417 lines
12 KiB
Go
Vendored
417 lines
12 KiB
Go
Vendored
// +build 386,!appengine amd64,!appengine arm,!appengine arm64,!appengine ppc64le,!appengine mipsle,!appengine mips64le,!appengine mips64p32le,!appengine wasm,!appengine
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package roaring
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import (
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"encoding/binary"
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"errors"
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"io"
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"reflect"
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"runtime"
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"unsafe"
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)
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func (ac *arrayContainer) writeTo(stream io.Writer) (int, error) {
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buf := uint16SliceAsByteSlice(ac.content)
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return stream.Write(buf)
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}
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func (bc *bitmapContainer) writeTo(stream io.Writer) (int, error) {
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if bc.cardinality <= arrayDefaultMaxSize {
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return 0, errors.New("refusing to write bitmap container with cardinality of array container")
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}
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buf := uint64SliceAsByteSlice(bc.bitmap)
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return stream.Write(buf)
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}
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func uint64SliceAsByteSlice(slice []uint64) []byte {
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// make a new slice header
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header := *(*reflect.SliceHeader)(unsafe.Pointer(&slice))
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// update its capacity and length
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header.Len *= 8
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header.Cap *= 8
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// instantiate result and use KeepAlive so data isn't unmapped.
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result := *(*[]byte)(unsafe.Pointer(&header))
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runtime.KeepAlive(&slice)
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// return it
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return result
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}
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func uint16SliceAsByteSlice(slice []uint16) []byte {
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// make a new slice header
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header := *(*reflect.SliceHeader)(unsafe.Pointer(&slice))
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// update its capacity and length
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header.Len *= 2
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header.Cap *= 2
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// instantiate result and use KeepAlive so data isn't unmapped.
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result := *(*[]byte)(unsafe.Pointer(&header))
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runtime.KeepAlive(&slice)
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// return it
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return result
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}
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func (bc *bitmapContainer) asLittleEndianByteSlice() []byte {
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return uint64SliceAsByteSlice(bc.bitmap)
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}
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// Deserialization code follows
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////
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// These methods (byteSliceAsUint16Slice,...) do not make copies,
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// they are pointer-based (unsafe). The caller is responsible to
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// ensure that the input slice does not get garbage collected, deleted
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// or modified while you hold the returned slince.
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////
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func byteSliceAsUint16Slice(slice []byte) (result []uint16) { // here we create a new slice holder
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if len(slice)%2 != 0 {
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panic("Slice size should be divisible by 2")
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}
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// reference: https://go101.org/article/unsafe.html
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// make a new slice header
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bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
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rHeader := (*reflect.SliceHeader)(unsafe.Pointer(&result))
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// transfer the data from the given slice to a new variable (our result)
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rHeader.Data = bHeader.Data
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rHeader.Len = bHeader.Len / 2
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rHeader.Cap = bHeader.Cap / 2
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// instantiate result and use KeepAlive so data isn't unmapped.
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runtime.KeepAlive(&slice) // it is still crucial, GC can free it)
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// return result
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return
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}
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func byteSliceAsUint64Slice(slice []byte) (result []uint64) {
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if len(slice)%8 != 0 {
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panic("Slice size should be divisible by 8")
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}
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// reference: https://go101.org/article/unsafe.html
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// make a new slice header
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bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
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rHeader := (*reflect.SliceHeader)(unsafe.Pointer(&result))
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// transfer the data from the given slice to a new variable (our result)
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rHeader.Data = bHeader.Data
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rHeader.Len = bHeader.Len / 8
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rHeader.Cap = bHeader.Cap / 8
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// instantiate result and use KeepAlive so data isn't unmapped.
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runtime.KeepAlive(&slice) // it is still crucial, GC can free it)
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// return result
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return
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}
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func byteSliceAsInterval16Slice(slice []byte) (result []interval16) {
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if len(slice)%4 != 0 {
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panic("Slice size should be divisible by 4")
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}
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// reference: https://go101.org/article/unsafe.html
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// make a new slice header
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bHeader := (*reflect.SliceHeader)(unsafe.Pointer(&slice))
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rHeader := (*reflect.SliceHeader)(unsafe.Pointer(&result))
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// transfer the data from the given slice to a new variable (our result)
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rHeader.Data = bHeader.Data
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rHeader.Len = bHeader.Len / 4
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rHeader.Cap = bHeader.Cap / 4
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// instantiate result and use KeepAlive so data isn't unmapped.
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runtime.KeepAlive(&slice) // it is still crucial, GC can free it)
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// return result
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return
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}
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// FromBuffer creates a bitmap from its serialized version stored in buffer.
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// It uses CRoaring's frozen bitmap format.
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//
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// The format specification is available here:
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// https://github.com/RoaringBitmap/CRoaring/blob/2c867e9f9c9e2a3a7032791f94c4c7ae3013f6e0/src/roaring.c#L2756-L2783
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//
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// The provided byte array (buf) is expected to be a constant.
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// The function makes the best effort attempt not to copy data.
