From c576dc8a517908c694c0ed19b430f927ae70c889 Mon Sep 17 00:00:00 2001
From: InsanePrawn <insane.prawny@gmail.com>
Date: Mon, 17 Apr 2023 21:57:30 +0200
Subject: [PATCH] utils: handle zstd compressed tarfiles

---
 utils.py | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 75 insertions(+), 9 deletions(-)

diff --git a/utils.py b/utils.py
index 0cfdae8..26a65ed 100644
--- a/utils.py
+++ b/utils.py
@@ -11,6 +11,7 @@ import subprocess
 import tarfile
 
 from dateutil.parser import parse as parsedate
+from io import BytesIO
 from shutil import which
 from typing import Any, Generator, IO, Optional, Union, Sequence
 
@@ -151,6 +152,63 @@ def is_zstd(data):
     return True
 
 
+class BackwardsReadableStream:
+    def __init__(self, stream):
+        self.stream = stream
+        self.buffer = bytearray()
+        self.position = 0
+
+    def read(self, size=-1):
+        data = b''
+        if size == -1:
+            # read all remaining data in stream
+            data = self.stream.read()
+        else:
+            not_read = (self.position + size) - len(self.buffer)
+            if not_read > 0:
+                # read up to size bytes from stream
+                data = self.stream.read(not_read)
+            else:
+                data = self.buffer[self.position:self.position+size+1]
+
+        old_position = self.position
+        new_position = self.position + len(data)
+        self.buffer.extend(data)
+        self.position = new_position
+        return self.buffer[old_position:new_position+1]
+
+    def seek(self, offset, whence=0):
+        if whence == 0:
+            # seek from beginning of buffer
+            self.position = offset
+        elif whence == 1:
+            # seek from current position
+            self.position += offset
+        elif whence == 2:
+            # seek from end of buffer
+            self.position = len(self.buffer) + offset
+        else:
+            raise ValueError("Invalid whence value")
+
+        # adjust position to be within buffer bounds
+        self.position = max(0, min(self.position, len(self.buffer)))
+
+    def tell(self):
+        return self.position
+
+    def readable(self):
+        return True
+
+    def seekable(self):
+        return True
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.stream.__exit__(exc_type, exc_value, traceback)
+
+
 def decompress_if_zstd(stream):
     """
     Given a byte stream, returns either the original stream or the decompressed stream
@@ -165,7 +223,7 @@ def decompress_if_zstd(stream):
     logging.debug(f"Decompressing {stream=}")
     import zstandard as zstd
     dctx = zstd.ZstdDecompressor()
-    return tarfile.open(fileobj=dctx.stream_reader(stream, read_size=4096), mode='r|')
+    return tarfile.open(fileobj=BytesIO(dctx.stream_reader(stream).read()), mode='r:tar')
 
 
 def open_tar(tar_file: str) -> tarfile.TarFile:
@@ -190,13 +248,21 @@ def read_files_from_tar_recursive(tar_file: str, paths: Sequence[str], append_sl
     paths = [f"{p.strip('/')}/" for p in paths]
     with open_tar(tar_file) as index:
         for member in index.getmembers():
-            for path in paths:
-                if member.isfile() and member.path.startswith(path):
-                    fd = index.extractfile(member)
-                    assert fd
-                    yield member.path, fd
-                    break
-            continue
+            file_path = member.path
+            if member.isfile() and check_file_matches(file_path, paths):
+                logging.debug(f"tar: Returning {file_path}")
+                fd = index.extractfile(member)
+                assert fd
+                yield file_path, fd
+            else:
+                logging.debug(f'tar: unmatched {file_path} for query {paths}')
+
+
+def check_file_matches(file_path: str, queries: list[str]) -> bool:
+    for query in queries:
+        if file_path.startswith(query):
+            return True
+    return False
 
 
 def extract_files_from_tar_generator(
@@ -205,7 +271,6 @@ def extract_files_from_tar_generator(
     remove_prefix: str = '',
     append_slash: bool = True,
 ):
-    assert os.path.exists(output_dir)
     remove_prefix = remove_prefix.strip('/')
     if append_slash and remove_prefix:
         remove_prefix += '/'
@@ -214,6 +279,7 @@ def extract_files_from_tar_generator(
         output_path = os.path.join(output_dir, file_path[len(remove_prefix):].lstrip('/'))
         os.makedirs(os.path.dirname(output_path), exist_ok=True)
         with open(output_path, 'wb') as f:
+            logging.debug(f"Extracting {file_path}")
             f.write(fd.read())