hfs_decmpfs.hpp

1. Overview

The hfs_decmpfs.hpp file handles Apple decmpfs compression metadata and decompression during file recovery.

This is an interface and data-contract file. It declares the public and internal types used by this subsystem, allowing implementation files and callers to share a stable compile-time contract.

Its paired source or interface file is hfs_decmpfs.cpp.

Primary responsibilities:

  • Recognize decmpfs headers
  • Decode inline compressed payloads
  • Process resource-fork compression layouts
  • Return decompressed file content

2. File Identity and Scope

  • Source path: src/hfs_decmpfs.hpp
  • Language: C++
  • File role: interface and data-contract file
  • Physical lines: 112
  • Non-empty lines: 100
  • SHA-256: 56883b4bc2255470946509b1857b542682e0b2139ce816d49a9bfc5752c6af77

Declared namespaces:

  • hfs

3. Dependencies

3.2 Standard and External Headers

  • cstdint
  • string
  • vector

These dependencies define the file’s compile-time integration with the recovery engine, GTK interface, on-disk format decoders, operating-system services, or C++ standard library.

4. Declared Types

  • struct DecmpfsHeader.

5. Constants and Configuration Values

  • constexpr uint32_t DECMPFS_MAGIC=0x66706D63
  • constexpr size_t DECMPFS_HEADER_SIZE=16
  • constexpr size_t kDecmpfsBlockSize=64*1024
  • constexpr uint32_t kCompressionType_None=1
  • constexpr uint32_t kCompressionType_ZlibInXattr=3
  • constexpr uint32_t kCompressionType_ZlibInRsrc=4
  • constexpr uint32_t kCompressionType_LzvnInXattr=7
  • constexpr uint32_t kCompressionType_LzvnInRsrc=8
  • constexpr uint32_t kCompressionType_LzfseInXattr=11
  • constexpr uint32_t kCompressionType_LzfseInRsrc=12

6. Data Members and Persistent State

The interface declares the following state-bearing members:

  • constexpr uint32_t DECMPFS_MAGIC=0x66706D63
  • constexpr size_t DECMPFS_HEADER_SIZE=16
  • constexpr size_t kDecmpfsBlockSize=64*1024
  • constexpr uint32_t kCompressionType_None=1
  • constexpr uint32_t kCompressionType_ZlibInXattr=3
  • constexpr uint32_t kCompressionType_ZlibInRsrc=4
  • constexpr uint32_t kCompressionType_LzvnInXattr=7
  • constexpr uint32_t kCompressionType_LzvnInRsrc=8
  • constexpr uint32_t kCompressionType_LzfseInXattr=11
  • constexpr uint32_t kCompressionType_LzfseInRsrc=12
  • uint32_t magic {0}
  • uint32_t type {0}
  • uint64_t size {0}

These members hold configuration, parser context, UI widgets, source references, progress state, recovered metadata, or temporary resources according to the owning type.

7. API and Function Inventory

The following callable interfaces or definitions were detected:

  • bool parse_decmpfs_header(const unsigned char*buf,DecmpfsHeader&out) – Reads or derives the requested information and returns or stores the decoded result.
  • bool decmpfs_supported(uint32_t type) – Implements the operation identified by this API and updates or returns the associated state.
  • bool decompress_resource_fork_zlib(const unsigned char*rsrc_buf,size_t rsrc_len,uint64_t expected_uncompressed_size,std::vector<unsigned char>&out,std::string&error) – Implements the operation identified by this API and updates or returns the associated state.
  • bool decompress_xattr_zlib(const unsigned char*xattr_buf,size_t xattr_len,uint64_t expected_uncompressed_size,std::vector<unsigned char>&out,std::string&error) – Implements the operation identified by this API and updates or returns the associated state.

8. Operational Flow

The subsystem represented by this file normally participates in the following flow:

  1. Recognize decmpfs headers.
  2. Decode inline compressed payloads.
  3. Process resource-fork compression layouts.
  4. Return decompressed file content.
  5. Expose or execute the detected APIs: parse_decmpfs_header, decmpfs_supported, decompress_resource_fork_zlib, decompress_xattr_zlib.
  6. Return explicit results, progress data, recovered records, or diagnostics to the calling layer.

9. Validation and Error Handling

  • Errors are propagated through Boolean results, error strings, logs, exceptions, or status records depending on the API.
  • Byte offsets, sizes and lengths must be validated before arithmetic and before every read to avoid overflow and out-of-bounds access.
  • On-disk structures are accepted only after validating signatures, magic values and structural constraints.
  • Input and output paths require existence checks, permission handling and safe destination construction.

10. Runtime, Concurrency, and Resource Management

  • Deterministic behavior: callers depend on explicit return values and stable data structures to distinguish successful recovery from partial or invalid results.

11. Security and Data-Recovery Considerations

  • Recovery code should prefer read-only source access and avoid writing to the original damaged medium.
  • Raw devices and image files are treated as untrusted binary input; every offset and length must remain bounded by the source size.

12. Implementation Considerations

  • Changes to public declarations can affect every translation unit that includes this header and should preserve binary and source compatibility where required.
  • State-bearing members should have explicit ownership and initialization semantics, especially for references, pointers, file descriptors and GTK widgets.
  • Large-device arithmetic uses 64-bit values; additions and multiplications should be checked before use as offsets or allocation sizes.

13. Integration with the Recovery Pipeline

  • The file belongs to the source-discovery, parsing or support layer.
  • Its results feed scanner, recovery or reporting modules through shared models.
  • The API should remain deterministic so higher layers can combine results safely.

14. Licensing and Provenance

No explicit copyright or software-license statement was detected in the opening section of this individual file. Distribution terms should therefore be verified against the project-level license and repository metadata.

The SHA-256 value in this document can be used to associate the generated documentation with the exact source version analyzed.

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