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GH-33823: [C++][IPC] Improve error messages when opening files that are the wrong format #49771

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GH-33823: [C++][IPC] Improve error messages when opening files that are the wrong format #49771

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abd2b9c
#33823 Improve err msgs when opening files that are the wrong format
RobertLD Apr 16, 2026
db7dd63
33823 Formatting + linting
RobertLD Apr 16, 2026
d025ab0
Update cpp/src/arrow/ipc/reader.cc
RobertLD Apr 24, 2026
1d9b536
Update cpp/src/arrow/ipc/message.cc
RobertLD Apr 24, 2026
407c134
33823 Add tests to verify new err msgs
RobertLD Apr 29, 2026
d01cb5d
33823 PR suggestions
RobertLD May 12, 2026
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11 changes: 11 additions & 0 deletions cpp/src/arrow/ipc/message.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -565,6 +565,17 @@ Status DecodeMessage(MessageDecoder* decoder, io::InputStream* file) {
auto metadata_length = decoder->next_required_size();
ARROW_ASSIGN_OR_RAISE(auto metadata, file->Read(metadata_length));
if (metadata->size() != metadata_length) {
// The first sizeof(int32_t) bytes of the Arrow file magic ("ARRO") may have been
// misread as metadata_length. Check if the remaining bytes complete the magic.
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@pitrou pitrou May 7, 2026

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How likely is it to have a metadata message exactly 1330795073 bytes long ("ARRO" decoded as a 32-bit little-endian integer)? Perhaps we can check up front instead of trying to read so much data?

cc @lidavidm @paleolimbot for opinions.

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@lidavidm lidavidm May 7, 2026

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Yeah, a gigabyte of metadata raises flags anyways

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@paleolimbot paleolimbot May 7, 2026

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In nanoarrow we check the first few bytes for the magic string and skip them (then attempt to read the rest of the input as an IPC stream). We've never run into a complaint about this not working but I'm not sure how widespread the usage is (we could add an option to turn it off or improve the error that occurs if we run into one). I think 1330795073 bytes of metadata would never reasonably occur on purpose.

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@RobertLD RobertLD May 12, 2026

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I moved the check to happen first, and avoid the large read if possible

const auto remaining_magic = internal::kArrowMagicBytes.substr(sizeof(int32_t));
if (metadata->size() >= static_cast<int64_t>(remaining_magic.size()) &&
std::string_view(reinterpret_cast<const char*>(metadata->data()),
remaining_magic.size()) == remaining_magic) {
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@pitrou pitrou May 7, 2026

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This would only work on a little-endian machine. We need to be endianness-agnostic (see ConsumeInitialData).

return Status::Invalid("Expected to read ", metadata_length,
" metadata bytes, but only read ", metadata->size(),
". This appears to be an Arrow IPC file. "
"Try the IPC file reader instead of the IPC stream reader.");
}
return Status::Invalid("Expected to read ", metadata_length, " metadata bytes, but ",
"only read ", metadata->size());
}
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4 changes: 3 additions & 1 deletion cpp/src/arrow/ipc/reader.cc
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Expand Up @@ -1890,7 +1890,9 @@ class RecordBatchFileReaderImpl : public RecordBatchFileReader {
const auto magic_start = buffer->data() + sizeof(int32_t);
if (std::string_view(reinterpret_cast<const char*>(magic_start), kMagicSize) !=
kArrowMagicBytes) {
return Status::Invalid("Not an Arrow file");
return Status::Invalid(
"Not an Arrow file. If this is an Arrow IPC streaming format file, use "
"the IPC stream reader instead.");
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}

int32_t footer_length = bit_util::FromLittleEndian(
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