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 const astring &huge_file::name() const { return _real_file->name(); }
48 void huge_file::flush() { _real_file->flush(); }
50 bool huge_file::truncate() { return _real_file->truncate(); }
52 double huge_file::length()
56 //trying to read to see if we're past endpoint.
57 // if this approach works, length may want to close and reopen file for
58 // reading, since we can't add any bytes to it for writing just to find
62 double save_posn = _file_pointer;
63 // skip to the beginning of the file so we can try to find the end.
65 _real_file->seek(0, byte_filer::FROM_START);
66 size_t naive_size = _real_file->length();
67 if (naive_size < _real_file->file_size_limit()) {
68 // lucked out; we are within normal file size limitations.
69 seek(save_posn, byte_filer::FROM_START);
70 return double(naive_size);
73 double best_highest = 0.0; // the maximum we've safely seeked to.
75 size_t big_jump = byte_filer::file_size_limit();
76 // try with the largest possible seek at first.
79 #ifdef DEBUG_HUGE_FILE
80 LOG(a_sprintf("best highest=%.0f", best_highest));
82 // iterate until we reach our exit condition, which seems like it must
83 // always occur eventually unless the file is being monkeyed with.
84 bool seek_ret = _real_file->seek(int(big_jump), byte_filer::FROM_CURRENT);
85 #ifdef DEBUG_HUGE_FILE
86 LOG(a_sprintf(" seek ret=%d", int(seek_ret)));
88 byte_array temp_bytes;
89 int bytes_read = _real_file->read(temp_bytes, 1);
92 #ifdef DEBUG_HUGE_FILE
93 LOG(a_sprintf(" read %d bytes", bytes_read));
95 bool at_eof = _real_file->eof();
96 #ifdef DEBUG_HUGE_FILE
97 LOG(a_sprintf(" at_eof=%d", int(at_eof)));
99 if (seek_ret && !at_eof) {
100 #ifdef DEBUG_HUGE_FILE
101 LOG("seek worked, incrementing best highest and trying same jump again");
103 // the seek worked, so we'll just jump forward again.
104 best_highest += double(big_jump);
105 _file_pointer += double(big_jump);
107 } else if (seek_ret && at_eof) {
108 #ifdef DEBUG_HUGE_FILE
109 LOG("seek worked but found eof exactly.");
111 // the seek did worked, but apparently we've also found the end point.
112 best_highest += double(big_jump);
113 _file_pointer += double(big_jump);
116 // that seek was too large, so we need to back down and try a smaller
118 #ifdef DEBUG_HUGE_FILE
119 LOG("seek failed, going back to best highest and trying same jump again");
122 _real_file->seek(0, byte_filer::FROM_START);
123 outcome worked = seek(best_highest, byte_filer::FROM_START);
124 // this uses our version to position at large sizes.
125 if (worked != OKAY) {
126 // this is a bad failure; it says that the file size changed or
127 // something malfunctioned. we should always be able to get back to
128 // the last good size we found if the file is static.
129 LOG(a_sprintf("failed to seek back to best highest %.0f on ",
130 best_highest) + _real_file->name());
131 // try to repair our ideas about the file by starting the process
133 //hmmm: count the number of times restarted and bail after N.
134 seek_ret = _real_file->seek(0, byte_filer::FROM_START);
137 // the heck with this. we can't even go back to the start. this
138 // file seems to be screwed up now.
139 LOG(astring("failed to seek back to start of file! on ")
140 + _real_file->name());
143 // reset the rest of the positions for our failed attempt to return
144 // to what we already thought was good.
146 big_jump = byte_filer::file_size_limit();
150 // okay, nothing bad happened when we went back to our last good point.
152 // success in finding the smallest place that we can't seek between.
153 #ifdef DEBUG_HUGE_FILE
154 LOG("got down to smallest big jump, 0!");
158 // formula expects that the maximum file size is a power of 2.
160 #ifdef DEBUG_HUGE_FILE
161 LOG(a_sprintf("restraining big jump down to %u.", big_jump));
167 // go back to where we started out.
