crosspoint-reader/lib/ZipFile/ZipFile.h

#pragma once
#include <SdFat.h>

#include <string>
#include <unordered_map>
#include <vector>

class ZipFile {
 public:
  struct FileStatSlim {
    uint16_t method;             // Compression method
    uint32_t compressedSize;     // Compressed size
    uint32_t uncompressedSize;   // Uncompressed size
    uint32_t localHeaderOffset;  // Offset of local file header
  };

  struct ZipDetails {
    uint32_t centralDirOffset;
    uint16_t totalEntries;
    bool isSet;
  };

  // Target for batch uncompressed size lookup (sorted by hash, then len)
  struct SizeTarget {
    uint64_t hash;   // FNV-1a 64-bit hash of normalized path
    uint16_t len;    // Length of path for collision reduction
    uint16_t index;  // Caller's index (e.g. spine index)
  };

  // FNV-1a 64-bit hash computed from char buffer (no std::string allocation)
  static uint64_t fnvHash64(const char* s, size_t len) {
    uint64_t hash = 14695981039346656037ull;
    for (size_t i = 0; i < len; i++) {
      hash ^= static_cast<uint8_t>(s[i]);
      hash *= 1099511628211ull;
    }
    return hash;
  }

 private:
  const std::string& filePath;
  FsFile file;
  ZipDetails zipDetails = {0, 0, false};
  std::unordered_map<std::string, FileStatSlim> fileStatSlimCache;

  // Cursor for sequential central-dir scanning optimization
  uint32_t lastCentralDirPos = 0;
  bool lastCentralDirPosValid = false;

  bool loadFileStatSlim(const char* filename, FileStatSlim* fileStat);
  long getDataOffset(const FileStatSlim& fileStat);
  bool loadZipDetails();

 public:
  explicit ZipFile(const std::string& filePath) : filePath(filePath) {}
  ~ZipFile() = default;
  // Zip file can be opened and closed by hand in order to allow for quick calculation of inflated file size
  // It is NOT recommended to pre-open it for any kind of inflation due to memory constraints
  bool isOpen() const { return !!file; }
  bool open();
  bool close();
  bool loadAllFileStatSlims();
  bool getInflatedFileSize(const char* filename, size_t* size);
  // Batch lookup: scan ZIP central dir once and fill sizes for matching targets.
  // targets must be sorted by (hash, len). sizes[target.index] receives uncompressedSize.
  // Returns number of targets matched.
  int fillUncompressedSizes(std::vector<SizeTarget>& targets, std::vector<uint32_t>& sizes);
  // Due to the memory required to run each of these, it is recommended to not preopen the zip file for multiple
  // These functions will open and close the zip as needed
  uint8_t* readFileToMemory(const char* filename, size_t* size = nullptr, bool trailingNullByte = false);
  bool readFileToStream(const char* filename, Print& out, size_t chunkSize);
};