93 lines
3.3 KiB
Rust
93 lines
3.3 KiB
Rust
//! JSON 序列化器——把 [`JsonValue`] 渲染回字符串。
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//! JSON serializer — renders a [`JsonValue`] back to a String.
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use crate::value::JsonValue;
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use std::fmt::Write;
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/// 将 [`JsonValue`] 序列化为紧凑的 JSON 字符串。
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/// Serialize a [`JsonValue`] to a compact JSON string.
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pub fn to_string(value: &JsonValue) -> String {
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let mut out = String::new();
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write_value(value, &mut out);
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out
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}
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/// 把一个值写入 `out`（递归处理数组与对象）。
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/// Write a value into `out` (recursing into arrays and objects).
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fn write_value(value: &JsonValue, out: &mut String) {
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match value {
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JsonValue::Null => out.push_str("null"),
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JsonValue::Bool(true) => out.push_str("true"),
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JsonValue::Bool(false) => out.push_str("false"),
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JsonValue::Num(n) => write_number(*n, out),
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JsonValue::Str(s) => write_string(s, out),
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JsonValue::Arr(items) => {
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out.push('[');
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for (i, item) in items.iter().enumerate() {
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if i > 0 {
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out.push(',');
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}
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write_value(item, out);
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}
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out.push(']');
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}
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JsonValue::Obj(entries) => {
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out.push('{');
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for (i, (key, val)) in entries.iter().enumerate() {
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if i > 0 {
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out.push(',');
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}
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write_string(key, out);
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out.push(':');
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write_value(val, out);
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}
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out.push('}');
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}
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}
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}
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/// 以 JSON 兼容形式渲染数字。整数打印时不带小数部分，符合常见预期
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/// （例如 `3` 而非 `3.0`）。
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/// Render a number in a JSON-compatible form. Integers print without a
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/// fractional part to match common expectations (e.g. `3` not `3.0`).
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fn write_number(n: f64, out: &mut String) {
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if n.is_finite() {
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// 整数走 i64 分支；浮点数走最短表示分支。
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// Integers take the i64 branch; fractional numbers take the shortest-repr branch.
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if n.fract() == 0.0 && n.abs() < 1e16 {
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let _ = write!(out, "{}", n as i64);
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} else {
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// 通过 format! 得到 Ryu 风格的最短表示：可往返且无需引入依赖。
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// Use Ryu-style shortest representation via format!: this gives
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// round-trippable floats without pulling in a dependency.
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let _ = write!(out, "{}", n);
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}
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} else {
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// JSON 无法表示无穷或 NaN；输出 null 以保持有效。
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// JSON has no representation for infinity or NaN. Emit null to stay valid.
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out.push_str("null");
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}
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}
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/// 将字符串转义并加上引号后写入 `out`。
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/// Escape and quote a string into `out`.
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fn write_string(s: &str, out: &mut String) {
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out.push('"');
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for c in s.chars() {
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match c {
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'"' => out.push_str("\\\""),
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'\\' => out.push_str("\\\\"),
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'\n' => out.push_str("\\n"),
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'\r' => out.push_str("\\r"),
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'\t' => out.push_str("\\t"),
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'\u{0008}' => out.push_str("\\b"),
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'\u{000C}' => out.push_str("\\f"),
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c if (c as u32) < 0x20 => {
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let _ = write!(out, "\\u{:04x}", c as u32);
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}
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c => out.push(c),
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}
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}
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out.push('"');
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}
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