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>
26 #define LOG(to_print) printf("%s::%s: %s\n", static_class_name(), func, astring(to_print).s())
28 //#define DEBUG_HUGE_FILE
29 // uncomment for noisy version.
31 using namespace basis;
33 namespace filesystem {
35 huge_file::huge_file(const astring &filename, const astring &permissions)
36 : _real_file(new byte_filer(filename, permissions)),
41 huge_file::~huge_file()
46 void huge_file::flush() { _real_file->flush(); }
48 bool huge_file::truncate() { return _real_file->truncate(); }
50 double huge_file::length()
54 //trying to read to see if we're past endpoint.
55 // if this approach works, length may want to close and reopen file for
56 // reading, since we can't add any bytes to it for writing just to find
60 double save_posn = _file_pointer;
61 // skip to the beginning of the file so we can try to find the end.
63 _real_file->seek(0, byte_filer::FROM_START);
64 size_t naive_size = _real_file->length();
65 if (naive_size < _real_file->file_size_limit()) {
66 // lucked out; we are within normal file size limitations.
67 seek(save_posn, byte_filer::FROM_START);
68 return double(naive_size);
71 double best_highest = 0.0; // the maximum we've safely seeked to.
73 size_t big_jump = byte_filer::file_size_limit();
74 // try with the largest possible seek at first.
77 #ifdef DEBUG_HUGE_FILE
78 LOG(a_sprintf("best highest=%.0f", best_highest));
80 // iterate until we reach our exit condition, which seems like it must
81 // always occur eventually unless the file is being monkeyed with.
82 bool seek_ret = _real_file->seek(int(big_jump), byte_filer::FROM_CURRENT);
83 #ifdef DEBUG_HUGE_FILE
84 LOG(a_sprintf(" seek ret=%d", int(seek_ret)));
86 byte_array temp_bytes;
87 int bytes_read = _real_file->read(temp_bytes, 1);
90 #ifdef DEBUG_HUGE_FILE
91 LOG(a_sprintf(" read %d bytes", bytes_read));
93 bool at_eof = _real_file->eof();
94 #ifdef DEBUG_HUGE_FILE
95 LOG(a_sprintf(" at_eof=%d", int(at_eof)));
97 if (seek_ret && !at_eof) {
98 #ifdef DEBUG_HUGE_FILE
99 LOG("seek worked, incrementing best highest and trying same jump again");
101 // the seek worked, so we'll just jump forward again.
102 best_highest += double(big_jump);
103 _file_pointer += double(big_jump);
105 } else if (seek_ret && at_eof) {
106 #ifdef DEBUG_HUGE_FILE
107 LOG("seek worked but found eof exactly.");
109 // the seek did worked, but apparently we've also found the end point.
110 best_highest += double(big_jump);
111 _file_pointer += double(big_jump);
114 // that seek was too large, so we need to back down and try a smaller
116 #ifdef DEBUG_HUGE_FILE
117 LOG("seek failed, going back to best highest and trying same jump again");
120 _real_file->seek(0, byte_filer::FROM_START);
121 outcome worked = seek(best_highest, byte_filer::FROM_START);
122 // this uses our version to position at large sizes.
123 if (worked != OKAY) {
124 // this is a bad failure; it says that the file size changed or
125 // something malfunctioned. we should always be able to get back to
126 // the last good size we found if the file is static.
127 LOG(a_sprintf("failed to seek back to best highest %.0f on ",
128 best_highest) + _real_file->name());
129 // try to repair our ideas about the file by starting the process
131 //hmmm: count the number of times restarted and bail after N.
132 seek_ret = _real_file->seek(0, byte_filer::FROM_START);
135 // the heck with this. we can't even go back to the start. this
136 // file seems to be screwed up now.
137 LOG(astring("failed to seek back to start of file! on ")
138 + _real_file->name());
141 // reset the rest of the positions for our failed attempt to return
142 // to what we already thought was good.
144 big_jump = byte_filer::file_size_limit();
148 // okay, nothing bad happened when we went back to our last good point.
150 // success in finding the smallest place that we can't seek between.
151 #ifdef DEBUG_HUGE_FILE
152 LOG("got down to smallest big jump, 0!");
156 // formula expects that the maximum file size is a power of 2.
