From 65353b6d52a31e808c07f9d4651b9473525dcd88 Mon Sep 17 00:00:00 2001
From: tidwall <joshbaker77@gmail.com>
Date: Sat, 30 Jan 2021 12:50:49 -0700
Subject: [PATCH] Removed reflect package

This commit removes the reflect package to avoid using the
reflect.SliceHeader and reflect.StringHeader structures. Instead
new sliceHeader and stringHeader stuctures have been added with
the same layout expect that they intentionally expose the data
field as an unsafe.Pointer instead of a uintptr.
---
 gjson.go | 51 ++++++++++++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 19 deletions(-)

diff --git a/gjson.go b/gjson.go
index 66965ba..4f988d0 100644
--- a/gjson.go
+++ b/gjson.go
@@ -3,7 +3,6 @@ package gjson
 
 import (
 	"encoding/json"
-	"reflect"
 	"strconv"
 	"strings"
 	"time"
@@ -2836,6 +2835,19 @@ func modValid(json, arg string) string {
 	return json
 }
 
+// stringHeader instead of reflect.StringHeader
+type stringHeader struct {
+	data unsafe.Pointer
+	len  int
+}
+
+// sliceHeader instead of reflect.SliceHeader
+type sliceHeader struct {
+	data unsafe.Pointer
+	len  int
+	cap  int
+}
+
 // 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.
@@ -2845,14 +2857,14 @@ func getBytes(json []byte, path string) Result {
 		// 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))
+		rawhi := *(*stringHeader)(unsafe.Pointer(&result.Raw))
+		strhi := *(*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 {
+		rawh := sliceHeader{data: rawhi.data, len: rawhi.len, cap: rawhi.len}
+		strh := sliceHeader{data: strhi.data, len: strhi.len, cap: rawhi.len}
+		if strh.data == nil {
 			// str is nil
-			if rawh.Data == 0 {
+			if rawh.data == nil {
 				// raw is nil
 				result.Raw = ""
 			} else {
@@ -2860,19 +2872,20 @@ func getBytes(json []byte, path string) Result {
 				result.Raw = string(*(*[]byte)(unsafe.Pointer(&rawh)))
 			}
 			result.Str = ""
-		} else if rawh.Data == 0 {
+		} else if rawh.data == nil {
 			// 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 {
+		} else if uintptr(strh.data) >= uintptr(rawh.data) &&
+			uintptr(strh.data)+uintptr(strh.len) <=
+				uintptr(rawh.data)+uintptr(rawh.len) {
 			// Str is a substring of Raw.
-			start := int(strh.Data - rawh.Data)
+			start := uintptr(strh.data) - uintptr(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]
+			result.Str = result.Raw[start : start+uintptr(strh.len)]
 		} else {
 			// safely copy both the raw and str slice headers to strings
 			result.Raw = string(*(*[]byte)(unsafe.Pointer(&rawh)))
@@ -2887,9 +2900,9 @@ func getBytes(json []byte, path string) Result {
 // 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)
+		jhdr := *(*stringHeader)(unsafe.Pointer(&json))
+		rhdr := *(*stringHeader)(unsafe.Pointer(&(c.value.Raw)))
+		c.value.Index = int(uintptr(rhdr.data) - uintptr(jhdr.data))
 		if c.value.Index < 0 || c.value.Index >= len(json) {
 			c.value.Index = 0
 		}
@@ -2897,10 +2910,10 @@ func fillIndex(json string, c *parseContext) {
 }
 
 func stringBytes(s string) []byte {
-	return *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
-		Data: (*reflect.StringHeader)(unsafe.Pointer(&s)).Data,
-		Len:  len(s),
-		Cap:  len(s),
+	return *(*[]byte)(unsafe.Pointer(&sliceHeader{
+		data: (*stringHeader)(unsafe.Pointer(&s)).data,
+		len:  len(s),
+		cap:  len(s),
 	}))
 }