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 == 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 = open(path, O_RDONLY | O_CLOEXEC);
+ size_t total_read = 0;
+ ssize_t rc;
+
+ if (fd < 0) {
+ warn_perror("Could not open %s", path);
+ return -1;
+ }
+
+ while (total_read < buf_size) {
+ rc = 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 == 0)
+ break;
+
+ total_read += rc;
+ }
+
+ close(fd);
+
+ if (total_read == buf_size) {
+ warn("File %s truncated, buffer too small", path);
+ return -2;
+ }
+
+ buf[total_read] = '\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 = read_file(path, buf, sizeof(buf));
+
+ if (bytes_read < 0)
+ return fallback;
+
+ if (bytes_read == 0) {
+ debug("Empty file %s", path);
+ return fallback;
+ }
+
+ errno = 0;
+ value = strtoimax(buf, &end, 10);
+ if (*end && *end != '\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 == 255.
+ * Plus 2 extra bytes for the sign and null terminator.
+ * See https://stackoverflow.com/a/10536254.
+ */
+#define INTMAX_STRLEN (sizeof(intmax_t) * 3 + 2)
+
/* inet address (- '\0') + port (u16) (- '\0') + ':' + '\0' */
#define SOCKADDR_INET_STRLEN \
(INET_ADDRSTRLEN-1 + UINT16_STRLEN-1 + sizeof(":"))
--
2.47.0