michael@0: // Copyright (c) 2009 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #include "base/file_descriptor_shuffle.h"
michael@0: 
michael@0: #include <errno.h>
michael@0: #include <unistd.h>
michael@0: 
michael@0: #include "base/eintr_wrapper.h"
michael@0: #include "base/logging.h"
michael@0: 
michael@0: namespace base {
michael@0: 
michael@0: bool PerformInjectiveMultimapDestructive(
michael@0:     InjectiveMultimap* m, InjectionDelegate* delegate) {
michael@0:   static const size_t kMaxExtraFDs = 16;
michael@0:   int extra_fds[kMaxExtraFDs];
michael@0:   unsigned next_extra_fd = 0;
michael@0: 
michael@0:   // DANGER: this function may not allocate.
michael@0: 
michael@0:   for (InjectiveMultimap::iterator i = m->begin(); i != m->end(); ++i) {
michael@0:     int temp_fd = -1;
michael@0: 
michael@0:     // We DCHECK the injectiveness of the mapping.
michael@0:     for (InjectiveMultimap::iterator j = i + 1; j != m->end(); ++j) {
michael@0:       DCHECK(i->dest != j->dest) << "Both fd " << i->source
michael@0:           << " and " << j->source << " map to " << i->dest;
michael@0:     }
michael@0: 
michael@0:     const bool is_identity = i->source == i->dest;
michael@0: 
michael@0:     for (InjectiveMultimap::iterator j = i + 1; j != m->end(); ++j) {
michael@0:       if (!is_identity && i->dest == j->source) {
michael@0:         if (temp_fd == -1) {
michael@0:           if (!delegate->Duplicate(&temp_fd, i->dest))
michael@0:             return false;
michael@0:           if (next_extra_fd < kMaxExtraFDs) {
michael@0:             extra_fds[next_extra_fd++] = temp_fd;
michael@0:           } else {
michael@0:               DLOG(ERROR) << "PerformInjectiveMultimapDestructive overflowed "
michael@0:                           << "extra_fds. Leaking file descriptors!";
michael@0:           }
michael@0:         }
michael@0: 
michael@0:         j->source = temp_fd;
michael@0:         j->close = false;
michael@0:       }
michael@0: 
michael@0:       if (i->close && i->source == j->dest)
michael@0:         i->close = false;
michael@0: 
michael@0:       if (i->close && i->source == j->source) {
michael@0:         i->close = false;
michael@0:         j->close = true;
michael@0:       }
michael@0:     }
michael@0: 
michael@0:     if (!is_identity) {
michael@0:       if (!delegate->Move(i->source, i->dest))
michael@0:         return false;
michael@0:     }
michael@0: 
michael@0:     if (!is_identity && i->close)
michael@0:       delegate->Close(i->source);
michael@0:   }
michael@0: 
michael@0:   for (unsigned i = 0; i < next_extra_fd; i++)
michael@0:     delegate->Close(extra_fds[i]);
michael@0: 
michael@0:   return true;
michael@0: }
michael@0: 
michael@0: bool PerformInjectiveMultimap(const InjectiveMultimap& m_in,
michael@0:                               InjectionDelegate* delegate) {
michael@0:     InjectiveMultimap m(m_in);
michael@0:     return PerformInjectiveMultimapDestructive(&m, delegate);
michael@0: }
michael@0: 
michael@0: bool FileDescriptorTableInjection::Duplicate(int* result, int fd) {
michael@0:   *result = HANDLE_EINTR(dup(fd));
michael@0:   return *result >= 0;
michael@0: }
michael@0: 
michael@0: bool FileDescriptorTableInjection::Move(int src, int dest) {
michael@0:   return HANDLE_EINTR(dup2(src, dest)) != -1;
michael@0: }
michael@0: 
michael@0: void FileDescriptorTableInjection::Close(int fd) {
michael@0:   HANDLE_EINTR(close(fd));
michael@0: }
michael@0: 
michael@0: }  // namespace base