Add SnappyEncoder/Decoder
The encoder/decoder should work. Haven't actually hooked it into the log
namer yet, though.
Change-Id: Id20be8161d46fe080f89eee8032103977574e7ad
Signed-off-by: James Kuszmaul <jabukuszmaul+collab@gmail.com>
diff --git a/aos/events/logging/BUILD b/aos/events/logging/BUILD
index 952c16d..ef2ffd7 100644
--- a/aos/events/logging/BUILD
+++ b/aos/events/logging/BUILD
@@ -122,6 +122,44 @@
)
cc_library(
+ name = "snappy_encoder",
+ srcs = [
+ "snappy_encoder.cc",
+ ],
+ hdrs = [
+ "snappy_encoder.h",
+ ],
+ target_compatible_with = ["@platforms//os:linux"],
+ visibility = ["//visibility:public"],
+ deps = [
+ ":buffer_encoder",
+ ":crc32",
+ ":logger_fbs",
+ "//aos:configuration_fbs",
+ "//aos/containers:resizeable_buffer",
+ "@com_github_google_flatbuffers//:flatbuffers",
+ "@com_github_google_glog//:glog",
+ "@com_google_absl//absl/types:span",
+ "@snappy//:snappy",
+ ],
+)
+
+cc_test(
+ name = "snappy_encoder_test",
+ srcs = [
+ "snappy_encoder_test.cc",
+ ],
+ shard_count = 4,
+ target_compatible_with = ["@platforms//os:linux"],
+ deps = [
+ ":buffer_encoder_param_test",
+ ":snappy_encoder",
+ "//aos/testing:googletest",
+ "@com_github_google_glog//:glog",
+ ],
+)
+
+cc_library(
name = "lzma_encoder",
srcs = [
"lzma_encoder.cc",
@@ -408,3 +446,12 @@
gen_reflections = 1,
target_compatible_with = ["@platforms//os:linux"],
)
+
+cc_library(
+ name = "crc32",
+ srcs = ["crc32.cc"],
+ hdrs = ["crc32.h"],
+ deps = [
+ "@com_google_absl//absl/types:span",
+ ],
+)
diff --git a/aos/events/logging/buffer_encoder_param_test.cc b/aos/events/logging/buffer_encoder_param_test.cc
index 825696e..e464a52 100644
--- a/aos/events/logging/buffer_encoder_param_test.cc
+++ b/aos/events/logging/buffer_encoder_param_test.cc
@@ -70,7 +70,9 @@
decoder->Read(chunk.data(), chunk.data() + chunk_size);
if (read_result + total_decoded_size != total_encoded_size) {
// We didn't read anything, so we should've read the complete chunk.
- ASSERT_EQ(read_result, chunk_size);
+ ASSERT_EQ(read_result, chunk_size)
+ << "Read " << read_result + total_decoded_size << " of "
+ << total_encoded_size << " expected bytes.";
}
// Eventually we'll get here, once the decoder is really sure it's done.
if (read_result == 0) {
diff --git a/aos/events/logging/crc32.cc b/aos/events/logging/crc32.cc
new file mode 100644
index 0000000..cd9d9fb
--- /dev/null
+++ b/aos/events/logging/crc32.cc
@@ -0,0 +1,67 @@
+#include "aos/events/logging/crc32.h"
+
+namespace aos {
+
+namespace {
+const uint32_t kCrc32Table[256] = {
+ 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
+ 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
+ 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
+ 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+ 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
+ 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
+ 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
+ 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+ 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
+ 0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
+ 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
+ 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+ 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
+ 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+ 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
+ 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+ 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
+ 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
+ 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
+ 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+ 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
+ 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
+ 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
+ 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+ 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
