Revert "Use getmntent when accessing /proc/mounts."

This reverts commit a382e2bdb2.

getmntent is not implemented in older Bionic versions.

Change-Id: I277dae9e4fd83f08de8099e856e8d8f45e39239d

mtdutils/mounts.c

@@ -14,7 +14,6 @@
  * limitations under the License.
  */
 
-#include <mntent.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -60,8 +59,10 @@ free_volume_internals(const MountedVolume *volume, int zero)
 int
 scan_mounted_volumes()
 {
-    FILE* fp;
-    struct mntent* mentry;
+    char buf[2048];
+    const char *bufp;
+    int fd;
+    ssize_t nbytes;
 
     if (g_mounts_state.volumes == NULL) {
         const int numv = 32;
@@ -83,20 +84,80 @@ scan_mounted_volumes()
     }
     g_mounts_state.volume_count = 0;
 
-    /* Open and read mount table entries. */
-    fp = setmntent(PROC_MOUNTS_FILENAME, "r");
-    if (fp == NULL) {
-        return -1;
+    /* Open and read the file contents.
+     */
+    fd = open(PROC_MOUNTS_FILENAME, O_RDONLY);
+    if (fd < 0) {
+        goto bail;
     }
-    while ((mentry = getmntent(fp)) != NULL) {
-        MountedVolume* v = &g_mounts_state.volumes[g_mounts_state.volume_count++];
-        v->device = strdup(mentry->mnt_fsname);
-        v->mount_point = strdup(mentry->mnt_dir);
-        v->filesystem = strdup(mentry->mnt_type);
-        v->flags = strdup(mentry->mnt_opts);
+    nbytes = read(fd, buf, sizeof(buf) - 1);
+    close(fd);
+    if (nbytes < 0) {
+        goto bail;
     }
-    endmntent(fp);
+    buf[nbytes] = '\0';
+
+    /* Parse the contents of the file, which looks like:
+     *
+     *     # cat /proc/mounts
+     *     rootfs / rootfs rw 0 0
+     *     /dev/pts /dev/pts devpts rw 0 0
+     *     /proc /proc proc rw 0 0
+     *     /sys /sys sysfs rw 0 0
+     *     /dev/block/mtdblock4 /system yaffs2 rw,nodev,noatime,nodiratime 0 0
+     *     /dev/block/mtdblock5 /data yaffs2 rw,nodev,noatime,nodiratime 0 0
+     *     /dev/block/mmcblk0p1 /sdcard vfat rw,sync,dirsync,fmask=0000,dmask=0000,codepage=cp437,iocharset=iso8859-1,utf8 0 0
+     *
+     * The zeroes at the end are dummy placeholder fields to make the
+     * output match Linux's /etc/mtab, but don't represent anything here.
+     */
+    bufp = buf;
+    while (nbytes > 0) {
+        char device[64];
+        char mount_point[64];
+        char filesystem[64];
+        char flags[128];
+        int matches;
+
+        /* %as is a gnu extension that malloc()s a string for each field.
+         */
+        matches = sscanf(bufp, "%63s %63s %63s %127s",
+                device, mount_point, filesystem, flags);
+
+        if (matches == 4) {
+            device[sizeof(device)-1] = '\0';
+            mount_point[sizeof(mount_point)-1] = '\0';
+            filesystem[sizeof(filesystem)-1] = '\0';
+            flags[sizeof(flags)-1] = '\0';
+
+            MountedVolume *v =
+                    &g_mounts_state.volumes[g_mounts_state.volume_count++];
+            v->device = strdup(device);
+            v->mount_point = strdup(mount_point);
+            v->filesystem = strdup(filesystem);
+            v->flags = strdup(flags);
+        } else {
+printf("matches was %d on <<%.40s>>\n", matches, bufp);
+        }
+
+        /* Eat the line.
+         */
+        while (nbytes > 0 && *bufp != '\n') {
+            bufp++;
+            nbytes--;
+        }
+        if (nbytes > 0) {
+            bufp++;
+            nbytes--;
+        }
+    }
+
     return 0;
+
+bail:
+//TODO: free the strings we've allocated.
+    g_mounts_state.volume_count = 0;
+    return -1;
 }
 
 const MountedVolume *