src/random_access_file.cpp

   1 /*
   2  * This file is part of OpenTTD.
   3  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
   4  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
   5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
   6  */
   7
   8  /** @file random_access_file.cpp Actual implementation of the RandomAccessFile class. */
   9
  10 #include "stdafx.h"
  11 #include "random_access_file_type.h"
  12
  13 #include "debug.h"
  14 #include "error_func.h"
  15 #include "fileio_func.h"
  16 #include "string_func.h"
  17
  18 #include "safeguards.h"
  19
  20 /**
  21  * Create the RandomAccesFile.
  22  * @param filename Name of the file at the disk.
  23  * @param subdir   The sub directory to search this file in.
  24  */
  25 RandomAccessFile::RandomAccessFile(const std::string &filename, Subdirectory subdir) : filename(filename)
  26 {
  27         this->file_handle = FioFOpenFile(filename, "rb", subdir);
  28         if (this->file_handle == nullptr) UserError("Cannot open file '{}'", filename);
  29
  30         /* When files are in a tar-file, the begin of the file might not be at 0. */
  31         long pos = ftell(this->file_handle);
  32         if (pos < 0) UserError("Cannot read file '{}'", filename);
  33
  34         /* Store the filename without path and extension */
  35         auto t = filename.rfind(PATHSEPCHAR);
  36         std::string name_without_path = filename.substr(t != std::string::npos ? t + 1 : 0);
  37         this->simplified_filename = name_without_path.substr(0, name_without_path.rfind('.'));
  38         strtolower(this->simplified_filename);
  39
  40         this->SeekTo((size_t)pos, SEEK_SET);
  41 }
  42
  43 /**
  44  * Close the file's file handle.
  45  */
  46 RandomAccessFile::~RandomAccessFile()
  47 {
  48         fclose(this->file_handle);
  49 }
  50
  51 /**
  52  * Get the filename of the opened file with the path from the SubDirectory and the extension.
  53  * @return Name of the file.
  54  */
  55 const std::string &RandomAccessFile::GetFilename() const
  56 {
  57         return this->filename;
  58 }
  59
  60 /**
  61  * Get the simplified filename of the opened file. The simplified filename is the name of the
  62  * file without the SubDirectory or extension in lower case.
  63  * @return Name of the file.
  64  */
  65 const std::string &RandomAccessFile::GetSimplifiedFilename() const
  66 {
  67         return this->simplified_filename;
  68 }
  69
  70 /**
  71  * Get position in the file.
  72  * @return Position in the file.
  73  */
  74 size_t RandomAccessFile::GetPos() const
  75 {
  76         return this->pos + (this->buffer - this->buffer_end);
  77 }
  78
  79 /**
  80  * Seek in the current file.
  81  * @param pos New position.
  82  * @param mode Type of seek (\c SEEK_CUR means \a pos is relative to current position, \c SEEK_SET means \a pos is absolute).
  83  */
  84 void RandomAccessFile::SeekTo(size_t pos, int mode)
  85 {
  86         if (mode == SEEK_CUR) pos += this->GetPos();
  87
  88         this->pos = pos;
  89         if (fseek(this->file_handle, this->pos, SEEK_SET) < 0) {
  90                 Debug(misc, 0, "Seeking in {} failed", this->filename);
  91         }
  92
  93         /* Reset the buffer, so the next ReadByte will read bytes from the file. */
  94         this->buffer = this->buffer_end = this->buffer_start;
  95 }
  96
  97 /**
  98  * Read a byte from the file.
  99  * @return Read byte.
 100  */
 101 byte RandomAccessFile::ReadByte()
 102 {
 103         if (this->buffer == this->buffer_end) {
 104                 this->buffer = this->buffer_start;
 105                 size_t size = fread(this->buffer, 1, RandomAccessFile::BUFFER_SIZE, this->file_handle);
 106                 this->pos += size;
 107                 this->buffer_end = this->buffer_start + size;
 108
 109                 if (size == 0) return 0;
 110         }
 111         return *this->buffer++;
 112 }
 113
 114 /**
 115  * Read a word (16 bits) from the file (in low endian format).
 116  * @return Read word.
 117  */
 118 uint16_t RandomAccessFile::ReadWord()
 119 {
 120         byte b = this->ReadByte();
 121         return (this->ReadByte() << 8) | b;
 122 }
 123
 124 /**
 125  * Read a double word (32 bits) from the file (in low endian format).
 126  * @return Read word.
 127  */
 128 uint32_t RandomAccessFile::ReadDword()
 129 {
 130         uint b = this->ReadWord();
 131         return (this->ReadWord() << 16) | b;
 132 }
 133
 134 /**
 135  * Read a block.
 136  * @param ptr  Destination buffer.
 137  * @param size Number of bytes to read.
 138  */
 139 void RandomAccessFile::ReadBlock(void *ptr, size_t size)
 140 {
 141         this->SeekTo(this->GetPos(), SEEK_SET);
 142         this->pos += fread(ptr, 1, size, this->file_handle);
 143 }
 144
 145 /**
 146  * Skip \a n bytes ahead in the file.
 147  * @param n Number of bytes to skip reading.
 148  */
 149 void RandomAccessFile::SkipBytes(size_t n)
 150 {
 151         assert(this->buffer_end >= this->buffer);
 152         size_t remaining = this->buffer_end - this->buffer;
 153         if (n <= remaining) {
 154                 this->buffer += n;
 155         } else {
 156                 this->SeekTo(n, SEEK_CUR);
 157         }
 158 }