Add bencode2json

bencode2json

@@ -0,0 +1,92 @@
+#!/usr/bin/env python3
+try:
+	from contextlib import nullcontext
+except ImportError:
+	# Python 3.6 and below
+	# One-liner because I can.
+	nullcontext = type("nc", (object,), {"__init__": (lambda self, v: setattr(self, "v", v)), "__enter__": (lambda self: self.v), "__exit__": (lambda self, *args, **kwargs: None)})
+import json
+import sys
+
+
+def parse_dict(f):
+	d = {}
+	while True:
+		c = f.read(1)
+		if c == b'e':
+			return d
+		elif b'0' <= c <= b'9':
+			key = parse_str(f, c)
+			value = parse_any(f)
+			d[key] = value
+		else:
+			raise ValueError(f'invalid bencode value: {c} instead of expected e or digit')
+
+
+def parse_list(f):
+	l = []
+	while True:
+		c = f.read(1)
+		if c == b'e':
+			return l
+		l.append(parse_any(f, c))
+
+
+def _parse_int_bytes(f, stopChar):
+	# Read until encountering a non-decimal character; if it isn't stopChar, raise a ValueError
+	v = b''
+	# Python 3.8+ (walrus)
+	#while b'0' <= (c := f.read(1)) <= b'9':
+	#	v += c
+	while True:
+		c = f.read(1)
+		if b'0' <= c <= b'9':
+			v += c
+		else:
+			break
+	if c == stopChar:
+		return v
+	raise ValueError(f'invalid bencode value: {c} instead of expected {stopChar}')
+
+
+def parse_int(f):
+	return int(_parse_int_bytes(f, b'e'))
+
+
+def parse_str(f, c):
+	v = _parse_int_bytes(f, b':')
+	length = int(c + v)
+	read = 0
+	buf = []
+	while read < length:
+		d = f.read(length - read)
+		buf.append(d)
+		read += len(d)
+	buf = b''.join(buf)
+	try:
+		return buf.decode('utf-8', 'strict')
+	except UnicodeDecodeError:
+		return buf.decode('iso-8859-1')
+
+
+def parse_any(f, c = None):
+	if c is None:
+		c = f.read(1)
+	if c == b'd':
+		return parse_dict(f)
+	elif c == b'l':
+		return parse_list(f)
+	elif c == b'i':
+		return parse_int(f)
+	elif b'0' <= c <= b'9':
+		return parse_str(f, c)
+	else:
+		raise ValueError(f'invalid bencode value: {c} instead of expected d, l, i, or digit')
+
+
+if sys.argv[1:]:
+	c = open(sys.argv[1], 'rb')
+else:
+	c = nullcontext(sys.stdin.buffer)
+with c as fp:
+	print(json.dumps(parse_any(fp)))