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/*************************************************************** -*- c++ -*-
* Copyright (c) 2003,2004 by Marcel Wiesweg *
* *
* 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. *
* *
***************************************************************************/
#include "packedstorage.h"
PackedStorage::PackedStorage(int maxMB)
: LegacyStorage(maxMB) {
}
#define TOC_SIZE 8
//The file structure is simple:
// TOC_SIZE*PageAddress contains the numbers of the following pages
// TOC_SIZE*TELETEXT_PAGESIZE contains the page data
//and the same again.
bool PackedStorage::seekTo(PageID page, int desc, bool create) {
lseek(desc, 0, SEEK_SET);
PageAddress addr[TOC_SIZE];
while (::read(desc, addr, sizeof(addr)) == sizeof(addr)) {
lseek(desc, 0, SEEK_CUR);
for (int index=0; index<TOC_SIZE; index++) {
if (addr[index]==page) {
lseek(desc, index*TELETEXT_PAGESIZE, SEEK_CUR);
return true;
} else if (addr[index].page==0) {
//0 means: no more pages follow
if (create) {
//rewind what was read
lseek(desc, -(off_t)sizeof(addr), SEEK_CUR);
//update index
addr[index]=page;
if (::write(desc, addr, sizeof(addr)) != sizeof(addr))
return false;
//seek to data position
lseek(desc, TELETEXT_PAGESIZE*index, SEEK_CUR);
return true;
} else
return false;
}
}
//seek over data area
lseek(desc, TELETEXT_PAGESIZE*TOC_SIZE, SEEK_CUR);
}
int oldSize=actualFileSize(lseek(desc, 0, SEEK_CUR));
if (create) {
//create a new set of a TOC and a TOC_SIZE*TELETEXT_PAGESIZE data area
memset(addr, 0, sizeof(addr));
//first entry is our page
addr[0]=page;
if (::write(desc, addr, sizeof(addr)) != sizeof(addr))
return false;
//seek beyond end of file
lseek(desc, (TELETEXT_PAGESIZE*TOC_SIZE)-1, SEEK_CUR);
//write one byte to enlarge the file to the sought position
char c=1;
if (::write(desc, &c, 1) != 1)
return false;
//Now, calculate new file size
byteCount += ( actualFileSize(lseek(desc, 0, SEEK_CUR)) - oldSize );
//seek to beginning of data, which is requested
lseek(desc, -(off_t)(TELETEXT_PAGESIZE*TOC_SIZE), SEEK_CUR);
return true;
} else
return false;
}
void PackedStorage::getFilename(char *buffer, int bufLength, PageID page) {
//This is a different scheme: page 576_07 will have the name 570s.vtx, the same as e.g. 571_01 or 575_00
//Think of "the five hundred seventies"
snprintf(buffer, bufLength, "%s/%s/%03xs.vtx", getRootDir(),
*page.channel.ToString(), (page.page & 0xFF0));
}
StorageHandle PackedStorage::openForWriting(PageID page) {
static bool wroteError=false;
char filename[PATH_MAX];
getFilename(filename, sizeof(filename), page);
//first try
int desc=open(filename, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (desc != -1) {
if (!seekTo(page, desc, true)) {
::close(desc);
return StorageHandle();
}
if ( maxBytes && byteCount>maxBytes )
freeSpace();
return (StorageHandle)desc;
}
//no space on disk? make some space available
if (errno == ENOSPC)
freeSpace();
//second try
desc=open(filename, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
if (desc==-1 && !wroteError) {
//report error to syslog - once!
wroteError=true;
esyslog("OSD-Teletext: Error opening teletext file %s: %s", filename, strerror(errno));
}
if (desc==-1)
return StorageHandle();
else if (!seekTo(page, desc, true)) {
::close(desc);
return StorageHandle();
}
if ( maxBytes && byteCount>maxBytes )
freeSpace();
return (StorageHandle)desc;
}
StorageHandle PackedStorage::openForReading(PageID page, bool countAsAccess) {
int desc;
if ( (desc=(int)LegacyStorage::openForReading(page, false))!= -1 ) {
if (!seekTo(page, desc, false)) {
//this is not an error condition here, may and shall happen!
::close(desc);
} else {
return (StorageHandle)desc;
}
}
return StorageHandle();
}
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