1 files changed, 97 insertions, 0 deletions
diff --git a/toolkit/components/glean/build_scripts/glean_parser_ext/string_table.py b/toolkit/components/glean/build_scripts/glean_parser_ext/string_table.py
new file mode 100644
index 0000000000..2cf5cb68e7
--- /dev/null
+++ b/toolkit/components/glean/build_scripts/glean_parser_ext/string_table.py
@@ -0,0 +1,97 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from io import StringIO
+
+
+class StringTable:
+    """Manages a string table and allows C style serialization to a file."""
+
+    def __init__(self):
+        self.current_index = 0
+        self.table = {}
+
+    def c_strlen(self, string):
+        """The length of a string including the null terminating character.
+        :param string: the input string.
+        """
+        return len(string) + 1
+
+    def stringIndex(self, string):
+        """Returns the index in the table of the provided string. Adds the string to
+        the table if it's not there.
+        :param string: the input string.
+        """
+        if string in self.table:
+            return self.table[string]
+        result = self.current_index
+        self.table[string] = result
+        self.current_index += self.c_strlen(string)
+        return result
+
+    def stringIndexes(self, strings):
+        """Returns a list of indexes for the provided list of strings.
+        Adds the strings to the table if they are not in it yet.
+        :param strings: list of strings to put into the table.
+        """
+        return [self.stringIndex(s) for s in strings]
+
+    def writeToString(self, name):
+        """Writes the string table to a string as a C const char array.
+
+        See `writeDefinition` for details
+
+        :param name: the name of the output array.
+        """
+
+        output = StringIO()
+        self.writeDefinition(output, name)
+        return output.getvalue()
+
+    def writeDefinition(self, f, name):
+        """Writes the string table to a file as a C const char array.
+
+        This writes out the string table as one single C char array for memory
+        size reasons, separating the individual strings with '\0' characters.
+        This way we can index directly into the string array and avoid the additional
+        storage costs for the pointers to them (and potential extra relocations for those).
+
+        :param f: the output stream.
+        :param name: the name of the output array.
+        """
+        entries = self.table.items()
+
+        # Avoid null-in-string warnings with GCC and potentially
+        # overlong string constants; write everything out the long way.
+        def explodeToCharArray(string):
+            def toCChar(s):
+                if s == "'":
+                    return "'\\''"
+                return "'%s'" % s
+
+            return ", ".join(map(toCChar, string))
+
+        f.write("#if defined(_MSC_VER) && !defined(__clang__)\n")
+        f.write("const char %s[] = {\n" % name)
+        f.write("#else\n")
+        f.write("constexpr char %s[] = {\n" % name)
+        f.write("#endif\n")
+        for string, offset in sorted(entries, key=lambda x: x[1]):
+            if "*/" in string:
+                raise ValueError(
+                    "String in string table contains unexpected sequence '*/': %s"
+                    % string
+                )
+
+            e = explodeToCharArray(string)
+            if e:
+                f.write(
+                    "  /* %5d - \"%s\" */ %s, '\\0',\n"
+                    % (offset, string, explodeToCharArray(string))
+                )
+            else:
+                f.write("  /* %5d - \"%s\" */ '\\0',\n" % (offset, string))
+        f.write("};\n\n")