+ 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
+ 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
+ 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+ 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
+ 0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
+ 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
+ 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+ 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
+ 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
+ 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+ 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+ 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
+ 0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
+ 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
+ 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+ 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
+ 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+ 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d};
+}
+
+uint32_t ComputeCrc32(const absl::Span<uint8_t> data) {
+ return AccumulateCrc32(data, std::nullopt);
+}
+
+uint32_t AccumulateCrc32(
+ const absl::Span<uint8_t> data,
+ std::optional<uint32_t> current_checksum) {
+ uint32_t crc =
+ current_checksum.has_value() ? current_checksum.value() : 0xFF'FF'FF'FF;
+ for (const uint8_t n : data) {
+ crc = kCrc32Table[(crc ^ n) & 0xFF] ^ (crc >> 8);
+ }
+ return crc;
+}
+
+} // namespace aos
diff --git a/aos/events/logging/crc32.h b/aos/events/logging/crc32.h
new file mode 100644
index 0000000..7d21704
--- /dev/null
+++ b/aos/events/logging/crc32.h
@@ -0,0 +1,11 @@
+#include "absl/types/span.h"
+
+namespace aos {
+
+uint32_t ComputeCrc32(const absl::Span<uint8_t> data);
+
+uint32_t AccumulateCrc32(
+ const absl::Span<uint8_t> data,
+ std::optional<uint32_t> current_checksum = std::nullopt);
+
+} // namespace aos
diff --git a/aos/events/logging/snappy_encoder.cc b/aos/events/logging/snappy_encoder.cc
new file mode 100644
index 0000000..d57b3dd
--- /dev/null
+++ b/aos/events/logging/snappy_encoder.cc
@@ -0,0 +1,249 @@
+#include "aos/events/logging/snappy_encoder.h"
+
+#include "aos/events/logging/crc32.h"
+#include "external/snappy/snappy.h"
+
+namespace aos::logger {
+// Snappy file format is a series of chunks. Each chunk consists of:
+// 1-byte: Format identifier.
+// 3-bytes: Little-endian chunk length, not counting the four bytes of format
+// + length.
+//
+// The relevant chunk identifiers are 0xff (header) and 0x00 (compressed data).
+// Compressed data's first four bytes are a CRC-32C that is masked by some
+// magic function. Technically the size of the uncompressed data per chunk
+// is supposed to be no more than 65536 bytes, but I am too lazy to enforce
+// that at the moment.
+// 0x01 is the type for uncompressed data, which has not been implemented here.
+namespace {
+const std::vector<uint8_t> kSnappyIdentifierChunk = {
+ 0xFF, 0x06, 0x00, 0x00, 's', 'N', 'a', 'P', 'p', 'Y'};
+
+// Magic mask that snappy's framing format requires for some reason.
+uint32_t MaskChecksum(uint32_t x) {
+ return ((x >> 15) | (x << 17)) + 0xa282ead8;
+}
+
+uint32_t SnappyChecksum(uint8_t *data, size_t size) {
+ return MaskChecksum(ComputeCrc32({data, size}));
+}
+} // namespace
+
+SnappyEncoder::SnappyEncoder(size_t chunk_size) : chunk_size_(chunk_size) {
+ queue_.emplace_back();
+ queue_.back().resize(kSnappyIdentifierChunk.size());
+ std::copy(kSnappyIdentifierChunk.begin(), kSnappyIdentifierChunk.end(),
+ queue_.back().begin());
+ total_bytes_ += queue_.back().size();
+}
+
+void SnappyEncoder::Finish() { EncodeCurrentBuffer(); }
+
+void SnappyEncoder::Encode(flatbuffers::DetachedBuffer &&in) {
+ accumulated_checksum_ =
+ AccumulateCrc32({in.data(), in.size()}, accumulated_checksum_);
+ buffer_source_.AppendBuffer(std::move(in));
+
