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Tue, 21 Oct 2025 17:56:02 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEZ4RSPFhdhRqrcoCinJYYWwS0Vyro5dmqzaJBwy8mtSN8gPzqZFwShx6dTr2WB3jRBXJhRzJ7ka3hdPYSWVek= X-Received: by 2002:a05:6402:f26:b0:639:5f23:5d10 with SMTP id 4fb4d7f45d1cf-63c1f6bf0cdmr13795245a12.17.1761094561936; Tue, 21 Oct 2025 17:56:01 -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: <20251021235059.0c5244e8@elisabeth> From: Yumei Huang Date: Wed, 22 Oct 2025 08:55:50 +0800 X-Gm-Features: AS18NWA9F4rttPqH_-w2tXwb7OdHeC2MeC6_Hbq8fjEamAFue98vDdy03uGULqQ Message-ID: Subject: Re: [PATCH v6 2/4] util: Introduce read_file() and read_file_integer() function To: Stefano Brivio X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 2z78PxqMg9iFeoATgIv4AknL045muD5tC3-PySyVA84_1761094562 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Message-ID-Hash: DHHIGKTGLWZNX3VU7OBFFHQMUUCF22WP X-Message-ID-Hash: DHHIGKTGLWZNX3VU7OBFFHQMUUCF22WP 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: passt-dev@passt.top, david@gibson.dropbear.id.au 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 5:51=E2=80=AFAM 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 *b= uf) > > > > 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_re= ad); > > > > + > > > > + 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 prototype = 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 iovcnt= , 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. > > > It's my fault. I should have waited to see if you have more comments > > before sending the new version. > > Thanks for understanding. My biggest problem with this is: where do I > comment now? On v4 or v6? Should I even read v5? > > Well, anyway, I'll directly review v6 (in a bit) to keep things sane. Sure, please go with v6. > > -- > Stefano > --=20 Thanks, Yumei Huang