Move blaze_util::Which to standalone library.

This method is only used by blaze_util_linux.cc so
instead of porting it to Windows, I'm moving it to
a separate library.

As part of this change I'm creating separate
libraries for other sources in //src/main/cpp/util
as well, so their dependencies are clearly defined
in the BUILD file, plus we can port them one by
one.

This is part of the effort of compiling Bazel on
Windows with the MSVC toolchain.

--
MOS_MIGRATED_REVID=134636777

src/main/cpp/BUILD

@@ -52,7 +52,14 @@ cc_library(
     deps = [
         "//src/main/cpp/util",
         "//src/main/cpp/util:blaze_exit_code",
-    ],
+    ] + select({
+        "//src:darwin": [],
+        "//src:darwin_x86_64": [],
+        "//src:freebsd": [],
+        "//src:windows": [],
+        "//src:windows_msvc": [],
+        "//conditions:default": ["//src/main/cpp/util:file_linux"],
+    }),
 )
 
 cc_library(

src/main/cpp/blaze_util_linux.cc

@@ -30,6 +30,7 @@
 #include "src/main/cpp/util/errors.h"
 #include "src/main/cpp/util/exit_code.h"
 #include "src/main/cpp/util/file.h"
+#include "src/main/cpp/util/file_linux.h"
 #include "src/main/cpp/util/port.h"
 #include "src/main/cpp/util/strings.h"
 

src/main/cpp/util/BUILD

@@ -3,12 +3,6 @@
 
 cc_library(
     name = "util",
-    srcs = [
-        "errors.cc",
-        "file.cc",
-        "numbers.cc",
-        "port.cc",
-    ],
     hdrs = [
         "errors.h",
         "file.h",
@@ -18,10 +12,59 @@ cc_library(
     visibility = ["//visibility:public"],
     deps = [
         ":blaze_exit_code",
+        ":errors",
+        ":file",
+        ":numbers",
+        ":port",
         ":strings",
     ],
 )
 
+cc_library(
+    name = "file_linux",
+    srcs = ["file_linux.cc"],
+    hdrs = ["file_linux.h"],
+    visibility = ["//src/main/cpp:__pkg__"],
+    deps = [
+        ":blaze_exit_code",
+        ":errors",
+        ":file",
+        ":strings",
+    ],
+)
+
+cc_library(
+    name = "file",
+    srcs = ["file.cc"],
+    hdrs = ["file.h"],
+    visibility = ["//src/tools/singlejar:__pkg__"],
+    deps = [
+        ":blaze_exit_code",
+        ":errors",
+        ":strings",
+    ],
+)
+
+cc_library(
+    name = "errors",
+    srcs = ["errors.cc"],
+    hdrs = ["errors.h"],
+    deps = [":port"],
+)
+
+cc_library(
+    name = "port",
+    srcs = ["port.cc"],
+    hdrs = ["port.h"],
+)
+
+cc_library(
+    name = "numbers",
+    srcs = ["numbers.cc"],
+    hdrs = ["numbers.h"],
+    deps = [":strings"],
+)
+
 cc_library(
     name = "md5",
     srcs = ["md5.cc"],

src/main/cpp/util/file.cc

@@ -15,7 +15,6 @@
 
 #include <limits.h>  // PATH_MAX
 #include <sys/stat.h>
-#include <unistd.h>  // access
 #include <cstdlib>
 #include <vector>
 
@@ -72,29 +71,4 @@ string JoinPath(const string &path1, const string &path2) {
   }
 }
 
-string Which(const string &executable) {
-  char *path_cstr = getenv("PATH");
-  if (path_cstr == NULL || path_cstr[0] == '\0') {
-    die(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR,
-               "Could not get PATH to find %s", executable.c_str());
-  }
-
-  string path(path_cstr);
-  std::vector<std::string> pieces = blaze_util::Split(path, ':');
-  for (auto piece : pieces) {
-    if (piece.empty()) {
-      piece = ".";
-    }
-
-    struct stat file_stat;
-    string candidate = blaze_util::JoinPath(piece, executable);
-    if (access(candidate.c_str(), X_OK) == 0 &&
-        stat(candidate.c_str(), &file_stat) == 0 &&
-        S_ISREG(file_stat.st_mode)) {
-      return candidate;
-    }
-  }
-  return "";
-}
-
 }  // namespace blaze_util

src/main/cpp/util/file.h

@@ -31,11 +31,6 @@ string Basename(const string &path);
 
 string JoinPath(const string &path1, const string &path2);
 
-// Checks each element of the PATH variable for executable. If none is found, ""
-// is returned.  Otherwise, the full path to executable is returned. Can die if
-// looking up PATH fails.
-string Which(const string &executable);
-
 }  // namespace blaze_util
 
 #endif  // BAZEL_SRC_MAIN_CPP_UTIL_FILE_H_

src/main/cpp/util/file_linux.cc

@@ -0,0 +1,55 @@
+// Copyright 2014 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+#include "src/main/cpp/util/file_linux.h"
+
+#include <sys/stat.h>
+#include <stdlib.h>  // getenv
+#include <unistd.h>  // access
+#include <vector>
+
+#include "src/main/cpp/util/file.h"
+#include "src/main/cpp/util/exit_code.h"
+#include "src/main/cpp/util/errors.h"
+#include "src/main/cpp/util/strings.h"
+
+using std::pair;
+
+namespace blaze_util {
+
+string Which(const string &executable) {
+  char *path_cstr = getenv("PATH");
+  if (path_cstr == NULL || path_cstr[0] == '\0') {
+    die(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR,
+        "Could not get PATH to find %s", executable.c_str());
+  }
+
+  string path(path_cstr);
+  std::vector<std::string> pieces = blaze_util::Split(path, ':');
+  for (auto piece : pieces) {
+    if (piece.empty()) {
+      piece = ".";
+    }
+
+    struct stat file_stat;
+    string candidate = blaze_util::JoinPath(piece, executable);
+    if (access(candidate.c_str(), X_OK) == 0 &&
+        stat(candidate.c_str(), &file_stat) == 0 &&
+        S_ISREG(file_stat.st_mode)) {
+      return candidate;
+    }
+  }
+  return "";
+}
+
+}  // namespace blaze_util

src/main/cpp/util/file_linux.h

@@ -0,0 +1,33 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This header file defines file utilities we only need under Linux.
+
+#ifndef BAZEL_SRC_MAIN_CPP_UTIL_FILE_LINUX_H_
+#define BAZEL_SRC_MAIN_CPP_UTIL_FILE_LINUX_H_
+
+#include <string>
+
+namespace blaze_util {
+
+using std::string;
+
+// Checks each element of the PATH variable for executable. If none is found, ""
+// is returned.  Otherwise, the full path to executable is returned. Can die if
+// looking up PATH fails.
+string Which(const string &executable);
+
+}  // namespace blaze_util
+
+#endif  // BAZEL_SRC_MAIN_CPP_UTIL_FILE_LINUX_H_