init

.venv/lib/python3.8/site-packages/mypyc/codegen/cstring.py

@@ -0,0 +1,54 @@
+"""Encode valid C string literals from Python strings.
+
+If a character is not allowed in C string literals, it is either emitted
+as a simple escape sequence (e.g. '\\n'), or an octal escape sequence
+with exactly three digits ('\\oXXX'). Question marks are escaped to
+prevent trigraphs in the string literal from being interpreted. Note
+that '\\?' is an invalid escape sequence in Python.
+
+Consider the string literal "AB\\xCDEF". As one would expect, Python
+parses it as ['A', 'B', 0xCD, 'E', 'F']. However, the C standard
+specifies that all hexadecimal digits immediately following '\\x' will
+be interpreted as part of the escape sequence. Therefore, it is
+unexpectedly parsed as ['A', 'B', 0xCDEF].
+
+Emitting ("AB\\xCD" "EF") would avoid this behaviour. However, we opt
+for simplicity and use octal escape sequences instead. They do not
+suffer from the same issue as they are defined to parse at most three
+octal digits.
+"""
+
+import string
+
+from typing_extensions import Final
+
+
+CHAR_MAP: Final = ["\\{:03o}".format(i) for i in range(256)]
+
+# It is safe to use string.printable as it always uses the C locale.
+for c in string.printable:
+    CHAR_MAP[ord(c)] = c
+
+# These assignments must come last because we prioritize simple escape
+# sequences over any other representation.
+for c in ('\'', '"', '\\', 'a', 'b', 'f', 'n', 'r', 't', 'v'):
+    escaped = '\\{}'.format(c)
+    decoded = escaped.encode('ascii').decode('unicode_escape')
+    CHAR_MAP[ord(decoded)] = escaped
+
+# This escape sequence is invalid in Python.
+CHAR_MAP[ord('?')] = r'\?'
+
+
+def encode_bytes_as_c_string(b: bytes) -> str:
+    """Produce contents of a C string literal for a byte string, without quotes."""
+    escaped = ''.join([CHAR_MAP[i] for i in b])
+    return escaped
+
+
+def c_string_initializer(value: bytes) -> str:
+    """Create initializer for a C char[]/ char * variable from a string.
+
+    For example, if value if b'foo', the result would be '"foo"'.
+    """
+    return '"' + encode_bytes_as_c_string(value) + '"'