From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-4.1 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id A791920254 for ; Sat, 25 Feb 2017 20:13:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751889AbdBYUNG (ORCPT ); Sat, 25 Feb 2017 15:13:06 -0500 Received: from cloud.peff.net ([104.130.231.41]:34123 "EHLO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbdBYUNG (ORCPT ); Sat, 25 Feb 2017 15:13:06 -0500 Received: (qmail 2843 invoked by uid 109); 25 Feb 2017 20:11:26 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.84) with SMTP; Sat, 25 Feb 2017 20:11:26 +0000 Received: (qmail 15058 invoked by uid 111); 25 Feb 2017 20:11:30 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.84) with SMTP; Sat, 25 Feb 2017 15:11:30 -0500 Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Sat, 25 Feb 2017 15:11:23 -0500 Date: Sat, 25 Feb 2017 15:11:23 -0500 From: Jeff King To: =?utf-8?B?UmVuw6k=?= Scharfe Cc: Git List , Junio C Hamano , Brandon Williams Subject: Re: [PATCH] strbuf: add strbuf_add_real_path() Message-ID: <20170225201123.ozrrfgim2rdctczv@sigill.intra.peff.net> References: <4d191b86-d36c-e3ec-99c6-d15baa6b659a@web.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4d191b86-d36c-e3ec-99c6-d15baa6b659a@web.de> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Sat, Feb 25, 2017 at 05:00:33PM +0100, René Scharfe wrote: > Add a function for appending the canonized absolute pathname of a given > path to a strbuf. It keeps the existing contents intact, as expected of > a function of the strbuf_add() family, while avoiding copying the result > if the given strbuf is empty. It's more consistent with the rest of the > strbuf API than strbuf_realpath(), which it's wrapping. > > Also add a semantic patch demonstrating its intended usage and apply it > to the current tree. Using strbuf_add_real_path() instead of calling > strbuf_addstr() and real_path() avoids an extra copy to a static buffer. It's also re-entrant, which real_path() is not. > +void strbuf_add_real_path(struct strbuf *sb, const char *path) > +{ > + if (sb->len) { > + struct strbuf resolved = STRBUF_INIT; > + strbuf_realpath(&resolved, path, 1); > + strbuf_addbuf(sb, &resolved); > + strbuf_release(&resolved); > + } else > + strbuf_realpath(sb, path, 1); > +} The wrapping here seems a little backwards. If strbuf_add_real_path() were the inner one, then we would not need this extra allocation. I know that the reasons are historical, but I don't think it would be impossible to teach the realpath code to do it. OTOH, it may not be worth the effort. It's not like strbuf_realpath() doesn't allocate secondary strbufs for its work already, so dropping one more is probably not that exciting. And certainly think your patch is an incremental improvement. Out of curiosity, I took a stab at the patch, which is below. Only lightly tested by me, and it does make the logic a bit more complicated to read, as you have to adjust for the original "base" in several places. diff --git a/abspath.c b/abspath.c index 2f0c26e0e..286072f48 100644 --- a/abspath.c +++ b/abspath.c @@ -12,9 +12,9 @@ int is_directory(const char *path) } /* removes the last path component from 'path' except if 'path' is root */ -static void strip_last_component(struct strbuf *path) +static void strip_last_component(struct strbuf *path, size_t base) { - size_t offset = offset_1st_component(path->buf); + size_t offset = base + offset_1st_component(path->buf + base); size_t len = path->len; /* Find start of the last component */ @@ -49,14 +49,15 @@ static void get_next_component(struct strbuf *next, struct strbuf *remaining) } /* copies root part from remaining to resolved, canonicalizing it on the way */ -static void get_root_part(struct strbuf *resolved, struct strbuf *remaining) +static void get_root_part(struct strbuf *resolved, struct strbuf *remaining, + size_t base) { int offset = offset_1st_component(remaining->buf); - strbuf_reset(resolved); + strbuf_setlen(resolved, base); strbuf_add(resolved, remaining->buf, offset); #ifdef GIT_WINDOWS_NATIVE - convert_slashes(resolved->buf); + convert_slashes(resolved->buf + base); #endif strbuf_remove(remaining, 0, offset); } @@ -78,8 +79,8 @@ static void get_root_part(struct strbuf *resolved, struct strbuf *remaining) * informative error message if there is a problem. Otherwise, return * NULL on errors (without generating any output). */ -char *strbuf_realpath(struct strbuf *resolved, const char *path, - int die_on_error) +char *strbuf_add_real_path(struct strbuf *resolved, const char *path, + int die_on_error) { struct strbuf remaining = STRBUF_INIT; struct strbuf next = STRBUF_INIT; @@ -87,6 +88,7 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, char *retval = NULL; int num_symlinks = 0; struct stat st; + size_t base = resolved->len; if (!*path) { if (die_on_error) @@ -96,9 +98,9 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, } strbuf_addstr(&remaining, path); - get_root_part(resolved, &remaining); + get_root_part(resolved, &remaining, base); - if (!resolved->len) { + if (resolved->len == base) { /* relative path; can use CWD as the initial resolved path */ if (strbuf_getcwd(resolved)) { if (die_on_error) @@ -118,7 +120,7 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, continue; /* '.' component */ } else if (next.len == 2 && !strcmp(next.buf, "..")) { /* '..' component; strip the last path component */ - strip_last_component(resolved); + strip_last_component(resolved, base); continue; } @@ -127,12 +129,12 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, strbuf_addch(resolved, '/'); strbuf_addbuf(resolved, &next); - if (lstat(resolved->buf, &st)) { + if (lstat(resolved->buf + base, &st)) { /* error out unless this was the last component */ if (errno != ENOENT || remaining.len) { if (die_on_error) die_errno("Invalid path '%s'", - resolved->buf); + resolved->buf + base); else goto error_out; } @@ -150,7 +152,7 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, goto error_out; } - len = strbuf_readlink(&symlink, resolved->buf, + len = strbuf_readlink(&symlink, resolved->buf + base, st.st_size); if (len < 0) { if (die_on_error) @@ -162,14 +164,14 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, if (is_absolute_path(symlink.buf)) { /* absolute symlink; set resolved to root */ - get_root_part(resolved, &symlink); + get_root_part(resolved, &symlink, base); } else { /* * relative symlink * strip off the last component since it will * be replaced with the contents of the symlink */ - strip_last_component(resolved); + strip_last_component(resolved, base); } /* @@ -202,6 +204,12 @@ char *strbuf_realpath(struct strbuf *resolved, const char *path, return retval; } +char *strbuf_realpath(struct strbuf *sb, const char *path, int die_on_error) +{ + strbuf_reset(sb); + return strbuf_add_real_path(sb, path, die_on_error); +} + const char *real_path(const char *path) { static struct strbuf realpath = STRBUF_INIT;