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// recstore.h
#pragma once
#include "../util/file.h"
namespace mongo {
using boost::uint32_t;
using boost::uint64_t;
/* Current version supports only consistent record sizes within a store. */
class BasicRecStore {
struct RecStoreHeader {
uint32_t version;
uint32_t recsize;
uint64_t leof; // logical eof, actual file might be prealloc'd further
uint64_t firstDeleted; // 0 = no deleted recs
uint32_t cleanShutdown; // 0 = clean
char reserved[8192-8-8-4-4-4]; // we want our records page-aligned in the file if they are a multiple of a page's size -- so we make this 8KB with that goal
RecStoreHeader() {
version = 65;
recsize = 0;
leof = sizeof(RecStoreHeader);
firstDeleted = 0;
cleanShutdown = 1;
memset(reserved, 0, sizeof(reserved));
}
};
public:
~BasicRecStore();
void init(const char *fn, unsigned recsize);
fileofs insert(const char *buf, unsigned len);
void update(fileofs o, const char *buf, unsigned len);
void remove(fileofs o, unsigned len);
void get(fileofs o, char *buf, unsigned len);
private:
void writeHeader();
File f;
fileofs len;
RecStoreHeader h; // h.reserved is wasteful here; fix later.
void write(fileofs ofs, const char *data, unsigned len) {
f.write(ofs, data, len);
massert("basicrecstore write io error", !f.bad());
}
};
/* --- implementation --- */
inline BasicRecStore::~BasicRecStore() {
h.cleanShutdown = 0;
if( f.is_open() ) {
writeHeader();
f.fsync();
}
}
inline void BasicRecStore::writeHeader() {
write(0, (const char *) &h, 28); // update header in file for new leof
uassert("file io error in BasicRecStore [1]", !f.bad());
}
inline fileofs BasicRecStore::insert(const char *buf, unsigned reclen) {
if( h.firstDeleted ) {
uasserted("deleted not yet implemented recstoreinsert");
}
massert("bad len", reclen == h.recsize);
fileofs ofs = h.leof;
h.leof += reclen;
if( h.leof > len ) {
// grow the file. we grow quite a bit to avoid excessive file system fragmentations
len += (len / 8) + h.recsize;
uassert( "recstore file too big for 32 bit", len <= 0x7fffffff || sizeof(std::streamoff) > 4 );
write(len, "", 0);
}
writeHeader();
write(ofs, buf, reclen);
uassert("file io error in BasicRecStore [2]", !f.bad());
return ofs;
}
/* so far, it's ok to read or update a subset of a record */
inline void BasicRecStore::update(fileofs o, const char *buf, unsigned len) {
assert(o <= h.leof && o >= sizeof(RecStoreHeader));
write(o, buf, len);
}
inline void BasicRecStore::get(fileofs o, char *buf, unsigned len) {
assert(o <= h.leof && o >= sizeof(RecStoreHeader));
f.read(o, buf, len);
massert("basicrestore::get I/O error", !f.bad());
}
inline void BasicRecStore::remove(fileofs o, unsigned len) {
uasserted("not yet implemented recstoreremove");
}
}
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