native_client_sdk/src/libraries/nacl_io/getdents_helper.cc

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "nacl_io/getdents_helper.h"
   6
   7 #include <assert.h>
   8 #include <errno.h>
   9 #include <string.h>
  10
  11 #include <algorithm>
  12
  13 #include "nacl_io/log.h"
  14 #include "nacl_io/osinttypes.h"
  15
  16 #include "sdk_util/macros.h"
  17
  18 namespace nacl_io {
  19
  20 GetDentsHelper::GetDentsHelper()
  21     : curdir_ino_(0), parentdir_ino_(0), init_defaults_(false) {
  22   Initialize();
  23 }
  24
  25 GetDentsHelper::GetDentsHelper(ino_t curdir_ino, ino_t parentdir_ino)
  26     : curdir_ino_(curdir_ino),
  27       parentdir_ino_(parentdir_ino),
  28       init_defaults_(true) {
  29   Initialize();
  30 }
  31
  32 void GetDentsHelper::Reset() {
  33   dirents_.clear();
  34   Initialize();
  35 }
  36
  37 void GetDentsHelper::Initialize() {
  38   if (init_defaults_) {
  39     // Add the default entries: "." and ".."
  40     AddDirent(curdir_ino_, ".", 1);
  41     AddDirent(parentdir_ino_, "..", 2);
  42   }
  43 }
  44
  45 void GetDentsHelper::AddDirent(ino_t ino, const char* name, size_t namelen) {
  46   assert(name != NULL);
  47   dirents_.push_back(dirent());
  48   dirent& entry = dirents_.back();
  49   entry.d_ino = ino;
  50   entry.d_reclen = sizeof(dirent);
  51
  52   if (namelen == 0)
  53     namelen = strlen(name);
  54
  55   size_t d_name_max = MEMBER_SIZE(dirent, d_name) - 1;  // -1 for \0.
  56   size_t copylen = std::min(d_name_max, namelen);
  57   strncpy(&entry.d_name[0], name, copylen);
  58   entry.d_name[copylen] = 0;
  59 }
  60
  61 Error GetDentsHelper::GetDents(size_t offs,
  62                                dirent* pdir,
  63                                size_t size,
  64                                int* out_bytes) const {
  65   *out_bytes = 0;
  66
  67   // If the buffer pointer is invalid, fail
  68   if (NULL == pdir) {
  69     LOG_TRACE("dirent pointer is NULL.");
  70     return EINVAL;
  71   }
  72
  73   // If the buffer is too small, fail
  74   if (size < sizeof(dirent)) {
  75     LOG_TRACE("dirent buffer size is too small: %" PRIuS " < %" PRIuS "",
  76         size, sizeof(dirent));
  77     return EINVAL;
  78   }
  79
  80   // Force size to a multiple of dirent
  81   size -= size % sizeof(dirent);
  82
  83   size_t max = dirents_.size() * sizeof(dirent);
  84   if (offs >= max) {
  85     // OK, trying to read past the end.
  86     return 0;
  87   }
  88
  89   if (offs + size >= max)
  90     size = max - offs;
  91
  92   memcpy(pdir, reinterpret_cast<const char*>(dirents_.data()) + offs, size);
  93   *out_bytes = size;
  94   return 0;
  95 }
  96
  97 }  // namespace nacl_io