Expose Env::GetTempDirectory() for use in C test.

This removes the use of the non-portable headers <sys/types.h> and <unistd.h> in c_test.c.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=188503102

db/c.cc

@@ -5,7 +5,6 @@
 #include "leveldb/c.h"
 
 #include <stdlib.h>
-#include <unistd.h>
 #include "leveldb/cache.h"
 #include "leveldb/comparator.h"
 #include "leveldb/db.h"
@@ -584,6 +583,18 @@ void leveldb_env_destroy(leveldb_env_t* env) {
   delete env;
 }
 
+char* leveldb_env_get_test_directory(leveldb_env_t* env) {
+  std::string result;
+  if (!env->rep->GetTestDirectory(&result).ok()) {
+    return NULL;
+  }
+
+  char* buffer = static_cast<char*>(malloc(result.size() + 1));
+  memcpy(buffer, result.data(), result.size());
+  buffer[result.size()] = '\0';
+  return buffer;
+}
+
 void leveldb_free(void* ptr) {
   free(ptr);
 }

db/c_test.c

@@ -8,24 +8,14 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <sys/types.h>
-#include <unistd.h>
 
 const char* phase = "";
-static char dbname[200];
 
 static void StartPhase(const char* name) {
   fprintf(stderr, "=== Test %s\n", name);
   phase = name;
 }
 
-static const char* GetTempDir(void) {
-    const char* ret = getenv("TEST_TMPDIR");
-    if (ret == NULL || ret[0] == '\0')
-        ret = "/tmp";
-    return ret;
-}
-
 #define CheckNoError(err)                                               \
   if ((err) != NULL) {                                                  \
     fprintf(stderr, "%s:%d: %s: %s\n", __FILE__, __LINE__, phase, (err)); \
@@ -162,21 +152,19 @@ int main(int argc, char** argv) {
   leveldb_options_t* options;
   leveldb_readoptions_t* roptions;
   leveldb_writeoptions_t* woptions;
+  char* dbname;
   char* err = NULL;
   int run = -1;
 
   CheckCondition(leveldb_major_version() >= 1);
   CheckCondition(leveldb_minor_version() >= 1);
 
-  snprintf(dbname, sizeof(dbname),
-           "%s/leveldb_c_test-%d",
-           GetTempDir(),
-           ((int) geteuid()));
-
   StartPhase("create_objects");
   cmp = leveldb_comparator_create(NULL, CmpDestroy, CmpCompare, CmpName);
   env = leveldb_create_default_env();
   cache = leveldb_cache_create_lru(100000);
+  dbname = leveldb_env_get_test_directory(env);
+  CheckCondition(dbname != NULL);
 
   options = leveldb_options_create();
   leveldb_options_set_comparator(options, cmp);
@@ -382,6 +370,7 @@ int main(int argc, char** argv) {
   leveldb_options_destroy(options);
   leveldb_readoptions_destroy(roptions);
   leveldb_writeoptions_destroy(woptions);
+  leveldb_free(dbname);
   leveldb_cache_destroy(cache);
   leveldb_comparator_destroy(cmp);
   leveldb_env_destroy(env);

include/leveldb/c.h

@@ -245,6 +245,9 @@ LEVELDB_EXPORT void leveldb_cache_destroy(leveldb_cache_t* cache);
 LEVELDB_EXPORT leveldb_env_t* leveldb_create_default_env();
 LEVELDB_EXPORT void leveldb_env_destroy(leveldb_env_t*);
 
+/* If not NULL, the returned buffer must be released using leveldb_free(). */
+LEVELDB_EXPORT char* leveldb_env_get_test_directory(leveldb_env_t*);
+
 /* Utility */
 
 /* Calls free(ptr).