere.

RawDocument

A slice of a BSON document (akin to std::str). This can be created from a RawDocumentBuf or any type that contains valid BSON data, including static binary literals, Vec, or arrays.

RawDocumentBuf

An owned BSON document (akin to std::path::PathBuf), backed by a buffer of raw BSON bytes. This can be created from a Vec<u8> or a crate::Document.

RawJavaScriptCodeWithScope

A BSON “code with scope” value backed by owned raw BSON.

RawJavaScriptCodeWithScopeRef

A BSON “code with scope” value referencing raw bytes stored elsewhere.

RawRegexRef

A BSON regex referencing raw bytes stored elsewhere.

Regex

Represents a BSON regular expression value.

Serializer

Serde Serializer

SerializerOptions

Options used to configure a Serializer.

Timestamp

Represents a BSON timestamp value.

Uuid

A struct modeling a BSON UUID value (i.e. a Binary value with subtype 4).

Enums

Bson

Possible BSON value types.

RawBson

A BSON value backed by owned raw BSON bytes.

RawBsonRef

A BSON value referencing raw bytes stored elsewhere.

UuidRepresentation

Enum of the possible representations to use when converting between Uuid and Binary. This enum is necessary because the different drivers used to have different ways of encoding UUIDs, with the BSON subtype: 0x03 (UUID old). If a UUID has been serialized with a particular representation, it MUST be deserialized with the same representation.

Functions

from_bson

Deserialize a T from the provided Bson value.

from_bson_with_options

Deserialize a T from the provided Bson value, configuring the underlying deserializer with the provided options.

from_document

Deserialize a T from the provided Document.

from_document_with_options

Deserialize a T from the provided Document, configuring the underlying deserializer with the provided options.

from_reader

Deserialize an instance of type T from an I/O stream of BSON.

from_reader_utf8_lossy

Deserialize an instance of type T from an I/O stream of BSON, replacing any invalid UTF-8 sequences with the Unicode replacement character.

from_slice

Deserialize an instance of type T from a slice of BSON bytes.

from_slice_utf8_lossy

Deserialize an instance of type T from a slice of BSON bytes, replacing any invalid UTF-8 sequences with the Unicode replacement character.

to_bson

Encode a T Serializable into a BSON Value.

to_bson_with_options

Encode a T into a Bson value, configuring the underlying serializer with the provided options.

to_document

Encode a T Serializable into a BSON Document.

to_document_with_options

Encode a T into a Document, configuring the underlying serializer with the provided options.

to_raw_document_buf

Serialize the given T as a RawDocumentBuf.

to_vec

Serialize the given T as a BSON byte vector.

Type Definitions

Array

Alias for Vec<Bson>.