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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,123 @@ | ||
| # Copyright (C) 2019 HERE Europe B.V. | ||
| # Licensed under MIT, see full license in LICENSE | ||
| # SPDX-License-Identifier: MIT | ||
| # License-Filename: LICENSE | ||
|
|
||
| from collections import namedtuple | ||
| LEVEL = 1 | ||
| ALTITUDE = 2 | ||
| ELEVATION = 3 | ||
| # Reserved values 4 and 5 should not be selectable | ||
| CUSTOM1 = 6 | ||
| CUSTOM2 = 7 | ||
| THIRD_DIM_MAP = {ALTITUDE: 'alt', ELEVATION: 'elv', LEVEL: 'lvl', CUSTOM1: 'cst1', CUSTOM2: 'cst2'} | ||
| FORMAT_VERSION = 1 | ||
|
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| __all__ = [ | ||
| 'decode', 'dict_decode', 'iter_decode', | ||
| 'get_third_dimension', 'decode_header', 'PolylineHeader' | ||
| ] | ||
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| DECODING_TABLE = [ | ||
| 62, -1, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, | ||
| 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, | ||
| 22, 23, 24, 25, -1, -1, -1, -1, 63, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, | ||
| 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 | ||
| ] | ||
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| PolylineHeader = namedtuple('PolylineHeader', 'precision,third_dim,third_dim_precision') | ||
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| def decode_header(decoder): | ||
| """Decode the polyline header from an `encoded_char`. Returns a PolylineHeader object.""" | ||
| version = next(decoder) | ||
| if version != FORMAT_VERSION: | ||
| raise ValueError('Invalid format version') | ||
| value = next(decoder) | ||
| precision = value & 15 | ||
| value >>= 4 | ||
| third_dim = value & 7 | ||
| third_dim_precision = (value >> 3) & 15 | ||
| return PolylineHeader(precision, third_dim, third_dim_precision) | ||
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| def get_third_dimension(encoded): | ||
| """Return the third dimension of an encoded polyline. | ||
| Possible returned values are: ABSENT, LEVEL, ALTITUDE, ELEVATION, CUSTOM1, CUSTOM2.""" | ||
| header = decode_header(decode_unsigned_values(encoded)) | ||
| return header.third_dim | ||
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| def decode_char(char): | ||
| """Decode a single char to the corresponding value""" | ||
| char_value = ord(char) | ||
|
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| try: | ||
| value = DECODING_TABLE[char_value - 45] | ||
| except IndexError: | ||
| raise ValueError('Invalid encoding') | ||
| if value < 0: | ||
| raise ValueError('Invalid encoding') | ||
| return value | ||
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| def to_signed(value): | ||
| """Decode the sign from an unsigned value""" | ||
| if value & 1: | ||
| value = ~value | ||
| value >>= 1 | ||
| return value | ||
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| def decode_unsigned_values(encoded): | ||
| """Return an iterator over encoded unsigned values part of an `encoded` polyline""" | ||
| result = shift = 0 | ||
|
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| for char in encoded: | ||
| value = decode_char(char) | ||
|
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| result |= (value & 0x1F) << shift | ||
| if (value & 0x20) == 0: | ||
| yield result | ||
| result = shift = 0 | ||
| else: | ||
| shift += 5 | ||
|
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||
| if shift > 0: | ||
| raise ValueError('Invalid encoding') | ||
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| def iter_decode(encoded): | ||
| """Return an iterator over coordinates. The number of coordinates are 2 or 3 | ||
| depending on the polyline content.""" | ||
|
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| last_lat = last_lng = last_z = 0 | ||
| decoder = decode_unsigned_values(encoded) | ||
|
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| header = decode_header(decoder) | ||
| factor_degree = 10.0 ** header.precision | ||
| factor_z = 10.0 ** header.third_dim_precision | ||
| third_dim = header.third_dim | ||
|
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||
| while True: | ||
| try: | ||
| last_lat += to_signed(next(decoder)) | ||
| except StopIteration: | ||
| return # sequence completed | ||
|
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||
| try: | ||
| last_lng += to_signed(next(decoder)) | ||
|
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| if third_dim: | ||
| last_z += to_signed(next(decoder)) | ||
| yield (last_lat / factor_degree, last_lng / factor_degree, last_z / factor_z) | ||
| else: | ||
| yield (last_lat / factor_degree, last_lng / factor_degree) | ||
| except StopIteration: | ||
| raise ValueError("Invalid encoding. Premature ending reached") | ||
|
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||
| def decode(encoded): | ||
| """Return a list of coordinates. The number of coordinates are 2 or 3 | ||
| depending on the polyline content.""" | ||
| return list(iter_decode(encoded)) |
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