+ if (buffer_source_.Available() >= chunk_size_) {
+ EncodeCurrentBuffer();
+ }
+}
+
+void SnappyEncoder::EncodeCurrentBuffer() {
+ if (buffer_source_.Available() == 0) {
+ return;
+ }
+ const uint32_t uncompressed_checksum =
+ MaskChecksum(accumulated_checksum_.value());
+ queue_.emplace_back();
+ constexpr size_t kPrefixSize = 8;
+ queue_.back().resize(kPrefixSize +
+ snappy::MaxCompressedLength(buffer_source_.Available()));
+ queue_.back().data()[0] = '\x00';
+ char *const compressed_start =
+ reinterpret_cast<char *>(queue_.back().data()) + kPrefixSize;
+ snappy::UncheckedByteArraySink snappy_sink(compressed_start);
+ const size_t compressed_size =
+ snappy::Compress(&buffer_source_, &snappy_sink);
+ CHECK_LT(compressed_size + kPrefixSize, queue_.back().size());
+ queue_.back().resize(compressed_size + kPrefixSize);
+ const size_t chunk_size = compressed_size + 4;
+ CHECK_LT(chunk_size, 1U << 24);
+ queue_.back().data()[1] = chunk_size & 0xFF;
+ queue_.back().data()[2] = (chunk_size >> 8) & 0xFF;
+ queue_.back().data()[3] = (chunk_size >> 16) & 0xFF;
+ queue_.back().data()[4] = uncompressed_checksum & 0xFF;
+ queue_.back().data()[5] = (uncompressed_checksum >> 8) & 0xFF;
+ queue_.back().data()[6] = (uncompressed_checksum >> 16) & 0xFF;
+ queue_.back().data()[7] = (uncompressed_checksum >> 24) & 0xFF;
+
+ total_bytes_ += queue_.back().size();
+
+ accumulated_checksum_.reset();
+ CHECK_EQ(0u, buffer_source_.Available());
+}
+
+void SnappyEncoder::Clear(int n) {
+ CHECK_GE(n, 0);
+ CHECK_LE(static_cast<size_t>(n), queue_size());
+ queue_.erase(queue_.begin(), queue_.begin() + n);
+}
+
+size_t SnappyEncoder::queued_bytes() const {
+ size_t bytes = 0;
+ for (const auto &buffer : queue_) {
+ bytes += buffer.size();
+ }
+ return bytes;
+}
+
+std::vector<absl::Span<const uint8_t>> SnappyEncoder::queue() const {
+ std::vector<absl::Span<const uint8_t>> queue;
+ queue.reserve(queue_.size());
+ for (const auto &buffer : queue_) {
+ queue.emplace_back(buffer.data(), buffer.size());
+ }
+ return queue;
+}
+
+size_t SnappyEncoder::DetachedBufferSource::Available() const {
+ size_t total_available = 0;
+ for (const flatbuffers::DetachedBuffer &buffer : buffers_) {
+ total_available += buffer.size();
+ }
+ return total_available;
+}
+
+const char *SnappyEncoder::DetachedBufferSource::Peek(size_t *length) {
+ *CHECK_NOTNULL(length) = buffers_[0].size() - index_into_first_buffer_;
+ return reinterpret_cast<char *>(buffers_[0].data()) +
+ index_into_first_buffer_;
+}
+
+void SnappyEncoder::DetachedBufferSource::Skip(size_t n) {
+ if (n == 0) {
+ return;
+ }
+
+ CHECK(!buffers_.empty());
+
+ index_into_first_buffer_ += n;
+ CHECK_LE(index_into_first_buffer_, buffers_[0].size())
+ << ": " << n << " is too large a skip.";
+ if (index_into_first_buffer_ == buffers_[0].size()) {
+ buffers_.erase(buffers_.begin());
+ index_into_first_buffer_ = 0;
+ }
+}
+
+void SnappyEncoder::DetachedBufferSource::AppendBuffer(
+ flatbuffers::DetachedBuffer &&buffer) {
+ buffers_.emplace_back(std::move(buffer));
+}
+
+size_t SnappyDecoder::Read(uint8_t *begin, uint8_t *end) {
+ // Decoding process:
+ // We maintain an uncompressed_buffer_ of data that may have been uncompressed
+ // in the past but which hasn't been read yet.
+ //
+ // When we run out of that buffer and need to actually read new data, we
+ // need to read things from the file in one-chunk units. Snappy expects to
+ // uncompress an entire chunk at once, so there isn't any value in attempting
+ // to be more incremental. Each chunk will be of some variable size (specified
+ // at the start of the chunk). Once we read and uncompress the chunk, we can
+ // then copy it into the user's buffer until either we run out of data and
+ // need to uncompress a new chunk or user's buffer runs out in which case
+ // we fill up their buffer and store the extra data in uncompressed_buffer_
+ // to be populated later.
