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GH-42102: [C++][Parquet] Add binary that extracts a footer from a par…
…quet file (#42174) ### Rationale for this change This binary will make it a lot easier for customers to share their parquet metadata with the community so that we can build a repository of footers that can be used for advancing the state of metadata in parquet. ### What changes are included in this PR? Usage from the file binary itself: ``` Usage: parquet-dump-footer -h|--help Print help and exit --no-scrub Do not scrub potentially confidential metadata --debug Output text represenation of footer for inspection --in <uri> Input file (required): must be an URI or an absolute local path --out <path> Output file (optional, default stdout) Dump the footer of a Parquet file to stdout or to a file, optionally with potentially confidential metadata scrubbed. ``` ### Are these changes tested? Manually on existing parquet files. ### Are there any user-facing changes? No. * GitHub Issue: #42102 Lead-authored-by: Alkis Evlogimenos <[email protected]> Co-authored-by: Antoine Pitrou <[email protected]> Signed-off-by: Antoine Pitrou <[email protected]>
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| // Licensed to the Apache Software Foundation (ASF) under one | ||
| // or more contributor license agreements. See the NOTICE file | ||
| // distributed with this work for additional information | ||
| // regarding copyright ownership. The ASF licenses this file | ||
| // to you under the Apache License, Version 2.0 (the | ||
| // "License"); you may not use this file except in compliance | ||
| // with the License. You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
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| #include <cstdint> | ||
| #include <cstring> | ||
| #include <fstream> | ||
| #include <iostream> | ||
| #include <optional> | ||
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| #include "arrow/filesystem/filesystem.h" | ||
| #include "arrow/util/endian.h" | ||
| #include "arrow/util/ubsan.h" | ||
| #include "parquet/metadata.h" | ||
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| namespace parquet { | ||
| namespace { | ||
| uint32_t ReadLE32(const void* p) { | ||
| uint32_t x = ::arrow::util::SafeLoadAs<uint32_t>(static_cast<const uint8_t*>(p)); | ||
| return ::arrow::bit_util::FromLittleEndian(x); | ||
| } | ||
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| void AppendLE32(uint32_t v, std::string* out) { | ||
| v = ::arrow::bit_util::ToLittleEndian(v); | ||
| out->append(reinterpret_cast<const char*>(&v), sizeof(v)); | ||
| } | ||
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| int DoIt(std::string in, bool scrub, bool json, std::string out) { | ||
| std::string path; | ||
| auto fs = ::arrow::fs::FileSystemFromUriOrPath(in, &path).ValueOrDie(); | ||
| auto file = fs->OpenInputFile(path).ValueOrDie(); | ||
| int64_t file_len = file->GetSize().ValueOrDie(); | ||
| if (file_len < 8) { | ||
| std::cerr << "File too short: " << in << "\n"; | ||
| return 3; | ||
| } | ||
| // First do an opportunistic read of up to 1 MiB to try and get the entire footer. | ||
| int64_t tail_len = std::min(file_len, int64_t{1} << 20); | ||
| std::string tail; | ||
| tail.resize(tail_len); | ||
| char* data = tail.data(); | ||
| file->ReadAt(file_len - tail_len, tail_len, data).ValueOrDie(); | ||
| if (auto magic = ReadLE32(data + tail_len - 4); magic != ReadLE32("PAR1")) { | ||
| std::cerr << "Not a Parquet file: " << in << "\n"; | ||
| return 4; | ||
| } | ||
| uint32_t metadata_len = ReadLE32(data + tail_len - 8); | ||
| if (tail_len >= metadata_len + 8) { | ||
| // The footer is entirely in the initial read. Trim to size. | ||
| tail = tail.substr(tail_len - (metadata_len + 8)); | ||
| } else { | ||
| // The footer is larger than the initial read, read again the exact size. | ||
| if (metadata_len > file_len) { | ||
| std::cerr << "File too short: " << in << "\n"; | ||
| return 5; | ||
| } | ||
| tail_len = metadata_len + 8; | ||
| tail.resize(tail_len); | ||
| data = tail.data(); | ||
| file->ReadAt(file_len - tail_len, tail_len, data).ValueOrDie(); | ||
| } | ||
| auto md = FileMetaData::Make(tail.data(), &metadata_len); | ||
| std::string ser = md->SerializeUnencrypted(scrub, json); | ||
| if (!json) { | ||
| AppendLE32(static_cast<uint32_t>(ser.size()), &ser); | ||
| ser.append("PAR1", 4); | ||
| } | ||
| std::optional<std::fstream> fout; | ||
| if (!out.empty()) fout.emplace(out, std::ios::out); | ||
| std::ostream& os = fout ? *fout : std::cout; | ||
| if (!os.write(ser.data(), ser.size())) { | ||
| std::cerr << "Failed to write to output file: " << out << "\n"; | ||
| return 6; | ||
| } | ||
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| return 0; | ||
| } | ||
| } // namespace | ||
| } // namespace parquet | ||
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| static int PrintHelp() { | ||
| std::cerr << R"(Usage: parquet-dump-footer | ||
| -h|--help Print help and exit | ||
| --no-scrub Do not scrub potentially confidential metadata | ||
| --debug Output text represenation of footer for inspection | ||
| --in <uri> Input file (required): must be an URI or an absolute local path | ||
| --out <path> Output file (optional, default stdout) | ||
| Dump the footer of a Parquet file to stdout or to a file, optionally with | ||
| potentially confidential metadata scrubbed. | ||
| )"; | ||
| return 1; | ||
| } | ||
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| int main(int argc, char** argv) { | ||
| bool scrub = true; | ||
| bool json = false; | ||
| std::string in; | ||
| std::string out; | ||
| for (int i = 1; i < argc; i++) { | ||
| char* arg = argv[i]; | ||
| if (!std::strcmp(arg, "-h") || !std::strcmp(arg, "--help")) { | ||
| return PrintHelp(); | ||
| } else if (!std::strcmp(arg, "--no-scrub")) { | ||
| scrub = false; | ||
| } else if (!std::strcmp(arg, "--json")) { | ||
| json = true; | ||
| } else if (!std::strcmp(arg, "--in")) { | ||
| if (i + 1 >= argc) return PrintHelp(); | ||
| in = argv[++i]; | ||
| } else if (!std::strcmp(arg, "--out")) { | ||
| if (i + 1 >= argc) return PrintHelp(); | ||
| out = argv[++i]; | ||
| } else { | ||
| // Unknown option. | ||
| return PrintHelp(); | ||
| } | ||
| } | ||
| if (in.empty()) return PrintHelp(); | ||
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| return parquet::DoIt(in, scrub, json, out); | ||
| } |