jsonb: Introduce JsonDom type and parsing/conversion

Author: blackbeam

README.md

@@ -52,9 +52,9 @@ column and protocol type correspondence:
 | `mysql_common::Deserialized<T : DeserializeOwned>` | MySql bytes parsed using `serde_json::from_str` |
 | `Option<T: FromValue>`               | Must be used for nullable columns to avoid errors         |
 | [`decimal::Decimal`]                 | MySql int, uint or bytes parsed using `Decimal::from_str`.<br>⚠️ Note that this type doesn't support full range of MySql `DECIMAL` type. |
-| [`bigdecimal::BigDecimal`] (v0.2.x)  | MySql int, uint, floats or bytes parsed using `BigDecimal::parse_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql `DECIMAL` type but it'll be serialized anyway. |
-| [`bigdecimal::BigDecimal`] (v0.3.x)  | MySql int, uint, floats or bytes parsed using `BigDecimal::parse_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql `DECIMAL` type but it'll be serialized anyway. |
-| [`bigdecimal::BigDecimal`] (v0.4.x)  | MySql int, uint, floats or bytes parsed using `BigDecimal::parse_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql `DECIMAL` type but it'll be serialized anyway. |
+| [`bigdecimal::BigDecimal`] (v0.2.x)  | MySql int, uint, floats or bytes parsed using `BigDecimal::parse_str_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql `DECIMAL` type but it'll be serialized anyway. |
+| [`bigdecimal::BigDecimal`] (v0.3.x)  | MySql int, uint, floats or bytes parsed using `BigDecimal::parse_str_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql `DECIMAL` type but it'll be serialized anyway. |
+| [`bigdecimal::BigDecimal`] (v0.4.x)  | MySql int, uint, floats or bytes parsed using `BigDecimal::parse_str_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql `DECIMAL` type but it'll be serialized anyway. |
 | `num_bigint::{BigInt, BigUint}`      | MySql int, uint or bytes parsed using `_::parse_bytes`.<br>⚠️ Note that range of this type is greater than supported by MySql integer types but it'll be serialized anyway (as decimal bytes string). |
 
 Also crate provides from-row convertion for the following list of types (see `FromRow` trait):
@@ -242,6 +242,9 @@ Supported derivations:
 *  `#[mysql(rename = "some_name")]` – overrides column name of a field
 *  `#[mysql(json)]` - column will be interpreted as a JSON string containing
    a value of a field type
+*  `#[mysql(with = path::to::convert_fn)]` – `convert_fn` will be used to deserialize
+   a field value (expects a function with a signature that mimics
+   `TryFrom<Value, Error=FromValueError>``)
 
 #### Example
 

src/binlog/decimal/mod.rs

@@ -49,7 +49,7 @@ pub const POWERS_10: [i32; DIG_PER_DEC + 1] = [
 ///
 /// *   serialization/deserialization to/from binary format
 ///     (see `read_bin` and `write_bin` functions);
-/// *   parsing from decimal string/buffer (see `Decimal::parse_bytes`, `FromStr` impl);
+/// *   parsing from decimal string/buffer (see `Decimal::parse_str_bytes`, `FromStr` impl);
 /// *   conversion to decimal string (using `Display`).
 ///
 /// # Notes
@@ -58,7 +58,7 @@ pub const POWERS_10: [i32; DIG_PER_DEC + 1] = [
 ///     i.e. both `rhs` and `lhs` will be serialized into temporary buffers;
 /// *   even though MySql's `string2decimal` function allows scientific notation,
 ///     this implementation denies it.
-#[derive(Default, Debug, Eq)]
+#[derive(Default, Debug, Eq, Clone)]
 pub struct Decimal {
     /// The number of *decimal* digits (NOT number of `Digit`s!) before the point.
     intg: usize,
@@ -75,13 +75,23 @@ impl Decimal {
         decimal_bin_size(self.intg + self.frac, self.frac)
     }
 
+    /// See [`Decimal::parse_str_bytes`].
+    #[deprecated = "use parse_str_bytes"]
     pub fn parse_bytes(bytes: &[u8]) -> Result<Self, ParseDecimalError> {
         match std::str::from_utf8(bytes) {
             Ok(string) => Decimal::from_str(string),
             Err(_) => Err(ParseDecimalError),
         }
     }
 
+    /// Runs `Decimal::from_str` on the given bytes. Errors if not UTF-8 or not a decimal string.
+    pub fn parse_str_bytes(bytes: &[u8]) -> Result<Self, ParseDecimalError> {
+        match std::str::from_utf8(bytes) {
+            Ok(string) => Decimal::from_str(string),
+            Err(_) => Err(ParseDecimalError),
+        }
+    }
+
     pub fn write_bin<T: Write>(&self, mut output: T) -> io::Result<()> {
         // result bits must be inverted if the sign is negative,
         // we'll XOR it with `mask` to achieve this.
@@ -139,6 +149,27 @@ impl Decimal {
         output.write_all(&out_buf)
     }
 
+    /// Reads packed representation of a [`Decimal`].
+    ///
+    /// Packed representation is:
+    ///
+    /// 1. precision (u8)
+    /// 2. scale (u8)
+    /// 3. serialized decimal value (see [`Decimal::read_bin`])
+    pub fn read_packed<T: Read>(mut input: T, keep_precision: bool) -> io::Result<Self> {
+        let mut precision_and_scale = [0_u8, 0_u8];
+        input.read_exact(&mut precision_and_scale)?;
+        Self::read_bin(
+            input,
+            precision_and_scale[0] as usize,
+            precision_and_scale[1] as usize,
+            keep_precision,
+        )
+    }
+
+    /// Reads serialized representation of a decimal value.
+    ///
+    /// The value is usually written in the packed form (see [`Decimal::read_packed`]).
     pub fn read_bin<T: Read>(
         mut input: T,
         precision: usize,

src/binlog/decimal/test/mod.rs

@@ -135,7 +135,7 @@ proptest! {
         let num = dbg!(&num);
 
         // test string2decimal
-        let dec = dbg!(super::Decimal::parse_bytes(num.as_bytes()).unwrap());
+        let dec = dbg!(super::Decimal::parse_str_bytes(num.as_bytes()).unwrap());
         let mysql_dec = dbg!(decimal_t::rust_string2decimal(num).unwrap());
         assert_eq!(dec.intg, mysql_dec.intg as usize);
         assert_eq!(dec.frac, mysql_dec.frac as usize);