1 /*****************************************************************************\
4 * Author : Chris Koeritz *
6 *******************************************************************************
7 * Copyright (c) 2007-$now By Author. This program is free software; you can *
8 * redistribute it and/or modify it under the terms of the GNU General Public *
9 * License as published by the Free Software Foundation; either version 2 of *
10 * the License or (at your option) any later version. This is online at: *
11 * http://www.fsf.org/copyleft/gpl.html *
12 * Please send any updates to: fred@gruntose.com *
13 \*****************************************************************************/
15 #include "byte_filer.h"
16 #include "huge_file.h"
18 #include <basis/byte_array.h>
19 #include <basis/functions.h>
20 #include <basis/guards.h>
25 #define LOG(to_print) printf("%s::%s: %s\n", static_class_name(), func, astring(to_print).s())
27 //#define DEBUG_HUGE_FILE
28 // uncomment for noisy version.
30 using namespace basis;
32 namespace filesystem {
34 huge_file::huge_file(const astring &filename, const astring &permissions)
35 : _real_file(new byte_filer(filename, permissions)),
40 huge_file::~huge_file()
45 void huge_file::flush() { _real_file->flush(); }
47 bool huge_file::truncate() { return _real_file->truncate(); }
49 double huge_file::length()
53 //trying to read to see if we're past endpoint.
54 // if this approach works, length may want to close and reopen file for
55 // reading, since we can't add any bytes to it for writing just to find
59 double save_posn = _file_pointer;
60 // skip to the beginning of the file so we can try to find the end.
62 _real_file->seek(0, byte_filer::FROM_START);
63 size_t naive_size = _real_file->length();
64 if (naive_size < _real_file->file_size_limit()) {
65 // lucked out; we are within normal file size limitations.
66 seek(save_posn, byte_filer::FROM_START);
67 return double(naive_size);
70 double best_highest = 0.0; // the maximum we've safely seeked to.
72 size_t big_jump = byte_filer::file_size_limit();
73 // try with the largest possible seek at first.
76 #ifdef DEBUG_HUGE_FILE
77 LOG(a_sprintf("best highest=%.0f", best_highest));
79 // iterate until we reach our exit condition, which seems like it must
80 // always occur eventually unless the file is being monkeyed with.
81 bool seek_ret = _real_file->seek(int(big_jump), byte_filer::FROM_CURRENT);
82 #ifdef DEBUG_HUGE_FILE
83 LOG(a_sprintf(" seek ret=%d", int(seek_ret)));
85 byte_array temp_bytes;
86 int bytes_read = _real_file->read(temp_bytes, 1);
89 #ifdef DEBUG_HUGE_FILE
90 LOG(a_sprintf(" read %d bytes", bytes_read));
92 bool at_eof = _real_file->eof();
93 #ifdef DEBUG_HUGE_FILE
94 LOG(a_sprintf(" at_eof=%d", int(at_eof)));
96 if (seek_ret && !at_eof) {
97 #ifdef DEBUG_HUGE_FILE
98 LOG("seek worked, incrementing best highest and trying same jump again");
100 // the seek worked, so we'll just jump forward again.
101 best_highest += double(big_jump);
102 _file_pointer += double(big_jump);
104 } else if (seek_ret && at_eof) {
105 #ifdef DEBUG_HUGE_FILE
106 LOG("seek worked but found eof exactly.");
108 // the seek did worked, but apparently we've also found the end point.
109 best_highest += double(big_jump);
110 _file_pointer += double(big_jump);
113 // that seek was too large, so we need to back down and try a smaller
115 #ifdef DEBUG_HUGE_FILE
116 LOG("seek failed, going back to best highest and trying same jump again");
119 _real_file->seek(0, byte_filer::FROM_START);
120 outcome worked = seek(best_highest, byte_filer::FROM_START);
121 // this uses our version to position at large sizes.
122 if (worked != OKAY) {
123 // this is a bad failure; it says that the file size changed or
124 // something malfunctioned. we should always be able to get back to
125 // the last good size we found if the file is static.
126 LOG(a_sprintf("failed to seek back to best highest %.0f on ",
127 best_highest) + _real_file->filename());
128 // try to repair our ideas about the file by starting the process
130 //hmmm: count the number of times restarted and bail after N.
131 seek_ret = _real_file->seek(0, byte_filer::FROM_START);
134 // the heck with this. we can't even go back to the start. this
135 // file seems to be screwed up now.
