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c-possum.go
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c-possum.go
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package possumC
/*
// Not sure how to statically just this library, so for now it's preferred to use CGO_LDFLAGS to do
// your own thing.
//#cgo LDFLAGS: -lpossum
#include "possum.h"
*/
import "C"
import (
"errors"
"fmt"
"github.com/anacrolix/generics"
"io/fs"
"math"
"runtime"
"time"
"unsafe"
)
var NoSuchKey = Error{
pec: C.NoSuchKey,
}
type Error struct {
pec C.PossumError
displayGoesHere string
}
const cErrorEnumNoSuchKey = C.NoSuchKey
func (me Error) Is(err error) bool {
if err == NoSuchKey || err == fs.ErrNotExist {
return me.pec == cErrorEnumNoSuchKey
}
return false
}
func (me Error) Error() string {
return fmt.Sprintf("possum error code %v", me.pec)
}
func mapError(err C.PossumError) error {
if err == C.NoError {
return nil
}
return Error{pec: err}
}
type Stat = C.PossumStat
func (me Stat) LastUsed() time.Time {
ts := me.last_used
return time.Unix(int64(ts.secs), int64(ts.nanos))
}
func (me Stat) Size() int64 {
return int64(me.size)
}
type Handle = C.Handle
func NewHandle(dir string) *Handle {
cDir := C.CString(dir)
defer C.free(unsafe.Pointer(cDir))
handle := C.possum_new(cDir)
return handle
}
func DropHandle(handle *Handle) {
C.possum_drop(handle)
}
func SingleDelete(handle *Handle, key string) (opt generics.Option[Stat], err error) {
pe := C.possum_single_delete(handle, BufFromString(key), &opt.Value)
switch pe {
case C.NoError:
opt.Ok = true
case C.NoSuchKey:
default:
err = mapError(pe)
}
return
}
func SingleStat(handle *Handle, key string) (opt generics.Option[Stat]) {
opt.Ok = bool(C.possum_single_stat(
handle,
BufFromString(key),
&opt.Value,
))
return
}
func WriteSingleBuf(handle *Handle, key string, buf []byte) (written uint, err error) {
written = uint(C.possum_single_write_buf(
handle,
BufFromString(key),
BufFromBytes(buf),
))
if written == math.MaxUint {
err = errors.New("unknown possum error")
}
return
}
func goListItems(items *C.PossumItem, itemsLen C.size_t) (goItems []Item) {
itemsSlice := unsafe.Slice(items, uint(itemsLen))
goItems = make([]Item, itemsLen)
for i, from := range itemsSlice {
to := &goItems[i]
to.Key = C.GoStringN(
(*C.char)(from.key.ptr),
C.int(from.key.size),
)
C.free(unsafe.Pointer(from.key.ptr))
to.Stat = from.stat
}
C.free(unsafe.Pointer(items))
return
}
func HandleListItems(handle *Handle, prefix string) (items []Item, err error) {
var cItems *C.PossumItem
var itemsLen C.size_t
err = mapError(C.possum_list_items(
handle,
BufFromString(prefix),
&cItems, &itemsLen))
if err != nil {
return
}
items = goListItems(cItems, itemsLen)
return
}
func SingleReadAt(handle *Handle, key string, buf []byte, offset uint64) (n int, err error) {
var pinner runtime.Pinner
defer pinner.Unpin()
pBuf := BufFromBytes(buf)
pinner.Pin(pBuf.ptr)
err = mapError(C.possum_single_read_at(
handle,
BufFromString(key),
&pBuf,
C.uint64_t(offset),
))
n = int(pBuf.size)
return
}
type Reader = *C.PossumReader
func NewReader(handle *Handle) (r Reader, err error) {
err = mapError(C.possum_reader_new(handle, &r))
return
}
func BufFromString(s string) C.PossumBuf {
return C.PossumBuf{
(*C.char)(unsafe.Pointer(unsafe.StringData(s))),
C.size_t(len(s)),
}
}
func BufFromBytes(b []byte) C.PossumBuf {
return C.PossumBuf{
(*C.char)(unsafe.Pointer(unsafe.SliceData(b))),
C.size_t(len(b)),
}
}
func ReaderAdd(r Reader, key string) (v Value, err error) {
err = mapError(C.possum_reader_add(r, BufFromString(key), &v))
return
}
func ReaderBegin(r Reader) error {
return mapError(C.possum_reader_begin(r))
}
func ReaderEnd(r Reader) {
C.possum_reader_end(r)
}
func ReaderListItems(r Reader, prefix string) (items []Item, err error) {
var cItems *C.PossumItem
var itemsLen C.size_t
err = mapError(C.possum_reader_list_items(r, BufFromString(prefix), &cItems, &itemsLen))
if err != nil {
return
}
items = goListItems(cItems, itemsLen)
return
}
type Value = *C.PossumValue
func ValueReadAt(v Value, buf []byte, offset int64) (n int, err error) {
pBuf := BufFromBytes(buf)
var pin runtime.Pinner
defer pin.Unpin()
pin.Pin(pBuf.ptr)
err = mapError(C.possum_value_read_at(v, &pBuf, C.uint64_t(offset)))
n = int(pBuf.size)
return
}
func ValueStat(v Value) (ret Stat) {
C.possum_value_stat(v, &ret)
return
}
type Item struct {
Key string
Stat
}
type Limits struct {
MaxValueLengthSum generics.Option[uint64]
DisableHolePunching bool
}
func CleanupSnapshots(h *Handle) error {
return mapError(C.possum_cleanup_snapshots(h))
}
func SetInstanceLimits(h *Handle, limits Limits) error {
var cLimits C.PossumLimits
cLimits.max_value_length_sum = C.uint64_t(limits.MaxValueLengthSum.UnwrapOr(math.MaxUint64))
cLimits.disable_hole_punching = C.bool(limits.DisableHolePunching)
return mapError(C.possum_set_instance_limits(h, &cLimits))
}
type Writer = *C.PossumWriter
func NewWriter(h *Handle) Writer {
return C.possum_new_writer(h)
}
type ValueWriter = *C.PossumValueWriter
func StartNewValue(w Writer) (vw ValueWriter, err error) {
err = mapError(C.possum_start_new_value(w, &vw))
return
}
func ValueWriterFd(vw ValueWriter) int {
return int(C.possum_value_writer_fd(vw))
}
func StageWrite(w Writer, key []byte, vw ValueWriter) error {
return mapError(C.possum_writer_stage(w, BufFromBytes(key), vw))
}
func CommitWriter(w Writer) error {
return mapError(C.possum_writer_commit(w))
}