Move the 'meta' dir to 'lib/cretonne/meta'.

The 'lib/cretonne' directory will be the new root of a stand-alone
cretonne crate containg both Python and Rust sources.

This is in preparation for publishing crates on crates.io.

lib/cretonne/meta/srcgen.py

@@ -0,0 +1,123 @@
+"""
+Source code generator.
+
+The `srcgen` module contains generic helper routines and classes for generating
+source code.
+
+"""
+from __future__ import absolute_import
+import sys
+import os
+import re
+
+
+class Formatter(object):
+    """
+    Source code formatter class.
+
+    - Collect source code to be written to a file.
+    - Keep track of indentation.
+
+    Indentation example:
+
+        >>> f = Formatter()
+        >>> f.line('Hello line 1')
+        >>> f.writelines()
+        Hello line 1
+        >>> f.indent_push()
+        >>> f.comment('Nested comment')
+        >>> f.indent_pop()
+        >>> f.format('Back {} again', 'home')
+        >>> f.writelines()
+        Hello line 1
+            // Nested comment
+        Back home again
+
+    """
+
+    shiftwidth = 4
+
+    def __init__(self):
+        self.indent = ''
+        self.lines = []
+
+    def indent_push(self):
+        """Increase current indentation level by one."""
+        self.indent += ' ' * self.shiftwidth
+
+    def indent_pop(self):
+        """Decrease indentation by one level."""
+        assert self.indent != '', 'Already at top level indentation'
+        self.indent = self.indent[0:-self.shiftwidth]
+
+    def line(self, s=None):
+        """Add an indented line."""
+        if s:
+            self.lines.append('{}{}\n'.format(self.indent, s))
+        else:
+            self.lines.append('\n')
+
+    def outdented_line(self, s):
+        """
+        Emit a line outdented one level.
+
+        This is used for '} else {' and similar things inside a single indented
+        block.
+        """
+        self.lines.append('{}{}\n'.format(self.indent[0:-self.shiftwidth], s))
+
+    def writelines(self, f=None):
+        """Write all lines to `f`."""
+        if not f:
+            f = sys.stdout
+        f.writelines(self.lines)
+
+    def update_file(self, filename, directory):
+        if directory is not None:
+            filename = os.path.join(directory, filename)
+        with open(filename, 'w') as f:
+            self.writelines(f)
+
+    class _IndentedScope(object):
+        def __init__(self, fmt, after):
+            self.fmt = fmt
+            self.after = after
+
+        def __enter__(self):
+            self.fmt.indent_push()
+
+        def __exit__(self, t, v, tb):
+            self.fmt.indent_pop()
+            if self.after:
+                self.fmt.line(self.after)
+
+    def indented(self, before=None, after=None):
+        """
+        Return a scope object for use with a `with` statement:
+
+            >>> f = Formatter()
+            >>> with f.indented('prefix {', '} suffix'):
+            ...     f.line('hello')
+            >>> f.writelines()
+            prefix {
+                hello
+            } suffix
+
+        The optional `before` and `after` parameters are surrounding lines
+        which are *not* indented.
+        """
+        if before:
+            self.line(before)
+        return self._IndentedScope(self, after)
+
+    def format(self, fmt, *args):
+        self.line(fmt.format(*args))
+
+    def comment(self, s):
+        """Add a comment line."""
+        self.line('// ' + s)
+
+    def doc_comment(self, s):
+        """Add a (multi-line) documentation comment."""
+        s = re.sub('^', self.indent + '/// ', s, flags=re.M) + '\n'
+        self.lines.append(s)