arrow_avro/reader/
cursor.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
3// distributed with this work for additional information
4// regarding copyright ownership.  The ASF licenses this file
5// to you under the Apache License, Version 2.0 (the
6// "License"); you may not use this file except in compliance
7// with the License.  You may obtain a copy of the License at
8//
9//   http://www.apache.org/licenses/LICENSE-2.0
10//
11// Unless required by applicable law or agreed to in writing,
12// software distributed under the License is distributed on an
13// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14// KIND, either express or implied.  See the License for the
15// specific language governing permissions and limitations
16// under the License.
17
18use crate::errors::AvroError;
19use crate::reader::vlq::read_varint;
20
21/// A wrapper around a byte slice, providing low-level decoding for Avro
22///
23/// <https://avro.apache.org/docs/1.11.1/specification/#encodings>
24#[derive(Debug)]
25pub(crate) struct AvroCursor<'a> {
26    buf: &'a [u8],
27    start_len: usize,
28}
29
30impl<'a> AvroCursor<'a> {
31    pub(crate) fn new(buf: &'a [u8]) -> Self {
32        Self {
33            buf,
34            start_len: buf.len(),
35        }
36    }
37
38    /// Returns the current cursor position
39    #[inline]
40    pub(crate) fn position(&self) -> usize {
41        self.start_len - self.buf.len()
42    }
43
44    /// Read a single `u8`
45    #[inline]
46    pub(crate) fn get_u8(&mut self) -> Result<u8, AvroError> {
47        match self.buf.first().copied() {
48            Some(x) => {
49                self.buf = &self.buf[1..];
50                Ok(x)
51            }
52            None => Err(AvroError::EOF("Unexpected EOF".to_string())),
53        }
54    }
55
56    #[inline]
57    pub(crate) fn get_bool(&mut self) -> Result<bool, AvroError> {
58        Ok(self.get_u8()? != 0)
59    }
60
61    pub(crate) fn read_vlq(&mut self) -> Result<u64, AvroError> {
62        let (val, offset) =
63            read_varint(self.buf).ok_or_else(|| AvroError::ParseError("bad varint".to_string()))?;
64        self.buf = &self.buf[offset..];
65        Ok(val)
66    }
67
68    #[inline]
69    pub(crate) fn get_int(&mut self) -> Result<i32, AvroError> {
70        let varint = self.read_vlq()?;
71        let val: u32 = varint
72            .try_into()
73            .map_err(|_| AvroError::ParseError("varint overflow".to_string()))?;
74        Ok((val >> 1) as i32 ^ -((val & 1) as i32))
75    }
76
77    #[inline]
78    pub(crate) fn get_long(&mut self) -> Result<i64, AvroError> {
79        let val = self.read_vlq()?;
80        Ok((val >> 1) as i64 ^ -((val & 1) as i64))
81    }
82
83    pub(crate) fn get_bytes(&mut self) -> Result<&'a [u8], AvroError> {
84        let len: usize = self
85            .get_long()?
86            .try_into()
87            .map_err(|_| AvroError::ParseError("offset overflow reading avro bytes".to_string()))?;
88
89        if self.buf.len() < len {
90            return Err(AvroError::EOF("Unexpected EOF reading bytes".to_string()));
91        }
92        let ret = &self.buf[..len];
93        self.buf = &self.buf[len..];
94        Ok(ret)
95    }
96
97    #[inline]
98    pub(crate) fn get_float(&mut self) -> Result<f32, AvroError> {
99        if self.buf.len() < 4 {
100            return Err(AvroError::EOF("Unexpected EOF reading float".to_string()));
101        }
102        let ret = f32::from_le_bytes(self.buf[..4].try_into().unwrap());
103        self.buf = &self.buf[4..];
104        Ok(ret)
105    }
106
107    #[inline]
108    pub(crate) fn get_double(&mut self) -> Result<f64, AvroError> {
109        if self.buf.len() < 8 {
110            return Err(AvroError::EOF("Unexpected EOF reading double".to_string()));
111        }
112        let ret = f64::from_le_bytes(self.buf[..8].try_into().unwrap());
113        self.buf = &self.buf[8..];
114        Ok(ret)
115    }
116
117    /// Read exactly `n` bytes from the buffer (e.g. for Avro `fixed`).
118    pub(crate) fn get_fixed(&mut self, n: usize) -> Result<&'a [u8], AvroError> {
119        if self.buf.len() < n {
120            return Err(AvroError::EOF("Unexpected EOF reading fixed".to_string()));
121        }
122        let ret = &self.buf[..n];
123        self.buf = &self.buf[n..];
124        Ok(ret)
125    }
126}
arrow_avro/reader/cursor.rs

arrow_avro/reader/
cursor.rs
