Clean up reading and writing in init.

This isn't particularly useful in and of itself, but it does introduce the
first (trivial) unit test, improves the documentation (including details
about how to debug init crashes), and made me aware of how unpleasant the
existing parser is.

I also fixed a bug in passing --- unless you thought the "peboot" and "pm"
commands were features...

Bug: 19217569
Change-Id: I6ab76129a543ce3ed3dab52ef2c638009874c3de

1 files changed, 49 insertions, 2 deletions

diff --git a/libutils/tests/file_test.cpp b/libutils/tests/file_test.cpp
index acf66a6..3703a49 100644
--- a/libutils/tests/file_test.cpp
+++ b/libutils/tests/file_test.cpp
@@ -17,21 +17,68 @@
 #include "utils/file.h"
 
 #include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
 #include <gtest/gtest.h>
 
+class TemporaryFile {
+ public:
+  TemporaryFile() {
+    init("/data/local/tmp");
+    if (fd == -1) {
+      init("/tmp");
+    }
+  }
+
+  ~TemporaryFile() {
+    close(fd);
+    unlink(filename);
+  }
+
+  int fd;
+  char filename[1024];
+
+ private:
+  void init(const char* tmp_dir) {
+    snprintf(filename, sizeof(filename), "%s/TemporaryFile-XXXXXX", tmp_dir);
+    fd = mkstemp(filename);
+  }
+};
+
 TEST(file, ReadFileToString_ENOENT) {
   std::string s("hello");
   errno = 0;
-  EXPECT_FALSE(android::ReadFileToString("/proc/does-not-exist", &s));
+  ASSERT_FALSE(android::ReadFileToString("/proc/does-not-exist", &s));
   EXPECT_EQ(ENOENT, errno);
   EXPECT_EQ("", s); // s was cleared.
 }
 
 TEST(file, ReadFileToString_success) {
   std::string s("hello");
-  EXPECT_TRUE(android::ReadFileToString("/proc/version", &s));
+  ASSERT_TRUE(android::ReadFileToString("/proc/version", &s)) << errno;
   EXPECT_GT(s.length(), 6U);
   EXPECT_EQ('\n', s[s.length() - 1]);
   s[5] = 0;
   EXPECT_STREQ("Linux", s.c_str());
 }
+
+TEST(file, WriteStringToFile) {
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+  ASSERT_TRUE(android::WriteStringToFile("abc", tf.filename)) << errno;
+  std::string s;
+  ASSERT_TRUE(android::ReadFileToString(tf.filename, &s)) << errno;
+  EXPECT_EQ("abc", s);
+}
+
+TEST(file, WriteStringToFd) {
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+  ASSERT_TRUE(android::WriteStringToFd("abc", tf.fd));
+
+  ASSERT_EQ(0, lseek(tf.fd, 0, SEEK_SET)) << errno;
+
+  std::string s;
+  ASSERT_TRUE(android::ReadFdToString(tf.fd, &s)) << errno;
+  EXPECT_EQ("abc", s);
+}