gjson_ngae.go

//+build !appengine

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)
		result = fromBytesGet(result)
	}
	return result
}

func fromBytesGet(result Result) Result {
	// 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
		}
	}
}