archive-r-python 0.1.20

Python bindings for archive_r: libarchive-based streaming traversal for recursive nested archives (no temp files, no large in-memory buffers)

archive_r Python Bindings

⚠️ Development Status: This library is currently under development. The API may change without notice.

Overview

Python bindings for archive_r, a libarchive-based library for processing many archive formats. It streams entry data directly from the source to recursively read nested archives without extracting to temporary files or loading large in-memory buffers. The bindings expose a Pythonic iterator API with context manager support.

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Installation

From PyPI

pip install archive_r_python

From Source

cd archive_r/bindings/python
pip install .

Development Installation (Editable Mode)

cd archive_r/bindings/python
pip install -e .

Building with Parent Build Script

cd archive_r
./build.sh --with-python

This builds the core library and Python bindings, placing artifacts in build/bindings/python/.

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Basic Usage

Simple Traversal

import archive_r

# Context manager ensures proper resource cleanup
with archive_r.Traverser("test.zip") as traverser:
    for entry in traverser:
        print(f"Path: {entry.path} (depth={entry.depth})")
        if entry.is_file:
            print(f"  Size: {entry.size} bytes")

Reading Entry Content

import archive_r

with archive_r.Traverser("archive.tar.gz") as traverser:
    for entry in traverser:
        if entry.is_file and entry.path.endswith('.txt'):
            # Read full content
            content = entry.read()
            print(f"Content of {entry.path}:")
            print(content.decode('utf-8', errors='replace'))

Chunked Reading (Large Files)

import archive_r

with archive_r.Traverser("large_archive.zip") as traverser:
    for entry in traverser:
        if entry.is_file:
            # Read in 8KB chunks
            chunk_size = 8192
            total_bytes = 0
            while True:
                chunk = entry.read(chunk_size)
                if not chunk:
                    break
                total_bytes += len(chunk)
                # Process chunk...
            
            print(f"{entry.path}: {total_bytes} bytes read")

Searching in Entry Content

import archive_r

def search_in_entry(entry, keyword):
    """Stream search within entry content (buffer boundary aware)"""
    overlap = b''
    buffer_size = 8192
    keyword_bytes = keyword.encode('utf-8')
    
    while True:
        chunk = entry.read(buffer_size)
        if not chunk:
            break
        
        search_text = overlap + chunk
        if keyword_bytes in search_text:
            return True
        
        # Preserve tail for next iteration
        if len(chunk) >= len(keyword_bytes) - 1:
            overlap = chunk[-(len(keyword_bytes) - 1):]
        else:
            overlap = chunk
    
    return False

with archive_r.Traverser("documents.zip") as traverser:
    for entry in traverser:
        if entry.is_file and entry.path.endswith('.txt'):
            if search_in_entry(entry, "important"):
                print(f"Found keyword in: {entry.path}")

Controlling Archive Descent

import archive_r

with archive_r.Traverser("test.zip") as traverser:
    for entry in traverser:
        # Don't expand Office files (they are ZIP internally)
        if entry.path.endswith(('.docx', '.xlsx', '.pptx')):
            entry.set_descent(False)
        
        print(f"Path: {entry.path}, Will descend: {entry.descent_enabled}")

You can also disable automatic descent globally:

# Disable automatic descent for all entries
with archive_r.Traverser("test.zip", descend_archives=False) as traverser:
    for entry in traverser:
        # Manually enable descent for specific entries
        if entry.path.endswith('.tar.gz'):
            entry.set_descent(True)

⚠️ Note: Reading entry content automatically disables descent. Call entry.set_descent(True) if you need to descend after reading.

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Path Representation

The Python bindings provide three ways to access entry paths:

with archive_r.Traverser("outer.zip") as traverser:
    for entry in traverser:
        # Full path including top-level archive
        # Example: "outer.zip/inner.tar/file.txt"
        print(f"path: {entry.path}")
        
        # Last element of path_hierarchy
        # Example: "inner.tar/file.txt"
        print(f"name: {entry.name}")
        
        # Path hierarchy as list
        # Example: ["outer.zip", "inner.tar/file.txt"]
        print(f"path_hierarchy: {entry.path_hierarchy}")

path_hierarchy is particularly useful when you need custom path separators or want to represent the nesting structure explicitly.

