/*
* open or create a database
*/
DBHANDLE db_open_error(const char* pathname, int oflags, ...)
{
DB *db;
int len, mode;
size_t i;
char asciiptr[PTR_SZ + 1], hash[(NHASH_DEF + 1) * PTR_SZ + 2];
struct stat statbuf;
len = strlen(pathname);
if ((db = _db_alloc(len)) == NULL)
err_dump("db_open: __db_alloc error for DB");
//初始化db结构体
db->nhash = NHASH_DEF;
db->hashoff = HASH_OFF;
strcpy(db->name, pathname);
strcat(db->name, ".idx");
//创建数据库文件
if (oflags & O_CREAT)
{
va_list ap;
va_start(ap, oflags);
mode = va_arg(ap, int);
va_end(ap);
/*打开索引文件和数据文件*/
db->idxfd = open(db->name, oflags, mode);
strcpy(db->name + len, ".dat");
db->datfd = open(db->name, oflags, mode);
}
/* Opening or Creating a database */
DB *db_open(const char *pathname, int oflag, int mode)
{
DB *db;
int i, len;
char asciiptr[PTR_SZ + 1], hash[(NHASH_DEF + 1) * PTR_SZ +2]; /* +2 for newline and NULL */
struct stat statbuff;
/* Allocating a Database structure and the buffer it requires. */
len = strlen(pathname);
if((db = _db_alloc(len)) == NULL)
err_dump("error");
db->oflag = oflag; /* saving a copy of the open flags */
/* Opening index file */
strcpy(db->name, pathname);
strcat(db->name, ".idx");
if((db->idxfd = open(db->name, oflag, mode)) < 0)
{
_db_free(db);
return(NULL);
}
/* Opening data file */
strcpy(db->name + len, ".dat");
if((db->datfd = open(db->name, oflag, mode)) < 0)
{
_db_free(db);
return(NULL);
}
/* If the database was created, then initialize it */
if((oflag & (O_CREAT | O_TRUNC)) == (O_CREAT | O_TRUNC))
{
/* write lock the entire file and so that, we can stat the file, check it's size & initialize it */
if(writew_lock(db->idxfd, 0, SEEK_SET, 0) < 0)
err_dump("error");
if(fstat(db->idxfd, &statbuff) < 0)
err_sys("error");
if(statbuff.st_size==0)
{
/*
We gotta build a list of (NHASH_DEF + 1) chain ptr with a value of 0.
The +1 is for free list pointer that precedes the hash table.
*/
sprintf(asciiptr, "%*d", PTR_SZ, 0);
hash[0] = 0;
for(i=0;i<(NHASH_DEF + 1);i++)
strcat(hash, asciiptr);
strcat(hash, "\n");
i = strlen(hash);
if(write(db->idxfd, hash, i) != i)
err_dump("error");
}
if(un_lock(db->idxfd, 0, SEEK_SET, 0) < 0)
err_dump("error");
}
db->nhash = NHASH_DEF; /* hash table size */
db->hashoff = HASH_OFF; /* offset in index file of hash table */
/* free list ptr always at FREE_OFF */
db_rewind(db);
return(db);
}
/*
* Open or create a database. Same arguments as open(2).
*/
DBHANDLE
db_open(const char *pathname, int oflag, ...)
{
DB *db;
int len, mode;
size_t i;
char asciiptr[PTR_SZ + 1],
hash[(NHASH_DEF + 1) * PTR_SZ + 2];
/* +2 for newline and null */
struct stat statbuff;
/*
* Allocate a DB structure, and the buffers it needs.
*/
len = strlen(pathname);
if ((db = _db_alloc(len)) == NULL)
err_dump("db_open: _db_alloc error for DB");
db->nhash = NHASH_DEF;/* hash table size */
db->hashoff = HASH_OFF; /* offset in index file of hash table */
strcpy(db->name, pathname);
strcat(db->name, ".idx");
if (oflag & O_CREAT) {
va_list ap;
va_start(ap, oflag);
mode = va_arg(ap, int);
va_end(ap);
/*
* Open index file and data file.
*/
db->idxfd = open(db->name, oflag, mode);
strcpy(db->name + len, ".dat");
db->datfd = open(db->name, oflag, mode);
} else {
