--- /dev/null
+/*****************************************************************************\
+* *
+* Name : huge_file *
+* Author : Chris Koeritz *
+* *
+*******************************************************************************
+* Copyright (c) 2007-$now By Author. This program 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; either version 2 of *
+* the License or (at your option) any later version. This is online at: *
+* http://www.fsf.org/copyleft/gpl.html *
+* Please send any updates to: fred@gruntose.com *
+\*****************************************************************************/
+
+#include "byte_filer.h"
+#include "huge_file.h"
+
+#include <basis/byte_array.h>
+#include <basis/functions.h>
+#include <basis/guards.h>
+
+#include <stdio.h>
+
+#undef LOG
+#define LOG(to_print) printf("%s::%s: %s\n", static_class_name(), func, astring(to_print).s())
+
+//#define DEBUG_HUGE_FILE
+ // uncomment for noisy version.
+
+using namespace basis;
+
+namespace filesystem {
+
+huge_file::huge_file(const astring &filename, const astring &permissions)
+: _real_file(new byte_filer(filename, permissions)),
+ _file_pointer(0)
+{
+}
+
+huge_file::~huge_file()
+{
+ WHACK(_real_file);
+}
+
+void huge_file::flush() { _real_file->flush(); }
+
+bool huge_file::truncate() { return _real_file->truncate(); }
+
+double huge_file::length()
+{
+ FUNCDEF("length");
+
+//trying to read to see if we're past endpoint.
+// if this approach works, length may want to close and reopen file for
+// reading, since we can't add any bytes to it for writing just to find
+// the length out.
+
+
+ double save_posn = _file_pointer;
+ // skip to the beginning of the file so we can try to find the end.
+ _file_pointer = 0;
+ _real_file->seek(0, byte_filer::FROM_START);
+ size_t naive_size = _real_file->length();
+ if (naive_size < _real_file->file_size_limit()) {
+ // lucked out; we are within normal file size limitations.
+ seek(save_posn, byte_filer::FROM_START);
+ return double(naive_size);
+ }
+
+ double best_highest = 0.0; // the maximum we've safely seeked to.
+
+ size_t big_jump = byte_filer::file_size_limit();
+ // try with the largest possible seek at first.
+
+ while (true) {
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf("best highest=%.0f", best_highest));
+#endif
+ // iterate until we reach our exit condition, which seems like it must
+ // always occur eventually unless the file is being monkeyed with.
+ bool seek_ret = _real_file->seek(int(big_jump), byte_filer::FROM_CURRENT);
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" seek ret=%d", int(seek_ret)));
+#endif
+ byte_array temp_bytes;
+ int bytes_read = _real_file->read(temp_bytes, 1);
+ if (bytes_read < 1)
+ seek_ret = false;
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" read %d bytes", bytes_read));
+#endif
+ bool at_eof = _real_file->eof();
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" at_eof=%d", int(at_eof)));
+#endif
+ if (seek_ret && !at_eof) {
+#ifdef DEBUG_HUGE_FILE
+ LOG("seek worked, incrementing best highest and trying same jump again");
+#endif
+ // the seek worked, so we'll just jump forward again.
+ best_highest += double(big_jump);
+ _file_pointer += double(big_jump);
+ continue;
+ } else if (seek_ret && at_eof) {
+#ifdef DEBUG_HUGE_FILE
+ LOG("seek worked but found eof exactly.");
+#endif
+ // the seek did worked, but apparently we've also found the end point.
+ best_highest += double(big_jump);
+ _file_pointer += double(big_jump);
+ break;
+ } else {
+ // that seek was too large, so we need to back down and try a smaller
+ // seek size.
+#ifdef DEBUG_HUGE_FILE
+ LOG("seek failed, going back to best highest and trying same jump again");
+#endif
+ _file_pointer = 0;
+ _real_file->seek(0, byte_filer::FROM_START);
+ outcome worked = seek(best_highest, byte_filer::FROM_START);
+ // this uses our version to position at large sizes.
+ if (worked != OKAY) {
+ // this is a bad failure; it says that the file size changed or
+ // something malfunctioned. we should always be able to get back to
+ // the last good size we found if the file is static.
+ LOG(a_sprintf("failed to seek back to best highest %.0f on ",
+ best_highest) + _real_file->filename());
+ // try to repair our ideas about the file by starting the process
+ // over.
+//hmmm: count the number of times restarted and bail after N.
+ seek_ret = _real_file->seek(0, byte_filer::FROM_START);
+ _file_pointer = 0;
+ if (!seek_ret) {
+ // the heck with this. we can't even go back to the start. this
+ // file seems to be screwed up now.
+ LOG(astring("failed to seek back to start of file! on ")
+ + _real_file->filename());
+ return 0;
+ }
+ // reset the rest of the positions for our failed attempt to return
+ // to what we already thought was good.
