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authorDaniel Burrows <Daniel_Burrows@alumni.brown.edu>2008-04-02 09:06:49 -0700
committerDaniel Burrows <Daniel_Burrows@alumni.brown.edu>2008-04-02 09:06:49 -0700
commitffc36991800aa50902d91b818c4422893e34a2c2 (patch)
treed569280cc5d6e969a6cef1ff07f65078405a5cd6 /apt-pkg/contrib/strutl.cc
parenta4dcbf1ce5fea58b54f37c5db9d8ba2c35b78eb4 (diff)
Fix ReadMessages to handle messages that are longer than 64000 bytes.
There's a bug in this code that needs to be fixed, but it existed prior to this change.
Diffstat (limited to 'apt-pkg/contrib/strutl.cc')
-rw-r--r--apt-pkg/contrib/strutl.cc44
1 files changed, 40 insertions, 4 deletions
diff --git a/apt-pkg/contrib/strutl.cc b/apt-pkg/contrib/strutl.cc
index a04c266ba..eacc7077a 100644
--- a/apt-pkg/contrib/strutl.cc
+++ b/apt-pkg/contrib/strutl.cc
@@ -658,11 +658,24 @@ string TimeRFC1123(time_t Date)
// ---------------------------------------------------------------------
/* This pulls full messages from the input FD into the message buffer.
It assumes that messages will not pause during transit so no
- fancy buffering is used. */
+ fancy buffering is used.
+
+ In particular: this reads blocks from the input until it believes
+ that it's run out of input text. Each block is terminated by a
+ double newline ('\n' followed by '\n'). As noted below, there is a
+ bug in this code: it assumes that all the blocks have been read if
+ it doesn't see additional text in the buffer after the last one is
+ parsed, which will cause it to lose blocks if the last block
+ coincides with the end of the buffer.
+ */
bool ReadMessages(int Fd, vector<string> &List)
{
char Buffer[64000];
char *End = Buffer;
+ // Represents any left-over from the previous iteration of the
+ // parse loop. (i.e., if a message is split across the end
+ // of the buffer, it goes here)
+ string PartialMessage;
while (1)
{
@@ -690,6 +703,7 @@ bool ReadMessages(int Fd, vector<string> &List)
// Pull the message out
string Message(Buffer,I-Buffer);
+ PartialMessage += Message;
// Fix up the buffer
for (; I < End && *I == '\n'; I++);
@@ -697,10 +711,32 @@ bool ReadMessages(int Fd, vector<string> &List)
memmove(Buffer,I,End-Buffer);
I = Buffer;
- List.push_back(Message);
+ List.push_back(PartialMessage);
+ PartialMessage.clear();
}
- if (End == Buffer)
- return true;
+ if (End != Buffer)
+ {
+ // If there's text left in the buffer, store it
+ // in PartialMessage and throw the rest of the buffer
+ // away. This allows us to handle messages that
+ // are longer than the static buffer size.
+ PartialMessage += string(Buffer, End);
+ End = Buffer;
+ }
+ else
+ {
+ // BUG ALERT: if a message block happens to end at a
+ // multiple of 64000 characters, this will cause it to
+ // terminate early, leading to a badly formed block and
+ // probably crashing the method. However, this is the only
+ // way we have to find the end of the message block. I have
+ // an idea of how to fix this, but it will require changes
+ // to the protocol (essentially to mark the beginning and
+ // end of the block).
+ //
+ // -- dburrows 2008-04-02
+ return true;
+ }
if (WaitFd(Fd) == false)
return false;