RetroArch/libretro-db/README.md
ZornTaov 450feb46cc
Update libretro-db/README.md
Looking through libretro-db/query.c I discovered the b prefix to strings that turns the string into binary, this is useful for searching up hexadecimal hashes.  This information was not described in the documentation, so I've added it before the Names only search to group with the other find commands, though it will work with get-names as well.
2019-07-18 14:02:17 -07:00

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# libretrodb
A small read only database
Mainly to be used by retroarch
# Usage
Files specified later in the chain **will override** earlier ones if the same key exists multiple times.
* To list out the content of a db `libretrodb_tool <db file> list`
* To create an index `libretrodb_tool <db file> create-index <index name> <field name>`
* To find an entry with an index `libretrodb_tool <db file> find <index name> <value>`
# Compiling a single DAT into a single RDB with `c_converter`
```
git clone https://github.com/libretro/libretro-super.git
cd libretro-super
./libretro-fetch.sh retroarch
cd retroarch
./configure
cd libretro-db
c_converter "NAME_OF_RDB_FILE.rdb" "NAME_OF_SOURCE_DAT.dat"
```
# Compiling multiple DATs into a single RDB with `c_converter`
Specify `rom.crc` as the second parameter to use CRC as the unique fingerprint.
```
git clone https://github.com/libretro/libretro-super.git
cd libretro-super
./libretro-fetch.sh retroarch
cd retroarch
./configure
cd libretro-db
c_converter "NAME_OF_RDB_FILE.rdb" "rom.crc" "NAME_OF_SOURCE_DAT_1.dat" "NAME_OF_SOURCE_DAT_2.dat" "NAME_OF_SOURCE_DAT_3.dat"
```
# Compiling all RDBs with libretro-build-database.sh
**This approach builds and uses the `c_converter` program to compile the databases**
```
git clone https://github.com/libretro/libretro-super.git
cd libretro-super
./libretro-fetch.sh retroarch
./libretro-build-database.sh
```
# Lua DAT file converter
To convert a dat file use:
~~~
dat_converter <db file> <dat file>
~~~
If you want to merge multiple dat files you need to run:
~~~
dat_converter <db file> <match key> <dat file> ...
~~~
for example:
~~~
dat_converter snes.rdb rom.crc snes1.dat snes2.dat
~~~
# Query examples
Some examples of queries you can use with libretrodbtool:
1) Glob pattern matching
Usecase : Search for all games starting with 'Street Fighter' in the 'name' field (glob pattern matching)
`libretrodb_tool <db file> find "{'name':glob('Street Fighter*')}"`
2) Combined number matching query
Usecase: Search for all games released on October 1995.
`libretrodb_tool <db file> find "{'releasemonth':10,'releaseyear':1995}"`
3) Hash matching query
Usecase: Search for any game matching a given crc32, in this case Soul Blazer (USA) for the SNES. Also works with serial, md5, and sha1.
`libretrodb_tool <db file> find "{'crc':b'31B965DB'}"`
4) Names only search
Usecase: Search for all games released on October 1995, wont print checksums, filename or rom size, only the game name.
`libretrodb_tool <db file> get-names "{'releasemonth':10,'releaseyear':1995}"`
# Writing Lua converters
In order to write you own converter you must have a lua file that implements the following functions:
~~~.lua
-- this function gets called before the db is created and should validate the
-- arguments and set up the ground for db insertion
function init(...)
local args = {...}
local script_name = args[1]
end
-- this is in iterator function. It is called before each insert.
-- the function should return a table for insertion or nil when there are no
-- more records to insert.
function get_value()
return {
key = "value", -- will be saved as string
num = 3, -- will be saved as int
bin = binary("some string"), -- will be saved as binary
unum = uint(3), -- will be saved as uint
some_bool = true, -- will be saved as bool
}
end
~~~