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//! # Serde-querystring //! serde-querystring is a deserializer for query strings. //! //! Query strings are often used to send data to a web server as part of a http request and //! they usually consist of a sequence of key/value pairs. //! While they are commonly used, they don't have a strong standard defining how they should be parsed, //! for anything more than just simple key/value pairs, so it is important to define how we are going to //! parse them, and what is considered an expected behaviour and what can be a bug. //! Serde-querystring tries to use the commonly used form `key[subkey]=value` pattern to provide //! a way to define different `Rust` data structures. //! //! ## Before we begin //! Formats used in de/serialization are either self-describing or non-self-describing which roughly //! means either you can imagine the backing data structure only by looking at the serialized format or not. //! //! For example when looking at a `json` file, whenever you see some data in `{...}` form you can say it's a //! map, same goes for `[...]` for a sequence/list. But for formats like query strings, by looking at //! `key[1]=value&key[2]=value` you can't decide if key is a map with 1 and 2 as it's own keys, //! or if it's a sequence with 2 elements. So it's the final data structure that defines how we //! should look at the data. //! //! So instead of defining the format itself, we define how we can represent a data structure using the format. //! //! ## Keys //! For every pair in a query string, there has to be a key(or key sequence) on the left hand side of `=` sign. //! If the key is of a simple form `key` we consider it a group name for its value, if it has subkeys in the form //! `key[subkey]` we read it as a group named `key` with some value that itself has a group called `subkey`. //! So the terms `group name` and `key` are interchangeable here. //! //! ## Value //! Values are the leaves of tree, meaning by looking at them we can instantly say what they are and //! we don't need to go any deeper to undestand their meaning, in other words, they can't have any sub value or //! sub keys(with one exception). //! //! | Types | Example valid representations | //! |-------|------------------------------| //! | `u64` `u32` `u16` `u8` | `210` | //! | `i64` `i32` `i16` `i8` | `210` `-210` | //! | `f64` `f32` | `1337` `-1337` `1337.4` `-1337.4` `1.4E5` `1.2e-4` `1.9e+4` | //! | `str` | `Hello` `World` | //! | `String` | `Hello+World` `Hello%25World` `Hello` | //! | `bool` | `on` `true` `1` for true and `off` `false` `0` for false | //! | `enum` unit variants | `Cold` `Dark` | //! | `Option`(*) | `123` `Hello` depending on inner value or ` ` for None | //! | `Vec` or `tuple` of values(*) | `210,340,450` | //! | new type `struct` | `123` `Cold,Warm` depending on inner value | //! //! * It is only considered a value if it consist of other values. //! //! ## Map/Struct //! A query string starts either by a `map` or a `struct` at its root, these two are represented in the same //! way and are considered the same kind of entity except when dealing with repeated keys(Described later). //! To represent them, we start from the root's fields and consider every one of them a key, if the value //! associated with that group/key also needs a sub group itself, we consider that group name as a subkey of main key. //! //! ### Example //! //! ```ignore //! struct Home{ //! lat: f64, //! long: f64 //! } //! ``` //! Will be represented as: `lat=1.5&long=3.5` //! //! ```ignore //! struct Area{ //! gym: Home, //! police: Home //! } //! ``` //! Will be represented as: `gym[lat]=1.5&gym[long]=3.5&police[lat]=1.5&police[long]=3.5` //! //! ```ignore //! type City = HashMap<String, Home>; //! ``` //! Will be also represented as: `gym[lat]=1.5&gym[long]=3.5&police[lat]=1.5&police[long]=3.5` //! //! * Ordering of the fields does not matter, they can be combined in any possible order and it shouldn't //! effect the result, unless there are repeated keys. //! * For structs it's an error to repeat the same key or subkey more than once, but for maps the values are //! overwritable. //! //! Validity of example cases //! //! | Case | `City` | `Area` | //! |---------------------------------------------------|--------|--------| //! | `gym[lat]=1.5&gym[long]=3.5` |- |X | //! | `...&police[lat]=1.5&police[long]=3.5` |X |X | //! | `gym[lat]=1.5&police[long]=3.5` |- |- | //! | `...