[PATCH 2/4] vcs-svn: replace buffer_read_string memory pool with a strbuf

[Jonathan Nieder <jrnieder@gmail.com>]

Date: Sat, 6 Nov 2010 12:01:28 -0500

obj_pool is inherently global and does not use the standard growing
factor alloc_nr, which makes it feel out of place in the git codebase.
Plus it is overkill for this application: all that is needed is a
buffer that can grow between requests to accomodate larger strings.
Use a strbuf instead.

As a side effect, this improves the error handling: allocation
failures will result in a clean exit instead of segfaults.  It would
be nice to add a test case (using ulimit or failmalloc) but that can
wait for another day.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
Requires jn/thinner-wrapper (from master) if contrib/svn-fe/svn-fe is
to build without linking to libz et al.

The initial size of the per-line buffer shrinks from 4096 to 0 (well,
maybe 16 or so).  strbuf_fread is not inline.  I haven't looked into
the effect on performance from these changes.

I find obj_pool tricky to use correctly (see 3c93983, vcs-svn: fix
intermittent repo_tree corruption, 2010-12-05 for example) so I look
forward to eliminating obj_pool from the vcs-svn/ dir altogether.
Excitingly enough, David has already done that, it seems[1].

[1] git://github.com/barrbrain/git.git vcs-svn-incremental

 vcs-svn/line_buffer.c |   16 ++++++----------
 1 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/vcs-svn/line_buffer.c b/vcs-svn/line_buffer.c
index f22c94f..6f32f28 100644
--- a/vcs-svn/line_buffer.c
+++ b/vcs-svn/line_buffer.c
@@ -5,15 +5,13 @@
 
 #include "git-compat-util.h"
 #include "line_buffer.h"
-#include "obj_pool.h"
+#include "strbuf.h"
 
 #define LINE_BUFFER_LEN 10000
 #define COPY_BUFFER_LEN 4096
 
-/* Create memory pool for char sequence of known length */
-obj_pool_gen(blob, char, 4096)
-
 static char line_buffer[LINE_BUFFER_LEN];
+static struct strbuf blob_buffer = STRBUF_INIT;
 static FILE *infile;
 
 int buffer_init(const char *filename)
@@ -58,11 +56,9 @@ char *buffer_read_line(void)
 
 char *buffer_read_string(uint32_t len)
 {
-	char *s;
-	blob_free(blob_pool.size);
-	s = blob_pointer(blob_alloc(len + 1));
-	s[fread(s, 1, len, infile)] = '\0';
-	return ferror(infile) ? NULL : s;
+	strbuf_reset(&blob_buffer);
+	strbuf_fread(&blob_buffer, len, infile);
+	return ferror(infile) ? NULL : blob_buffer.buf;
 }
 
 void buffer_copy_bytes(uint32_t len)
@@ -94,5 +90,5 @@ void buffer_skip_bytes(uint32_t len)
 
 void buffer_reset(void)
 {
-	blob_reset();
+	strbuf_release(&blob_buffer);
 }
-- 
1.7.2.3.554.gc9b5c.dirty