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| author | James Taylor <user234683@users.noreply.github.com> | 2018-06-30 23:34:46 -0700 |
|---|---|---|
| committer | James Taylor <user234683@tutanota.com> | 2018-06-30 23:34:46 -0700 |
| commit | 98157bf1bf1223ffa7556d2d21cfac6f07675f9d (patch) | |
| tree | 9863e438deec87bb309a435c0f4cb0eb0e455dcc /youtube/proto.py | |
| download | yt-local-98157bf1bf1223ffa7556d2d21cfac6f07675f9d.tar.lz yt-local-98157bf1bf1223ffa7556d2d21cfac6f07675f9d.tar.xz yt-local-98157bf1bf1223ffa7556d2d21cfac6f07675f9d.zip | |
initial commit
Diffstat (limited to 'youtube/proto.py')
| -rw-r--r-- | youtube/proto.py | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/youtube/proto.py b/youtube/proto.py new file mode 100644 index 0000000..9f9dbcc --- /dev/null +++ b/youtube/proto.py @@ -0,0 +1,65 @@ +from math import ceil
+import base64
+
+def byte(n):
+ return bytes((n,))
+
+
+def varint_encode(offset):
+ '''In this encoding system, for each 8-bit byte, the first bit is 1 if there are more bytes, and 0 is this is the last one.
+ The next 7 bits are data. These 7-bit sections represent the data in Little endian order. For example, suppose the data is
+ aaaaaaabbbbbbbccccccc (each of these sections is 7 bits). It will be encoded as:
+ 1ccccccc 1bbbbbbb 0aaaaaaa
+
+ This encoding is used in youtube parameters to encode offsets and to encode the length for length-prefixed data.
+ See https://developers.google.com/protocol-buffers/docs/encoding#varints for more info.'''
+ needed_bytes = ceil(offset.bit_length()/7) or 1 # (0).bit_length() returns 0, but we need 1 in that case.
+ encoded_bytes = bytearray(needed_bytes)
+ for i in range(0, needed_bytes - 1):
+ encoded_bytes[i] = (offset & 127) | 128 # 7 least significant bits
+ offset = offset >> 7
+ encoded_bytes[-1] = offset & 127 # leave first bit as zero for last byte
+
+ return bytes(encoded_bytes)
+
+
+def varint_decode(encoded):
+ decoded = 0
+ for i, byte in enumerate(encoded):
+ decoded |= (byte & 127) << 7*i
+
+ if not (byte & 128):
+ break
+ return decoded
+
+
+def string(field_number, data):
+ data = as_bytes(data)
+ return _proto_field(2, field_number, varint_encode(len(data)) + data)
+nested = string
+
+def uint(field_number, value):
+ return _proto_field(0, field_number, varint_encode(value))
+
+
+
+
+def _proto_field(wire_type, field_number, data):
+ ''' See https://developers.google.com/protocol-buffers/docs/encoding#structure '''
+ return varint_encode( (field_number << 3) | wire_type) + data
+
+
+
+def percent_b64encode(data):
+ return base64.urlsafe_b64encode(data).replace(b'=', b'%3D')
+
+
+def unpadded_b64encode(data):
+ return base64.urlsafe_b64encode(data).replace(b'=', b'')
+
+def as_bytes(value):
+ if isinstance(value, str):
+ return value.encode('ascii')
+ return value
+
+
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