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Use u8 slice instead of Bytes in function argument.

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Bytes is handy, but in decode_pg_control's case it's just complicating
things. Also, pass ControlFileData by ref to encode_pg_control().
This commit is contained in:
Heikki Linnakangas
2021-06-04 23:05:20 +03:00
parent d18cc8a3a8
commit 8147aa7e93
2 changed files with 27 additions and 16 deletions
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34
postgres_ffi/src/controlfile_utils.rs
View File

@@ -25,28 +25,36 @@
//!
use crate::{ControlFileData, PG_CONTROLFILEDATA_OFFSETOF_CRC, PG_CONTROL_FILE_SIZE};
use bytes::{Buf, Bytes, BytesMut};
use anyhow::{bail, Result};
use bytes::{Bytes, BytesMut};
// sizeof(ControlFileData)
const SIZEOF_CONTROLDATA: usize = std::mem::size_of::<ControlFileData>();
// offsetof(ControlFileData, crc)
const OFFSETOF_CRC: usize = PG_CONTROLFILEDATA_OFFSETOF_CRC as usize;
pub fn decode_pg_control(mut buf: Bytes) -> Result<ControlFileData, anyhow::Error> {
let mut b: [u8; SIZEOF_CONTROLDATA] = [0u8; SIZEOF_CONTROLDATA];
buf.copy_to_slice(&mut b);
///
/// Interpret a slice of bytes as a Postgres control file.
///
pub fn decode_pg_control(buf: &[u8]) -> Result<ControlFileData> {
// Check that the slice has the expected size. The control file is
// padded with zeros up to a 512 byte sector size, so accept a
// larger size too, so that the caller can just the whole file
// contents without knowing the exact size of the struct.
if buf.len() < SIZEOF_CONTROLDATA {
bail!("control file is too short");
}
let controlfile: ControlFileData;
// TODO: verify CRC
let mut data_without_crc: [u8; OFFSETOF_CRC] = [0u8; OFFSETOF_CRC];
data_without_crc.copy_from_slice(&b[0..OFFSETOF_CRC]);
let expectedcrc = crc32c::crc32c(&data_without_crc);
let mut b: [u8; SIZEOF_CONTROLDATA] = [0u8; SIZEOF_CONTROLDATA];
b.copy_from_slice(&buf[0..SIZEOF_CONTROLDATA]);
let expectedcrc = crc32c::crc32c(&b[0..OFFSETOF_CRC]);
controlfile = unsafe { std::mem::transmute::<[u8; SIZEOF_CONTROLDATA], ControlFileData>(b) };
if expectedcrc != controlfile.crc {
anyhow::bail!(
bail!(
"invalid CRC in control file: expected {:08X}, was {:08X}",
expectedcrc,
controlfile.crc
@@ -56,10 +64,14 @@ pub fn decode_pg_control(mut buf: Bytes) -> Result<ControlFileData, anyhow::Erro
Ok(controlfile)
}
pub fn encode_pg_control(controlfile: ControlFileData) -> Bytes {
///
/// Convert a struct representing a Postgres control file into raw bytes.
///
/// The CRC is recomputed to match the contents of the fields.
pub fn encode_pg_control(controlfile: &ControlFileData) -> Bytes {
let b: [u8; SIZEOF_CONTROLDATA];
b = unsafe { std::mem::transmute::<ControlFileData, [u8; SIZEOF_CONTROLDATA]>(controlfile) };
b = unsafe { std::mem::transmute::<ControlFileData, [u8; SIZEOF_CONTROLDATA]>(*controlfile) };
// Recompute the CRC
let mut data_without_crc: [u8; OFFSETOF_CRC] = [0u8; OFFSETOF_CRC];