forgejo/vendor/github.com/RoaringBitmap/roaring/serialization_littleendian.go
2022-01-01 16:26:27 +08:00

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