Add ScopedPipe.

This provides a similar wrapper to ScopedTmpFile for linux pipes.

Change-Id: I53b377085322f61d87525d215ecd703f13ae9ae7
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/3971918
Reviewed-by: Lei Zhang <thestig@chromium.org>

src/common/linux/scoped_pipe.cc

@@ -0,0 +1,128 @@
+// Copyright 2022 Google LLC
+//
+// 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.
+//     * Neither the name of Google LLC nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// 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 "common/linux/scoped_pipe.h"
+
+#include <unistd.h>
+
+#include "common/linux/eintr_wrapper.h"
+
+namespace google_breakpad {
+
+ScopedPipe::ScopedPipe() {
+  fds_[0] = -1;
+  fds_[1] = -1;
+}
+
+ScopedPipe::~ScopedPipe() {
+  CloseReadFd();
+  CloseWriteFd();
+}
+
+bool ScopedPipe::Init() {
+  return pipe(fds_) == 0;
+}
+
+void ScopedPipe::CloseReadFd() {
+  if (fds_[0] != -1) {
+    close(fds_[0]);
+    fds_[0] = -1;
+  }
+}
+
+void ScopedPipe::CloseWriteFd() {
+  if (fds_[1] != -1) {
+    close(fds_[1]);
+    fds_[1] = -1;
+  }
+}
+
+bool ScopedPipe::ReadLine(std::string& line) {
+  // Simple buffered file read. `read_buffer_` stores previously read bytes, and
+  // we either return a line from this buffer, or we append blocks of read bytes
+  // to the buffer until we have a complete line.
+  size_t eol_index = read_buffer_.find('\n');
+
+  // While we don't have a full line, and read pipe is valid.
+  while (eol_index == std::string::npos && GetReadFd() != -1) {
+    // Read a block of 128 bytes from the read pipe.
+    char read_buf[128];
+    ssize_t read_len = HANDLE_EINTR(
+      read(GetReadFd(), read_buf, sizeof(read_buf)));
+    if (read_len <= 0) {
+      // Pipe error, or pipe has been closed.
+      CloseReadFd();
+      break;
+    }
+
+    // Append the block, and check if we have a full line now.
+    read_buffer_.append(read_buf, read_len);
+    eol_index = read_buffer_.find('\n');
+  }
+
+  if (eol_index != std::string::npos) {
+    // We have a full line to output.
+    line = read_buffer_.substr(0, eol_index);
+    if (eol_index < read_buffer_.size()) {
+      read_buffer_ = read_buffer_.substr(eol_index + 1);
+    } else {
+      read_buffer_ = "";
+    }
+
+    return true;
+  }
+
+  if (read_buffer_.size()) {
+    // We don't have a full line to output, but we can only reach here if the
+    // pipe has closed and there are some bytes left at the end, so we should
+    // return those bytes.
+    line = std::move(read_buffer_);
+    read_buffer_ = "";
+
+    return true;
+  }
+
+  // We don't have any buffered data left, and the pipe has closed.
+  return false;
+}
+
+int ScopedPipe::Dup2WriteFd(int new_fd) const {
+  return dup2(fds_[1], new_fd);
+}
+
+bool ScopedPipe::WriteForTesting(const void* bytes, size_t bytes_len) {
+  ssize_t r = HANDLE_EINTR(write(GetWriteFd(), bytes, bytes_len));
+  if (r != static_cast<ssize_t>(bytes_len)) {
+    CloseWriteFd();
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace google_breakpad

