Introduce MetadataBytes wrapper for compiled-in metadata accessors#4016
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hjanuschka wants to merge 1 commit into
Open
Introduce MetadataBytes wrapper for compiled-in metadata accessors#4016hjanuschka wants to merge 1 commit into
hjanuschka wants to merge 1 commit into
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Replace the C-style `int <type>_size()` / `const void* <type>_get()` pair
in metadata.h, short_metadata.h and alternate_format.h with a single
`MetadataBytes Get<Type>()` accessor that returns a small RAII wrapper.
The default implementations shipped in this repo wrap the existing
static `data[]` arrays in a non-owning MetadataBytes, so the on-disk
layout and runtime behaviour are unchanged for upstream consumers.
The motivating use case is downstream embedders (e.g. Chromium) that
produce the metadata at runtime, for example by decompressing a
brotli-compressed blob on first use to save binary size. With the old
API such embedders had to either leak the decompressed buffer or do
gymnastics to free it after PhoneNumberUtil parsed it. With
MetadataBytes the typical call site
MetadataBytes bytes = GetMetadata();
collection->ParseFromArray(bytes.data(), bytes.size());
keeps the buffer alive for exactly as long as ParseFromArray() needs it
and then frees it when the wrapper goes out of scope, simply by having
the downstream-supplied implementation return an owning instance built
from a std::unique_ptr<uint8_t[]>.
CppMetadataGenerator and its tests are updated to emit the new API.
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Summary
Introduces a small
MetadataBytesRAII wrapper for the compiled-in metadatabuffers returned by the internal
metadata.h,short_metadata.handalternate_format.haccessors.The C-style API
is replaced by
where
MetadataBytesis a move-only handle that holds either:const void*+int size, orstd::unique_ptr<uint8_t[]>+int size(owning).The default implementations shipped in this repo continue to wrap the
existing
static const unsigned char data[]arrays with a non-owninginstance, so on-disk layout and runtime behaviour are unchanged for
upstream consumers.
CppMetadataGenerator(and its tests) are updated toemit the new API.
Backwards compatibility
These headers are library-internal (not part of the public API).
Related
Chromium CL discussion that motivated this:
https://chromium-review.googlesource.com/c/chromium/src/+/7928952