add hg and python

sys/lib/python/whichdb.py

@@ -0,0 +1,117 @@
+# !/usr/bin/env python
+"""Guess which db package to use to open a db file."""
+
+import os
+import struct
+import sys
+
+try:
+    import dbm
+    _dbmerror = dbm.error
+except ImportError:
+    dbm = None
+    # just some sort of valid exception which might be raised in the
+    # dbm test
+    _dbmerror = IOError
+
+def whichdb(filename):
+    """Guess which db package to use to open a db file.
+
+    Return values:
+
+    - None if the database file can't be read;
+    - empty string if the file can be read but can't be recognized
+    - the module name (e.g. "dbm" or "gdbm") if recognized.
+
+    Importing the given module may still fail, and opening the
+    database using that module may still fail.
+    """
+
+    # Check for dbm first -- this has a .pag and a .dir file
+    try:
+        f = open(filename + os.extsep + "pag", "rb")
+        f.close()
+        # dbm linked with gdbm on OS/2 doesn't have .dir file
+        if not (dbm.library == "GNU gdbm" and sys.platform == "os2emx"):
+            f = open(filename + os.extsep + "dir", "rb")
+            f.close()
+        return "dbm"
+    except IOError:
+        # some dbm emulations based on Berkeley DB generate a .db file
+        # some do not, but they should be caught by the dbhash checks
+        try:
+            f = open(filename + os.extsep + "db", "rb")
+            f.close()
+            # guarantee we can actually open the file using dbm
+            # kind of overkill, but since we are dealing with emulations
+            # it seems like a prudent step
+            if dbm is not None:
+                d = dbm.open(filename)
+                d.close()
+                return "dbm"
+        except (IOError, _dbmerror):
+            pass
+
+    # Check for dumbdbm next -- this has a .dir and a .dat file
+    try:
+        # First check for presence of files
+        os.stat(filename + os.extsep + "dat")
+        size = os.stat(filename + os.extsep + "dir").st_size
+        # dumbdbm files with no keys are empty
+        if size == 0:
+            return "dumbdbm"
+        f = open(filename + os.extsep + "dir", "rb")
+        try:
+            if f.read(1) in ("'", '"'):
+                return "dumbdbm"
+        finally:
+            f.close()
+    except (OSError, IOError):
+        pass
+
+    # See if the file exists, return None if not
+    try:
+        f = open(filename, "rb")
+    except IOError:
+        return None
+
+    # Read the start of the file -- the magic number
+    s16 = f.read(16)
+    f.close()
+    s = s16[0:4]
+
+    # Return "" if not at least 4 bytes
+    if len(s) != 4:
+        return ""
+
+    # Convert to 4-byte int in native byte order -- return "" if impossible
+    try:
+        (magic,) = struct.unpack("=l", s)
+    except struct.error:
+        return ""
+
+    # Check for GNU dbm
+    if magic == 0x13579ace:
+        return "gdbm"
+
+    # Check for old Berkeley db hash file format v2
+    if magic in (0x00061561, 0x61150600):
+        return "bsddb185"
+
+    # Later versions of Berkeley db hash file have a 12-byte pad in
+    # front of the file type
+    try:
+        (magic,) = struct.unpack("=l", s16[-4:])
+    except struct.error:
+        return ""
+
+    # Check for BSD hash
+    if magic in (0x00061561, 0x61150600):
+        return "dbhash"
+
+    # Unknown
+    return ""
+
+if __name__ == "__main__":
+    for filename in sys.argv[1:]:
+        print whichdb(filename) or "UNKNOWN", filename