1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
//! The Value enum, a loosely typed way of representing any valid JSON value.
//!
//! # Constructing JSON
//!
//! Serde JSON provides a [`json!` macro][macro] to build `serde_json::Value`
//! objects with very natural JSON syntax.
//!
//! ```
//! use serde_json::json;
//!
//! fn main() {
//!     // The type of `john` is `serde_json::Value`
//!     let john = json!({
//!         "name": "John Doe",
//!         "age": 43,
//!         "phones": [
//!             "+44 1234567",
//!             "+44 2345678"
//!         ]
//!     });
//!
//!     println!("first phone number: {}", john["phones"][0]);
//!
//!     // Convert to a string of JSON and print it out
//!     println!("{}", john.to_string());
//! }
//! ```
//!
//! The `Value::to_string()` function converts a `serde_json::Value` into a
//! `String` of JSON text.
//!
//! One neat thing about the `json!` macro is that variables and expressions can
//! be interpolated directly into the JSON value as you are building it. Serde
//! will check at compile time that the value you are interpolating is able to
//! be represented as JSON.
//!
//! ```
//! # use serde_json::json;
//! #
//! # fn random_phone() -> u16 { 0 }
//! #
//! let full_name = "John Doe";
//! let age_last_year = 42;
//!
//! // The type of `john` is `serde_json::Value`
//! let john = json!({
//!     "name": full_name,
//!     "age": age_last_year + 1,
//!     "phones": [
//!         format!("+44 {}", random_phone())
//!     ]
//! });
//! ```
//!
//! A string of JSON data can be parsed into a `serde_json::Value` by the
//! [`serde_json::from_str`][from_str] function. There is also
//! [`from_slice`][from_slice] for parsing from a byte slice `&[u8]` and
//! [`from_reader`][from_reader] for parsing from any `io::Read` like a File or
//! a TCP stream.
//!
//! ```
//! use serde_json::{json, Value, Error};
//!
//! fn untyped_example() -> Result<(), Error> {
//!     // Some JSON input data as a &str. Maybe this comes from the user.
//!     let data = r#"
//!         {
//!             "name": "John Doe",
//!             "age": 43,
//!             "phones": [
//!                 "+44 1234567",
//!                 "+44 2345678"
//!             ]
//!         }"#;
//!
//!     // Parse the string of data into serde_json::Value.
//!     let v: Value = serde_json::from_str(data)?;
//!
//!     // Access parts of the data by indexing with square brackets.
//!     println!("Please call {} at the number {}", v["name"], v["phones"][0]);
//!
//!     Ok(())
//! }
//! #
//! # untyped_example().unwrap();
//! ```
//!
//! [macro]: https://docs.serde.rs/serde_json/macro.json.html
//! [from_str]: https://docs.serde.rs/serde_json/de/fn.from_str.html
//! [from_slice]: https://docs.serde.rs/serde_json/de/fn.from_slice.html
//! [from_reader]: https://docs.serde.rs/serde_json/de/fn.from_reader.html

use crate::error::Error;
use crate::io;
use crate::lib::*;
use std::prelude::v1::*;

use serde::de::DeserializeOwned;
use serde::ser::Serialize;

pub use self::index::Index;
pub use self::ser::Serializer;
pub use crate::map::Map;
pub use crate::number::Number;

#[cfg(feature = "raw_value")]
pub use crate::raw::{to_raw_value, RawValue};

/// Represents any valid JSON value.
///
/// See the `serde_json::value` module documentation for usage examples.
#[derive(Clone, Eq, PartialEq)]
pub enum Value {
    /// Represents a JSON null value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(null);
    /// ```
    Null,

    /// Represents a JSON boolean.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(true);
    /// ```
    Bool(bool),

    /// Represents a JSON number, whether integer or floating point.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(12.5);
    /// ```
    Number(Number),

    /// Represents a JSON string.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!("a string");
    /// ```
    String(String),

    /// Represents a JSON array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!(["an", "array"]);
    /// ```
    Array(Vec<Value>),

