Added base58 decoder

trezorlib/tools.py

@@ -0,0 +1,55 @@
+__b58chars = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
+__b58base = len(__b58chars)
+
+
+def b58encode(v):
+    """ encode v, which is a string of bytes, to base58."""
+
+    long_value = 0L
+    for (i, c) in enumerate(v[::-1]):
+        long_value += (256 ** i) * ord(c)
+
+    result = ''
+    while long_value >= __b58base:
+        div, mod = divmod(long_value, __b58base)
+        result = __b58chars[mod] + result
+        long_value = div
+    result = __b58chars[long_value] + result
+
+    # Bitcoin does a little leading-zero-compression:
+    # leading 0-bytes in the input become leading-1s
+    nPad = 0
+    for c in v:
+        if c == '\0':
+            nPad += 1
+        else:
+            break
+
+    return (__b58chars[0] * nPad) + result
+
+
+def b58decode(v, length):
+    """ decode v into a string of len bytes."""
+    long_value = 0L
+    for (i, c) in enumerate(v[::-1]):
+        long_value += __b58chars.find(c) * (__b58base ** i)
+
+    result = ''
+    while long_value >= 256:
+        div, mod = divmod(long_value, 256)
+        result = chr(mod) + result
+        long_value = div
+    result = chr(long_value) + result
+
+    nPad = 0
+    for c in v:
+        if c == __b58chars[0]:
+            nPad += 1
+        else:
+            break
+
+    result = chr(0) * nPad + result
+    if length is not None and len(result) != length:
+        return None
+
+    return result