168 seek(0, byte_filer::FROM_START);
169 seek(save_posn, byte_filer::FROM_CURRENT);
170 #ifdef DEBUG_HUGE_FILE
171 LOG(a_sprintf("saying file len is %.0f.", best_highest + 1.0));
173 return best_highest + 1.0;
176 bool huge_file::good() const { return _real_file->good(); }
178 bool huge_file::eof() const { return _real_file->eof(); }
180 outcome huge_file::move_to(double absolute_posn)
182 #ifdef DEBUG_HUGE_FILE
185 double difference = absolute_posn - _file_pointer;
186 // calculate the size we want to offset.
187 #ifdef DEBUG_HUGE_FILE
188 LOG(a_sprintf("abs_pos=%.0f difference=%.0f old_filepoint=%.0f",
189 absolute_posn, difference, _file_pointer));
191 // if we're at the same place, we don't have to do anything.
192 if (difference < 0.000001) {
193 #ifdef DEBUG_HUGE_FILE
194 LOG("difference was minimal, saying we're done.");
198 while (absolute_value(difference) > 0.000001) {
199 double seek_size = minimum(double(byte_filer::file_size_limit() - 1),
200 absolute_value(difference));
202 seek_size *= -1.0; // flip sign of seek.
203 #ifdef DEBUG_HUGE_FILE
204 LOG(a_sprintf(" seeksize=%d", int(seek_size)));
206 bool seek_ret = _real_file->seek(int(seek_size),
207 byte_filer::FROM_CURRENT);
209 #ifdef DEBUG_HUGE_FILE
210 LOG(a_sprintf("failed to seek %d from current", int(seek_size)));
212 return FAILURE; // seek failed somehow.
214 _file_pointer += seek_size;
215 #ifdef DEBUG_HUGE_FILE
216 LOG(a_sprintf(" now_filepoint=%.0f", _file_pointer));
218 difference = absolute_posn - _file_pointer;
219 #ifdef DEBUG_HUGE_FILE
220 LOG(a_sprintf(" now_difference=%.0f", difference));
226 outcome huge_file::seek(double new_position, byte_filer::origins origin)
228 #ifdef DEBUG_HUGE_FILE
231 if (origin == byte_filer::FROM_CURRENT) {
232 return move_to(_file_pointer + new_position);
233 } else if (origin == byte_filer::FROM_START) {
235 if (!_real_file->seek(0, byte_filer::FROM_START))
237 return move_to(new_position);
238 } else if (origin == byte_filer::FROM_END) {
239 #ifdef DEBUG_HUGE_FILE
240 LOG("into precarious FROM_END case.");
242 double file_len = length(); // could take a scary long time possibly.
243 #ifdef DEBUG_HUGE_FILE
244 LOG(a_sprintf(" FROM_END got len %.0f.", file_len));
246 _file_pointer = file_len;
247 // it's safe, although not efficient, for us to call the length()
248 // method here. our current version of length() uses the byte_filer's
249 // seek method directly and only FROM_CURRENT and FROM_START from this
250 // class's seek method.
251 _real_file->seek(0, byte_filer::FROM_END);
252 return move_to(_file_pointer - new_position);
258 outcome huge_file::read(byte_array &to_fill, int desired_size, int &size_read)
262 int ret = _real_file->read(to_fill, desired_size);
264 return FAILURE; // couldn't read the bytes.
265 _file_pointer += double(size_read);
270 outcome huge_file::write(const byte_array &to_write, int &size_written)
274 int ret = _real_file->write(to_write);
276 return FAILURE; // couldn't write the bytes.
277 _file_pointer += double(size_written);
282 basis::outcome huge_file::touch()
284 if (filename(_real_file->name()).exists()) {
285 // file exists, so just update time.
286 int ret = utimes(_real_file->name().observe(), NIL);
290 // file doesn't exist yet.
293 outcome ret = write(junk, written);
294 if (ret != OKAY) ret;