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Metadata Access

Basic Metadata

Entry objects provide common metadata through properties:

with archive_r.Traverser("archive.tar") as traverser:
    for entry in traverser:
        print(f"Path: {entry.path}")
        print(f"  Type: {'file' if entry.is_file else 'directory'}")
        print(f"  Size: {entry.size} bytes")
        print(f"  Depth: {entry.depth}")

Extended Metadata

For additional metadata (permissions, ownership, timestamps), specify metadata_keys:

with archive_r.Traverser("archive.tar", metadata_keys=["uid", "gid", "mtime", "mode"]) as traverser:
    for entry in traverser:
        # Retrieve all specified metadata as dictionary
        metadata = entry.metadata()
        print(f"{entry.path}:")
        print(f"  UID: {metadata.get('uid')}")
        print(f"  GID: {metadata.get('gid')}")
        print(f"  Mode: {oct(metadata.get('mode', 0))}")
        
        # Or retrieve specific metadata
        mtime = entry.find_metadata("mtime")
        if mtime is not None:
            print(f"  Modified: {mtime}")

Available metadata keys depend on the archive format. Common keys include:

• uid, gid: User/group ID
• mtime, atime, ctime: Timestamps (Unix time)
• mode: File permissions
• uname, gname: User/group names
• hardlink, symlink: Link targets

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Processing Split Archives

For split archive files (e.g., .zip.001, .zip.002), use set_multi_volume_group():

import archive_r

with archive_r.Traverser("container.tar") as traverser:
    for entry in traverser:
        # Detect split archive parts
        if '.part' in entry.path:
            # Extract base name (e.g., "archive.zip.part001" → "archive.zip")
            pos = entry.path.rfind('.part')
            base_name = entry.path[:pos]
            entry.set_multi_volume_group(base_name)
        
        # After parent traversal, grouped parts are merged and expanded

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Format Specification

By default, all formats supported by libarchive are enabled. To restrict to specific formats:

# Enable only ZIP and TAR
with archive_r.Traverser("test.zip", formats=["zip", "tar"]) as traverser:
    for entry in traverser:
        print(entry.path)

Common format names: "7zip", "ar", "cab", "cpio", "iso9660", "lha", "rar", "tar", "warc", "xar", "zip"

💡 Tip: Exclude pseudo-formats like "mtree" and "raw" if you encounter false positives on non-archive files.

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Custom Stream Factories

You can provide custom stream objects (file-like objects with read() method) to override the default file opening behavior:

import archive_r
import io

# Register a custom stream factory
def custom_stream_factory(path):
    """Return a file-like object for the given path"""
    if path == "special_file.bin":
        # Return custom data source
        return io.BytesIO(b"custom content")
    # Return None to use default file opening
    return None

archive_r.register_stream_factory(custom_stream_factory)

with archive_r.Traverser("test.zip") as traverser:
    for entry in traverser:
        # When traverser needs to open "special_file.bin",
        # your factory will provide the BytesIO stream
        pass

Stream objects must provide:

• read(size): Read up to size bytes
• Optional: seek(offset, whence), tell() for seekable streams
• Optional: rewind() (defaults to seek(0, 0) if not provided)

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Error Handling

Fault Callbacks

Data errors (corrupted archives, I/O failures) are reported via callbacks without stopping traversal:

import archive_r

def fault_handler(fault_info):
    """Called when data errors occur during traversal"""
    print(f"Warning at {fault_info['hierarchy']}: {fault_info['message']}")
    if fault_info.get('errno'):
        print(f"  Error code: {fault_info['errno']}")

archive_r.on_fault(fault_handler)

with archive_r.Traverser("potentially_corrupted.zip") as traverser:
    for entry in traverser:
        # Valid entries are processed normally
        # Corrupted entries trigger fault_handler
        print(entry.path)

Read Errors

Errors during read() raise exceptions:

try:
    with archive_r.Traverser("test.zip") as traverser:
        for entry in traverser:
            if entry.is_file:
                content = entry.read()
except RuntimeError as e:
    print(f"Read error: {e}")

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Thread Safety

The Python bindings follow the same thread safety constraints as the C++ core:

• ✓ Thread-safe: Each thread can create and use its own Traverser instance independently
• ✗ Not thread-safe: A single Traverser or Entry instance must not be shared across threads

Example

import threading
import archive_r

# ✓ SAFE: Each thread has its own Traverser
def worker():
    with archive_r.Traverser("archive.tar.gz") as traverser:
        for entry in traverser:
            # Process entry...
            pass

t1 = threading.Thread(target=worker)
t2 = threading.Thread(target=worker)
t1.start()
t2.start()
t1.join()
t2.join()

# ✗ UNSAFE: Sharing a single Traverser instance across threads
shared_traverser = archive_r.Traverser("archive.tar.gz")
def unsafe_worker():
    for entry in shared_traverser:  # Race condition!
        pass

# Don't do this!
# t1 = threading.Thread(target=unsafe_worker)
# t2 = threading.Thread(target=unsafe_worker)

Additionally:

• Global registration functions (register_stream_factory, on_fault) should be called during single-threaded initialization
• Entry objects should not be shared between threads (they are tied to the Traverser's internal state)