    /// Represents a JSON object.
    ///
    /// By default the map is backed by a BTreeMap. Enable the `preserve_order`
    /// feature of serde_json to use IndexMap instead, which preserves
    /// entries in the order they are inserted into the map. In particular, this
    /// allows JSON data to be deserialized into a Value and serialized to a
    /// string while retaining the order of map keys in the input.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "an": "object" });
    /// ```
    Object(Map<String, Value>),
}

impl Debug for Value {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Value::Null => formatter.debug_tuple("Null").finish(),
            Value::Bool(v) => formatter.debug_tuple("Bool").field(&v).finish(),
            Value::Number(ref v) => Debug::fmt(v, formatter),
            Value::String(ref v) => formatter.debug_tuple("String").field(v).finish(),
            Value::Array(ref v) => {
                formatter.write_str("Array(")?;
                Debug::fmt(v, formatter)?;
                formatter.write_str(")")
            }
            Value::Object(ref v) => {
                formatter.write_str("Object(")?;
                Debug::fmt(v, formatter)?;
                formatter.write_str(")")
            }
        }
    }
}

struct WriterFormatter<'a, 'b: 'a> {
    inner: &'a mut fmt::Formatter<'b>,
}

impl<'a, 'b> io::Write for WriterFormatter<'a, 'b> {
    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
        fn io_error<E>(_: E) -> io::Error {
            // Error value does not matter because fmt::Display impl below just
            // maps it to fmt::Error
            io::Error::new(io::ErrorKind::Other, "fmt error")
        }
        let s = tri!(str::from_utf8(buf).map_err(io_error));
        tri!(self.inner.write_str(s).map_err(io_error));
        Ok(buf.len())
    }

    fn flush(&mut self) -> io::Result<()> {
        Ok(())
    }
}

impl fmt::Display for Value {
    /// Display a JSON value as a string.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let json = json!({ "city": "London", "street": "10 Downing Street" });
    ///
    /// // Compact format:
    /// //
    /// // {"city":"London","street":"10 Downing Street"}
    /// let compact = format!("{}", json);
    /// assert_eq!(compact,
    ///     "{\"city\":\"London\",\"street\":\"10 Downing Street\"}");
    ///
    /// // Pretty format:
    /// //
    /// // {
    /// //   "city": "London",
    /// //   "street": "10 Downing Street"
    /// // }
    /// let pretty = format!("{:#}", json);
    /// assert_eq!(pretty,
    ///     "{\n  \"city\": \"London\",\n  \"street\": \"10 Downing Street\"\n}");
    /// ```
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let alternate = f.alternate();
        let mut wr = WriterFormatter { inner: f };
        if alternate {
            // {:#}
            super::ser::to_writer_pretty(&mut wr, self).map_err(|_| fmt::Error)
        } else {
            // {}
            super::ser::to_writer(&mut wr, self).map_err(|_| fmt::Error)
        }
    }
}

fn parse_index(s: &str) -> Option<usize> {
    if s.starts_with('+') || (s.starts_with('0') && s.len() != 1) {
        return None;
    }
    s.parse().ok()
}

impl Value {
    /// Index into a JSON array or map. A string index can be used to access a
    /// value in a map, and a usize index can be used to access an element of an
    /// array.
    ///
    /// Returns `None` if the type of `self` does not match the type of the
    /// index, for example if the index is a string and `self` is an array or a
    /// number. Also returns `None` if the given key does not exist in the map
    /// or the given index is not within the bounds of the array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let object = json!({ "A": 65, "B": 66, "C": 67 });
    /// assert_eq!(*object.get("A").unwrap(), json!(65));
    ///
    /// let array = json!([ "A", "B", "C" ]);
    /// assert_eq!(*array.get(2).unwrap(), json!("C"));
    ///
    /// assert_eq!(array.get("A"), None);
    /// ```
    ///
    /// Square brackets can also be used to index into a value in a more concise
    /// way. This returns `Value::Null` in cases where `get` would have returned
    /// `None`.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let object = json!({
    ///     "A": ["a", "á", "à"],
    ///     "B": ["b", "b́"],
    ///     "C": ["c", "ć", "ć̣", "ḉ"],
    /// });
    /// assert_eq!(object["B"][0], json!("b"));
    ///
    /// assert_eq!(object["D"], json!(null));
    /// assert_eq!(object[0]["x"]["y"]["z"], json!(null));
    /// ```
    pub fn get<I: Index>(&self, index: I) -> Option<&Value> {
        index.index_into(self)
    }

