Stubbing out MBTiles support with some basic functions

TileStache/MBTiles.py

@@ -0,0 +1,86 @@
+from sqlite3 import connect
+from os.path import exists
+
+def create_tileset(filename, name, type, version, description, format, bounds=None):
+    """ Create a tileset 1.1 with the given filename and metadata.
+    
+        From the documentation:
+
+        The metadata table is used as a key/value store for settings.
+        Five keys are required:
+
+        name:
+          The plain-english name of the tileset.
+
+        type:
+          overlay or baselayer
+        
+        version:
+          The version of the tileset, as a plain number.
+
+        description:
+          A description of the layer as plain text.
+        
+        format:
+          The image file format of the tile data: png or jpg
+        
+        One row in metadata is suggested and, if provided, may enhance performance.
+
+        bounds:
+          The maximum extent of the rendered map area. Bounds must define
+          an area covered by all zoom levels. The bounds are represented in
+          WGS:84 - latitude and longitude values, in the OpenLayers Bounds
+          format - left, bottom, right, top. Example of the full earth:
+          -180.0,-85,180,85.
+    """
+    if format not in ('png', 'jpg'):
+        raise Exception('Format must be one of "png" or "jpg", not "%s"' % format)
+
+    db = connect(filename)
+
+    db.execute('CREATE TABLE metadata (name TEXT, value TEXT, PRIMARY KEY (name))')
+    db.execute('CREATE TABLE tiles (zoom_level INTEGER, tile_column INTEGER, tile_row INTEGER, tile_data BLOB)')
+    db.execute('CREATE UNIQUE INDEX coord ON tiles (zoom_level, tile_column, tile_row)')
+
+    db.execute('INSERT INTO metadata VALUES (?, ?)', ('name', name))
+    db.execute('INSERT INTO metadata VALUES (?, ?)', ('type', type))
+    db.execute('INSERT INTO metadata VALUES (?, ?)', ('version', version))
+    db.execute('INSERT INTO metadata VALUES (?, ?)', ('description', description))
+    db.execute('INSERT INTO metadata VALUES (?, ?)', ('format', format))
+
+    if bounds is not None:
+        db.execute('INSERT INTO metadata VALUES (?, ?)', ('bounds', bounds))
+
+    db.commit()
+    db.close()
+
+def tileset_exists(filename):
+    """ Return true if the tileset exists and appears to have the right tables.
+    """
+    if not exists(filename):
+        return False
+
+    # this always works
+    db = connect(filename)
+
+    try:
+        db.execute('SELECT name, value FROM metadata LIMIT 1')
+        db.execute('SELECT zoom_level, tile_column, tile_row, tile_data FROM tiles LIMIT 1')
+    except:
+        return False
+
+    return True
+
+def get_tile(filename, coord):
+    """
+    """
+    db = connect(filename)
+
+    format = db.execute("SELECT value FROM metadata WHERE name='format'").fetchone()[0]
+    content = db.execute("""SELECT tile_data FROM tiles
+                            WHERE zoom_level=? AND tile_column=? AND tile_row=?""",
+                         (coord.zoom, coord.column, coord.row)).fetchone()[0]
+
+    mime_type = {'png': 'image/png', 'jpg': 'image/jpeg'}[format]
+
+    return mime_type, content