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package bbolt
import (
"reflect"
"unsafe"
)
func unsafeAdd(base unsafe.Pointer, offset uintptr) unsafe.Pointer {
return unsafe.Pointer(uintptr(base) + offset)
}
func unsafeIndex(base unsafe.Pointer, offset uintptr, elemsz uintptr, n int) unsafe.Pointer {
return unsafe.Pointer(uintptr(base) + offset + uintptr(n)*elemsz)
}
func unsafeByteSlice(base unsafe.Pointer, offset uintptr, i, j int) []byte {
// See: https://github.com/golang/go/wiki/cgo#turning-c-arrays-into-go-slices
//
// This memory is not allocated from C, but it is unmanaged by Go's
// garbage collector and should behave similarly, and the compiler
// should produce similar code. Note that this conversion allows a
// subslice to begin after the base address, with an optional offset,
// while the URL above does not cover this case and only slices from
// index 0. However, the wiki never says that the address must be to
// the beginning of a C allocation (or even that malloc was used at
// all), so this is believed to be correct.
return (*[maxAllocSize]byte)(unsafeAdd(base, offset))[i:j:j]
}
// unsafeSlice modifies the data, len, and cap of a slice variable pointed to by
// the slice parameter. This helper should be used over other direct
// manipulation of reflect.SliceHeader to prevent misuse, namely, converting
// from reflect.SliceHeader to a Go slice type.
func unsafeSlice(slice, data unsafe.Pointer, len int) {
s := (*reflect.SliceHeader)(slice)
s.Data = uintptr(data)
s.Cap = len
s.Len = len
}
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