    /// Mutably index into a JSON array or map. A string index can be used to
    /// access a value in a map, and a usize index can be used to access an
    /// element of an array.
    ///
    /// Returns `None` if the type of `self` does not match the type of the
    /// index, for example if the index is a string and `self` is an array or a
    /// number. Also returns `None` if the given key does not exist in the map
    /// or the given index is not within the bounds of the array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut object = json!({ "A": 65, "B": 66, "C": 67 });
    /// *object.get_mut("A").unwrap() = json!(69);
    ///
    /// let mut array = json!([ "A", "B", "C" ]);
    /// *array.get_mut(2).unwrap() = json!("D");
    /// ```
    pub fn get_mut<I: Index>(&mut self, index: I) -> Option<&mut Value> {
        index.index_into_mut(self)
    }

    /// Returns true if the `Value` is an Object. Returns false otherwise.
    ///
    /// For any Value on which `is_object` returns true, `as_object` and
    /// `as_object_mut` are guaranteed to return the map representation of the
    /// object.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let obj = json!({ "a": { "nested": true }, "b": ["an", "array"] });
    ///
    /// assert!(obj.is_object());
    /// assert!(obj["a"].is_object());
    ///
    /// // array, not an object
    /// assert!(!obj["b"].is_object());
    /// ```
    pub fn is_object(&self) -> bool {
        self.as_object().is_some()
    }

    /// If the `Value` is an Object, returns the associated Map. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": { "nested": true }, "b": ["an", "array"] });
    ///
    /// // The length of `{"nested": true}` is 1 entry.
    /// assert_eq!(v["a"].as_object().unwrap().len(), 1);
    ///
    /// // The array `["an", "array"]` is not an object.
    /// assert_eq!(v["b"].as_object(), None);
    /// ```
    pub fn as_object(&self) -> Option<&Map<String, Value>> {
        match *self {
            Value::Object(ref map) => Some(map),
            _ => None,
        }
    }

    /// If the `Value` is an Object, returns the associated mutable Map.
    /// Returns None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut v = json!({ "a": { "nested": true } });
    ///
    /// v["a"].as_object_mut().unwrap().clear();
    /// assert_eq!(v, json!({ "a": {} }));
    /// ```
    pub fn as_object_mut(&mut self) -> Option<&mut Map<String, Value>> {
        match *self {
            Value::Object(ref mut map) => Some(map),
            _ => None,
        }
    }

    /// Returns true if the `Value` is an Array. Returns false otherwise.
    ///
    /// For any Value on which `is_array` returns true, `as_array` and
    /// `as_array_mut` are guaranteed to return the vector representing the
    /// array.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let obj = json!({ "a": ["an", "array"], "b": { "an": "object" } });
    ///
    /// assert!(obj["a"].is_array());
    ///
    /// // an object, not an array
    /// assert!(!obj["b"].is_array());
    /// ```
    pub fn is_array(&self) -> bool {
        self.as_array().is_some()
    }

    /// If the `Value` is an Array, returns the associated vector. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": ["an", "array"], "b": { "an": "object" } });
    ///
    /// // The length of `["an", "array"]` is 2 elements.
    /// assert_eq!(v["a"].as_array().unwrap().len(), 2);
    ///
    /// // The object `{"an": "object"}` is not an array.
    /// assert_eq!(v["b"].as_array(), None);
    /// ```
    pub fn as_array(&self) -> Option<&Vec<Value>> {
        match *self {
            Value::Array(ref array) => Some(&*array),
            _ => None,
        }
    }

