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Commit a7c4424e authored by Treehugger Robot's avatar Treehugger Robot Committed by Gerrit Code Review
Browse files

Merge "Add android::base::Readlink."

parents 5b136369 d3ff6e52

base/file.cpp

+26 −0
Original line number Diff line number Diff line
@@ -20,8 +20,10 @@ 
#include <fcntl.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <unistd.h>



#include <string>

#include <vector>



#include "android-base/macros.h"  // For TEMP_FAILURE_RETRY on Darwin.

#include "android-base/logging.h"
@@ -171,5 +173,29 @@ bool RemoveFileIfExists(const std::string& path, std::string* err) { 
  return true;

}



#if !defined(_WIN32)

bool Readlink(const std::string& path, std::string* result) {

  result->clear();



  // Most Linux file systems (ext2 and ext4, say) limit symbolic links to

  // 4095 bytes. Since we'll copy out into the string anyway, it doesn't

  // waste memory to just start there. We add 1 so that we can recognize

  // whether it actually fit (rather than being truncated to 4095).

  std::vector<char> buf(4095 + 1);

  while (true) {

    ssize_t size = readlink(path.c_str(), &buf[0], buf.size());

    // Unrecoverable error?

    if (size == -1) return false;

    // It fit! (If size == buf.size(), it may have been truncated.)

    if (static_cast<size_t>(size) < buf.size()) {

      result->assign(&buf[0], size);

      return true;

    }

    // Double our buffer and try again.

    buf.resize(buf.size() * 2);

  }

}

#endif



}  // namespace base

}  // namespace android

base/file_test.cpp

+26 −0
Original line number Diff line number Diff line
@@ -110,3 +110,29 @@ TEST(file, RemoveFileIfExist) { 
  ASSERT_FALSE(android::base::RemoveFileIfExists(td.path, &err));

  ASSERT_EQ("is not a regular or symbol link file", err);

}



TEST(file, Readlink) {

#if !defined(_WIN32)

  // Linux doesn't allow empty symbolic links.

  std::string min("x");

  // ext2 and ext4 both have PAGE_SIZE limits.

  std::string max(static_cast<size_t>(4096 - 1), 'x');



  TemporaryDir td;

  std::string min_path{std::string(td.path) + "/" + "min"};

  std::string max_path{std::string(td.path) + "/" + "max"};



  ASSERT_EQ(0, symlink(min.c_str(), min_path.c_str()));

  ASSERT_EQ(0, symlink(max.c_str(), max_path.c_str()));



  std::string result;



  result = "wrong";

  ASSERT_TRUE(android::base::Readlink(min_path, &result));

  ASSERT_EQ(min, result);



  result = "wrong";

  ASSERT_TRUE(android::base::Readlink(max_path, &result));

  ASSERT_EQ(max, result);

#endif

}

base/include/android-base/file.h

+4 −0
Original line number Diff line number Diff line
@@ -43,6 +43,10 @@ bool WriteFully(int fd, const void* data, size_t byte_count); 


bool RemoveFileIfExists(const std::string& path, std::string* err = nullptr);



#if !defined(_WIN32)

bool Readlink(const std::string& path, std::string* result);

#endif



}  // namespace base

}  // namespace android