25 lines
1.4 KiB
Markdown
25 lines
1.4 KiB
Markdown
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# Port Upstream PR #1027: ParsedText Word-Width Cache and Hyphenation Early Exit
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## Task
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Ported upstream PR #1027 (jpirnay) into the mod. The PR reduces `ParsedText::layoutAndExtractLines` CPU time by 5–9% via two independent optimizations.
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## Changes Made
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**`lib/Epub/Epub/ParsedText.cpp`** (single file):
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1. Added `#include <cstring>` for `memcpy`/`memcmp`
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2. Added 128-entry direct-mapped word-width cache in the anonymous namespace (`WordWidthCacheEntry`, FNV-1a hash, `cachedMeasureWordWidth`). 4 KB in BSS, zero heap allocation.
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3. Switched `calculateWordWidths` to use `cachedMeasureWordWidth` instead of `measureWordWidth`
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4. Added `lineBreakIndices.reserve(totalWordCount / 8 + 1)` in `computeLineBreaks`
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5. In `hyphenateWordAtIndex`: added reusable `prefix` string buffer (avoids per-iteration `substr` allocations) and early exit `break` when prefix exceeds available width (ascending byte-offset order means all subsequent candidates will also be too wide)
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**`mod/prs/MERGED.md`**: Added PR #1027 entry (TOC link + full section with context, changes, differences, discussion).
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## Key Adaptation
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The upstream PR targets `std::list`-based code, but our mod already uses `std::vector` (from PR #1038). List-specific optimizations (splice in `extractLine`, `std::next` vs `std::advance`, `continuesVec` pointer sync) were not applicable. Only the algorithmic improvements were ported.
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## Follow-up Items
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- None. Port is complete.
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