    /// If the `Value` is an Array, returns the associated mutable vector.
    /// Returns None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut v = json!({ "a": ["an", "array"] });
    ///
    /// v["a"].as_array_mut().unwrap().clear();
    /// assert_eq!(v, json!({ "a": [] }));
    /// ```
    pub fn as_array_mut(&mut self) -> Option<&mut Vec<Value>> {
        match *self {
            Value::Array(ref mut list) => Some(list),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a String. Returns false otherwise.
    ///
    /// For any Value on which `is_string` returns true, `as_str` is guaranteed
    /// to return the string slice.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": "some string", "b": false });
    ///
    /// assert!(v["a"].is_string());
    ///
    /// // The boolean `false` is not a string.
    /// assert!(!v["b"].is_string());
    /// ```
    pub fn is_string(&self) -> bool {
        self.as_str().is_some()
    }

    /// If the `Value` is a String, returns the associated str. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": "some string", "b": false });
    ///
    /// assert_eq!(v["a"].as_str(), Some("some string"));
    ///
    /// // The boolean `false` is not a string.
    /// assert_eq!(v["b"].as_str(), None);
    ///
    /// // JSON values are printed in JSON representation, so strings are in quotes.
    /// //
    /// //    The value is: "some string"
    /// println!("The value is: {}", v["a"]);
    ///
    /// // Rust strings are printed without quotes.
    /// //
    /// //    The value is: some string
    /// println!("The value is: {}", v["a"].as_str().unwrap());
    /// ```
    pub fn as_str(&self) -> Option<&str> {
        match *self {
            Value::String(ref s) => Some(s),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a Number. Returns false otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 1, "b": "2" });
    ///
    /// assert!(v["a"].is_number());
    ///
    /// // The string `"2"` is a string, not a number.
    /// assert!(!v["b"].is_number());
    /// ```
    pub fn is_number(&self) -> bool {
        match *self {
            Value::Number(_) => true,
            _ => false,
        }
    }

    /// Returns true if the `Value` is an integer between `i64::MIN` and
    /// `i64::MAX`.
    ///
    /// For any Value on which `is_i64` returns true, `as_i64` is guaranteed to
    /// return the integer value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let big = i64::max_value() as u64 + 10;
    /// let v = json!({ "a": 64, "b": big, "c": 256.0 });
    ///
    /// assert!(v["a"].is_i64());
    ///
    /// // Greater than i64::MAX.
    /// assert!(!v["b"].is_i64());
    ///
    /// // Numbers with a decimal point are not considered integers.
    /// assert!(!v["c"].is_i64());
    /// ```
    pub fn is_i64(&self) -> bool {
        match *self {
            Value::Number(ref n) => n.is_i64(),
            _ => false,
        }
    }

    /// Returns true if the `Value` is an integer between zero and `u64::MAX`.
    ///
    /// For any Value on which `is_u64` returns true, `as_u64` is guaranteed to
    /// return the integer value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 64, "b": -64, "c": 256.0 });
    ///
    /// assert!(v["a"].is_u64());
    ///
    /// // Negative integer.
    /// assert!(!v["b"].is_u64());
    ///
    /// // Numbers with a decimal point are not considered integers.
    /// assert!(!v["c"].is_u64());
    /// ```
    pub fn is_u64(&self) -> bool {
        match *self {
            Value::Number(ref n) => n.is_u64(),
            _ => false,
        }
    }

    /// Returns true if the `Value` is a number that can be represented by f64.
    ///
    /// For any Value on which `is_f64` returns true, `as_f64` is guaranteed to
    /// return the floating point value.
    ///
    /// Currently this function returns true if and only if both `is_i64` and
    /// `is_u64` return false but this is not a guarantee in the future.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 256.0, "b": 64, "c": -64 });
    ///
    /// assert!(v["a"].is_f64());
    ///
    /// // Integers.
    /// assert!(!v["b"].is_f64());
    /// assert!(!v["c"].is_f64());
    /// ```
    pub fn is_f64(&self) -> bool {
        match *self {
            Value::Number(ref n) => n.is_f64(),
            _ => false,
        }
    }

