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package vfs
import (
"bytes"
"context"
_ "embed"
"encoding/binary"
"github.com/tetratelabs/wazero/api"
"github.com/ncruces/go-sqlite3/internal/util"
"github.com/ncruces/go-sqlite3/util/sql3util"
)
func cksmWrapFile(file File, flags OpenFlag) File {
// Checksum only main databases.
if flags&OPEN_MAIN_DB == 0 {
return file
}
return &cksmFile{File: file}
}
type cksmFile struct {
File
verifyCksm bool
computeCksm bool
}
func (c *cksmFile) ReadAt(p []byte, off int64) (n int, err error) {
n, err = c.File.ReadAt(p, off)
p = p[:n]
if isHeader(p, off) {
c.init((*[100]byte)(p))
}
// Verify checksums.
if c.verifyCksm && sql3util.ValidPageSize(len(p)) {
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) {
if isHeader(p, off) {
c.init((*[100]byte)(p))
}
// Compute checksums.
if c.computeCksm && sql3util.ValidPageSize(len(p)) {
*(*[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 && value != "" {
// Do not allow page size changes on a checksum database.
return "", 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 {
if op == _FCNTL_PRAGMA {
rc := vfsFileControlImpl(ctx, mod, c, op, pArg)
if rc != _NOTFOUND {
return rc
}
}
return vfsFileControlImpl(ctx, mod, c.File, op, pArg)
}
func (c *cksmFile) init(header *[100]byte) {
if r := header[20] == 8; r != c.computeCksm {
c.computeCksm = r
c.verifyCksm = r
}
}
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
}
func isHeader(p []byte, off int64) bool {
return off == 0 && len(p) >= 100 && bytes.HasPrefix(p, []byte("SQLite format 3\000"))
}
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
}
|
