Enum sanakirja::value::UnsafeValue

pub enum UnsafeValue {
    Direct {
        p: *const u8,
        len: u64,
    },
    Large {
        offset: u64,
        len: u64,
    },
}

Unsafe values, the unsafe representation of a value.

Variants

Direct

A "direct" value, i.e. a value stored inline in tree pages. These values are limited to at most 506 bytes.

Fields of Direct

p: *const u8

Pointer to the first byte of this value.

len: u64

Length of this value, in bytes

Large

A "large" value, stored on a linked list of pages.

Fields of Large

offset: u64

Offset in the file to the first page of this value.

len: u64

Length of this value

Methods

impl UnsafeValue

pub fn len(&self) -> u64

Length of this unsafe value

pub unsafe fn as_slice<'a>(&self) -> &'a [u8]

Unsafely turn this value into a slice, if it is inlined on a page. Panics else.

pub fn from_slice(slice: &[u8]) -> UnsafeValue

Converts a slice of bytes into an unsafe value.

pub fn alloc_if_needed<T>(
    txn: &mut MutTxn<T>,
    value: &[u8]
) -> Result<UnsafeValue, Error>

Allocates a large value if needed, or else return a pointer to the given slice.

Trait Implementations

impl Representable for UnsafeValue

fn onpage_size(&self) -> u16

How much space this value occupies on the page (not counting alignment padding).

unsafe fn write_value(&self, ptr: *mut u8)

Write this value to a u8 pointer, guaranteed to be a multiple of self.alignment().

unsafe fn read_value(ptr: *const u8) -> Self

Read value from an onpage pointer, guaranteed to be a multiple of self.alignment().

unsafe fn cmp_value<T: LoadPage>(&self, txn: &T, y: Self) -> Ordering

Compare a value with an onpage value. The current transaction is sometimes helpful, for instance when the page only stores a pointer to another page.

fn drop_value<T, R>(&self, txn: &mut MutTxn<T>, _: &mut R) -> Result<(), Error>

How to free the pages used by this value. The default implementation doesn't do anything, which is fine for types stored directly on B tree pages.

type PageOffsets = IntoIter<u64>

An iterator over the offsets to pages contained in this value. Only values from this crate can generate non-empty iterators, but combined values (like tuples) must chain the iterators returned by method page_offsets.

fn page_offsets(&self) -> Self::PageOffsets

If this value is an offset to another page at offset offset, return Some(offset). Return None else.

fn alignment() -> Alignment

Alignment of this type. Allowed values are 1, 2, 4 and 8.

unsafe fn skip(p: *mut u8) -> *mut u8

First pointer strictly after this value's pointer. The default implementation is basically p.offset(self.onpage_size() as isize), but their might be more efficient implementations in some cases.

impl Clone for UnsafeValue

fn clone(&self) -> UnsafeValue

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for UnsafeValue

impl Debug for UnsafeValue

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.