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package vfs
import (
"bytes"
"context"
_ "embed"
"encoding/binary"
"strconv"
"github.com/tetratelabs/wazero/api"
"github.com/ncruces/go-sqlite3/internal/util"
"github.com/ncruces/go-sqlite3/util/sql3util"
)
func cksmWrapFile(name *Filename, flags OpenFlag, file File) File {
// Checksum only main databases and WALs.
if flags&(OPEN_MAIN_DB|OPEN_WAL) == 0 {
return file
}
cksm := cksmFile{File: file}
if flags&OPEN_WAL != 0 {
main, _ := name.DatabaseFile().(cksmFile)
cksm.cksmFlags = main.cksmFlags
} else {
cksm.cksmFlags = new(cksmFlags)
cksm.isDB = true
}
return cksm
}
type cksmFile struct {
File
*cksmFlags
isDB bool
}
type cksmFlags struct {
computeCksm bool
verifyCksm bool
inCkpt bool
pageSize int
}
func (c cksmFile) ReadAt(p []byte, off int64) (n int, err error) {
n, err = c.File.ReadAt(p, off)
// SQLite is reading the header of a database file.
if c.isDB && off == 0 && len(p) >= 100 &&
bytes.HasPrefix(p, []byte("SQLite format 3\000")) {
c.init(p)
}
// Verify checksums.
if c.verifyCksm && !c.inCkpt && len(p) == c.pageSize {
cksm1 := cksmCompute(p[:len(p)-8])
cksm2 := *(*[8]byte)(p[len(p)-8:])
if cksm1 != cksm2 {
return 0, _IOERR_DATA
}
}
return n, err
}
func (c cksmFile) WriteAt(p []byte, off int64) (n int, err error) {
// SQLite is writing the first page of a database file.
if c.isDB && off == 0 && len(p) >= 100 &&
bytes.HasPrefix(p, []byte("SQLite format 3\000")) {
c.init(p)
}
// Compute checksums.
if c.computeCksm && !c.inCkpt && len(p) == c.pageSize {
*(*[8]byte)(p[len(p)-8:]) = cksmCompute(p[:len(p)-8])
}
return c.File.WriteAt(p, off)
}
func (c cksmFile) Pragma(name string, value string) (string, error) {
switch name {
case "checksum_verification":
b, ok := sql3util.ParseBool(value)
if ok {
c.verifyCksm = b && c.computeCksm
}
if !c.verifyCksm {
return "0", nil
}
return "1", nil
case "page_size":
if c.computeCksm {
// Do not allow page size changes on a checksum database.
return strconv.Itoa(c.pageSize), nil
}
}
return "", _NOTFOUND
}
func (c cksmFile) DeviceCharacteristics() DeviceCharacteristic {
ret := c.File.DeviceCharacteristics()
if c.verifyCksm {
ret &^= IOCAP_SUBPAGE_READ
}
return ret
}
func (c cksmFile) fileControl(ctx context.Context, mod api.Module, op _FcntlOpcode, pArg ptr_t) _ErrorCode {
switch op {
case _FCNTL_CKPT_START:
c.inCkpt = true
case _FCNTL_CKPT_DONE:
c.inCkpt = false
}
if rc := vfsFileControlImpl(ctx, mod, c, op, pArg); rc != _NOTFOUND {
return rc
}
return vfsFileControlImpl(ctx, mod, c.File, op, pArg)
}
func (f *cksmFlags) init(header []byte) {
f.pageSize = 256 * int(binary.LittleEndian.Uint16(header[16:18]))
if r := header[20] == 8; r != f.computeCksm {
f.computeCksm = r
f.verifyCksm = r
}
}
func cksmCompute(a []byte) (cksm [8]byte) {
var s1, s2 uint32
for len(a) >= 8 {
s1 += binary.LittleEndian.Uint32(a[0:4]) + s2
s2 += binary.LittleEndian.Uint32(a[4:8]) + s1
a = a[8:]
}
if len(a) != 0 {
panic(util.AssertErr())
}
binary.LittleEndian.PutUint32(cksm[0:4], s1)
binary.LittleEndian.PutUint32(cksm[4:8], s2)
return
}
func (c cksmFile) SharedMemory() SharedMemory {
if f, ok := c.File.(FileSharedMemory); ok {
return f.SharedMemory()
}
return nil
}
func (c cksmFile) Unwrap() File {
return c.File
}
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