Hi Paul,
Paul Eggert <egg...@cs.ucla.edu> writes:
> Surely this would be much, much slower if the file seeks slowly,
> for example, if it is a tape drive.
>
> It might be helpful to use fstat to find the file's type and size,
> and to subtract the current file offset from its size
> (for file types where st_size is applicable).
thanks for the review, I have adjusted the patch accordingly.
Cheers,
Giuseppe
>From e1276fa005fee48e036132ebbd9b69bdef297249 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <gscriv...@gnu.org>
Date: Tue, 3 Aug 2010 15:40:19 +0200
Subject: [PATCH] read-file: Avoid memory reallocations with regular files.
* lib/read-file.c: Include <sys/types.h>, <sys/stat.h>, <unistd.h>.
(fread_file): With regular files, use the remaining length as the
initial buffer size.
---
ChangeLog | 7 +++++++
lib/read-file.c | 19 +++++++++++++++++++
2 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 4d24a34..a178f88 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2010-08-03 Giuseppe Scrivano <gscriv...@gnu.org>
+
+ read-file: Avoid memory reallocations with regular files.
+ * lib/read-file.c: Include <sys/types.h>, <sys/stat.h>, <unistd.h>.
+ (fread_file): With regular files, use the remaining length as the
+ initial buffer size.
+
2010-08-01 Bruno Haible <br...@clisp.org>
Integrate the regex documentation.
diff --git a/lib/read-file.c b/lib/read-file.c
index 6b655db..cf8af6b 100644
--- a/lib/read-file.c
+++ b/lib/read-file.c
@@ -18,6 +18,11 @@
#include <config.h>
+/* Get fstat. */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
#include "read-file.h"
/* Get realloc, free. */
@@ -38,6 +43,20 @@ fread_file (FILE * stream, size_t * length)
size_t alloc = 0;
size_t size = 0;
int save_errno;
+ struct stat st;
+
+ if (fstat (fileno (stream), &st) == 0 && S_ISREG (st.st_mode))
+ {
+ long pos = ftell (stream);
+ if (pos < 0)
+ return NULL;
+
+ alloc = st.st_size - pos + 1;
+
+ buf = malloc (alloc);
+ if (!buf)
+ return NULL;
+ }
for (;;)
{
--
1.7.1
