cdb(5) [netbsd man page]
CDB(5) BSD File Formats Manual CDB(5) NAME
cdb -- format of the constant database DESCRIPTION
The cdb database format provides a space-efficient (key,value) database. The format doesn't allow updates in any convenient form. The file overhead is around 5 bytes per key and 5 bytes per entry. Keys are not stored and it is the responsibility of the caller to validate matches. The index structure is based on a minimal perfect hash table, so exactly one entry has to be checked for a match. General Format The header record of a cdb database consists of the following: struct header_cdb { uint8_t magic[7]; uint8_t version; uint8_t description[16]; uint32_t data_size; uint32_t entries; uint32_t entries_index; uint32_t seed; }; All fields are in Little Endian byte order. This is followed by a description of the hash function of entries_index records. The size of each index entry is the logarithm of entries to base 256, rounded up. The index records are followed by the start offsets of the entries, followed by data_size. The offsets are relative to the end of the offset record table and are monotically increasing. The size of each offset record is the logarithm of data_size to base 256, rounded up. The offset table is followed by the entries in order. No separation or padding is added. Limitations The cdb file format is by design intended for a database that can be mapped into memory. The hard limit for the number of entries and keys is 3435973836. The total size of all values must be smaller than 4GiB. SEE ALSO
cdbr(3), cdbw(3) HISTORY
Support for the cdb format first appeared in NetBSD 6.0. AUTHORS
The cdbr and cdbw functions have been written by Joerg Sonnenberger <joerg@NetBSD.org>. BSD
April 27, 2010 BSD
Check Out this Related Man Page
CDBR(3) BSD Library Functions Manual CDBR(3) NAME
cdbr cdbr_open, cdbr_entries, cdbr_get, cdbr_find, cdbr_close, cdbr_write -- constant database access methods SYNOPSIS
struct cdbr * cdbr_open(const char *path, int flags); uint32_t cdbr_entries(struct cdbr *cdbr); int cdbr_get(struct cdbr *cdbr, uint32_t index, const void **data, size_t *datalen); int cdbr_find(struct cdbr *cdbr, const void *key, size_t keylen, const void **data, size_t *datalen); void cdbr_close(struct cdbr *cdbr); DESCRIPTION
The cdbr library provides a space efficient (key,value) database based on perfect hashing. A cdb database is opened for reading by calling cdbr_open(). The only supported value for flags is CDBR_DEFAULT. The function returns a handle to pass to the other functions. The database is closed by invoking cdbr_close(). All resources associated with the handle are freed and the memory returned by cdbr_get() and cdbr_find() is invalidated. The number of records in the database can be obtained by calling cdbr_entries(). Records can be obtained by record number using cdbr_get() or by key using cdbr_find(). Both functions return 0 on success and update data and datalen accordingly. The location *data remains valid until cdbr_close() is called. It is the responsibility of the caller of cdbr_find() to ensure that the key matches the returned data. The function returns the only possible match, but the database doesn't store the keys to minimize overhead. SEE ALSO
nbperf(1), cdbw(3), db(3), cdb(5) HISTORY
Support for the cdb format first appeared in NetBSD 6.0. AUTHORS
The cdbr and cdbw functions have been written by Joerg Sonnenberger <joerg@NetBSD.org>. BSD
March 3, 2010 BSD