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public/py/vendor_linux/skyfield/data/text_pck.py

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+# -*- coding: utf-8 -*-
+"""Parsing routines for JPL text PCK files.
+
+For an (incomplete) summary of the file format, look for the heading
+“NAIF Text Kernel Format” in the “PCK Required Reading”:
+
+https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/pck.html
+
+"""
+import re
+
+def load(lines, variables):
+    """Load PCK text kernel names and values into a ``variables`` dict."""
+    for name, equals, values in parse(lines):
+        if equals == b'=':
+            if len(values) == 1:
+                variables[name] = values[0]  # unbox a scalar value
+            else:
+                variables[name] = values
+        elif equals == b'+=':
+            old = variables.get(name)
+            if old is None:
+                old = variables[name] = []
+            elif not isinstance(old, list):
+                old = [old]  # box an earlier scalar before extending
+            old.extend(values)
+
+def parse(lines):
+    """Yield ``(name, equals, values)`` bytestrings from a PCK text kernel.
+
+    This merely reads raw assignment statements; it doesn’t combine
+    multiple ``+=`` assignments to create single values.  The byte
+    string ``equals`` will be either ``b'='`` or ``b'+='``.  Scalars are
+    returned as a ``values`` list one item long.
+
+    """
+    tokens = iter(_parse_tokens(lines))
+    for token in tokens:
+        name = token.decode('ascii')
+        equals = next(tokens)
+        if equals not in (b'=', b'+='):
+            raise ValueError('an equals sign is expected after %r' % name)
+        token = next(tokens)
+        if token == b'(':
+            values = []
+            for token in tokens:
+                if token == b')':
+                    break
+                values.append(_evaluate(token))
+        else:
+            values = [_evaluate(token)]
+        yield name, equals, values
+
+def _evaluate(token):
+    """Return a string, integer, or float parsed from a PCK text kernel."""
+    if token[0:1].startswith(b"'"):
+        return token[1:-1].decode('ascii')
+    if token.isdigit():
+        return int(token)
+    if token.startswith(b'@'):
+        raise NotImplementedError('TODO: need parser for dates,'
+                                  ' like @01-MAY-1991/16:25')
+    token = token.replace(b'D', b'E')  # for numbers like -1.4D-12
+    return float(token)
+
+_token_re = re.compile(b"[A-Za-z]\\w+|=|\\+=|\\(|\\)|'[^']*'|[^), ]+")
+
+def _parse_tokens(lines):
+    """Yield all the tokens inside the data segments of a PCK text file."""
+    lines = iter(lines)
+    for line in lines:
+        if b'\\begindata' not in line:
+            continue  # save cost of strip() on most lines
+        line = line.strip()
+        if line != b'\\begindata':
+            continue
+        for line in lines:
+            line = line.strip()
+            if line == b'\\begintext':
+                break
+            for token in _token_re.findall(line):
+                yield token