| 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 |
| } |