mirror of https://github.com/OpenTTD/OpenTTD.git
159 lines
4.4 KiB
C++
159 lines
4.4 KiB
C++
/*
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* This file is part of OpenTTD.
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* 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.
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* 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.
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* 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/>.
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*/
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/** @file random_access_file.cpp Actual implementation of the RandomAccessFile class. */
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#include "stdafx.h"
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#include "random_access_file_type.h"
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#include "debug.h"
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#include "error_func.h"
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#include "fileio_func.h"
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#include "string_func.h"
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#include "safeguards.h"
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/**
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* Create the RandomAccesFile.
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* @param filename Name of the file at the disk.
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* @param subdir The sub directory to search this file in.
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*/
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RandomAccessFile::RandomAccessFile(const std::string &filename, Subdirectory subdir) : filename(filename)
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{
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this->file_handle = FioFOpenFile(filename, "rb", subdir);
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if (this->file_handle == nullptr) UserError("Cannot open file '{}'", filename);
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/* When files are in a tar-file, the begin of the file might not be at 0. */
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long pos = ftell(this->file_handle);
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if (pos < 0) UserError("Cannot read file '{}'", filename);
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/* Store the filename without path and extension */
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auto t = filename.rfind(PATHSEPCHAR);
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std::string name_without_path = filename.substr(t != std::string::npos ? t + 1 : 0);
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this->simplified_filename = name_without_path.substr(0, name_without_path.rfind('.'));
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strtolower(this->simplified_filename);
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this->SeekTo(static_cast<size_t>(pos), SEEK_SET);
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}
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/**
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* Close the file's file handle.
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*/
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RandomAccessFile::~RandomAccessFile()
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{
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fclose(this->file_handle);
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}
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/**
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* Get the filename of the opened file with the path from the SubDirectory and the extension.
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* @return Name of the file.
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*/
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const std::string &RandomAccessFile::GetFilename() const
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{
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return this->filename;
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}
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/**
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* Get the simplified filename of the opened file. The simplified filename is the name of the
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* file without the SubDirectory or extension in lower case.
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* @return Name of the file.
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*/
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const std::string &RandomAccessFile::GetSimplifiedFilename() const
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{
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return this->simplified_filename;
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}
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/**
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* Get position in the file.
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* @return Position in the file.
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*/
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size_t RandomAccessFile::GetPos() const
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{
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return this->pos + (this->buffer - this->buffer_end);
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}
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/**
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* Seek in the current file.
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* @param pos New position.
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* @param mode Type of seek (\c SEEK_CUR means \a pos is relative to current position, \c SEEK_SET means \a pos is absolute).
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*/
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void RandomAccessFile::SeekTo(size_t pos, int mode)
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{
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if (mode == SEEK_CUR) pos += this->GetPos();
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this->pos = pos;
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if (fseek(this->file_handle, this->pos, SEEK_SET) < 0) {
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Debug(misc, 0, "Seeking in {} failed", this->filename);
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}
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/* Reset the buffer, so the next ReadByte will read bytes from the file. */
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this->buffer = this->buffer_end = this->buffer_start;
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}
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/**
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* Read a byte from the file.
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* @return Read byte.
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*/
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uint8_t RandomAccessFile::ReadByte()
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{
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if (this->buffer == this->buffer_end) {
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this->buffer = this->buffer_start;
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size_t size = fread(this->buffer, 1, RandomAccessFile::BUFFER_SIZE, this->file_handle);
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this->pos += size;
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this->buffer_end = this->buffer_start + size;
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if (size == 0) return 0;
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}
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return *this->buffer++;
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}
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/**
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* Read a word (16 bits) from the file (in low endian format).
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* @return Read word.
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*/
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uint16_t RandomAccessFile::ReadWord()
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{
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uint8_t b = this->ReadByte();
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return (this->ReadByte() << 8) | b;
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}
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/**
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* Read a double word (32 bits) from the file (in low endian format).
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* @return Read word.
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*/
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uint32_t RandomAccessFile::ReadDword()
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{
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uint b = this->ReadWord();
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return (this->ReadWord() << 16) | b;
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}
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/**
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* Read a block.
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* @param ptr Destination buffer.
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* @param size Number of bytes to read.
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*/
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void RandomAccessFile::ReadBlock(void *ptr, size_t size)
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{
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this->SeekTo(this->GetPos(), SEEK_SET);
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this->pos += fread(ptr, 1, size, this->file_handle);
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}
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/**
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* Skip \a n bytes ahead in the file.
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* @param n Number of bytes to skip reading.
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*/
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void RandomAccessFile::SkipBytes(size_t n)
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{
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assert(this->buffer_end >= this->buffer);
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size_t remaining = this->buffer_end - this->buffer;
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if (n <= remaining) {
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this->buffer += n;
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} else {
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this->SeekTo(n, SEEK_CUR);
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}
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}
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