From 0da32f28029fcdda90f4726269dfba760a5bc415 Mon Sep 17 00:00:00 2001
From: "Stephen R. van den Berg" <srb@cuci.nl>
Date: Thu, 17 May 2018 17:16:45 +0200
Subject: [PATCH] Stdio.Buffer: Eliminates race condition from read_cstring().
In addition it makes read_cstring():
- Restartable after buffer changes from range_error().
- Call range_error(0) just like sscanf().
- Faster.
The race condition occurred after a pause due to range_error(),
the subsequent io_rewind() at the end could not rewind far enough.
---
src/modules/_Stdio/buffer.cmod | 40 +++++++++++-----------------------
1 file changed, 13 insertions(+), 27 deletions(-)
diff --git a/src/modules/_Stdio/buffer.cmod b/src/modules/_Stdio/buffer.cmod
index 43a86025f2..d0ad267e47 100644
--- a/src/modules/_Stdio/buffer.cmod
+++ b/src/modules/_Stdio/buffer.cmod
@@ -1783,39 +1783,25 @@ PIKECLASS Buffer
*!
*! Note that pike string can not be longer than 0x7fffffff bytes (~2Gb).
*/
- PIKEFUN string(0..255) read_cstring( )
+ PIKEFUN string(0..255) read_cstring()
{
- LONGEST len;
Buffer *io = THIS;
- struct pike_string *s;
- ONERROR e;
- io_rewind_on_error( io, &e );
- len = 0;
- do {
- /* search the amount of data we know we have for each call to io_avail */
- while( io_len(io) )
+ do
+ if ( LIKELY(io_len(THIS)) )
{
- if( !io_read_byte_uc(io) )
- goto found_null;
- len++;
+ const char * start = io_read_pointer(io);
+ const char * end = memchr(start, 0, io_len(io));
+ if ( LIKELY(end) )
+ {
+ push_string(io_read_string(io, end - start));
+ io_read_byte_uc(io); /* consume the terminating \0 byte */
+ return;
+ }
}
- }
- while( io_avail( io, 1 ) );
- goto fail;
+ while ( UNLIKELY(io_range_error(THIS, 0)) );
- found_null:
- io_rewind( io, len+1 );
- s = io_read_string( io, len );
-
- if( LIKELY(s) ) {
- io_read_byte_uc(io); /* consume the terminating \0 byte */
- io_unset_rewind_on_error( io, &e );
- push_string(s);
- } else {
-fail: CALL_AND_UNSET_ONERROR(e);
- push_undefined();
- }
+ push_undefined();
}
/*! @decl Buffer read_hbuffer( int n )
--
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