136 LOG(astring("failed to seek back to start of file! on ")
137 + _real_file->filename());
140 // reset the rest of the positions for our failed attempt to return
141 // to what we already thought was good.
143 big_jump = byte_filer::file_size_limit();
147 // okay, nothing bad happened when we went back to our last good point.
149 // success in finding the smallest place that we can't seek between.
150 #ifdef DEBUG_HUGE_FILE
151 LOG("got down to smallest big jump, 0!");
155 // formula expects that the maximum file size is a power of 2.
157 #ifdef DEBUG_HUGE_FILE
158 LOG(a_sprintf("restraining big jump down to %u.", big_jump));
164 // go back to where we started out.
165 seek(0, byte_filer::FROM_START);
166 seek(save_posn, byte_filer::FROM_CURRENT);
167 #ifdef DEBUG_HUGE_FILE
168 LOG(a_sprintf("saying file len is %.0f.", best_highest + 1.0));
170 return best_highest + 1.0;
173 bool huge_file::good() const { return _real_file->good(); }
175 bool huge_file::eof() const { return _real_file->eof(); }
177 outcome huge_file::move_to(double absolute_posn)
179 #ifdef DEBUG_HUGE_FILE
182 double difference = absolute_posn - _file_pointer;
183 // calculate the size we want to offset.
184 #ifdef DEBUG_HUGE_FILE
185 LOG(a_sprintf("abs_pos=%.0f difference=%.0f old_filepoint=%.0f",
186 absolute_posn, difference, _file_pointer));
188 // if we're at the same place, we don't have to do anything.
189 if (difference < 0.000001) {
190 #ifdef DEBUG_HUGE_FILE
191 LOG("difference was minimal, saying we're done.");
195 while (absolute_value(difference) > 0.000001) {
196 double seek_size = minimum(double(byte_filer::file_size_limit() - 1),
197 absolute_value(difference));
199 seek_size *= -1.0; // flip sign of seek.
200 #ifdef DEBUG_HUGE_FILE
201 LOG(a_sprintf(" seeksize=%d", int(seek_size)));
203 bool seek_ret = _real_file->seek(int(seek_size),
204 byte_filer::FROM_CURRENT);
206 #ifdef DEBUG_HUGE_FILE
207 LOG(a_sprintf("failed to seek %d from current", int(seek_size)));
209 return FAILURE; // seek failed somehow.
211 _file_pointer += seek_size;
212 #ifdef DEBUG_HUGE_FILE
213 LOG(a_sprintf(" now_filepoint=%.0f", _file_pointer));
215 difference = absolute_posn - _file_pointer;
216 #ifdef DEBUG_HUGE_FILE
217 LOG(a_sprintf(" now_difference=%.0f", difference));
223 outcome huge_file::seek(double new_position, byte_filer::origins origin)
225 #ifdef DEBUG_HUGE_FILE
228 if (origin == byte_filer::FROM_CURRENT) {
229 return move_to(_file_pointer + new_position);
230 } else if (origin == byte_filer::FROM_START) {
232 if (!_real_file->seek(0, byte_filer::FROM_START))
234 return move_to(new_position);
235 } else if (origin == byte_filer::FROM_END) {
236 #ifdef DEBUG_HUGE_FILE
237 LOG("into precarious FROM_END case.");
239 double file_len = length(); // could take a scary long time possibly.
240 #ifdef DEBUG_HUGE_FILE
241 LOG(a_sprintf(" FROM_END got len %.0f.", file_len));
243 _file_pointer = file_len;
244 // it's safe, although not efficient, for us to call the length()
245 // method here. our current version of length() uses the byte_filer's
246 // seek method directly and only FROM_CURRENT and FROM_START from this
247 // class's seek method.
248 _real_file->seek(0, byte_filer::FROM_END);
249 return move_to(_file_pointer - new_position);
255 outcome huge_file::read(byte_array &to_fill, int desired_size, int &size_read)
259 int ret = _real_file->read(to_fill, desired_size);
261 return FAILURE; // couldn't read the bytes.
262 _file_pointer += double(size_read);
267 outcome huge_file::write(const byte_array &to_write, int &size_written)
271 int ret = _real_file->write(to_write);
273 return FAILURE; // couldn't write the bytes.
274 _file_pointer += double(size_written);