From 235c2987671222299042c7d920f83e21c7632ebb Mon Sep 17 00:00:00 2001
From: "Christopher N. Hesse" <raymanfx@gmail.com>
Date: Sun, 2 Apr 2017 17:20:16 +0200
Subject: [PATCH] lights_helper: I/O API cleanup

 * buf => buffer for consistency
 * explicitly cast strtol retval to int
 * close(NULL) is a no-op, remove superfluous checking
 * replace variying buffer sizes by INT_MAX_STRLEN
 * always return signed errno codes

Change-Id: I972e33e2435ec7d68a8ffdc5ab88a14d8005ff55
---
 liblights/lights_helper.c | 43 +++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/liblights/lights_helper.c b/liblights/lights_helper.c
index 5fd8b12..6ac18bf 100644
--- a/liblights/lights_helper.c
+++ b/liblights/lights_helper.c
@@ -33,41 +33,40 @@
  * @param path The absolute path string.
  * @return The Integer with decimal base, -1 or errno on error.
  */
-int read_int(char const *path)
+static int read_int(char const *path)
 {
     int fd, len;
-    int num_bytes = 10;
-    char buf[11];
-    int ret;
+    int ret = 0;
+    const int INT_MAX_STRLEN = 10;
+    char buffer[INT_MAX_STRLEN+1];
 
     fd = open(path, O_RDONLY);
     if (fd < 0) {
-        ret = errno;
+        ret = -errno;
         ALOGE("%s: failed to open %s (%s)", __func__, path, strerror(errno));
         goto exit;
     }
 
-    len = read(fd, buf, num_bytes - 1);
+    len = read(fd, buffer, INT_MAX_STRLEN-1);
     if (len < 0) {
-        ret = errno;
+        ret = -errno;
         ALOGE("%s: failed to read from %s (%s)", __func__, path, strerror(errno));
         goto exit;
     }
 
-    buf[len] = '\0';
+    buffer[len] = '\0';
 
-    // decimal base
+    /* now parse the integer from buffer */
     char *endptr = NULL;
-    ret = strtol(buf, &endptr, 10);
+    ret = (int) strtol(buffer, &endptr, 10);
     if (ret == 0 && endptr == NULL) {
         ret = -1;
-        ALOGE("%s: failed to extract number from string %s", __func__, buf);
+        ALOGE("%s: failed to extract number from string %s", __func__, buffer);
         goto exit;
     }
 
 exit:
-    if (fd >= 0)
-        close(fd);
+    close(fd);
     return ret;
 }
 
@@ -78,30 +77,30 @@ exit:
  * @param value The Integer value to be written.
  * @return 0 on success, errno on error.
  */
-int write_int(char const *path, const int value)
+static int write_int(char const *path, const int value)
 {
-    int fd, len;
+    int fd, len, num_bytes;
     int ret = 0;
+    const int INT_MAX_STRLEN = 10;
+    char buffer[INT_MAX_STRLEN+1];
 
     fd = open(path, O_WRONLY);
     if (fd < 0) {
-        ret = errno;
+        ret = -errno;
         ALOGE("%s: failed to open %s (%s)", __func__, path, strerror(errno));
         goto exit;
     }
 
-    char buffer[20];
-    int bytes = sprintf(buffer, "%d", value);
-    len = write(fd, buffer, bytes);
+    num_bytes = sprintf(buffer, "%d", value);
+    len = write(fd, buffer, num_bytes);
     if (len < 0) {
-        ret = errno;
+        ret = -errno;
         ALOGE("%s: failed to write to %s (%s)", __func__, path, strerror(errno));
         goto exit;
     }
 
 exit:
-    if (fd >= 0)
-        close(fd);
+    close(fd);
     return ret;
 }
 
-- 
2.20.1