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Wed, 22 Oct 2025 01:42:42 -0700 (PDT) X-Google-Smtp-Source: AGHT+IF7P4K9nEEWq+BpNIFqFeWze8CXw6Ld+jhpvRWsEWUin0vIKzfDLSkR8nJcFN6LtDgFXSrfrYHGtc/NEIAytaM= X-Received: by 2002:a05:6402:4444:b0:63e:b49:c9c3 with SMTP id 4fb4d7f45d1cf-63e0b49cd06mr4409488a12.31.1761122562065; Wed, 22 Oct 2025 01:42:42 -0700 (PDT) MIME-Version: 1.0 References: <20251017062838.21041-1-yuhuang@redhat.com> <20251017062838.21041-3-yuhuang@redhat.com> <20251019120712.6f232804@elisabeth> <20251021235059.0c5244e8@elisabeth> In-Reply-To: From: Yumei Huang Date: Wed, 22 Oct 2025 16:42:31 +0800 X-Gm-Features: AS18NWBY-GLmWF05CKPDlYwMA7hm2h9SUe09q9RvZuIFtPxkrnIfW_xmR3UHkxw Message-ID: Subject: Re: [PATCH v6 2/4] util: Introduce read_file() and read_file_integer() function To: David Gibson X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xJS4yNkRyHCJkBnYpJhVjufxtjchvc2TmNkT6BXqHOQ_1761122563 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Message-ID-Hash: 63R5NROL2XPLOQDNVQF376LWUVDTKY7I X-Message-ID-Hash: 63R5NROL2XPLOQDNVQF376LWUVDTKY7I X-MailFrom: yuhuang@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Stefano Brivio , passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Wed, Oct 22, 2025 at 9:01=E2=80=AFAM David Gibson wrote: > > On Tue, Oct 21, 2025 at 11:50:59PM +0200, Stefano Brivio wrote: > > On Tue, 21 Oct 2025 17:32:58 +0800 > > Yumei Huang wrote: > > > > > On Sun, Oct 19, 2025 at 6:07=E2=80=AFPM Stefano Brivio wrote: > > > > > > > > On Fri, 17 Oct 2025 14:28:36 +0800 > > > > Yumei Huang wrote: > > > > > > > > > Signed-off-by: Yumei Huang > > > > > --- > > > > > util.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++++= ++++++ > > > > > util.h | 8 ++++++ > > > > > 2 files changed, 92 insertions(+) > > > > > > > > > > diff --git a/util.c b/util.c > > > > > index c492f90..5c8c4bc 100644 > > > > > --- a/util.c > > > > > +++ b/util.c > > > > > @@ -579,6 +579,90 @@ int write_file(const char *path, const char = *buf) > > > > > return len =3D=3D 0 ? 0 : -1; > > > > > } > > > > > > > > > > +/** > > > > > + * read_file() - Read contents of file into a buffer > > > > > + * @path: File to read > > > > > + * @buf: Buffer to store file contents > > > > > + * @buf_size: Size of buffer > > > > > + * > > > > > + * Return: number of bytes read on success, -1 on any error, -2 = on truncation > > > > > +*/ > > > > > +ssize_t read_file(const char *path, char *buf, size_t buf_size) > > > > > +{ > > > > > + int fd =3D open(path, O_RDONLY | O_CLOEXEC); > > > > > + size_t total_read =3D 0; > > > > > + ssize_t rc; > > > > > + > > > > > + if (fd < 0) { > > > > > + warn_perror("Could not open %s", path); > > > > > + return -1; > > > > > + } > > > > > + > > > > > + while (total_read < buf_size) { > > > > > + rc =3D read(fd, buf + total_read, buf_size - total_= read); > > > > > + > > > > > + if (rc < 0) { > > > > > + warn_perror("Couldn't read from %s", path); > > > > > + close(fd); > > > > > + return -1; > > > > > + } > > > > > + > > > > > + if (rc =3D=3D 0) > > > > > + break; > > > > > + > > > > > + total_read +=3D rc; > > > > > + } > > > > > + > > > > > + close(fd); > > > > > + > > > > > + if (total_read =3D=3D buf_size) { > > > > > + warn("File %s truncated, buffer too small", path); > > > > > + return -2; > > > > > + } > > > > > + > > > > > + buf[total_read] =3D '\0'; > > > > > + > > > > > + return total_read; > > > > > +} > > > > > + > > > > > +/** > > > > > + * read_file_integer() - Read an integer value from a file > > > > > + * @path: File to read > > > > > + * @fallback: Default value if file can't be read > > > > > + * > > > > > + * Return: Integer value, fallback on failure > > > > > +*/ > > > > > +intmax_t read_file_integer(const char *path, intmax_t fallback) > > > > > +{ > > > > > + char buf[INTMAX_STRLEN]; > > > > > + ssize_t bytes_read; > > > > > + intmax_t value; > > > > > + char *end; > > > > > + > > > > > + bytes_read =3D read_file(path, buf, sizeof(buf)); > > > > > + > > > > > + if (bytes_read < 0) > > > > > + return fallback; > > > > > + > > > > > + if (bytes_read =3D=3D 0) { > > > > > + debug("Empty file %s", path); > > > > > + return fallback; > > > > > + } > > > > > + > > > > > + errno =3D 0; > > > > > + value =3D strtoimax(buf, &end, 10); > > > > > + if (*end && *end !