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138 lines
8.3 KiB
138 lines
8.3 KiB
// Copyright (C) MongoDB, Inc. 2017-present. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); you may |
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// not use this file except in compliance with the License. You may obtain |
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// a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
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// Package bson is a library for reading, writing, and manipulating BSON. BSON is a binary serialization format used to |
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// store documents and make remote procedure calls in MongoDB. The BSON specification is located at https://bsonspec.org. |
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// The BSON library handles marshalling and unmarshalling of values through a configurable codec system. For a description |
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// of the codec system and examples of registering custom codecs, see the bsoncodec package. |
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// |
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// Raw BSON |
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// |
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// The Raw family of types is used to validate and retrieve elements from a slice of bytes. This |
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// type is most useful when you want do lookups on BSON bytes without unmarshaling it into another |
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// type. |
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// |
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// Example: |
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// var raw bson.Raw = ... // bytes from somewhere |
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// err := raw.Validate() |
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// if err != nil { return err } |
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// val := raw.Lookup("foo") |
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// i32, ok := val.Int32OK() |
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// // do something with i32... |
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// |
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// Native Go Types |
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// |
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// The D and M types defined in this package can be used to build representations of BSON using native Go types. D is a |
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// slice and M is a map. For more information about the use cases for these types, see the documentation on the type |
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// definitions. |
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// |
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// Note that a D should not be constructed with duplicate key names, as that can cause undefined server behavior. |
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// |
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// Example: |
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// bson.D{{"foo", "bar"}, {"hello", "world"}, {"pi", 3.14159}} |
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// bson.M{"foo": "bar", "hello": "world", "pi": 3.14159} |
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// |
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// When decoding BSON to a D or M, the following type mappings apply when unmarshalling: |
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// |
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// 1. BSON int32 unmarshals to an int32. |
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// 2. BSON int64 unmarshals to an int64. |
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// 3. BSON double unmarshals to a float64. |
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// 4. BSON string unmarshals to a string. |
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// 5. BSON boolean unmarshals to a bool. |
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// 6. BSON embedded document unmarshals to the parent type (i.e. D for a D, M for an M). |
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// 7. BSON array unmarshals to a bson.A. |
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// 8. BSON ObjectId unmarshals to a primitive.ObjectID. |
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// 9. BSON datetime unmarshals to a primitive.DateTime. |
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// 10. BSON binary unmarshals to a primitive.Binary. |
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// 11. BSON regular expression unmarshals to a primitive.Regex. |
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// 12. BSON JavaScript unmarshals to a primitive.JavaScript. |
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// 13. BSON code with scope unmarshals to a primitive.CodeWithScope. |
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// 14. BSON timestamp unmarshals to an primitive.Timestamp. |
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// 15. BSON 128-bit decimal unmarshals to an primitive.Decimal128. |
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// 16. BSON min key unmarshals to an primitive.MinKey. |
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// 17. BSON max key unmarshals to an primitive.MaxKey. |
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// 18. BSON undefined unmarshals to a primitive.Undefined. |
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// 19. BSON null unmarshals to nil. |
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// 20. BSON DBPointer unmarshals to a primitive.DBPointer. |
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// 21. BSON symbol unmarshals to a primitive.Symbol. |
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// |
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// The above mappings also apply when marshalling a D or M to BSON. Some other useful marshalling mappings are: |
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// |
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// 1. time.Time marshals to a BSON datetime. |
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// 2. int8, int16, and int32 marshal to a BSON int32. |
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// 3. int marshals to a BSON int32 if the value is between math.MinInt32 and math.MaxInt32, inclusive, and a BSON int64 |
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// otherwise. |
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// 4. int64 marshals to BSON int64. |
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// 5. uint8 and uint16 marshal to a BSON int32. |
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// 6. uint, uint32, and uint64 marshal to a BSON int32 if the value is between math.MinInt32 and math.MaxInt32, |
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// inclusive, and BSON int64 otherwise. |
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// 7. BSON null and undefined values will unmarshal into the zero value of a field (e.g. unmarshalling a BSON null or |
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// undefined value into a string will yield the empty string.). |
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// |
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// Structs |
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// |
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// Structs can be marshalled/unmarshalled to/from BSON or Extended JSON. When transforming structs to/from BSON or Extended |
