Struct fixed_buffer::FixedBuf [−][src]
pub struct FixedBuf<const SIZE: usize> { /* fields omitted */ }
Expand description
FixedBuf is a fixed-length byte buffer. You can write bytes to it and then read them back.
It is not a circular buffer. Call shift
periodically to
move unread bytes to the front of the buffer.
Implementations
Makes a new empty buffer with space for SIZE
bytes.
Be careful of stack overflows!
Makes a new empty buffer.
Consumes mem
and uses it as the internal memory array.
Makes a new full buffer containing the bytes in mem
.
Reading the buffer will return the bytes in mem
.
Consumes mem
and uses it as the internal memory array.
Drops the struct and returns its internal array.
Returns the number of unread bytes in the buffer.
Example:
let mut buf: FixedBuf<16> = FixedBuf::new();
assert_eq!(0, buf.len());
buf.write_str("abc");
assert_eq!(3, buf.len());
buf.read_bytes(2);
assert_eq!(1, buf.len());
buf.shift();
assert_eq!(1, buf.len());
buf.read_all();
assert_eq!(0, buf.len());
Returns true if there are unread bytes in the buffer.
Example:
let mut buf: FixedBuf<16> = FixedBuf::new();
assert!(buf.is_empty());
buf.write_str("abc").unwrap();
assert!(!buf.is_empty());
buf.read_all();
assert!(buf.is_empty());
Copies all readable bytes to a string. Includes printable ASCII characters as-is. Converts non-printable characters to strings like “\n” and “\x19”.
Uses
core::ascii::escape_default
(https://doc.rust-lang.org/core/ascii/fn.escape_default.html
internally to escape each byte.
This function is useful for printing byte slices to logs and comparing byte slices in tests.
Example test:
use fixed_buffer::FixedBuf;
let mut buf: FixedBuf<8> = FixedBuf::new();
buf.write_str("abc");
buf.write_str("€");
assert_eq!("abc\\xe2\\x82\\xac", buf.escape_ascii());
Borrows the entire internal memory buffer. This is a low-level function.
Returns the slice of readable bytes in the buffer.
After processing some bytes from the front of the slice,
call read
to consume the bytes.
This is a low-level method.
You probably want to use
std::io::Read::read
or
tokio::io::AsyncReadExt::read
, implemented for FixedBuffer in
fixed_buffer_tokio::AsyncReadExt
.
Reads a single byte from the buffer.
Panics if the buffer is empty.
Reads a single byte from the buffer.
Returns None
if the buffer is empty.
Reads bytes from the buffer.
Panics if the buffer does not contain enough bytes.
Reads bytes from the buffer.
Returns None
if the buffer does not contain num_bytes
bytes.
Reads all the bytes from the buffer.
The buffer becomes empty and subsequent writes can fill the whole buffer.
Reads bytes from the buffer and copies them into dest
.
Returns the number of bytes copied.
Returns 0
when the buffer is empty or dest
is zero-length.
Reads byte from the buffer and copies them into dest
, filling it,
and returns ()
.
Returns None
if the buffer does not contain enough bytes tp fill dest
.
Returns ()
if dest
is zero-length.
Try to parse the buffer contents with f
.
f
must return None
to indicate that the buffer
contains an incomplete data record.
When try_parse
returns None, the caller should add more data to the
buffer and call try_parse
again.
Undoes any reads that f
made to the buffer if it returns None
.
f
should not write to the buffer.
If f
writes to the buffer and then returns None
,
the buffer’s contents will become corrupted.
Example
#[derive(Debug)]
enum ReadError {
BufferFull,
EOF,
TooLong,
NotUtf8,
}
fn parse_record<const SIZE: usize>(buf: &mut FixedBuf<SIZE>)
-> Option<Result<String, ReadError>>
{
let len = buf.try_read_byte()? as usize;
if len > SIZE - 1 {
return Some(Err(ReadError::TooLong));
}
let bytes = buf.try_read_bytes(len)?.to_vec();
Some(String::from_utf8(bytes)
.map_err(|_| ReadError::NotUtf8))
}
let mut buf: FixedBuf<16> = FixedBuf::new();
loop {
// Try reading bytes into the buffer.
match read_input(&mut buf) {
Err(ReadError::EOF) if buf.is_empty() => break,
other => other?,
}
// Try parsing bytes into records.
loop {
if let Some(result) = buf.try_parse(parse_record) {
let record = result?;
process_record(record)?;
} else {
// Stop parsing and try reading more bytes.
break;
}
}
}
Reads from reader
once and writes the data into the buffer.
Returns InvalidData
if there is no empty space in the buffer.
See shift
.
Writes s
into the buffer, after any unread bytes.
Returns Err
if the buffer doesn’t have enough free space at the end
for the whole string.
See shift
.
Example:
let mut buf: FixedBuf<8> = FixedBuf::new();
buf.write_str("123").unwrap();
buf.write_str("456").unwrap();
assert_eq!("123456", buf.escape_ascii());
buf.write_str("78").unwrap();
buf.write_str("9").unwrap_err(); // End of buffer is full.
Tries to write data
into the buffer, after any unread bytes.
Returns Ok(data.len())
if it wrote all of the bytes.
Returns NotEnoughSpaceError
if the buffer doesn’t have enough free space at the end for all of the bytes.