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// Only little endian is supported. The function will err if it detects a big
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// endian serialized file.
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// You should take care not to modify buff as it will likely result in
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// unexpected program behavior.
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// If said buffer comes from a memory map, it's advisable to give it read
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// only permissions, either at creation or by calling Mprotect from the
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// golang.org/x/sys/unix package.
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//
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// Resulting bitmaps are effectively immutable in the following sense:
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// a copy-on-write marker is used so that when you modify the resulting
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// bitmap, copies of selected data (containers) are made.
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// You should *not* change the copy-on-write status of the resulting
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// bitmaps (SetCopyOnWrite).
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//
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// If buf becomes unavailable, then a bitmap created with
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// FromBuffer would be effectively broken. Furthermore, any
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// bitmap derived from this bitmap (e.g., via Or, And) might
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// also be broken. Thus, before making buf unavailable, you should
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// call CloneCopyOnWriteContainers on all such bitmaps.
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//
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func (rb *Bitmap) FrozenView(buf []byte) error {
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return rb.highlowcontainer.frozenView(buf)
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}
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/* Verbatim specification from CRoaring.
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*
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* FROZEN SERIALIZATION FORMAT DESCRIPTION
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*
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* -- (beginning must be aligned by 32 bytes) --
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* <bitset_data> uint64_t[BITSET_CONTAINER_SIZE_IN_WORDS * num_bitset_containers]
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* <run_data> rle16_t[total number of rle elements in all run containers]
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* <array_data> uint16_t[total number of array elements in all array containers]
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* <keys> uint16_t[num_containers]
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* <counts> uint16_t[num_containers]
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* <typecodes> uint8_t[num_containers]
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* <header> uint32_t
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*
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* <header> is a 4-byte value which is a bit union of FROZEN_COOKIE (15 bits)
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* and the number of containers (17 bits).
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*
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* <counts> stores number of elements for every container.
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* Its meaning depends on container type.
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* For array and bitset containers, this value is the container cardinality minus one.
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* For run container, it is the number of rle_t elements (n_runs).
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*
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* <bitset_data>,<array_data>,<run_data> are flat arrays of elements of
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* all containers of respective type.
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*
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* <*_data> and <keys> are kept close together because they are not accessed
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* during deserilization. This may reduce IO in case of large mmaped bitmaps.
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* All members have their native alignments during deserilization except <header>,
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* which is not guaranteed to be aligned by 4 bytes.
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*/
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const FROZEN_COOKIE = 13766
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var (
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FrozenBitmapInvalidCookie = errors.New("header does not contain the FROZEN_COOKIE")
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FrozenBitmapBigEndian = errors.New("loading big endian frozen bitmaps is not supported")
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FrozenBitmapIncomplete = errors.New("input buffer too small to contain a frozen bitmap")
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FrozenBitmapOverpopulated = errors.New("too many containers")
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FrozenBitmapUnexpectedData = errors.New("spurious data in input")
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FrozenBitmapInvalidTypecode = errors.New("unrecognized typecode")
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FrozenBitmapBufferTooSmall = errors.New("buffer too small")
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)
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func (ra *roaringArray) frozenView(buf []byte) error {
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if len(buf) < 4 {
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return FrozenBitmapIncomplete
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}
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headerBE := binary.BigEndian.Uint32(buf[len(buf)-4:])
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if headerBE & 0x7fff == FROZEN_COOKIE {
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return FrozenBitmapBigEndian
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}
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header := binary.LittleEndian.Uint32(buf[len(buf)-4:])
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buf = buf[:len(buf)-4]
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if header & 0x7fff != FROZEN_COOKIE {
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return FrozenBitmapInvalidCookie
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}
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nCont := int(header >> 15)
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if nCont > (1 << 16) {
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return FrozenBitmapOverpopulated
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}
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// 1 byte per type, 2 bytes per key, 2 bytes per count.
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if len(buf) < 5*nCont {
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return FrozenBitmapIncomplete
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}
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types := buf[len(buf)-nCont:]
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buf = buf[:len(buf)-nCont]
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counts := byteSliceAsUint16Slice(buf[len(buf)-2*nCont:])
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buf = buf[:len(buf)-2*nCont]
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keys := byteSliceAsUint16Slice(buf[len(buf)-2*nCont:])
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buf = buf[:len(buf)-2*nCont]
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nBitmap, nArray, nRun := uint64(0), uint64(0), uint64(0)
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nArrayEl, nRunEl := uint64(0), uint64(0)
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for i, t := range types {
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switch (t) {
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case 1:
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nBitmap++
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case 2:
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nArray++
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nArrayEl += uint64(counts[i])+1
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case 3:
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nRun++
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nRunEl += uint64(counts[i])
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default:
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return FrozenBitmapInvalidTypecode
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}
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}
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if uint64(len(buf)) < (1 << 13)*nBitmap + 4*nRunEl + 2*nArrayEl {
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return FrozenBitmapIncomplete
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}
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bitsetsArena := byteSliceAsUint64Slice(buf[:(1 << 13)*nBitmap])
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buf = buf[(1 << 13)*nBitmap:]
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runsArena := byteSliceAsInterval16Slice(buf[:4*nRunEl])
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buf = buf[4*nRunEl:]
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arraysArena := byteSliceAsUint16Slice(buf[:2*nArrayEl])
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buf = buf[2*nArrayEl:]
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if len(buf) != 0 {
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return FrozenBitmapUnexpectedData
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}
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// TODO: maybe arena_alloc all this.
