APBCDB

• constant - You generate a database once, then look up keys in it. You cannot mix reads and writes.
• key-value - Apbcdb stores key-value pairs.
  • Both keys and values are strings (byte sequences).
  • Any richer structure in values must be imposed by the application.
  • Values can only be retrieved by primary key.
• library - Apbcdb is a library for C programmers. It cannot be used directly by users.

Advantages

• Fast lookups.
• Multiple readers can share the db efficiently.
• UTF-8 safe and binary-safe. Merely stores byte sequences.
• C API for DB creation.
• Clear, maintainable code.
• Permissive license.

Performance

• 1.8 GHz machine; 1GB RAM
• Lookup keys were randomly distributed.
• 50% of lookup keys were present in the database.

How to use APBCDB

General

• Include apbcdb.h
• All functions return a result code.
  • Always check it.
  • If it's nonzero, it's one of the errors listed in the header file.
  • Don't proceed past an error result.
• Add the apbcdb directory to your project and link with:
  • apbcdb_writer.o
  • apbcdb_reader.o
  • apbindex/apbindex.o

Creating a DB

apbcdb_writer w;
int rc;

rc = apbcdb_begin_write(&w, "phonebook.dat");

rc = apbcdb_add_entry(&w, strlen("Bob Smith"), "Bob Smith",
                          strlen("408.921.9191"), "408.921.9191");

rc = apbcdb_add_entry(&w, strlen("Jen Rapp"), "Jen Rapp",
                          strlen("714.334.5543"), "714.334.5543");

rc = apbcdb_end_write(&w);
/* this creates phonebook.dat.idx; both files must be present to read */

Reading a DB

apbcdb_reader r;
int rc;
char val[0x400];
uint vallen;

rc = apbcdb_ropen(&r, "phonebook.dat");
vallen = sizeof(val);
rc = apbcdb_get(&r, "Bob Smith", strlen("Bob Smith"), val, &vallen);
/* now val contains Bob's phone number, and vallen contains the
 * phone number's length */
rc = apbcdb_rclose(&r);

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