1 files changed, 92 insertions, 0 deletions
diff --git a/js/xpconnect/loader/script_cache.py b/js/xpconnect/loader/script_cache.py
new file mode 100755
index 0000000000..bd3a746fcf
--- /dev/null
+++ b/js/xpconnect/loader/script_cache.py
@@ -0,0 +1,92 @@
+#!/usr/bin/env python
+# 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/.
+
+import io
+import os
+import struct
+import sys
+
+MAGIC = b"mozXDRcachev002\0"
+
+
+def usage():
+    print(
+        """Usage: script_cache.py <file.bin> ...
+
+        Decodes and prints out the contents of a startup script cache file
+        (e.g., startupCache/scriptCache.bin) in human-readable form."""
+    )
+
+    sys.exit(1)
+
+
+class ProcessTypes:
+    Uninitialized = 0
+    Parent = 1
+    Web = 2
+    Extension = 3
+    Privileged = 4
+
+    def __init__(self, val):
+        self.val = val
+
+    def __str__(self):
+        res = []
+        if self.val & (1 << self.Uninitialized):
+            raise Exception("Uninitialized process type")
+        if self.val & (1 << self.Parent):
+            res.append("Parent")
+        if self.val & (1 << self.Web):
+            res.append("Web")
+        if self.val & (1 << self.Extension):
+            res.append("Extension")
+        if self.val & (1 << self.Privileged):
+            res.append("Privileged")
+        return "|".join(res)
+
+
+class InputBuffer(object):
+    def __init__(self, data):
+        self.data = data
+        self.offset = 0
+
+    @property
+    def remaining(self):
+        return len(self.data) - self.offset
+
+    def unpack(self, fmt):
+        res = struct.unpack_from(fmt, self.data, self.offset)
+        self.offset += struct.calcsize(fmt)
+        return res
+
+    def unpack_str(self):
+        (size,) = self.unpack("<H")
+        res = self.data[self.offset : self.offset + size].decode("utf-8")
+        self.offset += size
+        return res
+
+
+if len(sys.argv) < 2 or not os.path.exists(sys.argv[1]):
+    usage()
+
+for filename in sys.argv[1:]:
+    with io.open(filename, "rb") as f:
+        magic = f.read(len(MAGIC))
+        if magic != MAGIC:
+            raise Exception("Bad magic number")
+
+        (hdrSize,) = struct.unpack("<I", f.read(4))
+
+        hdr = InputBuffer(f.read(hdrSize))
+
+        i = 0
+        while hdr.remaining:
+            i += 1
+            print("{}: {}".format(i, hdr.unpack_str()))
+            print("  Key:       {}".format(hdr.unpack_str()))
+            print("  Offset:    {:>9,}".format(*hdr.unpack("<I")))
+            print("  Size:      {:>9,}".format(*hdr.unpack("<I")))
+            print("  Processes: {}".format(ProcessTypes(*hdr.unpack("B"))))
+            print("")