GoToSocial/vendor/github.com/ncruces/go-sqlite3/blob.go

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package sqlite3
import (
"io"
"github.com/ncruces/go-sqlite3/internal/util"
)
// ZeroBlob represents a zero-filled, length n BLOB
// that can be used as an argument to
// [database/sql.DB.Exec] and similar methods.
type ZeroBlob int64
// Blob is an handle to an open BLOB.
//
// It implements [io.ReadWriteSeeker] for incremental BLOB I/O.
//
// https://sqlite.org/c3ref/blob.html
type Blob struct {
c *Conn
bytes int64
offset int64
handle uint32
}
var _ io.ReadWriteSeeker = &Blob{}
// OpenBlob opens a BLOB for incremental I/O.
//
// https://sqlite.org/c3ref/blob_open.html
func (c *Conn) OpenBlob(db, table, column string, row int64, write bool) (*Blob, error) {
c.checkInterrupt()
defer c.arena.mark()()
blobPtr := c.arena.new(ptrlen)
dbPtr := c.arena.string(db)
tablePtr := c.arena.string(table)
columnPtr := c.arena.string(column)
var flags uint64
if write {
flags = 1
}
r := c.call("sqlite3_blob_open", uint64(c.handle),
uint64(dbPtr), uint64(tablePtr), uint64(columnPtr),
uint64(row), flags, uint64(blobPtr))
if err := c.error(r); err != nil {
return nil, err
}
blob := Blob{c: c}
blob.handle = util.ReadUint32(c.mod, blobPtr)
blob.bytes = int64(c.call("sqlite3_blob_bytes", uint64(blob.handle)))
return &blob, nil
}
// Close closes a BLOB handle.
//
// It is safe to close a nil, zero or closed Blob.
//
// https://sqlite.org/c3ref/blob_close.html
func (b *Blob) Close() error {
if b == nil || b.handle == 0 {
return nil
}
r := b.c.call("sqlite3_blob_close", uint64(b.handle))
b.handle = 0
return b.c.error(r)
}
// Size returns the size of the BLOB in bytes.
//
// https://sqlite.org/c3ref/blob_bytes.html
func (b *Blob) Size() int64 {
return b.bytes
}
// Read implements the [io.Reader] interface.
//
// https://sqlite.org/c3ref/blob_read.html
func (b *Blob) Read(p []byte) (n int, err error) {
if b.offset >= b.bytes {
return 0, io.EOF
}
avail := b.bytes - b.offset
want := int64(len(p))
if want > avail {
want = avail
}
defer b.c.arena.mark()()
ptr := b.c.arena.new(uint64(want))
r := b.c.call("sqlite3_blob_read", uint64(b.handle),
uint64(ptr), uint64(want), uint64(b.offset))
err = b.c.error(r)
if err != nil {
return 0, err
}
b.offset += want
if b.offset >= b.bytes {
err = io.EOF
}
copy(p, util.View(b.c.mod, ptr, uint64(want)))
return int(want), err
}
// WriteTo implements the [io.WriterTo] interface.
//
// https://sqlite.org/c3ref/blob_read.html
func (b *Blob) WriteTo(w io.Writer) (n int64, err error) {
if b.offset >= b.bytes {
return 0, nil
}
want := int64(1024 * 1024)
avail := b.bytes - b.offset
if want > avail {
want = avail
}
defer b.c.arena.mark()()
ptr := b.c.arena.new(uint64(want))
for want > 0 {
r := b.c.call("sqlite3_blob_read", uint64(b.handle),
uint64(ptr), uint64(want), uint64(b.offset))
err = b.c.error(r)
if err != nil {
return n, err
}
mem := util.View(b.c.mod, ptr, uint64(want))
m, err := w.Write(mem[:want])
b.offset += int64(m)
n += int64(m)
if err != nil {
return n, err
}
if int64(m) != want {
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// notest // Write misbehaving
return n, io.ErrShortWrite
}
avail = b.bytes - b.offset
if want > avail {
want = avail
}
}
return n, nil
}
// Write implements the [io.Writer] interface.
//
// https://sqlite.org/c3ref/blob_write.html
func (b *Blob) Write(p []byte) (n int, err error) {
defer b.c.arena.mark()()
ptr := b.c.arena.bytes(p)
r := b.c.call("sqlite3_blob_write", uint64(b.handle),
uint64(ptr), uint64(len(p)), uint64(b.offset))
err = b.c.error(r)
if err != nil {
return 0, err
}
b.offset += int64(len(p))
return len(p), nil
}
// ReadFrom implements the [io.ReaderFrom] interface.
//
// https://sqlite.org/c3ref/blob_write.html
func (b *Blob) ReadFrom(r io.Reader) (n int64, err error) {
want := int64(1024 * 1024)
avail := b.bytes - b.offset
if l, ok := r.(*io.LimitedReader); ok && want > l.N {
want = l.N
}
if want > avail {
want = avail
}
if want < 1 {
want = 1
}
defer b.c.arena.mark()()
ptr := b.c.arena.new(uint64(want))
for {
mem := util.View(b.c.mod, ptr, uint64(want))
m, err := r.Read(mem[:want])
if m > 0 {
r := b.c.call("sqlite3_blob_write", uint64(b.handle),
uint64(ptr), uint64(m), uint64(b.offset))
err := b.c.error(r)
if err != nil {
return n, err
}
b.offset += int64(m)
n += int64(m)
}
if err == io.EOF {
return n, nil
}
if err != nil {
return n, err
}
avail = b.bytes - b.offset
if want > avail {
want = avail
}
if want < 1 {
want = 1
}
}
}
// Seek implements the [io.Seeker] interface.
func (b *Blob) Seek(offset int64, whence int) (int64, error) {
switch whence {
default:
return 0, util.WhenceErr
case io.SeekStart:
break
case io.SeekCurrent:
offset += b.offset
case io.SeekEnd:
offset += b.bytes
}
if offset < 0 {
return 0, util.OffsetErr
}
b.offset = offset
return offset, nil
}
// Reopen moves a BLOB handle to a new row of the same database table.
//
// https://sqlite.org/c3ref/blob_reopen.html
func (b *Blob) Reopen(row int64) error {
err := b.c.error(b.c.call("sqlite3_blob_reopen", uint64(b.handle), uint64(row)))
b.bytes = int64(b.c.call("sqlite3_blob_bytes", uint64(b.handle)))
b.offset = 0
return err
}