On Tue, Dec 02, 2025 at 11:00:04AM +0800, Yumei Huang wrote:
Signed-off-by: Yumei Huang
Reviewed-by: David Gibson
--- util.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ util.h | 1 + 2 files changed, 92 insertions(+)
diff --git a/util.c b/util.c index ab23463..4fdb611 100644 --- a/util.c +++ b/util.c @@ -589,6 +589,97 @@ int write_file(const char *path, const char *buf) return len == 0 ? 0 : -1; }
+/** + * 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 failure + */ +static ssize_t read_file(const char *path, char *buf, size_t buf_size) +{ + size_t total_read = 0; + int fd; + + if (!buf_size) + return -EINVAL; + + fd = open(path, O_RDONLY | O_CLOEXEC); + + if (fd < 0) + return -errno; + + while (total_read < buf_size) { + ssize_t rc = read(fd, buf + total_read, buf_size - total_read); + + if (rc < 0) { + int errno_save = errno; + close(fd); + return -errno_save; + } + + if (rc == 0) + break; + + total_read += rc; + } + + close(fd); + + if (total_read == buf_size) { + buf[buf_size - 1] = '\0'; + return -ENOBUFS; + } + + buf[total_read] = '\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 = read_file(path, buf, sizeof(buf)); + + if (bytes_read < 0) + goto error; + + if (bytes_read == 0) { + debug("Empty file %s", path); + goto error; + } + + errno = 0; + value = strtoimax(buf, &end, 10); + if (*end && *end != '\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("Couldn't read %s, using %"PRIdMAX" as default value", + path, fallback); + return fallback; +} + #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 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); -- 2.51.1
-- 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