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doc: update readme on Pretouch (#70)

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Yi Duan 2021-08-11 17:35:23 +08:00 committed by GitHub
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@ -147,7 +147,7 @@ if err := dc.Decode(&data); err != nil {
print(e.Description()) print(e.Description())
/*"Syntax error at index 3: invalid char\n\n\t[[[}]]\n\t...^..\n"*/ /*"Syntax error at index 3: invalid char\n\n\t[[[}]]\n\t...^..\n"*/
println(fmt.Sprintf("%q", self.Description())) println(fmt.Sprintf("%q", e.Description()))
} }
/*Decode: Syntax error at index 3: invalid char*/ /*Decode: Syntax error at index 3: invalid char*/
@ -158,7 +158,7 @@ if err := dc.Decode(&data); err != nil {
## Tips ## Tips
### Pretouch ### Pretouch
Since Sonic uses JIT(just-in-time) compiling for decoder/encoder, huge schema may cause request-timeout. For better stability, we suggest to use `Pretouch()` for more-than-10000-field schema(struct) before `Marshal()/Unmarshal()`. Since Sonic uses [golang-asm](https://github.com/twitchyliquid64/golang-asm) as JIT assembler, which is NOT very suitable for runtime compiling, first-hit running of a huge schema may cause request-timeout or even process-OOM. For better stability, we advise to **use `Pretouch()` for huge-schema or compact-memory application** before `Marshal()/Unmarshal()`.
```go ```go
import ( import (
"reflect" "reflect"
@ -170,6 +170,7 @@ func init() {
err := sonic.Pretouch(reflect.TypeOf(v)) err := sonic.Pretouch(reflect.TypeOf(v))
} }
``` ```
**CAUSION:** use the **STRUCT instead of its POINTER** to `Pretouch()`, otherwish it won't work when you pass the pointer to `Marshal()/Unmarshal()`!
### Pass string or []byte? ### Pass string or []byte?
For alignment to encoding/json, we provide API to pass `[]byte` as arguement, but the string-to-bytes copy is conducted at the same time considering safety, which may lose performance when origin json is huge. Therefore, you can use `UnmarshalString`, `GetFromString` to pass string, as long as your origin data is string or **nocopy-cast** is safe for your []byte. For alignment to encoding/json, we provide API to pass `[]byte` as arguement, but the string-to-bytes copy is conducted at the same time considering safety, which may lose performance when origin json is huge. Therefore, you can use `UnmarshalString`, `GetFromString` to pass string, as long as your origin data is string or **nocopy-cast** is safe for your []byte.