"""
*******************************************************************************
*   BTChip Bitcoin Hardware Wallet Python API
*   (c) 2014 BTChip - 1BTChip7VfTnrPra5jqci7ejnMguuHogTn
*
*  Licensed under the Apache License, Version 2.0 (the "License");
*  you may not use this file except in compliance with the License.
*  You may obtain a copy of the License at
*
*      http://www.apache.org/licenses/LICENSE-2.0
*
*   Unless required by applicable law or agreed to in writing, software
*   distributed under the License is distributed on an "AS IS" BASIS,
*   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*  See the License for the specific language governing permissions and
*   limitations under the License.
********************************************************************************
"""

from btchipException import BTChipException

def readVarint(buffer, offset):
	varintSize = 0
	value = 0
	if (buffer[offset] < 0xfd):
		value = buffer[offset]
		varintSize = 1
	elif (buffer[offset] == 0xfd):
		value = (buffer[offset + 2] << 8) | (buffer[offset + 1])
		varintSize = 3
	elif (buffer[offset] == 0xfe):
		value = (buffer[offset + 4] << 24) | (buffer[offset + 3] << 16) | (buffer[offset + 2] << 8) | (buffer[offset + 1])
		varintSize = 5
	else:
		raise BTChipException("unsupported varint")
	return { "value": value, "size": varintSize }

def writeVarint(value, buffer):
	if (value < 0xfd):
		buffer.append(value)
	elif (value <= 0xffff):
		buffer.append(0xfd)
		buffer.append(value & 0xff)
		buffer.append((value >> 8) & 0xff)
	elif (value <= 0xffffffff):
		buffer.append(0xfe)
		buffer.append(value & 0xff)
		buffer.append((value >> 8) & 0xff)
		buffer.append((value >> 16) & 0xff)
		buffer.append((value >> 24) & 0xff)
	else:
		raise BTChipException("unsupported encoding")
	return buffer

def getVarintSize(value):
	if (value < 0xfd):
		return 1
	elif (value <= 0xffff):
		return 3
	elif (value <= 0xffffffff):
		return 5
	else:
		raise BTChipException("unsupported encoding")
