libcutils: move cutils/files.h to cutils/android_get_control_file.h

files.[h|cpp] is bound to be abused with junk, replace with
android_get_control_file.[h|cpp]. Plus some sundry cleanup.

Test: gTest libcutils-tests, logd-unit-tests, liblog-unit-tests,
      logcat-unit-tests and init_tests
Bug: 32450474
Change-Id: Ibd4a7aa4624ea19a43d1f98a3c71ac37805d36b5

1 files changed, 109 insertions, 0 deletions

diff --git a/libcutils/android_get_control_file.cpp b/libcutils/android_get_control_file.cpp
new file mode 100644
index 000000000..496fbbfe6
--- /dev/null
+++ b/libcutils/android_get_control_file.cpp
@@ -0,0 +1,109 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <cutils/android_get_control_file.h>
+
+#include "android_get_control_env.h"
+
+LIBCUTILS_HIDDEN int __android_get_control_from_env(const char* prefix,
+                                                    const char* name) {
+    if (!prefix || !name) return -1;
+
+    char *key = NULL;
+    if (asprintf(&key, "%s%s", prefix, name) < 0) return -1;
+    if (!key) return -1;
+
+    char *cp = key;
+    while (*cp) {
+        if (!isalnum(*cp)) *cp = '_';
+        ++cp;
+    }
+
+    const char* val = getenv(key);
+    free(key);
+    if (!val) return -1;
+
+    errno = 0;
+    long fd = strtol(val, NULL, 10);
+    if (errno) return -1;
+
+    // validity checking
+    if ((fd < 0) || (fd > INT_MAX)) return -1;
+
+    // Since we are inheriting an fd, it could legitimately exceed _SC_OPEN_MAX
+
+    // Still open?
+#if defined(F_GETFD) // Linux lowest overhead
+    if (TEMP_FAILURE_RETRY(fcntl(fd, F_GETFD)) < 0) return -1;
+#elif defined(F_GETFL) // Mac host lowest overhead
+    if (fcntl(fd, F_GETFL) < 0) return -1;
+#else // Hail Mary pass
+    struct stat s;
+    if (fstat(fd, &s) < 0) return -1;
+#endif
+
+    return static_cast<int>(fd);
+}
+
+int android_get_control_file(const char* path) {
+    int fd = __android_get_control_from_env(ANDROID_FILE_ENV_PREFIX, path);
+
+#if defined(__linux__)
+    // Find file path from /proc and make sure it is correct
+    char *proc = NULL;
+    if (asprintf(&proc, "/proc/self/fd/%d", fd) < 0) return -1;
+    if (!proc) return -1;
+
+    size_t len = strlen(path);
+    // readlink() does not guarantee a nul byte, len+2 so we catch truncation.
+    char *buf = static_cast<char *>(calloc(1, len + 2));
+    if (!buf) {
+        free(proc);
+        return -1;
+    }
+    ssize_t ret = TEMP_FAILURE_RETRY(readlink(proc, buf, len + 1));
+    free(proc);
+    int cmp = (len != static_cast<size_t>(ret)) || strcmp(buf, path);
+    free(buf);
+    if (ret < 0) return -1;
+    if (cmp != 0) return -1;
+    // It is what we think it is
+#endif
+
+    return fd;
+}