src/common/linux/scoped_pipe.h

@@ -0,0 +1,115 @@
+// Copyright 2022 Google LLC
+//
+// 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.
+//     * Neither the name of Google LLC nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// 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.
+
+#ifndef COMMON_LINUX_SCOPED_PIPE_H_
+#define COMMON_LINUX_SCOPED_PIPE_H_
+
+#include <stdint.h>
+#include <string>
+
+namespace google_breakpad {
+
+// Small RAII wrapper for a pipe pair.
+//
+// Example (both ends of pipe in same process):
+//   ScopedPipe tmp;
+//   std::string line;
+//   if (tmp.Init() && tmp.Write(bytes, bytes_len)) {
+//     tmp.CloseWriteFd();
+//     while (tmp.ReadLine(&line)) {
+//       std::cerr << line << std::endl;
+//     }
+//   }
+//
+// Example (reading output from a child process):
+//   ScopedPipe tmp;
+//   if (fork()) {
+//     // Parent process, read from the read end of the pipe.
+//     std::string line;
+//     while (tmp.ReadLine(line)) {
+//       // Process output...
+//     }
+//     // Close read pipe once done processing the output that we wanted, this
+//     // should ensure that the child process exits even if we didn't read all
+//     // of the output.
+//     tmp.CloseReadFd();
+//     // Parent process should handle waiting for child to exit here...
+//   } else {
+//     // Child process, close the read fd and dup the write fd before exec'ing.
+//     tmp.CloseReadFd();
+//     tmp.Dup2WriteFd(STDOUT_FILENO);
+//     tmp.Dup2WriteFd(STDERR_FILENO);
+//     execl("some-command", "some-arguments");
+//   }
+class ScopedPipe {
+ public:
+  ScopedPipe();
+  ~ScopedPipe();
+
+  // Creates the pipe pair - returns false on error.
+  bool Init();
+
+  // Close the read pipe. This only needs to be used when the read pipe needs to
+  // be closed earlier.
+  void CloseReadFd();
+
+  // Close the write pipe. This only needs to be used when the write pipe needs
+  // to be closed earlier.
+  void CloseWriteFd();
+
+  // Reads characters until newline or end of pipe. On read failure this will
+  // close the read pipe, but continue to return true and read buffered lines
+  // until the internal buffering is exhausted. This will block if there is no
+  // data available on the read pipe.
+  bool ReadLine(std::string& line);
+
+  // Writes bytes to the write end of the pipe, returns false and closes write
+  // pipe on failure.
+  bool WriteForTesting(const void* bytes, size_t bytes_len);
+
+  // Calls the dup2 system call to replace any existing open file descriptor
+  // with number new_fd with a copy of the current write end file descriptor
+  // for the pipe.
+  int Dup2WriteFd(int new_fd) const;
+
+ private:
+  int GetReadFd() const {
+    return fds_[0];
+  }
+
+  int GetWriteFd() const {
+    return fds_[1];
+  }
+
+  int fds_[2];
+  std::string read_buffer_;
+};
+
+}  // namespace google_breakpad
+
+#endif // COMMON_LINUX_SCOPED_PIPE_H_

src/common/linux/scoped_pipe_unittest.cc

@@ -0,0 +1,71 @@
+// Copyright 2022 Google LLC
+//
+// 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.
+//     * Neither the name of Google LLC nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// 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.
+
+// scoped_pipe_unittest.cc: Unit tests for google_breakpad::ScopedPipe.
+
+#include "common/linux/scoped_pipe.h"
+
+#include "breakpad_googletest_includes.h"
+
+namespace google_breakpad {
+
+TEST(ScopedPipeTest, WriteAndClose) {
+  const char kTestData[] = "One\nTwo\nThree";
+  ScopedPipe pipe;
+  std::string line;
+
+  ASSERT_TRUE(pipe.Init());
+  ASSERT_TRUE(pipe.WriteForTesting(kTestData, strlen(kTestData)));
+  pipe.CloseWriteFd();
+
+  ASSERT_TRUE(pipe.ReadLine(line));
+  ASSERT_EQ(line, "One");
+  ASSERT_TRUE(pipe.ReadLine(line));
+  ASSERT_EQ(line, "Two");
+  ASSERT_TRUE(pipe.ReadLine(line));
+  ASSERT_EQ(line, "Three");
+  ASSERT_FALSE(pipe.ReadLine(line));
+}
+
+TEST(ScopedPipeTest, MultipleWrites) {
+  const char kTestDataOne[] = "One\n";
+  const char kTestDataTwo[] = "Two\n";
+  ScopedPipe pipe;
+  std::string line;
+
+  ASSERT_TRUE(pipe.Init());
+  ASSERT_TRUE(pipe.WriteForTesting(kTestDataOne, strlen(kTestDataOne)));
+  ASSERT_TRUE(pipe.ReadLine(line));
+  ASSERT_EQ(line, "One");
+
+  ASSERT_TRUE(pipe.WriteForTesting(kTestDataTwo, strlen(kTestDataTwo)));
+  ASSERT_TRUE(pipe.ReadLine(line));
+  ASSERT_EQ(line, "Two");
+}
+
+}  // namespace google_breakpad