158 #ifdef DEBUG_HUGE_FILE
159 LOG(a_sprintf("restraining big jump down to %u.", big_jump));
165 // go back to where we started out.
166 seek(0, byte_filer::FROM_START);
167 seek(save_posn, byte_filer::FROM_CURRENT);
168 #ifdef DEBUG_HUGE_FILE
169 LOG(a_sprintf("saying file len is %.0f.", best_highest + 1.0));
171 return best_highest + 1.0;
174 bool huge_file::good() const { return _real_file->good(); }
176 bool huge_file::eof() const { return _real_file->eof(); }
178 outcome huge_file::move_to(double absolute_posn)
180 #ifdef DEBUG_HUGE_FILE
183 double difference = absolute_posn - _file_pointer;
184 // calculate the size we want to offset.
185 #ifdef DEBUG_HUGE_FILE
186 LOG(a_sprintf("abs_pos=%.0f difference=%.0f old_filepoint=%.0f",
187 absolute_posn, difference, _file_pointer));
189 // if we're at the same place, we don't have to do anything.
190 if (difference < 0.000001) {
191 #ifdef DEBUG_HUGE_FILE
192 LOG("difference was minimal, saying we're done.");
196 while (absolute_value(difference) > 0.000001) {
197 double seek_size = minimum(double(byte_filer::file_size_limit() - 1),
198 absolute_value(difference));
200 seek_size *= -1.0; // flip sign of seek.
201 #ifdef DEBUG_HUGE_FILE
202 LOG(a_sprintf(" seeksize=%d", int(seek_size)));
204 bool seek_ret = _real_file->seek(int(seek_size),
205 byte_filer::FROM_CURRENT);
207 #ifdef DEBUG_HUGE_FILE
208 LOG(a_sprintf("failed to seek %d from current", int(seek_size)));
210 return FAILURE; // seek failed somehow.
212 _file_pointer += seek_size;
213 #ifdef DEBUG_HUGE_FILE
214 LOG(a_sprintf(" now_filepoint=%.0f", _file_pointer));
216 difference = absolute_posn - _file_pointer;
217 #ifdef DEBUG_HUGE_FILE
218 LOG(a_sprintf(" now_difference=%.0f", difference));
224 outcome huge_file::seek(double new_position, byte_filer::origins origin)
226 #ifdef DEBUG_HUGE_FILE
229 if (origin == byte_filer::FROM_CURRENT) {
230 return move_to(_file_pointer + new_position);
231 } else if (origin == byte_filer::FROM_START) {
233 if (!_real_file->seek(0, byte_filer::FROM_START))
235 return move_to(new_position);
236 } else if (origin == byte_filer::FROM_END) {
237 #ifdef DEBUG_HUGE_FILE
238 LOG("into precarious FROM_END case.");
240 double file_len = length(); // could take a scary long time possibly.
241 #ifdef DEBUG_HUGE_FILE
242 LOG(a_sprintf(" FROM_END got len %.0f.", file_len));
244 _file_pointer = file_len;
245 // it's safe, although not efficient, for us to call the length()
246 // method here. our current version of length() uses the byte_filer's
247 // seek method directly and only FROM_CURRENT and FROM_START from this
248 // class's seek method.
249 _real_file->seek(0, byte_filer::FROM_END);
250 return move_to(_file_pointer - new_position);
256 outcome huge_file::read(byte_array &to_fill, int desired_size, int &size_read)
260 int ret = _real_file->read(to_fill, desired_size);
262 return FAILURE; // couldn't read the bytes.
263 _file_pointer += double(size_read);
268 outcome huge_file::write(const byte_array &to_write, int &size_written)
272 int ret = _real_file->write(to_write);
274 return FAILURE; // couldn't write the bytes.
275 _file_pointer += double(size_written);
280 basis::outcome huge_file::touch()
282 if (filename(_real_file->name()).exists()) {
283 // file exists, so just update time.
284 int ret = utimes(_real_file->name().observe(), NIL);
288 // file doesn't exist yet.
291 outcome ret = write(junk, written);
292 if (ret != OKAY) ret;