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// JSON, the following rules apply: |
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// |
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// 1. Only exported fields in structs will be marshalled or unmarshalled. |
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// |
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// 2. When marshalling a struct, each field will be lowercased to generate the key for the corresponding BSON element. |
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// For example, a struct field named "Foo" will generate key "foo". This can be overridden via a struct tag (e.g. |
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// `bson:"fooField"` to generate key "fooField" instead). |
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// |
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// 3. An embedded struct field is marshalled as a subdocument. The key will be the lowercased name of the field's type. |
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// |
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// 4. A pointer field is marshalled as the underlying type if the pointer is non-nil. If the pointer is nil, it is |
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// marshalled as a BSON null value. |
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// |
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// 5. When unmarshalling, a field of type interface{} will follow the D/M type mappings listed above. BSON documents |
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// unmarshalled into an interface{} field will be unmarshalled as a D. |
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// |
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// The encoding of each struct field can be customized by the "bson" struct tag. |
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// |
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// This tag behavior is configurable, and different struct tag behavior can be configured by initializing a new |
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// bsoncodec.StructCodec with the desired tag parser and registering that StructCodec onto the Registry. By default, JSON tags |
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// are not honored, but that can be enabled by creating a StructCodec with JSONFallbackStructTagParser, like below: |
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// |
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// Example: |
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// structcodec, _ := bsoncodec.NewStructCodec(bsoncodec.JSONFallbackStructTagParser) |
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// |
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// The bson tag gives the name of the field, possibly followed by a comma-separated list of options. |
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// The name may be empty in order to specify options without overriding the default field name. The following options can be used |
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// to configure behavior: |
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// |
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// 1. omitempty: If the omitempty struct tag is specified on a field, the field will not be marshalled if it is set to |
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// the zero value. Fields with language primitive types such as integers, booleans, and strings are considered empty if |
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// their value is equal to the zero value for the type (i.e. 0 for integers, false for booleans, and "" for strings). |
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// Slices, maps, and arrays are considered empty if they are of length zero. Interfaces and pointers are considered |
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// empty if their value is nil. By default, structs are only considered empty if the struct type implements the |
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// bsoncodec.Zeroer interface and the IsZero method returns true. Struct fields whose types do not implement Zeroer are |
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// never considered empty and will be marshalled as embedded documents. |
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// NOTE: It is recommended that this tag be used for all slice and map fields. |
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// |
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// 2. minsize: If the minsize struct tag is specified on a field of type int64, uint, uint32, or uint64 and the value of |
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// the field can fit in a signed int32, the field will be serialized as a BSON int32 rather than a BSON int64. For other |
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// types, this tag is ignored. |
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// |
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// 3. truncate: If the truncate struct tag is specified on a field with a non-float numeric type, BSON doubles unmarshalled |
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// into that field will be truncated at the decimal point. For example, if 3.14 is unmarshalled into a field of type int, |
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// it will be unmarshalled as 3. If this tag is not specified, the decoder will throw an error if the value cannot be |
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// decoded without losing precision. For float64 or non-numeric types, this tag is ignored. |
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// |
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// 4. inline: If the inline struct tag is specified for a struct or map field, the field will be "flattened" when |
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// marshalling and "un-flattened" when unmarshalling. This means that all of the fields in that struct/map will be |
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// pulled up one level and will become top-level fields rather than being fields in a nested document. For example, if a |
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// map field named "Map" with value map[string]interface{}{"foo": "bar"} is inlined, the resulting document will be |
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// {"foo": "bar"} instead of {"map": {"foo": "bar"}}. There can only be one inlined map field in a struct. If there are |
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// duplicated fields in the resulting document when an inlined struct is marshalled, the inlined field will be overwritten. |
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// If there are duplicated fields in the resulting document when an inlined map is marshalled, an error will be returned. |
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// This tag can be used with fields that are pointers to structs. If an inlined pointer field is nil, it will not be |
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// marshalled. For fields that are not maps or structs, this tag is ignored. |
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// |
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// Marshalling and Unmarshalling |
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// |
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// Manually marshalling and unmarshalling can be done with the Marshal and Unmarshal family of functions. |
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package bson
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