gjson/gjson_ngae.go

78 lines
2.4 KiB
Go

//+build !appengine
//+build !js
package gjson
import (
"reflect"
"unsafe"
)
// getBytes casts the input json bytes to a string and safely returns the
// results as uniquely allocated data. This operation is intended to minimize
// copies and allocations for the large json string->[]byte.
func getBytes(json []byte, path string) Result {
var result Result
if json != nil {
// unsafe cast to string
result = Get(*(*string)(unsafe.Pointer(&json)), path)
// safely get the string headers
rawhi := *(*reflect.StringHeader)(unsafe.Pointer(&result.Raw))
strhi := *(*reflect.StringHeader)(unsafe.Pointer(&result.Str))
// create byte slice headers
rawh := reflect.SliceHeader{Data: rawhi.Data, Len: rawhi.Len}
strh := reflect.SliceHeader{Data: strhi.Data, Len: strhi.Len}
if strh.Data == 0 {
// str is nil
if rawh.Data == 0 {
// raw is nil
result.Raw = ""
} else {
// raw has data, safely copy the slice header to a string
result.Raw = string(*(*[]byte)(unsafe.Pointer(&rawh)))
}
result.Str = ""
} else if rawh.Data == 0 {
// raw is nil
result.Raw = ""
// str has data, safely copy the slice header to a string
result.Str = string(*(*[]byte)(unsafe.Pointer(&strh)))
} else if strh.Data >= rawh.Data &&
int(strh.Data)+strh.Len <= int(rawh.Data)+rawh.Len {
// Str is a substring of Raw.
start := int(strh.Data - rawh.Data)
// safely copy the raw slice header
result.Raw = string(*(*[]byte)(unsafe.Pointer(&rawh)))
// substring the raw
result.Str = result.Raw[start : start+strh.Len]
} else {
// safely copy both the raw and str slice headers to strings
result.Raw = string(*(*[]byte)(unsafe.Pointer(&rawh)))
result.Str = string(*(*[]byte)(unsafe.Pointer(&strh)))
}
}
return result
}
// fillIndex finds the position of Raw data and assigns it to the Index field
// of the resulting value. If the position cannot be found then Index zero is
// used instead.
func fillIndex(json string, c *parseContext) {
if len(c.value.Raw) > 0 && !c.calcd {
jhdr := *(*reflect.StringHeader)(unsafe.Pointer(&json))
rhdr := *(*reflect.StringHeader)(unsafe.Pointer(&(c.value.Raw)))
c.value.Index = int(rhdr.Data - jhdr.Data)
if c.value.Index < 0 || c.value.Index >= len(json) {
c.value.Index = 0
}
}
}
func stringBytes(s string) []byte {
return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
Data: (*reflect.StringHeader)(unsafe.Pointer(&s)).Data,
Len: len(s),
Cap: len(s),
}))
}