From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753006Ab2INNPQ (ORCPT ); Fri, 14 Sep 2012 09:15:16 -0400 Received: from fieldses.org ([174.143.236.118]:56975 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751306Ab2INNPN (ORCPT ); Fri, 14 Sep 2012 09:15:13 -0400 Date: Fri, 14 Sep 2012 09:14:57 -0400 From: "J. Bruce Fields" To: Jim Rees Cc: Bernd Petrovitsch , Jan Engelhardt , linux-kernel@vger.kernel.org Subject: Re: [PATCH] strings: helper for maximum decimal encoding of an unsigned integer Message-ID: <20120914131457.GA19666@fieldses.org> References: <20120821212910.GD18637@fieldses.org> <1347614276.26071.15.camel@thorin> <20120914123014.GB29160@umich.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120914123014.GB29160@umich.edu> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 14, 2012 at 08:30:14AM -0400, Jim Rees wrote: > But I still like my way better. Yeah. It looks less mysterious once you realize it's just a straightforward application of the usual coincidence 2^10 = 1024 ~ 1000 = 10^3 How about this? Also with some more defines because I like typing char buf[ULONG_STR_MAX + 1]; better than char bug[base10len(unsigned long) + 1]; --b. commit 59a620640cd05d3d29e678ff893cfe266091fba7 Author: J. Bruce Fields Date: Wed Aug 15 17:41:47 2012 -0400 strings: helper for maximum decimal encoding of an unsigned integer I've seen a couple examples recently where we've gotten this wrong. Maybe something like this would help? Suggested-by: Jim Rees Signed-off-by: J. Bruce Fields diff --git a/include/linux/string.h b/include/linux/string.h index ffe0442..38da7a0 100644 --- a/include/linux/string.h +++ b/include/linux/string.h @@ -126,6 +126,27 @@ extern void argv_free(char **argv); extern bool sysfs_streq(const char *s1, const char *s2); extern int strtobool(const char *s, bool *res); +/* + * length of the decimal representation of an integer, not including any + * sign or null termination. Just an approximation, but it's right for + * unsigned types of size 1 to 26 bytes: + */ +#define base10len(i) (sizeof(i) * 8 * 3 / 10 + 1) + +/* Actually a slight overestimate in the signed 64-bit case: */ + +#define UCHAR_STR_MAX base10len(char) +#define CHAR_STR_MAX base10len(char) + 1 +#define UINT_STR_MAX base10len(int) +#define INT_STR_MAX base10len(int) + 1 +#define ULONG_STR_MAX base10len(long) +#define LONG_STR_MAX base10len(long) + 1 + +#define U32_STR_MAX base10len(u32) +#define S32_STR_MAX base10len(u32) + 1 +#define U64_STR_MAX base10len(u64) +#define S64_STR_MAX base10len(u64) + 1 + #ifdef CONFIG_BINARY_PRINTF int vbin_printf(u32 *bin_buf, size_t size, const char *fmt, va_list args); int bstr_printf(char *buf, size_t size, const char *fmt, const u32 *bin_buf); diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index 2afd2a8..d80d482 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -1409,7 +1409,7 @@ static ssize_t read_flush(struct file *file, char __user *buf, size_t count, loff_t *ppos, struct cache_detail *cd) { - char tbuf[20]; + char tbuf[ULONG_STR_MAX + 1]; unsigned long p = *ppos; size_t len;