Add support for non-seekable file handles in a bit of awkard way. It …

…is only possible to determine seekability with the io.open API, however the Array API doesn't support it.

packetparser/pcap.py

@@ -239,8 +239,9 @@ class PcapFile(PacketContainer):
     time
     """
 
-    def __init__(self, data, file_handle):
+    def __init__(self, data, file_handle, seekable=True):
         self.file_handle = file_handle
+        self.seekable = seekable
 
         new = {}
         new.update(PcapHeaderStructure.defaults())
@@ -289,8 +290,9 @@ def write_frame(self, frame):
         pass
 
     @classmethod
-    def parse_header(cls, file_handle):
-        file_handle.seek(0)
+    def parse_header(cls, file_handle, seekable=True):
+        if seekable:
+            file_handle.seek(0)
 
         header_frame_array = array.array('B')
         header_frame_array.fromfile(
@@ -301,11 +303,13 @@ def parse_header(cls, file_handle):
         pcap_header_struct = PcapHeaderStructure.unpack(header_frame_array)
         data = pcap_header_struct.data
 
-        return cls(data, file_handle)
+        return cls(data, file_handle, seekable=seekable)
 
     def frames(self):
         # Start parsing right after the PCAP header.
-        self.file_handle.seek(PcapHeaderStructure.struct.size)
+
+        if self.seekable:
+            self.file_handle.seek(PcapHeaderStructure.struct.size)
 
         # TODO: For now we support 127, 80211 RadioTap only.
         extra = {

pcap_info.py

@@ -102,7 +102,13 @@ def print_pcap_file_info(pcap_file):
         sys.exit(1)  # EXIT_FAILURE
 
     for filename in sys.argv[1:]:
-        file_handle = open(filename, 'rb')
-        pcap_file = PcapFile.parse_header(file_handle)
+        if filename == '-':
+            file_handle = sys.stdin
+            seekable = False
+        else:
+            file_handle = open(filename, 'rb')
+            seekable = True
+
+        pcap_file = PcapFile.parse_header(file_handle, seekable=seekable)
 
         print_pcap_file_info(pcap_file)