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containers := make([]container, nCont)
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bitsets := make([]bitmapContainer, nBitmap)
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arrays := make([]arrayContainer, nArray)
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runs := make([]runContainer16, nRun)
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needCOW := make([]bool, nCont)
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iBitset, iArray, iRun := uint64(0), uint64(0), uint64(0)
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for i, t := range types {
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needCOW[i] = true
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switch (t) {
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case 1:
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containers[i] = &bitsets[iBitset]
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bitsets[iBitset].cardinality = int(counts[i])+1
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bitsets[iBitset].bitmap = bitsetsArena[:1024]
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bitsetsArena = bitsetsArena[1024:]
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iBitset++
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case 2:
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containers[i] = &arrays[iArray]
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sz := int(counts[i])+1
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arrays[iArray].content = arraysArena[:sz]
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arraysArena = arraysArena[sz:]
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iArray++
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case 3:
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containers[i] = &runs[iRun]
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runs[iRun].iv = runsArena[:counts[i]]
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runsArena = runsArena[counts[i]:]
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iRun++
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}
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}
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// Not consuming the full input is a bug.
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if iBitset != nBitmap || len(bitsetsArena) != 0 ||
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iArray != nArray || len(arraysArena) != 0 ||
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iRun != nRun || len(runsArena) != 0 {
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panic("we missed something")
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}
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ra.keys = keys
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ra.containers = containers
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ra.needCopyOnWrite = needCOW
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ra.copyOnWrite = true
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return nil
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}
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func (bm *Bitmap) GetFrozenSizeInBytes() uint64 {
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nBits, nArrayEl, nRunEl := uint64(0), uint64(0), uint64(0)
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for _, c := range bm.highlowcontainer.containers {
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switch v := c.(type) {
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case *bitmapContainer:
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nBits++
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case *arrayContainer:
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nArrayEl += uint64(len(v.content))
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case *runContainer16:
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nRunEl += uint64(len(v.iv))
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}
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}
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return 4 + 5*uint64(len(bm.highlowcontainer.containers)) +
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(nBits << 13) + 2*nArrayEl + 4*nRunEl
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}
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func (bm *Bitmap) Freeze() ([]byte, error) {
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sz := bm.GetFrozenSizeInBytes()
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buf := make([]byte, sz)
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_, err := bm.FreezeTo(buf)
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return buf, err
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}
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func (bm *Bitmap) FreezeTo(buf []byte) (int, error) {
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containers := bm.highlowcontainer.containers
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nCont := len(containers)
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nBits, nArrayEl, nRunEl := 0, 0, 0
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for _, c := range containers {
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switch v := c.(type) {
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case *bitmapContainer:
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nBits++
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case *arrayContainer:
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nArrayEl += len(v.content)
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case *runContainer16:
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nRunEl += len(v.iv)
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}
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}
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serialSize := 4 + 5*nCont + (1 << 13)*nBits + 4*nRunEl + 2*nArrayEl
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if len(buf) < serialSize {
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return 0, FrozenBitmapBufferTooSmall
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}
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bitsArena := byteSliceAsUint64Slice(buf[:(1 << 13)*nBits])
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buf = buf[(1 << 13)*nBits:]
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runsArena := byteSliceAsInterval16Slice(buf[:4*nRunEl])
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buf = buf[4*nRunEl:]
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arraysArena := byteSliceAsUint16Slice(buf[:2*nArrayEl])
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buf = buf[2*nArrayEl:]
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keys := byteSliceAsUint16Slice(buf[:2*nCont])
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buf = buf[2*nCont:]
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counts := byteSliceAsUint16Slice(buf[:2*nCont])
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buf = buf[2*nCont:]
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types := buf[:nCont]
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buf = buf[nCont:]
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header := uint32(FROZEN_COOKIE|(nCont << 15))
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binary.LittleEndian.PutUint32(buf[:4], header)
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copy(keys, bm.highlowcontainer.keys[:])
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for i, c := range containers {
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switch v := c.(type) {
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case *bitmapContainer:
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copy(bitsArena, v.bitmap)
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bitsArena = bitsArena[1024:]
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counts[i] = uint16(v.cardinality-1)
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types[i] = 1
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case *arrayContainer:
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copy(arraysArena, v.content)
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arraysArena = arraysArena[len(v.content):]
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elems := len(v.content)
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counts[i] = uint16(elems-1)
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types[i] = 2
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case *runContainer16:
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copy(runsArena, v.iv)
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runs := len(v.iv)
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runsArena = runsArena[runs:]
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counts[i] = uint16(runs)
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types[i] = 3
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}
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}
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return serialSize, nil
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}
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