Initial open-source commit of Emboss.
diff --git a/front_end/tokenizer.py b/front_end/tokenizer.py
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+++ b/front_end/tokenizer.py
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+# Copyright 2019 Google LLC
+#
+# 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
+#
+# https://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.
+
+"""Tokenization for the Emboss definition language.
+
+This module exports the tokenize function and various errors.
+
+In addition, a couple of lists are exported for the use of
+generate_grammar_md.py:
+
+LITERAL_TOKEN_PATTERNS: A list of literal strings which are matched against
+ input.
+REGEX_TOKEN_PATTERNS: A list of regexes used for tokenization.
+ REGEX_TOKEN_PATTERNS[n].regex is an re.RegexObject
+ (REGEX_TOKEN_PATTERNS[n].regex.pattern contains the text of the pattern), and
+ REGEX_TOKEN_PATTERNS[n].symbol is the name of the symbol assigned to tokens
+ which match the pattern.
+"""
+
+import collections
+import re
+
+from util import error
+from util import parser_types
+
+
+def tokenize(text, file_name):
+ # TODO(bolms): suppress end-of-line, indent, and dedent tokens between matched
+ # delimiters ([], (), and {}).
+ """Tokenizes its argument.
+
+ Arguments:
+ text: The raw text of a .emb file.
+ file_name: The name of the file to use in errors.
+
+ Returns:
+ A tuple of:
+ a list of parser_types.Tokens or None
+ a possibly-empty list of errors.
+ """
+ tokens = []
+ indent_stack = [""]
+ line_number = 0
+ for line in text.splitlines():
+ line_number += 1
+
+ # _tokenize_line splits the actual text into tokens.
+ line_tokens, errors = _tokenize_line(line, line_number, file_name)
+ if errors:
+ return None, errors
+
+ # Lines with only whitespace and comments are not used for Indent/Dedent
+ # calculation, and do not produce end-of-line tokens.
+ for token in line_tokens:
+ if token.symbol != "Comment":
+ break
+ else:
+ tokens.extend(line_tokens)
+ tokens.append(parser_types.Token(
+ '"\\n"', "\n", parser_types.make_location(
+ (line_number, len(line) + 1), (line_number, len(line) + 1))))
+ continue
+
+ # Leading whitespace is whatever .lstrip() removes.
+ leading_whitespace = line[0:len(line) - len(line.lstrip())]
+ if leading_whitespace == indent_stack[-1]:
+ # If the current leading whitespace is equal to the last leading
+ # whitespace, do not emit an Indent or Dedent token.
+ pass
+ elif leading_whitespace.startswith(indent_stack[-1]):
+ # If the current leading whitespace is longer than the last leading
+ # whitespace, emit an Indent token. For the token text, take the new
+ # part of the whitespace.
+ tokens.append(
+ parser_types.Token(
+ "Indent", leading_whitespace[len(indent_stack[-1]):],
+ parser_types.make_location(
+ (line_number, len(indent_stack[-1]) + 1),
+ (line_number, len(leading_whitespace) + 1))))
+ indent_stack.append(leading_whitespace)
+ else:
+ # Otherwise, search for the unclosed indentation level that matches
+ # the current indentation level. Emit a Dedent token for each
+ # newly-closed indentation level.
+ for i in range(len(indent_stack) - 1, -1, -1):
+ if leading_whitespace == indent_stack[i]:
+ break
+ tokens.append(
+ parser_types.Token("Dedent", "", parser_types.make_location(
+ (line_number, len(leading_whitespace) + 1),
+ (line_number, len(leading_whitespace) + 1))))
+ del indent_stack[i]
+ else:
+ return None, [[error.error(
+ file_name, parser_types.make_location(
+ (line_number, 1), (line_number, len(leading_whitespace) + 1)),
+ "Bad indentation")]]
+
+ tokens.extend(line_tokens)
+
+ # Append an end-of-line token (for non-whitespace lines).
+ tokens.append(parser_types.Token(
+ '"\\n"', "\n", parser_types.make_location(
+ (line_number, len(line) + 1), (line_number, len(line) + 1))))
+ for i in range(len(indent_stack) - 1):
+ tokens.append(parser_types.Token("Dedent", "", parser_types.make_location(
+ (line_number + 1, 1), (line_number + 1, 1))))
+ return tokens, []
+
+# Token patterns used by _tokenize_line.
+LITERAL_TOKEN_PATTERNS = (
+ "[ ] ( ) : = + - * . ? == != && || < > <= >= , "
+ "$static_size_in_bits $is_statically_sized "
+ "$max $present $upper_bound $lower_bound "
+ "$size_in_bits $size_in_bytes "
+ "$max_size_in_bits $max_size_in_bytes $min_size_in_bits $min_size_in_bytes "
+ "$default struct bits enum external import as if let").split()
+_T = collections.namedtuple("T", ["regex", "symbol"])
+REGEX_TOKEN_PATTERNS = [
+ # Words starting with variations of "emboss reserved" are reserved for
+ # internal use by the Emboss compiler.
