restoring decompressor while errors are fixed

--HG--
extra : convert_revision : svn%3Ab85faa78-f9eb-468e-a121-7cced6da292c%40501

scrapy/trunk/scrapy/utils/decompressor.py

@@ -0,0 +1,72 @@
+"""
+Utility for autodetecting and decompressing responses
+"""
+
+import zipfile
+import tarfile
+import gzip
+import bz2
+from scrapy.http import ResponseBody
+try:
+    from cStringIO import StringIO
+except:
+    from StringIO import StringIO
+
+class Decompressor(object):
+    class ArchiveIsEmpty(Exception):
+        pass
+    
+    def __init__(self):
+        self.decompressors = {'tar': self.is_tar, 'zip': self.is_zip,
+                              'gz': self.is_gzip, 'bz2': self.is_bzip2}        
+    
+    def is_tar(self, response):
+        try:
+            tar_file = tarfile.open(name='tar.tmp', fileobj=self.archive)
+        except tarfile.ReadError:
+            return False
+        if tar_file.members:
+            return response.replace(body=ResponseBody(tar_file.extractfile(tar_file.members[0]).read()))
+        else:
+            raise self.ArchiveIsEmpty
+    
+    def is_zip(self, response):
+        try:
+            zip_file = zipfile.ZipFile(self.archive)
+        except zipfile.BadZipfile:
+            return False
+        namelist = zip_file.namelist()
+        if namelist:
+            return response.replace(body=ResponseBody(zip_file.read(namelist[0])))
+        else:
+            raise self.ArchiveIsEmpty
+            
+    def is_gzip(self, response):
+        try:
+            gzip_file = gzip.GzipFile(fileobj=self.archive)
+            decompressed_body = gzip_file.read()
+        except IOError:
+            return False
+        return response.replace(body=decompressed_body)
+            
+    def is_bzip2(self, response):
+        try:
+            decompressed_body = bz2.decompress(self.body)
+        except IOError:
+            return False
+        return response.replace(body=ResponseBody(decompressed_body))
+    
+    def extract_winfo(self, response):
+        self.body = response.body.to_string()
+        self.archive = StringIO()
+        self.archive.write(self.body)
+        
+        for decompressor in self.decompressors.keys():
+            self.archive.seek(0)
+            new_response = self.decompressors[decompressor](response)
+            if new_response:
+                return new_response, decompressor
+        return response, ''
+        
+    def extract(self, response):
+        return self.extract_winfo(response)[0]