57 lines
2.1 KiB
C++
57 lines
2.1 KiB
C++
#pragma once
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#include <string>
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/**
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* Calculate KOReader document ID (partial MD5 hash).
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*
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* KOReader identifies documents using a partial MD5 hash of the file content.
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* The algorithm reads 1024 bytes at specific offsets and computes the MD5 hash
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* of the concatenated data.
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*
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* Offsets are calculated as: 1024 << (2*i) for i = -1 to 10
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* Producing: 256, 1024, 4096, 16384, 65536, 262144, 1048576, 4194304,
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* 16777216, 67108864, 268435456, 1073741824 bytes
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*
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* If an offset is beyond the file size, it is skipped.
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*/
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class KOReaderDocumentId {
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public:
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/**
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* Calculate the KOReader document hash for a file (binary/content-based).
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*
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* @param filePath Path to the file (typically an EPUB)
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* @return 32-character lowercase hex string, or empty string on failure
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*/
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static std::string calculate(const std::string& filePath);
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/**
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* Calculate document hash from filename only (filename-based sync mode).
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* This is simpler and works when files have the same name across devices.
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*
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* @param filePath Path to the file (only the filename portion is used)
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* @return 32-character lowercase hex MD5 of the filename
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*/
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static std::string calculateFromFilename(const std::string& filePath);
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private:
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// Size of each chunk to read at each offset
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static constexpr size_t CHUNK_SIZE = 1024;
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// Number of offsets to try (i = -1 to 10, so 12 offsets)
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static constexpr int OFFSET_COUNT = 12;
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// Calculate offset for index i: 1024 << (2*i)
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static size_t getOffset(int i);
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// Hash cache helpers
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// Returns the path to the per-book cache file that stores the precomputed hash.
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// Uses the same directory convention as the Epub cache (/.crosspoint/epub_<hash>/).
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static std::string getCacheFilePath(const std::string& filePath);
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// Returns the cached hash if the file size matches, or empty string on miss/invalidation.
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static std::string loadCachedHash(const std::string& cacheFilePath, size_t fileSize);
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// Persists the computed hash alongside the file size used to compute it.
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static void saveCachedHash(const std::string& cacheFilePath, size_t fileSize, const std::string& hash);
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};
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