1use crate::compression::{CompressionCodec, CODEC_METADATA_KEY};
21use crate::reader::vlq::VLQDecoder;
22use crate::schema::{Schema, SCHEMA_METADATA_KEY};
23use arrow_schema::ArrowError;
24
25#[derive(Debug)]
26enum HeaderDecoderState {
27 Magic,
29 BlockCount,
31 BlockLen,
33 KeyLen,
35 Key,
37 ValueLen,
39 Value,
41 Sync,
43 Finished,
45}
46
47#[derive(Debug, Clone)]
49pub struct Header {
50 meta_offsets: Vec<usize>,
51 meta_buf: Vec<u8>,
52 sync: [u8; 16],
53}
54
55impl Header {
56 pub fn metadata(&self) -> impl Iterator<Item = (&[u8], &[u8])> {
58 let mut last = 0;
59 self.meta_offsets.chunks_exact(2).map(move |w| {
60 let start = last;
61 last = w[1];
62 (&self.meta_buf[start..w[0]], &self.meta_buf[w[0]..w[1]])
63 })
64 }
65
66 pub fn get(&self, key: impl AsRef<[u8]>) -> Option<&[u8]> {
68 self.metadata()
69 .find_map(|(k, v)| (k == key.as_ref()).then_some(v))
70 }
71
72 pub fn sync(&self) -> [u8; 16] {
74 self.sync
75 }
76
77 pub fn compression(&self) -> Result<Option<CompressionCodec>, ArrowError> {
79 let v = self.get(CODEC_METADATA_KEY);
80
81 match v {
82 None | Some(b"null") => Ok(None),
83 Some(b"deflate") => Ok(Some(CompressionCodec::Deflate)),
84 Some(b"snappy") => Ok(Some(CompressionCodec::Snappy)),
85 Some(b"zstandard") => Ok(Some(CompressionCodec::ZStandard)),
86 Some(v) => Err(ArrowError::ParseError(format!(
87 "Unrecognized compression codec \'{}\'",
88 String::from_utf8_lossy(v)
89 ))),
90 }
91 }
92
93 pub fn schema(&self) -> Result<Option<Schema<'_>>, ArrowError> {
95 self.get(SCHEMA_METADATA_KEY)
96 .map(|x| {
97 serde_json::from_slice(x).map_err(|e| {
98 ArrowError::ParseError(format!("Failed to parse Avro schema JSON: {e}"))
99 })
100 })
101 .transpose()
102 }
103}
104
105#[derive(Debug)]
110pub struct HeaderDecoder {
111 state: HeaderDecoderState,
112 vlq_decoder: VLQDecoder,
113
114 meta_offsets: Vec<usize>,
116 meta_buf: Vec<u8>,
118
119 sync_marker: [u8; 16],
121
122 tuples_remaining: usize,
124 bytes_remaining: usize,
126}
127
128impl Default for HeaderDecoder {
129 fn default() -> Self {
130 Self {
131 state: HeaderDecoderState::Magic,
132 meta_offsets: vec![],
133 meta_buf: vec![],
134 sync_marker: [0; 16],
135 vlq_decoder: Default::default(),
136 tuples_remaining: 0,
137 bytes_remaining: MAGIC.len(),
138 }
139 }
140}
141
142const MAGIC: &[u8; 4] = b"Obj\x01";
143
144impl HeaderDecoder {
145 pub fn decode(&mut self, mut buf: &[u8]) -> Result<usize, ArrowError> {
157 let max_read = buf.len();
158 while !buf.is_empty() {
159 match self.state {
160 HeaderDecoderState::Magic => {
161 let remaining = &MAGIC[MAGIC.len() - self.bytes_remaining..];
162 let to_decode = buf.len().min(remaining.len());
163 if !buf.starts_with(&remaining[..to_decode]) {
164 return Err(ArrowError::ParseError("Incorrect avro magic".to_string()));
165 }
166 self.bytes_remaining -= to_decode;
167 buf = &buf[to_decode..];
168 if self.bytes_remaining == 0 {
169 self.state = HeaderDecoderState::BlockCount;
170 }
171 }
172 HeaderDecoderState::BlockCount => {
173 if let Some(block_count) = self.vlq_decoder.long(&mut buf) {
174 match block_count.try_into() {
175 Ok(0) => {
