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
+    
+    
+\ No newline at end of file