See shift
.
Example:
let mut buf: FixedBuf<8> = FixedBuf::new();
assert_eq!(3, buf.write_bytes("123".as_bytes()).unwrap());
assert_eq!(3, buf.write_bytes("456".as_bytes()).unwrap());
assert_eq!("123456", buf.escape_ascii());
assert_eq!(2, buf.write_bytes("78".as_bytes()).unwrap()); // Fills buffer.
buf.write_bytes("9".as_bytes()).unwrap_err(); // Error, buffer is full.
Returns the writable part of the buffer.
To use this, first modify bytes at the beginning of the slice.
Then call wrote(usize)
to commit those bytes into the buffer and make them available for reading.
Returns an empty slice when the end of the buffer is full.
See shift
.
This is a low-level method.
You probably want to use
std::io::Write::write
or
tokio::io::AsyncWriteExt::write
,
implemented for FixedBuffer in
fixed_buffer_tokio::AsyncWriteExt
.
Example:
let mut buf: FixedBuf<8> = FixedBuf::new();
buf.writable()[0] = 'a' as u8;
buf.writable()[1] = 'b' as u8;
buf.writable()[2] = 'c' as u8;
buf.wrote(3);
assert_eq!("abc", buf.escape_ascii());
Commits bytes into the buffer.
Call this after writing to the front of the
writable
slice.
This is a low-level method.
Panics when there is not num_bytes
free at the end of the buffer.
See writable()
.
Recovers buffer space.
The buffer is not circular. After you read bytes, the space at the beginning of the buffer is unused. Call this method to move unread data to the beginning of the buffer and recover the space. This makes the free space available for writes, which go at the end of the buffer.
This is a low-level function.
Use read_frame
instead.
Calls deframer_fn
to check if the buffer contains a complete frame.
Consumes the frame bytes from the buffer
and returns the range of the frame’s contents in the internal memory.
Use mem
to immutably borrow the internal memory and
construct the slice with &buf.mem()[range]
.
This is necessary because deframe
borrows self
mutably but
read_frame
needs to borrow it immutably and return a slice.
Returns None
if the buffer is empty or contains an incomplete frame.
Returns InvalidData
when deframer_fn
returns an error.
Reads from reader
into the buffer.
After each read, calls deframer_fn
to check if the buffer now contains a complete frame.
Consumes the frame bytes from the buffer
and returns a slice with the frame contents.
Returns None
when reader
reaches EOF and the buffer is empty.
Returns UnexpectedEof
when reader
reaches EOF and the buffer contains an incomplete frame.
Returns InvalidData
when deframer_fn
returns an error or the buffer fills up.
Calls shift
before reading.
Provided deframer functions:
Example
let mut buf: FixedBuf<32> = FixedBuf::new();
let mut input = std::io::Cursor::new(b"aaa\r\nbbb\n\nccc\n");
loop {
if let Some(line) =
buf.read_frame(&mut input, deframe_line).unwrap() {
println!("{}", escape_ascii(line));
} else {
// EOF.
break;
}
}
// Prints:
// aaa
// bbb
//
// ccc
Deframer Function deframe_fn
Checks if data
contains an entire frame.
Never panics.
Returns Err(MalformedInputError)
if data
contains a malformed frame.
Returns Ok(None)
if data
contains an incomplete frame.
The caller will read more data and call deframe
again.
Returns Ok((range, len))
when data
contains a complete well-formed
frame of length len
and contents &data[range]
.
A frame is a sequence of bytes containing a payload and metadata prefix or suffix bytes. The metadata define where the payload starts and ends. Popular frame protocols include line-delimiting (CSV), hexadecimal length prefix (HTTP chunked transfer encoding), and binary length prefix (TLS).
If the caller removes len
bytes from the front of data
, then
data
should start with the next frame, ready to call deframe
again.
A line-delimited deframer returns range
so that &data[range]
contains the entire line without the
final b'\n'
or b"\r\n"
.
It returns len
that counts the bytes of
the entire line and the final b'\n'
or b"\r\n"
.
Example
A CRLF-terminated line deframer:
assert_eq!(Ok(None), deframe_crlf(b""));
assert_eq!(Ok(None), deframe_crlf(b"abc"));
assert_eq!(Ok(None), deframe_crlf(b"abc\r"));
assert_eq!(Ok(None), deframe_crlf(b"abc\n"));
assert_eq!(Ok(Some((0..3, 5))), deframe_crlf(b"abc\r\n"));
assert_eq!(Ok(Some((0..3, 5))), deframe_crlf(b"abc\r\nX"));
Trait Implementations
This method returns an ordering between self
and other
values if one exists. Read more
This method tests less than (for self
and other
) and is used by the <
operator. Read more
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more
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 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
read_buf
)Pull some bytes from this source into the specified buffer. Read more
read_buf
)Read the exact number of bytes required to fill buf
. Read more
Creates a “by reference” adaptor for this instance of Read
. Read more
Creates an adapter which will chain this stream with another. Read more
Write a buffer into this writer, returning how many bytes were written. Read more
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
Auto Trait Implementations
impl<const SIZE: usize> RefUnwindSafe for FixedBuf<SIZE>
Blanket Implementations
Mutably borrows from an owned value. Read more