zhicheng/db
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A New DBM in Pure C
Demo:
=====
db_t db;
db_option_t option;
option.table = 256; /* table number,keep this small if data not too much */
option.bucket = 256; /* initialize bucket number in per table,will incrase when key add */
option.rdonly = 0;
if (db_open(&db, /* data file */ "foo.db", /* index file */ "foo.db", &option) != DB_OK) {
fprintf(stderr, "open db failed\n");
return 0;
}
if (db_put(&db, "hi", strlen(...), "hello,world", strlen(...)) != DB_OK) {
fprintf(stderr, "NOT OK\n");
}
if ((len = db_get(&db, "hi", strlen(...), val, sizeof(val))) == 0) {
fprintf(stderr, "NOT FOUND\n");
}
db_close(&db);
Limited:
========
In 32 bit platform database file size is limited 4GiB*
Key/Value length is 32 bit unsigned int
*Depends Your Operation System,Mostly can't get 4GiB map
Design:
=======
+----------+
| |
| header |
| |
+----------+
| table[0] |---------+
+----------+ |
| table[1] |------------+
+----------+ | |
| table[2] | | |
+----------+ | |
| . | | |
| . | | |
| . | | |
+----------+ | |
| table[N] | | |
+----------+ | |
+-----| bucket[0]|<--------| |
| +----------+ |
| | bucket[1]| |
| +----------+ |
+--------| bucket[2]| |
| | +----------+ |
| | | . | |
| | | . |<-----------+
| | | . |
| | +----------+
| | | bucket[N]|
| | +----------+
| +---->| klen |
| +----------+
| | vlen |
| +----------+
| | . |
| | klen |
| | bytes |
| | . |
| +----------+
| | . |
| | vlen |
| | bytes |
| | . |
| +----------+
+------->| klen |
+----------+
| vlen |
+----------+
| . |
| klen |
| bytes |
| . |
+----------+
| . |
| vlen |
| bytes |
| . |
+----------+
| . |
| . |
| . |
+----------+
Goal:
=====
Keep it simple, stupid
Next Release will has Dynamic Hash Implementation*
And Mmap Maybe not required.
*Litwin, Witold (1980), "Linear hashing: A new tool for file and table addressing"
FAQ:
====
Q: Do you use `mmap'? What if I don't want use `mmap'?
A: Yes.Just use others,there is a lot of key/value database you can choose.
Q: I tried this library,It's waste to much disk space and memory!
A: I'll write compaction function later,will reduce disk space in high update application,you can use db-export and db-import to a new database file.The future compaction function will do same thing.Memory is control by the kernel,Sorry.
Q: Compression?
A: Maybe.
Q: Encryption?
A: Maybe.
Q: I use this in my Web Server,I have a problem!
A: Please contact the author.
Q: I use this in my Mobile Phone,I have a problem!
A: Please contact the author.
Q: I want do X,Will be OK?
A: Just try.If don't,Please contact the author.
Q: I have a problem!
A: Please contact the author.
License:
========
Public Domain License