json_pointer/
ptr.rs

1use crate::parser::{parse, ParseError};
2use serde_json::Value;
3use std::fmt::{Display, Formatter};
4use std::fmt::Result as FmtResult;
5use std::fmt::Write;
6use std::marker::PhantomData;
7use std::ops::{Index, IndexMut};
8use std::str::FromStr;
9
10/// A JSON Pointer.
11///
12/// Create a new JSON pointer with [`JsonPointer::new`](#method.new), or parse one from a
13/// string with [`str::parse()`](https://doc.rust-lang.org/std/primitive.str.html#method.parse).
14#[derive(Clone, Debug, Eq, PartialEq)]
15pub struct JsonPointer<S: AsRef<str>, C: AsRef<[S]>> {
16    ref_toks: C,
17    _phantom: PhantomData<S>,
18}
19
20impl<S: AsRef<str>, C: AsRef<[S]>> JsonPointer<S, C> {
21    /// Creates a new JsonPointer from the given reference tokens.
22    pub fn new(ref_toks: C) -> JsonPointer<S, C> {
23        JsonPointer {
24            ref_toks: ref_toks,
25            _phantom: PhantomData,
26        }
27    }
28
29    /// Attempts to get a reference to a value from the given JSON value,
30    /// returning an error if it can't be found.
31    pub fn get<'json>(&self, val: &'json Value) -> Result<&'json Value, IndexError> {
32        self.ref_toks.as_ref().iter().fold(Ok(val), |val, tok| val.and_then(|val| {
33            let tok = tok.as_ref();
34            match *val {
35                Value::Object(ref obj) => obj.get(tok).ok_or_else(|| IndexError::NoSuchKey(tok.to_owned())),
36                Value::Array(ref arr) => {
37                    let idx = if tok == "-" {
38                        arr.len()
39                    } else if let Ok(idx) = tok.parse() {
40                        idx
41                    } else {
42                        return Err(IndexError::NoSuchKey(tok.to_owned()));
43                    };
44                    arr.get(idx).ok_or(IndexError::OutOfBounds(idx))
45                },
46                _ => Err(IndexError::NotIndexable),
47            }
48        }))
49    }
50
51    /// Attempts to get a mutable reference to a value from the given JSON
52    /// value, returning an error if it can't be found.
53    pub fn get_mut<'json>(&self, val: &'json mut Value) -> Result<&'json mut Value, IndexError> {
54        self.ref_toks.as_ref().iter().fold(Ok(val), |val, tok| val.and_then(|val| {
55            let tok = tok.as_ref();
56            match *val {
57                Value::Object(ref mut obj) => obj.get_mut(tok).ok_or_else(|| IndexError::NoSuchKey(tok.to_owned())),
58                Value::Array(ref mut arr) => {
59                    let idx = if tok == "-" {
60                        arr.len()
61                    } else if let Ok(idx) = tok.parse() {
62                        idx
63                    } else {
64                        return Err(IndexError::NoSuchKey(tok.to_owned()));
65                    };
66                    arr.get_mut(idx).ok_or(IndexError::OutOfBounds(idx))
67                },
68                _ => Err(IndexError::NotIndexable),
69            }
70        }))
71    }
72
73    /// Attempts to get an owned value from the given JSON value, returning an
74    /// error if it can't be found.
75    pub fn get_owned(&self, val: Value) -> Result<Value, IndexError> {
76        self.ref_toks.as_ref().iter().fold(Ok(val), |val, tok| val.and_then(|val| {
77            let tok = tok.as_ref();
78            match val {
79                Value::Object(mut obj) => obj.remove(tok).ok_or_else(|| IndexError::NoSuchKey(tok.to_owned())),
80                Value::Array(mut arr) => {
81                    let idx = if tok == "-" {
82                        arr.len()
83                    } else if let Ok(idx) = tok.parse() {
84                        idx
85                    } else {
86                        return Err(IndexError::NoSuchKey(tok.to_owned()));
87                    };
88                    if idx >= arr.len() {
89                        Err(IndexError::OutOfBounds(idx))
90                    } else {
91                        Ok(arr.swap_remove(idx))
92                    }
93                },
94                _ => Err(IndexError::NotIndexable),
95            }
96        }))
97    }
98
99    /// Converts a JSON pointer to a string in URI Fragment Identifier
100    /// Representation, including the leading `#`.
101    pub fn uri_fragment(&self) -> String {
102        fn legal_fragment_byte(b: u8) -> bool {
103            match b {
104                0x21 | 0x24 | 0x26..=0x3b | 0x3d | 0x3f..=0x5a | 0x5f | 0x61..=0x7a => true,
105                _ => false,
106            }
107        }
108
109        let mut s = "#".to_string();
110        for part in self.ref_toks.as_ref().iter() {
111            s += "/";
112            for b in part.as_ref().bytes() {
113                if legal_fragment_byte(b) {
114                    s.push(b as char)
115                } else {
116                    write!(s, "%{:02x}", b).unwrap()
117                }
118            }
119        }
120        s
121    }
122}
123
124impl<S: AsRef<str>> JsonPointer<S, Vec<S>> {
125    /// Adds a component to the JSON pointer.
126    pub fn push(&mut self, component: S) {
127        self.ref_toks.push(component);
128    }
129
130    /// Removes and returns the last component from the JSON pointer.
131    pub fn pop(&mut self) -> Option<S> {
132        self.ref_toks.pop()
133    }
134}
135
136impl<S: AsRef<str>, C: AsRef<[S]>> Display for JsonPointer<S, C> {
137    fn fmt(&self, fmt: &mut Formatter) -> FmtResult {
138        for part in self.ref_toks.as_ref().iter() {
139            write!(fmt, "/")?;
140            for ch in part.as_ref().chars() {
141                match ch {
142                    '~' => write!(fmt, "~0"),
143                    '/' => write!(fmt, "~1"),
144                    c => write!(fmt, "{}", c),
145                }?
146            }
147        }
148        Ok(())
149    }
150}
151
152impl FromStr for JsonPointer<String, Vec<String>> {
153    type Err = ParseError;
154    fn from_str(s: &str) -> Result<Self, Self::Err> {
155        parse(s)
156    }
157}
158
159/// An error that can be encountered when indexing using a JSON pointer.
160#[derive(Clone, Debug, PartialEq)]
161pub enum IndexError {
162    /// The pointer pointed to a nonexistent key.
163    NoSuchKey(String),
164    /// The pointer resulted in trying to index a non-indexable type.
165    NotIndexable,
166    /// The pointer pointed to an out-of-bounds value in an array.
167    OutOfBounds(usize),
168}
169
170impl<'a, S: AsRef<str>, C: AsRef<[S]>> Index<&'a JsonPointer<S, C>> for Value {
171    type Output = Value;
172    fn index(&self, ptr: &'a JsonPointer<S, C>) -> &Value {
173        ptr.get(self).unwrap()
174    }
175}
176
177impl<'a, S: AsRef<str>, C: AsRef<[S]>> IndexMut<&'a JsonPointer<S, C>> for Value {
178    fn index_mut(&mut self, ptr: &'a JsonPointer<S, C>) -> &mut Value {
179        ptr.get_mut(self).unwrap()
180    }
181}
json_pointer/ptr.rs

json_pointer/
ptr.rs
