107 lines
3.8 KiB
Python
107 lines
3.8 KiB
Python
import builtins
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from flask import Response
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import functools
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import os
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# 4MiB chunks
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CHUNK_SIZE = 4_194_304
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# ASCII value for space
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SPACE = ord(' ')
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# ASCII value for zero
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ZERO = ord('0')
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# Specification de l'entête du fichier
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# Numéro Nom Début Taille Description
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# 1 name 0 100 Nom du fichier
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# 2 mode 100 8 Permissions
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# 3 uid 108 8 Propriétaire (inutilisé si format étendu)
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# 4 gid 116 8 Groupe (inutilisé si format étendu)
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# 5 size 124 12 Taille du fichier en octets.
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# 6 mtime 136 12 Dernière modification en temps Unix.
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# 7 chksum 148 8 Somme de contrôle de l'en-tête où ce champ est considéré comme rempli d'espaces (32)
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# 8 type flag 156 1 Type de fichier
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# 9 linkname 157 100 Nom du fichier pointé par ce lien symbolique (Si le type indique un lien symbolique)
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def header_chunk(filename: str, filepath: str) -> bytes:
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# Returns the octal representation without the initial
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def oct(i: int) -> str:
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return builtins.oct(i)[2:]
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stat = os.stat(filepath)
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buffer = bytearray(512)
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# Field 1: filename on 100 bytes
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buffer[0:len(filename)] = filename.encode('ascii')
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# Field 2: mode, on 8 bytes, octal, last byte must be \x00, so we set only the first 7 bytes
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buffer[100:107] = oct(stat.st_mode).rjust(7, '0').encode('ascii')
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# Field 3: owner, on 8 bytes, octal, last byte must be \x00, so we set only the first 7 bytes
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buffer[108:115] = oct(stat.st_uid).rjust(7, '0').encode('ascii')
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# Field 4: group, on 8 bytes, octal, last byte must be \x00, so we set only the first 7 bytes
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buffer[116:123] = oct(stat.st_gid).rjust(7, '0').encode('ascii')
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# Field 5: file size in bytes, on 12 bytes, octal, last byte must be \x00, so we set only the first 11 bytes
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buffer[124:135] = oct(stat.st_size).rjust(11, '0').encode('ascii')
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# Field 6: last modified, on 12 bytes, octal, last byte must be \x00, so we set only the first 11 bytes
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buffer[136:147] = oct(int(stat.st_mtime)).rjust(11, '0').encode('ascii')
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# Field 7: checksum, we fill it at the end
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# Field 8: type flag, 0 because we only have regular files
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buffer[156] = ZERO
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# Field 9: linkname, \x00s because we only have regular files
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# POSIX 1003.1-1990: 255 empty bytes
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# Compute the checksum: we start at 256 which are the 8 fields of checksum filled with spaces (32 * 8)
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checksum = oct(functools.reduce(lambda x, y: x + y, buffer, 256)).rjust(6, '0').encode('ascii')
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buffer[148:154] = checksum
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# Don't ask me why, but the checksum must end with b'\x00 ', so we skip the \x00 and write the space
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buffer[155] = SPACE
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return bytes(buffer)
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class TarSender:
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def __init__(self):
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self.files: dict[str, str] = {}
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def add_file(self, filename: str, filepath: str):
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self.files[filename] = filepath
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def response(self):
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def generate():
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for name, file in self.files.items():
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yield header_chunk(name, file)
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bytes_sent = 0
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with open(file, 'rb') as f:
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while True:
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bytes = f.read(CHUNK_SIZE)
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if len(bytes) == 0:
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break
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bytes_sent += len(bytes)
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yield bytes
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# Because tar use records of 512 bytes, we need to pad the
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# file with zeroes to fill the last chunk
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yield b'\x00' * (512 - bytes_sent % 512)
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return Response(
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generate(),
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mimetype='application/x-tar',
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headers={'Content-Disposition': 'attachment; filename="archive.tar"'}
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)
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