Struct rusqlite::blob::Blob [−][src]
pub struct Blob<'conn> { /* fields omitted */ }
Expand description
feature = "blob"
Handle to an open BLOB. See
rusqlite::blob
documentation for in-depth discussion.
Implementations
Write buf
to self
starting at write_start
, returning an error if
write_start + buf.len()
is past the end of the blob.
If an error is returned, no data is written.
Note: the blob cannot be resized using this function – that must be
done using SQL (for example, an UPDATE
statement).
Note: This is part of the positional I/O API, and thus takes an absolute
position write to, instead of using the internal position that can be
manipulated by the std::io
traits.
Unlike the similarly named FileExt::write_at
function
(from std::os::unix
), it’s always an error to perform a “short write”.
An alias for write_at
provided for compatibility with the conceptually
equivalent std::os::unix::FileExt::write_all_at
function from libstd:
Read as much as possible from offset
to offset + buf.len()
out of
self
, writing into buf
. On success, returns the number of bytes
written.
If there’s insufficient data in self
, then the returned value will be
less than buf.len()
.
See also Blob::raw_read_at
, which can take an uninitialized buffer,
or Blob::read_at_exact
which returns an error if the entire buf
is
not read.
Note: This is part of the positional I/O API, and thus takes an absolute
position to read from, instead of using the internal position that can
be manipulated by the std::io
traits. Consequently, it does not change
that value either.
Read as much as possible from offset
to offset + buf.len()
out of
self
, writing into buf
. On success, returns the portion of buf
which was initialized by this call.
If there’s insufficient data in self
, then the returned value will be
shorter than buf
.
See also Blob::read_at
, which takes a &mut [u8]
buffer instead of
a slice of MaybeUninit<u8>
.
Note: This is part of the positional I/O API, and thus takes an absolute
position to read from, instead of using the internal position that can
be manipulated by the std::io
traits. Consequently, it does not change
that value either.
Equivalent to Blob::read_at
, but returns a BlobSizeError
if buf
is not fully initialized.
Equivalent to Blob::raw_read_at
, but returns a BlobSizeError
if
buf
is not fully initialized.
Move a BLOB handle to a new row.
Failure
Will return Err
if the underlying SQLite BLOB reopen call fails.
Trait Implementations
Read data from a BLOB incrementally. Will return Ok(0) if the end of the blob has been reached.
Failure
Will return Err
if the underlying SQLite read call fails.
Like read
, except that it reads into a slice of buffers. Read more
can_vector
)Determines if this Read
er has an efficient read_vectored
implementation. Read more
read_initializer
)Determines if this Read
er can work with buffers of uninitialized
memory. Read more
Read all bytes until EOF in this source, placing them into buf
. Read more
Read all bytes until EOF in this source, appending them to buf
. Read more
Read the exact number of bytes required to fill buf
. Read more
Creates a “by reference” adapter for this instance of Read
. Read more
Creates an adapter which will chain this stream with another. Read more
seek_stream_len
)Returns the length of this stream (in bytes). Read more
Write data into a BLOB incrementally. Will return Ok(0)
if the end of
the blob has been reached; consider using Write::write_all(buf)
if you want to get an error if the entirety of the buffer cannot be
written.
This function may only modify the contents of the BLOB; it is not possible to increase the size of a BLOB using this API.
Failure
Will return Err
if the underlying SQLite write call fails.
Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more
can_vector
)Determines if this Write
r has an efficient write_vectored
implementation. Read more
Attempts to write an entire buffer into this writer. Read more
write_all_vectored
)Attempts to write multiple buffers into this writer. Read more
Writes a formatted string into this writer, returning any error encountered. Read more