+ _T(re.compile(r"EmbossReserved[A-Za-z0-9]*"), "BadWord"),
+ _T(re.compile(r"emboss_reserved[_a-z0-9]*"), "BadWord"),
+ _T(re.compile(r"EMBOSS_RESERVED[_A-Z0-9]*"), "BadWord"),
+ _T(re.compile(r'"(?:[^"\n\\]|\\[n\\"])*"'), "String"),
+ _T(re.compile("[0-9]+"), "Number"),
+ _T(re.compile("[0-9]{1,3}(?:_[0-9]{3})*"), "Number"),
+ _T(re.compile("0x[0-9a-fA-F]+"), "Number"),
+ _T(re.compile("0x_?[0-9a-fA-F]{1,4}(?:_[0-9a-fA-F]{4})*"), "Number"),
+ _T(re.compile("0x_?[0-9a-fA-F]{1,8}(?:_[0-9a-fA-F]{8})*"), "Number"),
+ _T(re.compile("0b[01]+"), "Number"),
+ _T(re.compile("0b_?[01]{1,4}(?:_[01]{4})*"), "Number"),
+ _T(re.compile("0b_?[01]{1,8}(?:_[01]{8})*"), "Number"),
+ _T(re.compile("true|false"), "BooleanConstant"),
+ _T(re.compile("[a-z][a-z_0-9]*"), "SnakeWord"),
+ # Single-letter ShoutyWords (like "A") and single-letter-followed-by-number
+ # ShoutyWords ("A100") are disallowed due to ambiguity with CamelWords. A
+ # ShoutyWord must start with an upper case letter and contain at least one
+ # more upper case letter or '_'.
+ _T(re.compile("[A-Z][A-Z_0-9]*[A-Z_][A-Z_0-9]*"), "ShoutyWord"),
+ # A CamelWord starts with A-Z and contains at least one a-z, and no _.
+ _T(re.compile("[A-Z][a-zA-Z0-9]*[a-z][a-zA-Z0-9]*"), "CamelWord"),
+ _T(re.compile("-- .*"), "Documentation"),
+ _T(re.compile("--$"), "Documentation"),
+ _T(re.compile("--.*"), "BadDocumentation"),
+ _T(re.compile(r"\s+"), None),
+ _T(re.compile("#.*"), "Comment"),
+ # BadWord and BadNumber are a catch-alls for words and numbers so that
+ # something like "abcDef" doesn't tokenize to [SnakeWord, CamelWord].
+ #
+ # This is preferable to returning an error because the BadWord and BadNumber
+ # token types can be used in example-based errors.
+ _T(re.compile("[0-9][bxBX]?[0-9a-fA-F_]*"), "BadNumber"),
+ _T(re.compile("[a-zA-Z_$0-9]+"), "BadWord"),
+]
+del _T
+
+
+def _tokenize_line(line, line_number, file_name):
+ """Tokenizes a single line of input.
+
+ Arguments:
+ line: The line of text to tokenize.
+ line_number: The line number (used when constructing token objects).
+ file_name: The name of a file to use in errors.
+
+ Returns:
+ A tuple of:
+ A list of token objects or None.
+ A possibly-empty list of errors.
+ """
+ tokens = []
+ offset = 0
+ while offset < len(line):
+ best_candidate = ""
+ best_candidate_symbol = None
+ # Find the longest match. Ties go to the first match. This way, keywords
+ # ("struct") are matched as themselves, but words that only happen to start
+ # with keywords ("structure") are matched as words.
+ #
+ # There is never a reason to try to match a literal after a regex that
+ # could also match that literal, so check literals first.
+ for literal in LITERAL_TOKEN_PATTERNS:
+ if line[offset:].startswith(literal) and len(literal) > len(
+ best_candidate):
+ best_candidate = literal
+ # For Emboss, the name of a literal token is just the literal in quotes,
+ # so that the grammar can read a little more naturally, e.g.:
+ #
+ # expression -> expression "+" expression
+ #
+ # instead of
+ #
+ # expression -> expression Plus expression
+ best_candidate_symbol = '"' + literal + '"'
+ for pattern in REGEX_TOKEN_PATTERNS:
+ match_result = pattern.regex.match(line[offset:])
+ if match_result and len(match_result.group(0)) > len(best_candidate):
+ best_candidate = match_result.group(0)
+ best_candidate_symbol = pattern.symbol
+ if not best_candidate:
+ return None, [[error.error(
+ file_name, parser_types.make_location(
+ (line_number, offset + 1), (line_number, offset + 2)),
+ "Unrecognized token")]]
+ if best_candidate_symbol:
+ tokens.append(parser_types.Token(
+ best_candidate_symbol, best_candidate, parser_types.make_location(
+ (line_number, offset + 1),
+ (line_number, offset + len(best_candidate) + 1))))
+ offset += len(best_candidate)
+ return tokens, None
