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