=3D '\n') { > > > > > + debug("Invalid format in %s", path); > > > > > + return fallback; > > > > > + } > > > > > + if (errno) { > > > > > + debug("Invalid value in %s: %s", path, buf); > > > > > + return fallback; > > > > > + } > > > > > + > > > > > + return value; > > > > > +} > > > > > + > > > > > #ifdef __ia64__ > > > > > /* Needed by do_clone() below: glibc doesn't export the prototyp= e of __clone2(), > > > > > * use the description from clone(2). > > > > > diff --git a/util.h b/util.h > > > > > index 22eaac5..3f9f296 100644 > > > > > --- a/util.h > > > > > +++ b/util.h > > > > > @@ -222,6 +222,8 @@ void pidfile_write(int fd, pid_t pid); > > > > > int __daemon(int pidfile_fd, int devnull_fd); > > > > > int fls(unsigned long x); > > > > > int write_file(const char *path, const char *buf); > > > > > +ssize_t read_file(const char *path, char *buf, size_t buf_size); > > > > > +intmax_t read_file_integer(const char *path, intmax_t fallback); > > > > > int write_all_buf(int fd, const void *buf, size_t len); > > > > > int write_remainder(int fd, const struct iovec *iov, size_t iovc= nt, size_t skip); > > > > > int read_all_buf(int fd, void *buf, size_t len); > > > > > @@ -250,6 +252,12 @@ static inline const char *af_name(sa_family_= t af) > > > > > > > > > > #define UINT16_STRLEN (sizeof("65535")) > > > > > > > > > > +/* Each byte expands to at most 3 decimal digits since 0xff =3D= =3D 255. > > > > > + * Plus 2 extra bytes for the sign and null terminator. > > > > > + * See https://stackoverflow.com/a/10536254. > > > > > > > > This is not an acceptable form of attribution according to the > > > > CC BY-SA 3.0 terms. See: > > > > > > > > https://stackoverflow.com/help/licensing > > > > https://creativecommons.org/licenses/by-sa/3.0/ > > > > > > > > and checksum.h in this tree for some examples of how to combine > > > > different licensing terms in a single file, in a way that's > > > > human-readable but still machine-friendly (for license / compliance > > > > scanners such as REUSE). > > > > > > > > As I commented on a previous version, anyway, I don't think we need > > > > this at all. I guess my comment was ignored though. > > > > > > I guess you meant the comment of suggesting using BUFSIZ in V2? > > > > Right, but on v4, and that was just Friday for everybody involved... > > > > > David replied as quote: > > > > > > "We could use BUFSIZ, but it's massive overkill for > > > reading a single integer: 8192 versus ~21 bytes (or ~42 bytes if > > > intmax_t were 128-bit)." > > > > I wanted to reply to that because sure, BUFSIZ is typically 8192 bytes > > on glibc and 1024 with musl, but adding 10 or 8192 to the stack pointer > > doesn't really make a difference. > > > > It's not like we allocate that memory anyway, and I don't think any of > > that memory (or unused holes on the stack we create) is prefetched. And > > regardless of all that... we don't use these functions on any data > > path, it's just during configuration. It can be (relatively) slow. > > Right. Sorry, I didn't follow up yet, but after I wrote that, Stefano > convinced me that BUFSIZ is fine. I originally suggested avoiding the > arbitrary buffer largely because I thought having an INTMAX_STRLEN > constant might be useful for other reasons too, but honestly, not > very. I will update that in v7. > > -- > David Gibson (he or they) | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you, not the other wa= y > | around. > http://www.ozlabs.org/~dgibson --=20 Thanks, Yumei Huang