From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202510 header.b=eD5jKQx5; dkim-atps=neutral Received: from mail.ozlabs.org (mail.ozlabs.org [IPv6:2404:9400:2221:ea00::3]) by passt.top (Postfix) with ESMTPS id 0E32B5A0271 for ; Wed, 26 Nov 2025 05:13:07 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202510; t=1764130374; bh=ooGvPww6Mf6xyLofoxXS20DUi6Op+VadgBzfLfndmso=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eD5jKQx5m+6c3vLw73UvkXsZbeJ8TRcW1P0rO+TfwawOcSbEPNq/Y63Ig8/wMDZUN QWKMBXpseYEEbeqbaSzEEIR5j5iJDgedIKBTreKSHvEcKjkwwp9yfmjEeiBa8mAwu6 PsbwHW9lEECuZbdtXSOAmwQAE/07Cc/bjYQOxg48dxfbnWzzL9UjHwPfxGx5TeHJjz dCV2Jq7572dgjVw9zMBYQ2AJztG0wozLHwb4nuQG1K6PDH211Rvrpyis265tOWbJF4 S4oSyZ2ZkYNawOvQDZenvsbeAGXCz/DqvNJPwEXx9Oh78X28SWE6P+NqbSQRJYaaMO HLea9kOpGtJKg== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4dGR465mwrz4wCk; Wed, 26 Nov 2025 15:12:54 +1100 (AEDT) Date: Wed, 26 Nov 2025 15:07:25 +1100 From: David Gibson To: Yumei Huang Subject: Re: [PATCH v9 2/5] util: Introduce read_file() and read_file_integer() function Message-ID: References: <20251125072638.88896-1-yuhuang@redhat.com> <20251125072638.88896-3-yuhuang@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ifVBq6GR4Woapz9V" Content-Disposition: inline In-Reply-To: <20251125072638.88896-3-yuhuang@redhat.com> Message-ID-Hash: FKFH3U6RTVJURUYJNAXBGCYUWVYPRBK5 X-Message-ID-Hash: FKFH3U6RTVJURUYJNAXBGCYUWVYPRBK5 X-MailFrom: dgibson@gandalf.ozlabs.org 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: passt-dev@passt.top, sbrivio@redhat.com 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: --ifVBq6GR4Woapz9V Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Nov 25, 2025 at 03:26:35PM +0800, Yumei Huang wrote: > Signed-off-by: Yumei Huang > --- > util.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > util.h | 1 + > 2 files changed, 91 insertions(+) >=20 > diff --git a/util.c b/util.c > index ab23463..c56f920 100644 > --- a/util.c > +++ b/util.c > @@ -589,6 +589,96 @@ int write_file(const char *path, const char *buf) > return len =3D=3D 0 ? 0 : -1; > } > =20 > +/** > + * read_file() - Read contents of file into a NULL-terminated buffer > + * @path: Path to file to read > + * @buf: Buffer to store file contents > + * @buf_size: Size of buffer > + * > + * Return: number of bytes read on success, negative error code on failu= re > + */ > +static 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; > + > + if (fd < 0) > + return -errno; > + > + if (!buf_size) { > + close(fd); > + return -EINVAL; > + } Nit: usually it's preferable to put the error checks with the least "impact" first. So in this case, it would be slightly better to check buf_size first, before even opening the file. What you have is still correct though, so this isn't worth a respin. > + > + while (total_read < buf_size) { > + ssize_t rc =3D read(fd, buf + total_read, buf_size - total_read); > + > + if (rc < 0) { > + int errno_save =3D errno; > + close(fd); > + return -errno_save; > + } > + > + if (rc =3D=3D 0) > + break; > + > + total_read +=3D rc; > + } > + > + close(fd); > + > + if (total_read =3D=3D buf_size) { > + buf[buf_size - 1] =3D '\0'; > + return -ENOBUFS; > + } > + > + buf[total_read] =3D '\0'; > + > + return total_read; > +} > + > +/** > + * read_file_integer() - Read an integer value from a file > + * @path: Path to 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) > +{ > + ssize_t bytes_read; > + char buf[BUFSIZ]; > + intmax_t value; > + char *end; > + > + bytes_read =3D read_file(path, buf, sizeof(buf)); > + > + if (bytes_read < 0) > + goto error; > + > + if (bytes_read =3D=3D 0) { > + debug("Empty file %s", path); > + goto error; > + } > + > + errno =3D 0; > + value =3D strtoimax(buf, &end, 10); > + if (*end && *end !=3D '\n') { > + debug("Non-numeric content in %s", path); > + goto error; > + } > + if (errno) { > + debug("Out of range value in %s: %s", path, buf); > + goto error; > + } > + > + return value; > + > +error: > + debug("Using %"PRIdMAX" as default value", fallback); I think this does need to say what it's using this default for. So something like: "Couldn't read %s, using %"PRIdMAX"d as default value" > + return fallback; > +} > + > #ifdef __ia64__ > /* Needed by do_clone() below: glibc doesn't export the prototype of __c= lone2(), > * use the description from clone(2). > diff --git a/util.h b/util.h > index a0b2ada..6dec14b 100644 > --- a/util.h > +++ b/util.h > @@ -229,6 +229,7 @@ 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); > +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 iovcnt, size= _t skip); > int read_all_buf(int fd, void *buf, size_t len); > --=20 > 2.51.1 >=20 --=20 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 way | around. http://www.ozlabs.org/~dgibson --ifVBq6GR4Woapz9V Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmkmfPwACgkQzQJF27ox 2Gc8xQ//SAzCZWYwQLcvnKuqhfunrlZOJ/F3coHQATID/V14FTRsPjd87Lrqyivu RTkBNCp8EpHMSIKoCGaSZmN3x3/DqmKrLyTtWQeEtN5qT9yk86LjhGFsM1suoryN DX30V8zPMLk5Ullxy0p4mEd2NNCJFoHZUGb+GUL7DYUG+EUPvx1nqxdwANGU21z8 fKf/Gg9XzrrRU9ixO85p8bJn6rOlC1q6sEi9vEoj/+F2tue2b3Etmc70kw7LIScV OVpvJMp72gAUpb45yHQM6/W8zViZEFkJ2xeHXH8mJxRvmhXWSquCLkpApd9foGuM dTCFoVGBm3WI0z19GG9NOhI6/y1W07h7ItURd82DTLVd0W4XqGkI7XxEEyhW5cbf Kg51US9yMKCdQf488y07uMA93VbtVvzYnjotMwfkQuqK8gTvr1AYqZM3NexYqIFP Gd5n6nUuywvxCMNxU+DHQcuZkAI68K9xttz7wgpuo4jw9miEopTuoPCdquXAujyN /owMSxnnFr1Ocpr+91vZeO2Eu+47SUegpohGwexxlgXpbKPKPpKDkfwD8T90nqbF Zw/gYkL7X2eYp0fHftzG0PDK/5HybQDIUVMb2sm59XY0e+g4h0036NBTg2aGP34S XTn0Yd3KLmsgtub1moLZN8Uw0EiUF+d1BPOkv7KbnvN2IG95xuo= =dceu -----END PGP SIGNATURE----- --ifVBq6GR4Woapz9V--