+ _file_pointer = 0;
+ big_jump = byte_filer::file_size_limit();
+ best_highest = 0;
+ continue;
+ }
+ // okay, nothing bad happened when we went back to our last good point.
+ if (big_jump <= 0) {
+ // success in finding the smallest place that we can't seek between.
+#ifdef DEBUG_HUGE_FILE
+ LOG("got down to smallest big jump, 0!");
+#endif
+ break;
+ }
+ // formula expects that the maximum file size is a power of 2.
+ big_jump /= 2;
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf("restraining big jump down to %u.", big_jump));
+#endif
+ continue;
+ }
+ }
+
+ // go back to where we started out.
+ seek(0, byte_filer::FROM_START);
+ seek(save_posn, byte_filer::FROM_CURRENT);
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf("saying file len is %.0f.", best_highest + 1.0));
+#endif
+ return best_highest + 1.0;
+}
+
+bool huge_file::good() const { return _real_file->good(); }
+
+bool huge_file::eof() const { return _real_file->eof(); }
+
+outcome huge_file::move_to(double absolute_posn)
+{
+#ifdef DEBUG_HUGE_FILE
+ FUNCDEF("move_to");
+#endif
+ double difference = absolute_posn - _file_pointer;
+ // calculate the size we want to offset.
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf("abs_pos=%.0f difference=%.0f old_filepoint=%.0f",
+ absolute_posn, difference, _file_pointer));
+#endif
+ // if we're at the same place, we don't have to do anything.
+ if (difference < 0.000001) {
+#ifdef DEBUG_HUGE_FILE
+ LOG("difference was minimal, saying we're done.");
+#endif
+ return OKAY;
+ }
+ while (absolute_value(difference) > 0.000001) {
+ double seek_size = minimum(double(byte_filer::file_size_limit() - 1),
+ absolute_value(difference));
+ if (difference < 0)
+ seek_size *= -1.0; // flip sign of seek.
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" seeksize=%d", int(seek_size)));
+#endif
+ bool seek_ret = _real_file->seek(int(seek_size),
+ byte_filer::FROM_CURRENT);
+ if (!seek_ret) {
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf("failed to seek %d from current", int(seek_size)));
+#endif
+ return FAILURE; // seek failed somehow.
+ }
+ _file_pointer += seek_size;
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" now_filepoint=%.0f", _file_pointer));
+#endif
+ difference = absolute_posn - _file_pointer;
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" now_difference=%.0f", difference));
+#endif
+ }
+ return OKAY;
+}
+
+outcome huge_file::seek(double new_position, byte_filer::origins origin)
+{
+#ifdef DEBUG_HUGE_FILE
+ FUNCDEF("seek");
+#endif
+ if (origin == byte_filer::FROM_CURRENT) {
+ return move_to(_file_pointer + new_position);
+ } else if (origin == byte_filer::FROM_START) {
+ _file_pointer = 0;
+ if (!_real_file->seek(0, byte_filer::FROM_START))
+ return FAILURE;
+ return move_to(new_position);
+ } else if (origin == byte_filer::FROM_END) {
+#ifdef DEBUG_HUGE_FILE
+ LOG("into precarious FROM_END case.");
+#endif
+ double file_len = length(); // could take a scary long time possibly.
+#ifdef DEBUG_HUGE_FILE
+ LOG(a_sprintf(" FROM_END got len %.0f.", file_len));
+#endif
+ _file_pointer = file_len;
+ // it's safe, although not efficient, for us to call the length()
+ // method here. our current version of length() uses the byte_filer's
+ // seek method directly and only FROM_CURRENT and FROM_START from this
+ // class's seek method.
+ _real_file->seek(0, byte_filer::FROM_END);
+ return move_to(_file_pointer - new_position);
+ }
+ // unknown origin.
+ return BAD_INPUT;
+}
+
+outcome huge_file::read(byte_array &to_fill, int desired_size, int &size_read)
+{
+// FUNCDEF("read");
+ size_read = 0;
+ int ret = _real_file->read(to_fill, desired_size);
+ if (ret < 0)
+ return FAILURE; // couldn't read the bytes.
+ _file_pointer += double(size_read);
+ size_read = ret;
+ return OKAY;
+}
+
+outcome huge_file::write(const byte_array &to_write, int &size_written)
+{
+// FUNCDEF("write");
+ size_written = 0;
+ int ret = _real_file->write(to_write);
+ if (ret < 0)
+ return FAILURE; // couldn't write the bytes.
+ _file_pointer += double(size_written);
+ size_written = ret;
+ return OKAY;
+}
+
+} //namespace.
+
projects / feisty_meow.git / blobdiff