    /// If the `Value` is an integer, represent it as i64 if possible. Returns
    /// None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let big = i64::max_value() as u64 + 10;
    /// let v = json!({ "a": 64, "b": big, "c": 256.0 });
    ///
    /// assert_eq!(v["a"].as_i64(), Some(64));
    /// assert_eq!(v["b"].as_i64(), None);
    /// assert_eq!(v["c"].as_i64(), None);
    /// ```
    pub fn as_i64(&self) -> Option<i64> {
        match *self {
            Value::Number(ref n) => n.as_i64(),
            _ => None,
        }
    }

    /// If the `Value` is an integer, represent it as u64 if possible. Returns
    /// None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 64, "b": -64, "c": 256.0 });
    ///
    /// assert_eq!(v["a"].as_u64(), Some(64));
    /// assert_eq!(v["b"].as_u64(), None);
    /// assert_eq!(v["c"].as_u64(), None);
    /// ```
    pub fn as_u64(&self) -> Option<u64> {
        match *self {
            Value::Number(ref n) => n.as_u64(),
            _ => None,
        }
    }

    /// If the `Value` is a number, represent it as f64 if possible. Returns
    /// None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": 256.0, "b": 64, "c": -64 });
    ///
    /// assert_eq!(v["a"].as_f64(), Some(256.0));
    /// assert_eq!(v["b"].as_f64(), Some(64.0));
    /// assert_eq!(v["c"].as_f64(), Some(-64.0));
    /// ```
    pub fn as_f64(&self) -> Option<f64> {
        match *self {
            Value::Number(ref n) => n.as_f64(),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a Boolean. Returns false otherwise.
    ///
    /// For any Value on which `is_boolean` returns true, `as_bool` is
    /// guaranteed to return the boolean value.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": false, "b": "false" });
    ///
    /// assert!(v["a"].is_boolean());
    ///
    /// // The string `"false"` is a string, not a boolean.
    /// assert!(!v["b"].is_boolean());
    /// ```
    pub fn is_boolean(&self) -> bool {
        self.as_bool().is_some()
    }

    /// If the `Value` is a Boolean, returns the associated bool. Returns None
    /// otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": false, "b": "false" });
    ///
    /// assert_eq!(v["a"].as_bool(), Some(false));
    ///
    /// // The string `"false"` is a string, not a boolean.
    /// assert_eq!(v["b"].as_bool(), None);
    /// ```
    pub fn as_bool(&self) -> Option<bool> {
        match *self {
            Value::Bool(b) => Some(b),
            _ => None,
        }
    }

    /// Returns true if the `Value` is a Null. Returns false otherwise.
    ///
    /// For any Value on which `is_null` returns true, `as_null` is guaranteed
    /// to return `Some(())`.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": null, "b": false });
    ///
    /// assert!(v["a"].is_null());
    ///
    /// // The boolean `false` is not null.
    /// assert!(!v["b"].is_null());
    /// ```
    pub fn is_null(&self) -> bool {
        self.as_null().is_some()
    }

    /// If the `Value` is a Null, returns (). Returns None otherwise.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let v = json!({ "a": null, "b": false });
    ///
    /// assert_eq!(v["a"].as_null(), Some(()));
    ///
    /// // The boolean `false` is not null.
    /// assert_eq!(v["b"].as_null(), None);
    /// ```
    pub fn as_null(&self) -> Option<()> {
        match *self {
            Value::Null => Some(()),
            _ => None,
        }
    }

