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
  15 #include "sdk_util/macros.h"
  16
  17 namespace nacl_io {
  18
  19 GetDentsHelper::GetDentsHelper()
  20     : curdir_ino_(0), parentdir_ino_(0), init_defaults_(false) {
  21   Initialize();
  22 }
  23
  24 GetDentsHelper::GetDentsHelper(ino_t curdir_ino, ino_t parentdir_ino)
  25     : curdir_ino_(curdir_ino),
  26       parentdir_ino_(parentdir_ino),
  27       init_defaults_(true) {
  28   Initialize();
  29 }
  30
  31 void GetDentsHelper::Reset() {
  32   dirents_.clear();
  33   Initialize();
  34 }
  35
  36 void GetDentsHelper::Initialize() {
  37   if (init_defaults_) {
  38     // Add the default entries: "." and ".."
  39     AddDirent(curdir_ino_, ".", 1);
  40     AddDirent(parentdir_ino_, "..", 2);
  41   }
  42 }
  43
  44 void GetDentsHelper::AddDirent(ino_t ino, const char* name, size_t namelen) {
  45   assert(name != NULL);
  46   dirents_.push_back(dirent());
  47   dirent& entry = dirents_.back();
  48   entry.d_ino = ino;
  49   entry.d_off = sizeof(dirent);
  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: %d < %d", size, sizeof(dirent));
  76     return EINVAL;
  77   }
  78
  79   // Force size to a multiple of dirent
  80   size -= size % sizeof(dirent);
  81
  82   size_t max = dirents_.size() * sizeof(dirent);
  83   if (offs >= max) {
  84     // OK, trying to read past the end.
  85     return 0;
  86   }
  87
  88   if (offs + size >= max)
  89     size = max - offs;
  90
  91   memcpy(pdir, reinterpret_cast<const char*>(dirents_.data()) + offs, size);
  92   *out_bytes = size;
  93   return 0;
  94 }
  95
  96 }  // namespace nacl_io