Thomas Pelletier
60 lines
1.4 KiB
Go
60 lines
1.4 KiB
Go
package unsafe
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import (
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"fmt"
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"reflect"
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"unsafe"
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)
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const maxInt = uintptr(int(^uint(0) >> 1))
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func SubsliceOffset(data []byte, subslice []byte) int {
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datap := (*reflect.SliceHeader)(unsafe.Pointer(&data))
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hlp := (*reflect.SliceHeader)(unsafe.Pointer(&subslice))
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if hlp.Data < datap.Data {
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panic(fmt.Errorf("subslice address (%d) is before data address (%d)", hlp.Data, datap.Data))
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}
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offset := hlp.Data - datap.Data
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if offset > maxInt {
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panic(fmt.Errorf("slice offset larger than int (%d)", offset))
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}
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intoffset := int(offset)
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if intoffset > datap.Len {
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panic(fmt.Errorf("slice offset (%d) is farther than data length (%d)", intoffset, datap.Len))
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}
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if intoffset+hlp.Len > datap.Len {
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panic(fmt.Errorf("slice ends (%d+%d) is farther than data length (%d)", intoffset, hlp.Len, datap.Len))
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}
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return intoffset
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}
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func BytesRange(start []byte, end []byte) []byte {
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if start == nil || end == nil {
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panic("cannot call BytesRange with nil")
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}
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startp := (*reflect.SliceHeader)(unsafe.Pointer(&start))
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endp := (*reflect.SliceHeader)(unsafe.Pointer(&end))
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if startp.Data > endp.Data {
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panic(fmt.Errorf("start pointer address (%d) is after end pointer address (%d)", startp.Data, endp.Data))
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}
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l := startp.Len
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endLen := int(endp.Data-startp.Data) + endp.Len
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if endLen > l {
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l = endLen
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}
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if l > startp.Cap {
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panic(fmt.Errorf("range length is larger than capacity"))
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}
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return start[:l]
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}
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