    /// Looks up a value by a JSON Pointer.
    ///
    /// JSON Pointer defines a string syntax for identifying a specific value
    /// within a JavaScript Object Notation (JSON) document.
    ///
    /// A Pointer is a Unicode string with the reference tokens separated by `/`.
    /// Inside tokens `/` is replaced by `~1` and `~` is replaced by `~0`. The
    /// addressed value is returned and if there is no such value `None` is
    /// returned.
    ///
    /// For more information read [RFC6901](https://tools.ietf.org/html/rfc6901).
    ///
    /// # Examples
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let data = json!({
    ///     "x": {
    ///         "y": ["z", "zz"]
    ///     }
    /// });
    ///
    /// assert_eq!(data.pointer("/x/y/1").unwrap(), &json!("zz"));
    /// assert_eq!(data.pointer("/a/b/c"), None);
    /// ```
    pub fn pointer(&self, pointer: &str) -> Option<&Value> {
        if pointer.is_empty() {
            return Some(self);
        }
        if !pointer.starts_with('/') {
            return None;
        }
        let tokens = pointer
            .split('/')
            .skip(1)
            .map(|x| x.replace("~1", "/").replace("~0", "~"));
        let mut target = self;

        for token in tokens {
            let target_opt = match *target {
                Value::Object(ref map) => map.get(&token),
                Value::Array(ref list) => parse_index(&token).and_then(|x| list.get(x)),
                _ => return None,
            };
            if let Some(t) = target_opt {
                target = t;
            } else {
                return None;
            }
        }
        Some(target)
    }

    /// Looks up a value by a JSON Pointer and returns a mutable reference to
    /// that value.
    ///
    /// JSON Pointer defines a string syntax for identifying a specific value
    /// within a JavaScript Object Notation (JSON) document.
    ///
    /// A Pointer is a Unicode string with the reference tokens separated by `/`.
    /// Inside tokens `/` is replaced by `~1` and `~` is replaced by `~0`. The
    /// addressed value is returned and if there is no such value `None` is
    /// returned.
    ///
    /// For more information read [RFC6901](https://tools.ietf.org/html/rfc6901).
    ///
    /// # Example of Use
    ///
    /// ```
    /// use serde_json::Value;
    ///
    /// fn main() {
    ///     let s = r#"{"x": 1.0, "y": 2.0}"#;
    ///     let mut value: Value = serde_json::from_str(s).unwrap();
    ///
    ///     // Check value using read-only pointer
    ///     assert_eq!(value.pointer("/x"), Some(&1.0.into()));
    ///     // Change value with direct assignment
    ///     *value.pointer_mut("/x").unwrap() = 1.5.into();
    ///     // Check that new value was written
    ///     assert_eq!(value.pointer("/x"), Some(&1.5.into()));
    ///     // Or change the value only if it exists
    ///     value.pointer_mut("/x").map(|v| *v = 1.5.into());
    ///
    ///     // "Steal" ownership of a value. Can replace with any valid Value.
    ///     let old_x = value.pointer_mut("/x").map(Value::take).unwrap();
    ///     assert_eq!(old_x, 1.5);
    ///     assert_eq!(value.pointer("/x").unwrap(), &Value::Null);
    /// }
    /// ```
    pub fn pointer_mut(&mut self, pointer: &str) -> Option<&mut Value> {
        if pointer.is_empty() {
            return Some(self);
        }
        if !pointer.starts_with('/') {
            return None;
        }
        let tokens = pointer
            .split('/')
            .skip(1)
            .map(|x| x.replace("~1", "/").replace("~0", "~"));
        let mut target = self;

        for token in tokens {
            // borrow checker gets confused about `target` being mutably borrowed too many times because of the loop
            // this once-per-loop binding makes the scope clearer and circumvents the error
            let target_once = target;
            let target_opt = match *target_once {
                Value::Object(ref mut map) => map.get_mut(&token),
                Value::Array(ref mut list) => {
                    parse_index(&token).and_then(move |x| list.get_mut(x))
                }
                _ => return None,
            };
            if let Some(t) = target_opt {
                target = t;
            } else {
                return None;
            }
        }
        Some(target)
    }

    /// Takes the value out of the `Value`, leaving a `Null` in its place.
    ///
    /// ```
    /// # use serde_json::json;
    /// #
    /// let mut v = json!({ "x": "y" });
    /// assert_eq!(v["x"].take(), json!("y"));
    /// assert_eq!(v, json!({ "x": null }));
    /// ```
    pub fn take(&mut self) -> Value {
        mem::replace(self, Value::Null)
    }
}

