mkdtemp.h

// Copyright (c) 2012, Google Inc.
// All rights reserved.
//
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// 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.
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// this software without specific prior written permission.
//
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// mkdtemp() wasn't declared in <stdlib.h> until NDK r9b due to a simple
// packaging bug (the function has always been implemented in all versions
// of the C library). This header is provided to build Breakpad with earlier
// NDK revisions (e.g. the one used by Chromium). It may be removed in the
// future once all major projects upgrade to use a more recent NDK.
//
// The reason this is inlined here is to avoid linking a new object file
// into each unit test program (i.e. keep build files simple).

#ifndef GOOGLE_BREAKPAD_COMMON_ANDROID_TESTING_MKDTEMP_H
#define GOOGLE_BREAKPAD_COMMON_ANDROID_TESTING_MKDTEMP_H

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>

// Using a macro renaming trick here is necessary when building against
// NDK r9b. Otherwise the compiler will complain that calls to mkdtemp()
// are ambiguous.
#define mkdtemp breakpad_mkdtemp

namespace {

char* breakpad_mkdtemp(char* path) {
  if (path == NULL) {
    errno = EINVAL;
    return NULL;
  }

  // 'path' must be terminated with six 'X'
  const char kSuffix[] = "XXXXXX";
  const size_t kSuffixLen = strlen(kSuffix);
  char* path_end = path + strlen(path);

  if (static_cast<size_t>(path_end - path) < kSuffixLen ||
      memcmp(path_end - kSuffixLen, kSuffix, kSuffixLen) != 0) {
    errno = EINVAL;
    return NULL;
  }

  // If 'path' contains a directory separator, check that it exists to
  // avoid looping later.
  char* sep = strrchr(path, '/');
  if (sep != NULL) {
    struct stat st;
    int ret;
    *sep = '\0';  // temporarily zero-terminate the dirname.
    ret = stat(path, &st);
    *sep = '/';   // restore full path.
    if (ret < 0)
      return NULL;
    if (!S_ISDIR(st.st_mode)) {
      errno = ENOTDIR;
      return NULL;
    }
  }

  // Loop. On each iteration, replace the XXXXXX suffix with a random
  // number.
  int tries;
  for (tries = 128; tries > 0; tries--) {
    int random = rand() % 1000000;

    snprintf(path_end - kSuffixLen, kSuffixLen + 1, "%0d", random);
    if (mkdir(path, 0700) == 0)
      return path;  // Success

    if (errno != EEXIST)
      return NULL;
  }

  assert(errno == EEXIST);
  return NULL;
}

}  // namespace

#endif  // GOOGLE_BREAKPAD_COMMON_ANDROID_TESTING_MKDTEMP_H