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Support partial reading of string tables #326

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merged 2 commits into from
Jun 16, 2021

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@mstange mstange commented Jun 15, 2021

Before this PR, StringTables are read in their entirety and do not make use of the partial read ability of ReadRef. This is fine in most cases, but it is problematic for the dyld shared cache.
The dyld shared cache has a shared string table which is about 340MB big. Only a fraction of those strings are needed by each embedded library. For example, if I dump all AppKit symbols with their names from the dyld shared cache on macOS 11.3, this patch reduces the number of bytes read from 347.4 MB to 4.8 MB.

This patch makes use of the relatively new read_bytes_at_until method. But it also extends it by one parameter, upper_bound, so that the string table's size can be honored.

We currently have a hardcoded limit of 4096 bytes for the string length in the ReadCache. It's possible that this limit is not appropriate in all the cases where read_bytes_at_until is now called. But I'm not changing it in this patch.

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Thanks! Hopefully Wasm will get mmap support eventually.

src/read/coff/symbol.rs Outdated Show resolved Hide resolved
src/read/coff/section.rs Outdated Show resolved Hide resolved
src/read/util.rs Outdated Show resolved Hide resolved
src/read/read_ref.rs Outdated Show resolved Hide resolved
src/read/read_cache.rs Outdated Show resolved Hide resolved
src/read/pe/section.rs Outdated Show resolved Hide resolved
src/read/macho/load_command.rs Outdated Show resolved Hide resolved
@philipc philipc merged commit 8273ea3 into gimli-rs:master Jun 16, 2021
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mstange commented Jul 19, 2021

@philipc Could you make a release which contains this commit?

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philipc commented Jul 19, 2021

Can it wait a week or so? I'm currently hoping to get an alternative to #325 implemented before doing a release.

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mstange commented Jul 19, 2021

Sure, that's fine.

mcbegamerxx954 pushed a commit to mcbegamerxx954/object that referenced this pull request Jun 15, 2024
Support partial reading of string tables
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