176 self.state = HeaderDecoderState::Sync;
177 self.bytes_remaining = 16;
178 }
179 Ok(remaining) => {
180 self.tuples_remaining = remaining;
181 self.state = HeaderDecoderState::KeyLen;
182 }
183 Err(_) => {
184 self.tuples_remaining = block_count.unsigned_abs() as _;
185 self.state = HeaderDecoderState::BlockLen;
186 }
187 }
188 }
189 }
190 HeaderDecoderState::BlockLen => {
191 if self.vlq_decoder.long(&mut buf).is_some() {
192 self.state = HeaderDecoderState::KeyLen
193 }
194 }
195 HeaderDecoderState::Key => {
196 let to_read = self.bytes_remaining.min(buf.len());
197 self.meta_buf.extend_from_slice(&buf[..to_read]);
198 self.bytes_remaining -= to_read;
199 buf = &buf[to_read..];
200 if self.bytes_remaining == 0 {
201 self.meta_offsets.push(self.meta_buf.len());
202 self.state = HeaderDecoderState::ValueLen;
203 }
204 }
205 HeaderDecoderState::Value => {
206 let to_read = self.bytes_remaining.min(buf.len());
207 self.meta_buf.extend_from_slice(&buf[..to_read]);
208 self.bytes_remaining -= to_read;
209 buf = &buf[to_read..];
210 if self.bytes_remaining == 0 {
211 self.meta_offsets.push(self.meta_buf.len());
212
213 self.tuples_remaining -= 1;
214 match self.tuples_remaining {
215 0 => self.state = HeaderDecoderState::BlockCount,
216 _ => self.state = HeaderDecoderState::KeyLen,
217 }
218 }
219 }
220 HeaderDecoderState::KeyLen => {
221 if let Some(len) = self.vlq_decoder.long(&mut buf) {
222 self.bytes_remaining = len as _;
223 self.state = HeaderDecoderState::Key;
224 }
225 }
226 HeaderDecoderState::ValueLen => {
227 if let Some(len) = self.vlq_decoder.long(&mut buf) {
228 self.bytes_remaining = len as _;
229 self.state = HeaderDecoderState::Value;
230 }
231 }
232 HeaderDecoderState::Sync => {
233 let to_decode = buf.len().min(self.bytes_remaining);
234 let write = &mut self.sync_marker[16 - to_decode..];
235 write[..to_decode].copy_from_slice(&buf[..to_decode]);
236 self.bytes_remaining -= to_decode;
237 buf = &buf[to_decode..];
238 if self.bytes_remaining == 0 {
239 self.state = HeaderDecoderState::Finished;
240 }
241 }
242 HeaderDecoderState::Finished => return Ok(max_read - buf.len()),
243 }
244 }
245 Ok(max_read)
246 }
247
248 pub fn flush(&mut self) -> Option<Header> {
250 match self.state {
251 HeaderDecoderState::Finished => {
252 self.state = HeaderDecoderState::Magic;
253 Some(Header {
254 meta_offsets: std::mem::take(&mut self.meta_offsets),
255 meta_buf: std::mem::take(&mut self.meta_buf),
256 sync: self.sync_marker,
257 })
258 }
259 _ => None,
260 }
261 }
262}
263
264#[cfg(test)]
265mod test {
266 use super::*;
267 use crate::codec::{AvroDataType, AvroField};
268 use crate::reader::read_header;
269 use crate::schema::SCHEMA_METADATA_KEY;
270 use crate::test_util::arrow_test_data;
271 use arrow_schema::{DataType, Field, Fields, TimeUnit};
272 use std::fs::File;
273 use std::io::{BufRead, BufReader};
274
275 #[test]
276 fn test_header_decode() {
277 let mut decoder = HeaderDecoder::default();
278 for m in MAGIC {
279 decoder.decode(std::slice::from_ref(m)).unwrap();
280 }
281
282 let mut decoder = HeaderDecoder::default();
