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Use "read" to fetch misaligned 64bit values from bundle header #63431

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merged 3 commits into from
Jan 7, 2022
Merged

Use "read" to fetch misaligned 64bit values from bundle header #63431

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c48425e
Use "read" to fetch misaligned 64bit values
VSadov Jan 6, 2022
6bcb50e
remove read_direct
VSadov Jan 6, 2022
dddb853
rename read() -> read_byte()
VSadov Jan 6, 2022
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13 changes: 8 additions & 5 deletions src/native/corehost/bundle/file_entry.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,13 +19,16 @@ file_entry_t file_entry_t::read(reader_t &reader, uint32_t bundle_major_version,
// First read the fixed-sized portion of file-entry
file_entry_fixed_t fixed_data;

fixed_data.offset = *(int64_t*)reader.read_direct(sizeof(int64_t));
fixed_data.size = *(int64_t*)reader.read_direct(sizeof(int64_t));
// NB: the file data is potentially unaligned, thus we use "read" to fetch 64bit values
reader.read(&fixed_data.offset, sizeof(int64_t));
reader.read(&fixed_data.size, sizeof(int64_t));

// compressedSize is present only in v6+ headers
fixed_data.compressedSize = bundle_major_version >= 6 ?
*(int64_t*)reader.read_direct(sizeof(int64_t)) :
0;
fixed_data.compressedSize = 0;
if (bundle_major_version >= 6)
{
reader.read(&fixed_data.compressedSize, sizeof(int64_t));
}

fixed_data.type = *(file_type_t*)reader.read_direct(sizeof(file_type_t));
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What is the size of file_type_t here and how is it guaranteed to be aligned? or do reads of its size not need aligning?

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It is an enum with base uint8_t, defined here:

runtime/src/native/corehost/bundle/file_type.h

Line 19 in 7fc4b6a

enum file_type_t : uint8_t


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