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Advanced Examples

Full Example: Recursive Archive Analyzer

import archive_r
import sys
from collections import defaultdict

def analyze_archive(archive_path):
    """Analyze archive contents and print statistics"""
    stats = defaultdict(int)
    file_types = defaultdict(int)
    
    with archive_r.Traverser(archive_path, metadata_keys=["mtime"]) as traverser:
        for entry in traverser:
            stats['total_entries'] += 1
            
            if entry.is_file:
                stats['files'] += 1
                stats['total_size'] += entry.size
                
                # Count by extension
                if '.' in entry.name:
                    ext = entry.name.rsplit('.', 1)[1]
                    file_types[ext] += 1
                
                # Find largest file
                if entry.size > stats.get('max_file_size', 0):
                    stats['max_file_size'] = entry.size
                    stats['max_file_path'] = entry.path
            else:
                stats['directories'] += 1
            
            # Track maximum depth
            if entry.depth > stats.get('max_depth', 0):
                stats['max_depth'] = entry.depth
    
    # Print results
    print(f"\nArchive Analysis: {archive_path}")
    print(f"  Total entries: {stats['total_entries']}")
    print(f"  Files: {stats['files']}")
    print(f"  Directories: {stats['directories']}")
    print(f"  Total size: {stats['total_size']:,} bytes")
    print(f"  Maximum depth: {stats['max_depth']}")
    
    if 'max_file_path' in stats:
        print(f"  Largest file: {stats['max_file_path']} ({stats['max_file_size']:,} bytes)")
    
    if file_types:
        print("\n  File types:")
        for ext, count in sorted(file_types.items(), key=lambda x: x[1], reverse=True)[:10]:
            print(f"    .{ext}: {count}")

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print("Usage: python analyze.py <archive_path>")
        sys.exit(1)
    
    analyze_archive(sys.argv[1])

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Testing

Run the Python binding tests:

cd archive_r/bindings/python
python -m unittest discover test

Or use the project-wide test runner:

cd archive_r
./bindings/python/run_binding_tests.sh

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API Reference

Module: archive_r

Class: Traverser

Constructor:

Traverser(
    roots,                           # str or list of str/list (path hierarchy)
    formats=None,                    # list of format names (default: all)
    descend_archives=True,           # automatically expand archives
    metadata_keys=None,              # list of metadata keys to capture
    passphrases=None                 # list of passphrases for encrypted archives
)

Methods:

• __iter__(): Returns self (iterator protocol)
• __next__(): Returns next Entry or raises StopIteration
• __enter__(): Context manager entry (returns self)
• __exit__(exc_type, exc_val, exc_tb): Context manager exit

Class: Entry

Properties:

• path: Full path string (read-only)
• name: Last element of path hierarchy (read-only)
• path_hierarchy: List representation of path (read-only)
• depth: Nesting depth (read-only)
• is_file: True if entry is a file (read-only)
• size: File size in bytes, 0 for directories (read-only)
• descent_enabled: Whether this entry will be expanded as an archive (read-only)

Methods:

• read(size=None): Read entry content (bytes). If size is omitted, reads all remaining data
• set_descent(enabled): Enable/disable archive expansion for this entry
• set_multi_volume_group(group_name): Register this entry as part of a split archive group
• metadata(): Return dictionary of all captured metadata
• find_metadata(key): Return value for specific metadata key, or None if not found

Function: register_stream_factory

archive_r.register_stream_factory(factory_func)

Register a callback to provide custom stream objects for file access.

Parameters:

• factory_func: Callable that takes a file path (str) and returns a file-like object or None

Stream object requirements:

• Must provide read(size) method
• Optional: seek(offset, whence), tell(), rewind()

Function: on_fault

archive_r.on_fault(callback)

Register a callback to receive fault notifications during traversal.

Parameters:

• callback: Callable that takes a dict with keys:
  • hierarchy: List of path components where fault occurred
  • message: Human-readable error description
  • errno: Optional error number from system calls

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Packaging

Building Wheels

cd archive_r
./build.sh --package-python

This creates wheel (.whl) and source distribution (.tar.gz) in build/bindings/python/dist/.

Manual Packaging

cd bindings/python
python setup.py sdist bdist_wheel

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Requirements

• Python 3.8 or later
• libarchive 3.x (runtime dependency)
• setuptools, wheel (build dependencies)
• pybind11 >= 2.6.0 (build dependency, automatically vendored during packaging)

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License

The Python bindings are distributed under the MIT License, consistent with the archive_r core library.

Third-Party Licenses

• pybind11: BSD-style License (used for C++/Python interfacing)
• libarchive: New BSD License (runtime dependency)

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See Also

• archive_r Core Documentation
• Ruby Bindings
• Example Scripts

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