283 assert_eq!(decoder.decode(MAGIC).unwrap(), 4);
284
285 let mut decoder = HeaderDecoder::default();
286 decoder.decode(b"Ob").unwrap();
287 let err = decoder.decode(b"s").unwrap_err().to_string();
288 assert_eq!(err, "Parser error: Incorrect avro magic");
289 }
290
291 fn decode_file(file: &str) -> Header {
292 let file = File::open(file).unwrap();
293 read_header(BufReader::with_capacity(100, file)).unwrap()
294 }
295
296 #[test]
297 fn test_header() {
298 let header = decode_file(&arrow_test_data("avro/alltypes_plain.avro"));
299 let schema_json = header.get(SCHEMA_METADATA_KEY).unwrap();
300 let expected = br#"{"type":"record","name":"topLevelRecord","fields":[{"name":"id","type":["int","null"]},{"name":"bool_col","type":["boolean","null"]},{"name":"tinyint_col","type":["int","null"]},{"name":"smallint_col","type":["int","null"]},{"name":"int_col","type":["int","null"]},{"name":"bigint_col","type":["long","null"]},{"name":"float_col","type":["float","null"]},{"name":"double_col","type":["double","null"]},{"name":"date_string_col","type":["bytes","null"]},{"name":"string_col","type":["bytes","null"]},{"name":"timestamp_col","type":[{"type":"long","logicalType":"timestamp-micros"},"null"]}]}"#;
301 assert_eq!(schema_json, expected);
302 let schema: Schema<'_> = serde_json::from_slice(schema_json).unwrap();
303 let field = AvroField::try_from(&schema).unwrap();
304
305 assert_eq!(
306 field.field(),
307 Field::new(
308 "topLevelRecord",
309 DataType::Struct(Fields::from(vec![
310 Field::new("id", DataType::Int32, true),
311 Field::new("bool_col", DataType::Boolean, true),
312 Field::new("tinyint_col", DataType::Int32, true),
313 Field::new("smallint_col", DataType::Int32, true),
314 Field::new("int_col", DataType::Int32, true),
315 Field::new("bigint_col", DataType::Int64, true),
316 Field::new("float_col", DataType::Float32, true),
317 Field::new("double_col", DataType::Float64, true),
318 Field::new("date_string_col", DataType::Binary, true),
319 Field::new("string_col", DataType::Binary, true),
320 Field::new(
321 "timestamp_col",
322 DataType::Timestamp(TimeUnit::Microsecond, Some("+00:00".into())),
323 true
324 ),
325 ])),
326 false
327 )
328 );
329
330 assert_eq!(
331 u128::from_le_bytes(header.sync()),
332 226966037233754408753420635932530907102
333 );
334
335 let header = decode_file(&arrow_test_data("avro/fixed_length_decimal.avro"));
336
337 let meta: Vec<_> = header
338 .metadata()
339 .map(|(k, _)| std::str::from_utf8(k).unwrap())
340 .collect();
341
342 assert_eq!(
343 meta,
344 &["avro.schema", "org.apache.spark.version", "avro.codec"]
345 );
346
347 let schema_json = header.get(SCHEMA_METADATA_KEY).unwrap();
348 let expected = br#"{"type":"record","name":"topLevelRecord","fields":[{"name":"value","type":[{"type":"fixed","name":"fixed","namespace":"topLevelRecord.value","size":11,"logicalType":"decimal","precision":25,"scale":2},"null"]}]}"#;
349 assert_eq!(schema_json, expected);
350 let _schema: Schema<'_> = serde_json::from_slice(schema_json).unwrap();
351 assert_eq!(
352 u128::from_le_bytes(header.sync()),
353 325166208089902833952788552656412487328
354 );
355 }
356}