Big-endian fix: GUID handling #49813
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| @@ -77,6 +77,24 @@ public static unsafe BlobContentId FromHash(byte[] hashCode) | |||
| guidPtr[7] = (byte)((guidPtr[7] & 0x0f) | (4 << 4)); | |||
| guidPtr[8] = (byte)((guidPtr[8] & 0x3f) | (2 << 6)); | |||
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| // the code above assumed the host is little-endian; if this is not the case, | |||
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Would it be better to just construct the Guid using Guid (int a, short b, short c, byte d, byte e, byte f, byte g, byte h, byte i, byte j, byte k) constructor instead of all the unsafe code and swapping bytes?
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Hmm, I initially tried to use a Guid constructor :-) The first thing I tried was the Guid (ReadOnlySpan<byte>) constructor, which failed since the file is apparently also compiled against frameworks where spans are not available. Then I tried the Guid (byte[]) constructor, which worked, but I was told this would be an unacceptable performance regression due to the extra allocation ... That's when I went back to this solution that leaves the LE code path unaffected.
I can certainly try the separate-element constructor you point out, if that would be an acceptable change on the LE path.
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I think the separate-element constructor would be acceptable for both LE and BE paths here.
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Patch updated accordingly.
* Fix Utf8Formatter.Guid on big-endian systems (first three fields are stored in native byte order, not always little-endian) * Use Guid constructor in BlobContentId.FromHash to remove endian-dependent code accessing the structure directly
src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/BlobContentId.cs
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src/libraries/System.Reflection.Metadata/src/System/Reflection/Metadata/BlobContentId.cs
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Fix Utf8Formatter.Guid on big-endian systems
(first three fields are stored in native byte order, not always
little-endian)
Fix low-level Guid structure access in BlobContentId.FromHash
(byte-swap first three fields on big-endian platforms)