我的程序解析了足够大的json文档(30MB),在CPU速度慢的机器上花了70ms,我想加快这个过程,我发现27%的解析发生在我的foo_document_type_deserialize
中,是否有可能改进这个功能,可能有办法在这里跳过String
分配:let s = String::deserialize(deserializer)?;
?
我完全确定表示枚举值的字符串不包含像\b \f \n \r \t \" \\
这样的特殊json字符,因此使用非转义字符串应该是安全的。
use serde::{Deserialize, Deserializer};
#[derive(Deserialize, Debug, Clone)]
#[serde(rename_all = "camelCase")]
pub struct FooDocument {
// other fields...
#[serde(rename = "type")]
#[serde(deserialize_with = "foo_document_type_deserialize")]
doc_type: FooDocumentType,
}
fn foo_document_type_deserialize<'de, D>(deserializer: D) -> Result<FooDocumentType, D::Error>
where
D: Deserializer<'de>,
{
use self::FooDocumentType::*;
let s = String::deserialize(deserializer)?;
match s.as_str() {
"tir lim bom bom" => Ok(Var1),
"hgga;hghau" => Ok(Var2),
"hgueoqtyhit4t" => Ok(Var3),
"Text" | "Type not detected" | "---" => Ok(Unknown),
_ => Err(serde::de::Error::custom(format!(
"Unsupported foo document type '{}'",
s
))),
}
}
#[derive(Debug, Clone, Copy)]
pub enum FooDocumentType {
Unknown,
Var1,
Var2,
Var3,
}
您编写的自定义impl是serde_derive可以生成的形式:
#[derive(Deserialize, Debug)]
pub enum FooDocumentType {
#[serde(rename = "Text", alias = "Type not detected", alias = "---")]
Unknown,
#[serde(rename = "tir lim bom bom")]
Var1,
#[serde(rename = "hgga;hghau")]
Var2,
#[serde(rename = "hgueoqtyhit4t")]
Var3,
}
生成的派生代码不会分配内存,并且在测量以下内容时,与代码相比,快速微基准测试的速度快2倍:
serde_json::from_str::<FooDocument>(r#"{"type":"hgga;hghau"}"#).unwrap()