z-compressed dumps and loads

1 files changed, 17 insertions, 12 deletions

diff --git a/coverage/sqldata.py b/coverage/sqldata.py
index ea4922ca..00a72b9f 100644
--- a/coverage/sqldata.py
+++ b/coverage/sqldata.py
@@ -15,9 +15,10 @@ import itertools
 import os
 import sqlite3
 import sys
+import zlib
 
 from coverage.backward import get_thread_id, iitems
-from coverage.backward import bytes_to_ints, binary_bytes, zip_longest
+from coverage.backward import bytes_to_ints, binary_bytes, zip_longest, to_bytes, to_string
 from coverage.debug import NoDebugging, SimpleReprMixin
 from coverage import env
 from coverage.files import PathAliases
@@ -219,8 +220,11 @@ class CoverageData(SimpleReprMixin):
     def _open_db(self):
         if self._debug.should('dataio'):
             self._debug.write("Opening data file {!r}".format(self._filename))
-        self._dbs[get_thread_id()] = db = SqliteDb(self._filename, self._debug)
-        with db:
+        self._dbs[get_thread_id()] = SqliteDb(self._filename, self._debug)
+        self._read_db()
+
+    def _read_db(self):
+        with self._dbs[get_thread_id()] as db:
             try:
                 schema_version, = db.execute("select version from coverage_schema").fetchone()
             except Exception as exc:
@@ -264,22 +268,23 @@ class CoverageData(SimpleReprMixin):
 
     __bool__ = __nonzero__
 
-    def dump(self):                                         # pragma: debugging
-        """Write a dump of the database."""
-        if self._debug:
-            with self._connect() as con:
-                self._debug.write(con.dump())
-
+    @contract(returns='bytes')
     def dumps(self):
         with self._connect() as con:
-            return con.dump()
+            return b'z' + zlib.compress(to_bytes(con.dump()))
 
+    @contract(data='bytes')
     def loads(self, data):
         if self._debug.should('dataio'):
             self._debug.write("Loading data into data file {!r}".format(self._filename))
+        if data[:1] != b'z':
+            raise CoverageException("Unrecognized serialization: {!r} (head of {} bytes)".format(data[:40], len(data)))
+        script = to_string(zlib.decompress(data[1:]))
         self._dbs[get_thread_id()] = db = SqliteDb(self._filename, self._debug)
         with db:
-            db.executescript(data)
+            db.executescript(script)
+        self._read_db()
+        self._have_used = True
 
     def _file_id(self, filename, add=False):
         """Get the file id for `filename`.
@@ -858,7 +863,7 @@ class SqliteDb(SimpleReprMixin):
             self.debug.write("Executing script with {} chars".format(len(script)))
         self.con.executescript(script)
 
-    def dump(self):                                         # pragma: debugging
+    def dump(self):
         """Return a multi-line string, the dump of the database."""
         return "\n".join(self.con.iterdump())