forked from mirror/go-json
88 lines
1.4 KiB
Go
88 lines
1.4 KiB
Go
package runtime
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import (
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"reflect"
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"unsafe"
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)
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type SliceHeader struct {
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Data unsafe.Pointer
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Len int
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Cap int
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}
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const (
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maxAcceptableTypeAddrRange = 1024 * 1024 * 2 // 2 Mib
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)
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type TypeAddr struct {
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BaseTypeAddr uintptr
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MaxTypeAddr uintptr
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AddrRange uintptr
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}
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var (
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typeAddr *TypeAddr
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alreadyAnalyzed bool
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)
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//go:linkname typelinks reflect.typelinks
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func typelinks() ([]unsafe.Pointer, [][]int32)
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//go:linkname rtypeOff reflect.rtypeOff
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func rtypeOff(unsafe.Pointer, int32) unsafe.Pointer
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func AnalyzeTypeAddr() *TypeAddr {
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defer func() {
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alreadyAnalyzed = true
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}()
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if alreadyAnalyzed {
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return typeAddr
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}
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sections, offsets := typelinks()
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if len(sections) != 1 {
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return nil
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}
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if len(offsets) != 1 {
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return nil
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}
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section := sections[0]
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offset := offsets[0]
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var (
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min uintptr = uintptr(^uint(0))
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max uintptr = 0
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)
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for i := 0; i < len(offset); i++ {
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typ := (*Type)(rtypeOff(section, offset[i]))
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addr := uintptr(unsafe.Pointer(typ))
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if min > addr {
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min = addr
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}
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if max < addr {
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max = addr
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}
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if typ.Kind() == reflect.Ptr {
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addr = uintptr(unsafe.Pointer(typ.Elem()))
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if min > addr {
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min = addr
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}
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if max < addr {
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max = addr
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}
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}
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}
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addrRange := max - min
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if addrRange == 0 {
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return nil
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}
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if addrRange > maxAcceptableTypeAddrRange {
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return nil
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}
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typeAddr = &TypeAddr{
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BaseTypeAddr: min,
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MaxTypeAddr: max,
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AddrRange: addrRange,
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}
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return typeAddr
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}
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