/// The default value is `Value::Null`.
///
/// This is useful for handling omitted `Value` fields when deserializing.
///
/// # Examples
///
/// ```
/// # use serde::Deserialize;
/// use serde_json::Value;
///
/// #[derive(Deserialize)]
/// struct Settings {
///     level: i32,
///     #[serde(default)]
///     extras: Value,
/// }
///
/// # fn try_main() -> Result<(), serde_json::Error> {
/// let data = r#" { "level": 42 } "#;
/// let s: Settings = serde_json::from_str(data)?;
///
/// assert_eq!(s.level, 42);
/// assert_eq!(s.extras, Value::Null);
/// #
/// #     Ok(())
/// # }
/// #
/// # try_main().unwrap()
/// ```
impl Default for Value {
    fn default() -> Value {
        Value::Null
    }
}

mod de;
mod from;
mod index;
mod partial_eq;
mod ser;

/// Convert a `T` into `serde_json::Value` which is an enum that can represent
/// any valid JSON data.
///
/// # Example
///
/// ```
/// use serde::Serialize;
/// use serde_json::json;
///
/// use std::error::Error;
///
/// #[derive(Serialize)]
/// struct User {
///     fingerprint: String,
///     location: String,
/// }
///
/// fn compare_json_values() -> Result<(), Box<Error>> {
///     let u = User {
///         fingerprint: "0xF9BA143B95FF6D82".to_owned(),
///         location: "Menlo Park, CA".to_owned(),
///     };
///
///     // The type of `expected` is `serde_json::Value`
///     let expected = json!({
///         "fingerprint": "0xF9BA143B95FF6D82",
///         "location": "Menlo Park, CA",
///     });
///
///     let v = serde_json::to_value(u).unwrap();
///     assert_eq!(v, expected);
///
///     Ok(())
/// }
/// #
/// # compare_json_values().unwrap();
/// ```
///
/// # Errors
///
/// This conversion can fail if `T`'s implementation of `Serialize` decides to
/// fail, or if `T` contains a map with non-string keys.
///
/// ```
/// use std::collections::BTreeMap;
///
/// fn main() {
///     // The keys in this map are vectors, not strings.
///     let mut map = BTreeMap::new();
///     map.insert(vec![32, 64], "x86");
///
///     println!("{}", serde_json::to_value(map).unwrap_err());
/// }
/// ```
// Taking by value is more friendly to iterator adapters, option and result
// consumers, etc. See https://github.com/serde-rs/json/pull/149.
pub fn to_value<T>(value: T) -> Result<Value, Error>
where
    T: Serialize,
{
    value.serialize(Serializer)
}

/// Interpret a `serde_json::Value` as an instance of type `T`.
///
/// # Example
///
/// ```
/// use serde::Deserialize;
/// use serde_json::json;
///
/// #[derive(Deserialize, Debug)]
/// struct User {
///     fingerprint: String,
///     location: String,
/// }
///
/// fn main() {
///     // The type of `j` is `serde_json::Value`
///     let j = json!({
///         "fingerprint": "0xF9BA143B95FF6D82",
///         "location": "Menlo Park, CA"
///     });
///
///     let u: User = serde_json::from_value(j).unwrap();
///     println!("{:#?}", u);
/// }
/// ```
///
/// # Errors
///
/// This conversion can fail if the structure of the Value does not match the
/// structure expected by `T`, for example if `T` is a struct type but the Value
/// contains something other than a JSON map. It can also fail if the structure
/// is correct but `T`'s implementation of `Deserialize` decides that something
/// is wrong with the data, for example required struct fields are missing from
/// the JSON map or some number is too big to fit in the expected primitive
/// type.
pub fn from_value<T>(value: Value) -> Result<T, Error>
where
    T: DeserializeOwned,
{
    T::deserialize(value)
}