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

arrow_cast/
base64.rs
