cleaned up encode_varint for segwit script op_push

karask · karask · commit eb15ee330c3c · 2021-06-23T14:07:41.000+03:00
diff --git a/README.rst b/README.rst
@@ -3,7 +3,7 @@ python-bitcoin-utils
 
 This is a bitcoin library that provides tools/utilities to interact with the Bitcoin network. One of the primary goals of the library is to explain the low-level details of Bitcoin. The code is easy to read and properly documented explaining in detail all the thorny aspects of the implementation. It is a low-level library which assumes some high-level understanding of how Bitcoin works. In the future this might change.
 
-This is an early version of the library (v0.5.1) and currently, it supports private/public keys, all type of addresses and creation of any transaction (incl. segwit) with all SIGHASH types. All script op codes are included. Timelock and non-standanrd transactions are supported. Currently, a simple node proxy exists to enable easy calls to a Bitcoin core node. Extra functionality will be added continuously and the documentation will be improved as the work progresses.
+This is an early version of the library (v0.5.2) and currently, it supports private/public keys, all type of addresses and creation of any transaction (incl. segwit) with all SIGHASH types. All script op codes are included. Timelock and non-standanrd transactions are supported. Currently, a simple node proxy exists to enable easy calls to a Bitcoin core node. Extra functionality will be added continuously and the documentation will be improved as the work progresses.
 
 The API documentation can be build with Sphinx but is also available as a PDF for convenience. One can currently use the library for experimenting and learning the inner workings of Bitcoin. It is not meant for production yet and parts of the API might be updated with new versions.
 
diff --git a/bitcoinutils/__init__.py b/bitcoinutils/__init__.py
@@ -1,2 +1,2 @@
-__version__ = '0.5.1'
+__version__ = '0.5.2'
 
diff --git a/bitcoinutils/script.py b/bitcoinutils/script.py
@@ -12,7 +12,7 @@
 import struct
 import copy
 import hashlib
-from bitcoinutils.utils import prepend_compact_size, to_bytes, vi_to_int
+from bitcoinutils.utils import prepend_varint, to_bytes, vi_to_int
 from binascii import unhexlify, hexlify
 
 import bitcoinutils.keys
@@ -314,16 +314,14 @@ def _op_push_data(self, data):
 
     def _segwit_op_push_data(self, data):
         # expects data in hexadecimal characters and converts to bytes with
-        # compact_size (or var_int) length prefix.
+        # varint (or compact size) length prefix.
         #
         # TODO maybe, for convenience, also accept objects for public keys,
         # addresses, etc. and use isinstance and convert manually
         data_bytes = unhexlify(data)
 
-        # prepend compact size lenth to data bytes
-        compact_size_data = prepend_compact_size(data_bytes)
-
-        return compact_size_data
+        # return prepended varint (compact size) length to data bytes
+        return prepend_varint(data_bytes)
 
 
 
diff --git a/bitcoinutils/utils.py b/bitcoinutils/utils.py
@@ -24,27 +24,31 @@ def to_satoshis(num):
 
 
 '''
-Counts bytes and returns them with their compact size (or varint) prepended.
-Accepts bytes and returns bytes. The length should be specified in
-little-endian (which is why we reverse the array bytes).
+Counts bytes and returns them with their varint (or compact size) prepended.
+Accepts bytes and returns bytes.
+'''
+def prepend_varint(data):
+    varint_bytes = encode_varint( len(data) )
+    return varint_bytes + data
+
+
+'''
+Encode a potentially very large integer into varint bytes. The length should be
+specified in little-endian.
 
 https://bitcoin.org/en/developer-reference#compactsize-unsigned-integers
 '''
-def prepend_compact_size(data):
-    prefix = b''
-    size = len(data)
-    if size >= 0 and size <= 252:
-        prefix = unhexlify(format(size, '02x').encode())
-    elif size >= 253 and size <= 0xffff:
-        prefix = b'\xfd' + unhexlify(format(size, '04x'))[::-1]
-    elif size >= 0x10000 and size <= 0xffffffff:
-        prefix = b'\xfe' + unhexlify(format(size, '08x'))[::-1]
-    elif size >= 0x100000000 and size <= 0xffffffffffffffff:
-        prefix = b'\xff' + unhexlify(format(size, '016x'))[::-1]
+def encode_varint(i):
+    if i < 253:
+        return bytes([i])
+    elif i < 0x10000:
+        return b'\xfd' +  i.to_bytes(2, 'little')
+    elif i < 0x100000000:
+        return b'\xfe' +  i.to_bytes(4, 'little')
+    elif i < 0x10000000000000000:
+        return b'\xff' +  i.to_bytes(8, 'little')
     else:
-        raise ValueError("Data size not between 0 and 0xffffffffffffffff")
-
-    return prefix + data
+        raise ValueError("Integer is too large: %d" % i)
 
 
 '''
diff --git a/docs/conf.py b/docs/conf.py
@@ -58,9 +58,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = u'0.5.1'
+version = u'0.5.2'
 # The full version, including alpha/beta/rc tags.
-release = u'0.5.1'
+release = u'0.5.2'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.

Original file line number	Diff line number	Diff line change
`@@ -1,2 +1,2 @@`
`1`		`-__version__ = '0.5.1'`
	`1`	`+__version__ = '0.5.2'`
`2`	`2`