Feature: lua now file_ident aware #8850
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jtdavis777
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| self:PrependUOffsetTRelative(rootTable) | ||
| local hasFid = fileIdentifier ~= nil | ||
| if hasFid then | ||
| assert(#fileIdentifier == 4, "File identifier must be exactly 4 bytes") |
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This is checked by flatc, so doesn't need to be checked here again if this function is typically called by generated code?
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this function is technically accessible by the low level public API -- I have added a convenience function to call it from the generated code but that function is brand new. Most lua users will be interating with the Finish calls below and could pass a bad value in here. The below code will only add the first 4 bytes, so it wouldn't break, but I figure its better to tell the user of the problem than let it silently succeed.
lua/flatbuffers/builder.lua
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| self.minalign, | ||
| (sizePrefix and 4 or 0) + | ||
| 4 + | ||
| (hasFid and 4 or 0) |
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This is a slow language that likely does not do common subexpression elimination, so wouldn't do (hasFid and 4 or 0) twice. In fact, maybe instead of hasFid use sizeFid which can have values 0 or 4 and can function both as bool and as value.
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fileid and sizeprefix are orthogonal concerns, but I can break the subexpression out. Lua also treats 0 as truthy...
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Lua builder code and generated code now handles file_ident properly.
Fixes #8641