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- package danger
- import (
- "fmt"
- "reflect"
- "unsafe"
- )
- const maxInt = uintptr(int(^uint(0) >> 1))
- func SubsliceOffset(data []byte, subslice []byte) int {
- datap := (*reflect.SliceHeader)(unsafe.Pointer(&data))
- hlp := (*reflect.SliceHeader)(unsafe.Pointer(&subslice))
- if hlp.Data < datap.Data {
- panic(fmt.Errorf("subslice address (%d) is before data address (%d)", hlp.Data, datap.Data))
- }
- offset := hlp.Data - datap.Data
- if offset > maxInt {
- panic(fmt.Errorf("slice offset larger than int (%d)", offset))
- }
- intoffset := int(offset)
- if intoffset > datap.Len {
- panic(fmt.Errorf("slice offset (%d) is farther than data length (%d)", intoffset, datap.Len))
- }
- if intoffset+hlp.Len > datap.Len {
- panic(fmt.Errorf("slice ends (%d+%d) is farther than data length (%d)", intoffset, hlp.Len, datap.Len))
- }
- return intoffset
- }
- func BytesRange(start []byte, end []byte) []byte {
- if start == nil || end == nil {
- panic("cannot call BytesRange with nil")
- }
- startp := (*reflect.SliceHeader)(unsafe.Pointer(&start))
- endp := (*reflect.SliceHeader)(unsafe.Pointer(&end))
- if startp.Data > endp.Data {
- panic(fmt.Errorf("start pointer address (%d) is after end pointer address (%d)", startp.Data, endp.Data))
- }
- l := startp.Len
- endLen := int(endp.Data-startp.Data) + endp.Len
- if endLen > l {
- l = endLen
- }
- if l > startp.Cap {
- panic(fmt.Errorf("range length is larger than capacity"))
- }
- return start[:l]
- }
- func Stride(ptr unsafe.Pointer, size uintptr, offset int) unsafe.Pointer {
- // TODO: replace with unsafe.Add when Go 1.17 is released
- // https://github.com/golang/go/issues/40481
- return unsafe.Pointer(uintptr(ptr) + uintptr(int(size)*offset))
- }
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