+
+ uint8_t *current_output = begin;
+ if (uncompressed_buffer_.size() > 0) {
+ const size_t amount_to_copy =
+ std::min<size_t>(uncompressed_buffer_.size(), end - current_output);
+ std::memcpy(current_output, uncompressed_buffer_.data(), amount_to_copy);
+ current_output += amount_to_copy;
+ uncompressed_buffer_.erase_front(amount_to_copy);
+ }
+
+ while (current_output != end) {
+ uint8_t header[4];
+ const size_t read_length = underlying_decoder_->Read(header, header + 4);
+ if (read_length == 0) {
+ break;
+ }
+ if (read_length != 4u) {
+ LOG(WARNING) << "Logfile data is truncated.";
+ break;
+ }
+ const uint8_t chunk_type = header[0];
+ const size_t chunk_size = header[1] + (header[2] << 8) + (header[3] << 16);
+ compressed_buffer_.resize(chunk_size);
+ if (chunk_size !=
+ underlying_decoder_->Read(compressed_buffer_.data(),
+ compressed_buffer_.data() + chunk_size)) {
+ LOG(WARNING) << "Logfile data is truncated.";
+ break;
+ }
+ if (chunk_type == 0xFF) {
+ // Start of file, don't bother
+ // checking the contents.
+ continue;
+ } else if (chunk_type == 0x00) {
+ // Note: This section uses CHECKs rather than terminating more silently
+ // because any of these CHECK's failing implies outright data corruption
+ // rather than mere truncation.
+ CHECK_LT(4u, compressed_buffer_.size()) << ": Missing checksum.";
+ const uint32_t checksum = compressed_buffer_.data()[0] +
+ (compressed_buffer_.data()[1] << 8) +
+ (compressed_buffer_.data()[2] << 16) +
+ (compressed_buffer_.data()[3] << 24);
+
+ const char *input_data =
+ reinterpret_cast<char *>(compressed_buffer_.data() + 4);
+ const size_t input_size = compressed_buffer_.size() - 4;
+
+ size_t uncompressed_length;
+ CHECK(snappy::GetUncompressedLength(input_data, input_size,
+ &uncompressed_length));
+
+ // If the user's buffer can fit the entire uncompressed data, we
+ // will uncompress directly into their buffer. Otherwise, we uncompress
+ // into a separate buffer and then copy the correct number of bytes out
+ // to fill up the user's buffer.
+ // TODO(james): In the future, overload a snappy::Sink to avoid
+ // unnecessary copies by extracting the initial N bytes directly into
+ // the user's buffer.
+ if (end > (uncompressed_length + current_output)) {
+ CHECK(snappy::RawUncompress(input_data, input_size,
+ reinterpret_cast<char *>(current_output)))
+ << ": Corrupted snappy chunk.";
+ CHECK_EQ(checksum, SnappyChecksum(current_output, uncompressed_length))
+ << ": Checksum mismatch.";
+
+ current_output += uncompressed_length;
+ } else {
+ uncompressed_buffer_.resize(uncompressed_length);
+ CHECK(snappy::RawUncompress(
+ input_data, input_size,
+ reinterpret_cast<char *>(uncompressed_buffer_.data())))
+ << ": Corrupted snappy chunk.";
+ CHECK_EQ(checksum, SnappyChecksum(uncompressed_buffer_.data(),
+ uncompressed_buffer_.size()))
+ << ": Checksum mismatch.";
+ std::memcpy(current_output, uncompressed_buffer_.data(),
+ end - current_output);
+ uncompressed_buffer_.erase_front(end - current_output);
+ current_output = end;
+ }
+ } else {
+ // Unimplemented.
+ LOG(FATAL) << "Unsupported snappy chunk type "
+ << static_cast<int>(chunk_type);
+ }
+ }
+ total_output_ += current_output - begin;
+
+ return current_output - begin;
+}
+
+} // namespace aos::logger
diff --git a/aos/events/logging/snappy_encoder.h b/aos/events/logging/snappy_encoder.h
new file mode 100644
index 0000000..57a9a21
--- /dev/null
+++ b/aos/events/logging/snappy_encoder.h
@@ -0,0 +1,92 @@
+#ifndef AOS_EVENTS_LOGGING_SNAPPY_ENCODER_H_
+#define AOS_EVENTS_LOGGING_SNAPPY_ENCODER_H_
+
+#include <string_view>
+
+#include "absl/types/span.h"
+#include "aos/containers/resizeable_buffer.h"
+#include "aos/events/logging/buffer_encoder.h"
+#include "aos/events/logging/logger_generated.h"
+#include "external/snappy/snappy-sinksource.h"
+#include "external/snappy/snappy.h"
+#include "flatbuffers/flatbuffers.h"
+
+namespace aos::logger {
+
+// Encodes buffers using snappy.