&gym[long]=1.5&police[lat]=3.5` |X |X | //! | `...&gym[long]=1.5&police[lat]=3.5` |-(**) |-(**) | //! //! * (*)`X` means valid `-` means invalid `...` means continue from above //! * (**) More on that on Repeated keys //! //! ## Sequences/Vectors/Tuples/Lists //! Sequences are defined as a finite ordered set of groups, the group names in a sequence can be either empty //! as in `key[]`, a string/name as in `key[first]` or a number as in `key[1]`. Here's what each kind of group //! name can be used for: //! - Empty: They can be used to represent some unspecified index for a value(as defined in `Value` section). //! it can't have subkeys unless there are only one subkey(and subkey of subkey..) possible for it. //! - String: They can be used to represent an unspecified index, and can also have subkeys. //! - Number: Same as String but will also define the order. //! * Keys in a sequence are read as the same order as they are defined, unspecified here means not defining a //! specific order for a key and depending on the default order. //! * In case of combining ordered and unordered, all unordered elements will come before ordered ones. //! * In case of repeating a key, we only consider the ***last group*** defined. More on that on //! "Repeated keys" section. //! //! ### Example //! For a struct with only one field `a` of type `Vec<T>` for some type `T` //! //! | Value | Example valid representation | //! |---------------------|---------------------------------------------------| //! | `[1,2]` | `a[]=1&a[]=2` | //! | `[1,2]` | `a[g2]=1&a[g1]=2` | //! | `[2]` | `a[group]=1&a[group]=2` | //! | `[2,1]` | `a[2]=1&a[1]=2` | //! | `[3,2,1]` | `a[2]=1&a[1]=2&a[]=3` | //! | `[{X:1,Y:2}]` as map| `a[group][X]=1&a[group][Y]=2` | //! //! ## Enums //! Enums in general can be represented the way as a map //! //! ### Example //! For a struct defined as below //! ```no_run //! struct Game{ //! last: Event //! } //! //! // modified from rust by example book //! enum Event { //! PageLoad, //! KeyPress(char), //! Paste(String), //! Click { x: i64, y: i64 }, //! Missed(i32, i32), //! } //! ``` //! Here's how we represent different kinds of `Event`: //! //! | Value | Example valid representation | //! |---------------------|---------------------------------------------------| //! |`PageLoad` |`last=PageLoad` is valid as unit variants are value| //! |`PageLoad` |`last[PageLoad]=` is valid as value is unit | //! |`KeyPress('W')` |`last[KeyPress]=W` | //! |`Paste("Hello")` |`last[Paste]=Hello` | //! |`Click{x:400,y:640}` |`last[Click][x]=400&last[Click][y]=640` | //! |`Missed(200,400)` |`last[Missed]=200,400` list of values is a value | //! |`Missed(200,400)` |`last[Missed][]=200&last[Missed][]=400` | //! |`Missed(200,400)` |`last[Missed][1]=200&last[Missed][2]=400` | //! //! ## Repeated keys //! Though the keys in a map or list are overwritable, repeating keys assosiated with a struct is an error, //! and as we consider keys, group names, the data structure in that level decides if it allows repeating or not. //! Ex. for `map` of `struct`s it is not allowed, for `struct` with `map` fields it is allowed, for `struct` of //! `map` fields containing `struct` as values it is again not allowed. //! //! Being overwritable for keys with subkeys(ex. Enums or Lists) creates a situation where we can't decide //! what the final value should be, consider the example from `Enum` section, and the following query string: //! //! `last[Click][x]=400&last[Missed][]=200&last[Missed][]=400&last[Click][y]=640` //! //! In this kind of situations, to keep consistency with other kinds of keys, we only consider the //! `last defined group`, so in the above example although the last key belongs to `Click` group name, we only //! consider `Missed` group as it is defined after `Click`. //! //! #### Exception //! //! One exception is when there are enums in a map or sequence, and one of the enums are defined as a //! value. In that case we visit the values first and we ignore the subkeys. So the following query strings //! are all considered `PageLoad`. //! //! `last=PageLoad&last[KeyPress]=C` //! //! `last[KeyPress]=C&last=PageLoad` //! //! `last=PageUnload&last[KeyPress]=C&last=PageLoad` //! //! To overcome this, you can define all enum variants at the sublevel, ex: //! //! `last[PageLoad]=&last[KeyPress]=C` //! mod de; mod error; pub use de::{from_bytes, from_str}; pub use error::Error;