arrow_cast/
base64.rs

1// Licensed to the Apache Software Foundation (ASF) under one
2// or more contributor license agreements.  See the NOTICE file
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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
18//! Functions for converting data in [`GenericBinaryArray`] such as [`StringArray`] to/from base64 encoded strings
19//!
20//! [`StringArray`]: arrow_array::StringArray
21
22use arrow_array::{Array, GenericBinaryArray, GenericStringArray, OffsetSizeTrait};
23use arrow_buffer::{Buffer, OffsetBuffer};
24use arrow_schema::ArrowError;
25use base64::encoded_len;
26use base64::engine::Config;
27
28pub use base64::prelude::*;
29
30/// Base64 encode each element of `array` with the provided [`Engine`]
31///
32/// # Panics
33///
34/// Panics if the `Engine` emits output that is not valid UTF-8. A correct
35/// `Engine` never does, but it is a safe trait so a misbehaving impl could;
36/// validating keeps the returned [`GenericStringArray`] sound (#10284).
37pub fn b64_encode<E: Engine, O: OffsetSizeTrait>(
38    engine: &E,
39    array: &GenericBinaryArray<O>,
40) -> GenericStringArray<O> {
41    let lengths = array.offsets().windows(2).map(|w| {
42        let len = w[1].as_usize() - w[0].as_usize();
43        encoded_len(len, engine.config().encode_padding()).unwrap()
44    });
45    let offsets = OffsetBuffer::<O>::from_lengths(lengths);
46    let buffer_len = offsets.last().unwrap().as_usize();
47    let mut buffer = vec![0_u8; buffer_len];
48    let mut offset = 0;
49
50    for i in 0..array.len() {
51        let len = engine
52            .encode_slice(array.value(i), &mut buffer[offset..])
53            .unwrap();
54        offset += len;
55    }
56    assert_eq!(offset, buffer_len);
57
58    // `try_new` validates UTF-8 instead of trusting the (safe-trait) Engine.
59    GenericStringArray::try_new(offsets, Buffer::from_vec(buffer), array.nulls().cloned())
60        .expect("Engine produced invalid UTF-8")
61}
62
63/// Base64 decode each element of `array` with the provided [`Engine`]
64pub fn b64_decode<E: Engine, O: OffsetSizeTrait>(
65    engine: &E,
66    array: &GenericBinaryArray<O>,
67) -> Result<GenericBinaryArray<O>, ArrowError> {
68    let estimated_len = array.values().len(); // This is an overestimate
69    let mut buffer = vec![0; estimated_len];
70
71    let mut offsets = Vec::with_capacity(array.len() + 1);
72    offsets.push(O::usize_as(0));
73    let mut offset = 0;
74
75    for v in array.iter() {
76        if let Some(v) = v {
77            let len = engine.decode_slice(v, &mut buffer[offset..]).unwrap();
78            // This cannot overflow as `len` is less than `v.len()` and `a` is valid
79            offset += len;
80        }
81        offsets.push(O::usize_as(offset));
82    }
83
84    // Safety: offsets monotonically increasing by construction
85    let offsets = unsafe { OffsetBuffer::new_unchecked(offsets.into()) };
86
87    GenericBinaryArray::try_new(offsets, Buffer::from_vec(buffer), array.nulls().cloned())
88}
89
90#[cfg(test)]
91mod tests {
92    use super::*;
93    use arrow_array::BinaryArray;
94    use rand::{RngExt, rng};
95
96    fn test_engine<E: Engine>(e: &E, a: &BinaryArray) {
97        let encoded = b64_encode(e, a);
98        encoded.to_data().validate_full().unwrap();
99
100        let to_decode = encoded.into();
101        let decoded = b64_decode(e, &to_decode).unwrap();
102        decoded.to_data().validate_full().unwrap();
103
104        assert_eq!(&decoded, a);
105    }
106
107    #[test]
108    #[cfg_attr(miri, ignore)] // Takes too long
109    fn test_b64() {
110        let mut rng = rng();
111        let len = rng.random_range(1024..1050);
112        let data: BinaryArray = (0..len)
113            .map(|_| {
114                let len = rng.random_range(0..16);
115                Some((0..len).map(|_| rng.random::<u8>()).collect::<Vec<u8>>())
116            })
117            .collect();
118
119        test_engine(&BASE64_STANDARD, &data);
120        test_engine(&BASE64_STANDARD_NO_PAD, &data);
121    }
122
123    /// Safe-Rust `Engine` that writes invalid UTF-8 into the encode buffer
124    /// (#10284). `b64_encode` must reject it rather than build an unsound
125    /// `StringArray`.
126    struct EvilEngine;
127
128    impl Engine for EvilEngine {
129        type Config = <base64::engine::GeneralPurpose as Engine>::Config;
130        type DecodeEstimate = <base64::engine::GeneralPurpose as Engine>::DecodeEstimate;
131
132        fn internal_encode(&self, input: &[u8], output: &mut [u8]) -> usize {
133            BASE64_STANDARD.internal_encode(input, output)
134        }
135        fn internal_decoded_len_estimate(&self, input_len: usize) -> Self::DecodeEstimate {
136            BASE64_STANDARD.internal_decoded_len_estimate(input_len)
137        }
138        fn internal_decode(
139            &self,
140            input: &[u8],
141            output: &mut [u8],
142            estimate: Self::DecodeEstimate,
143        ) -> Result<base64::engine::DecodeMetadata, base64::DecodeSliceError> {
144            BASE64_STANDARD.internal_decode(input, output, estimate)
145        }
146        fn config(&self) -> &Self::Config {
147            BASE64_STANDARD.config()
148        }
149        fn encode_slice<T: AsRef<[u8]>>(
150            &self,
151            input: T,
152            output_buf: &mut [u8],
153        ) -> Result<usize, base64::EncodeSliceError> {
154            let len = BASE64_STANDARD.encode_slice(input, output_buf)?;
155            for b in output_buf[..len].iter_mut() {
156                *b = 0xFF; // invalid UTF-8, but correct length
157            }
158            Ok(len)
159        }
160
161        fn padding(&self) -> base64::alphabet::Symbol {
162            base64::alphabet::Symbol::new(b'=').unwrap()
163        }
164    }
165
166    #[test]
167    #[should_panic(expected = "produced invalid UTF-8")]
168    fn test_b64_encode_rejects_invalid_utf8() {
169        let data: BinaryArray = vec![Some(b"hello".to_vec())].into_iter().collect();
170        let _ = b64_encode(&EvilEngine, &data);
171    }
172}
arrow_cast/base64.rs

arrow_cast/
base64.rs