+class SnappyEncoder final : public DetachedBufferEncoder {
+ public:
+ explicit SnappyEncoder(size_t chunk_size = 32768);
+
+ void Encode(flatbuffers::DetachedBuffer &&in) final;
+ void Finish() final;
+ void Clear(int n) final;
+ std::vector<absl::Span<const uint8_t>> queue() const final;
+ size_t queued_bytes() const final;
+ size_t total_bytes() const final { return total_bytes_; }
+ size_t queue_size() const final { return queue_.size(); }
+
+ private:
+ class DetachedBufferSource : public snappy::Source {
+ public:
+ size_t Available() const final;
+ const char *Peek(size_t *length) final;
+ void Skip(size_t n) final;
+ void AppendBuffer(flatbuffers::DetachedBuffer &&buffer);
+
+ private:
+ std::vector<flatbuffers::DetachedBuffer> buffers_;
+ size_t index_into_first_buffer_ = 0;
+ };
+
+ // Flushes buffer_source_ and stores the compressed buffer in queue_.
+ void EncodeCurrentBuffer();
+
+ // To queue up data:
+ // 1) When Encode is called, we use AppendBuffer to store the DetachedBuffer
+ // in buffer_source_.
+ // 2) Once we've queued up at least chunk_size_ data in buffer_source_, we
+ // use snappy to compress all the data. This flushes everything out of
+ // buffer_source_ and adds a single buffer to queue_. Note that we do
+ // not split up flatbuffer buffers to ensure that we produce chunks of
+ // exactly chunk_size_ uncompressed data--if we get a 1MB DetachedBuffer
+ // we will compress it all at once.
+ // 3) queue_ is the data that is actually read by queue() and cleared by
+ // Clear() to be written to disk.
+ const size_t chunk_size_;
+ DetachedBufferSource buffer_source_;
+ std::optional<uint32_t> accumulated_checksum_;
+ std::vector<ResizeableBuffer> queue_;
+ size_t total_bytes_ = 0;
+};
+
+// Decompresses data with snappy.
+class SnappyDecoder final : public DataDecoder {
+ public:
+ explicit SnappyDecoder(std::unique_ptr<DataDecoder> underlying_decoder)
+ : underlying_decoder_(std::move(underlying_decoder)) {}
+ explicit SnappyDecoder(std::string_view filename)
+ : SnappyDecoder(std::make_unique<DummyDecoder>(filename)) {}
+
+ size_t Read(uint8_t *begin, uint8_t *end) final;
+ std::string_view filename() const final {
+ return underlying_decoder_->filename();
+ }
+
+ private:
+ // decoder to use for reading data out of the file itself.
+ std::unique_ptr<DataDecoder> underlying_decoder_;
+ // Buffer to use for reading data from the file. This being a member variable
+ // is purely an optimization to avoid constant reallocations on every call to
+ // Read().
+ ResizeableBuffer compressed_buffer_;
+ // Buffer of any uncompressed data that we've read but which hasn't yet been
+ // consumed by a call to Read().
+ ResizeableBuffer uncompressed_buffer_;
+
+ size_t total_output_ = 0;
+};
+
+} // namespace aos::logger
+
+#endif // AOS_EVENTS_LOGGING_SNAPPY_ENCODER_H_
diff --git a/aos/events/logging/snappy_encoder_test.cc b/aos/events/logging/snappy_encoder_test.cc
new file mode 100644
index 0000000..3334602
--- /dev/null
+++ b/aos/events/logging/snappy_encoder_test.cc
@@ -0,0 +1,20 @@
+#include "aos/events/logging/snappy_encoder.h"
+
+#include "aos/events/logging/buffer_encoder_param_test.h"
+#include "aos/util/file.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace aos::logger::testing {
+
+INSTANTIATE_TEST_SUITE_P(
+ Snappy, BufferEncoderTest,
+ ::testing::Combine(::testing::Values([]() {
+ return std::make_unique<SnappyEncoder>();
+ }),
+ ::testing::Values([](std::string_view filename) {
+ return std::make_unique<SnappyDecoder>(filename);
+ }),
+ ::testing::Range(0, 100)));
+
+} // namespace aos::logger::testing