Things may still change

Very untested as of now

c-lookup-table

Compile Time Generic Dynamic Lookup Table in C.

First Things First

On it's own, no code is being compiled. You first have to include and implement a lookup table of your desires. For that, there are two macros.

#include "lutd.h"
LUTD_INCLUDE(N, A, T, M);
LUTD_IMPLEMENT(N, A, T, M, H, C, F);

1. N - Name - the resulting name of the lookup table struct
2. A - Abbreviation - functions get prefixed with that
3. T - Type - the type of your elements within the lookup table
4. M - Mode - storage type, either BY_VAL (by value) or BY_REF (by reference)
5. H - Hash - provide a hashing function for your elements (required)
6. C - Compare - provide a comparing function for your elements - if none provided, default to memcmp
7. F - Free - provide a freeing function for your elements, if available

The lookup table only stores how many times something with an equal hash has been added. If something was added a second time, it will only increase the count, and not copy the data into the table.

Examples

• example int BY_VAL, no C and no F provided
• example person BY_REF, C and F provided
• I used this lookup table in my Timers interpreter (BY_REF, C provided but no F provided)
• This lookup table is extensively used in c-nexus and c-file-tagger and provides the base for my string c-string.
• to compile run make (have to be in the examples directory)
• to clean run make clean (if you're on cygwin, run OS= make clean

Design Considerations

• Both BY_VAL and BY_REF can be used on either basic types or (complex) structs.

Metaprogramming

Advantages

• Compiler optimized code
• Flexibility, reusability (generics / templates)
• Type safety

Disadvantages

• Maintenance challenges
• Debugging difficulties
• Compilation overhead

How to use it

Available Functions

The A## means the A specified in the two macros.

• A##_init initialize lookup table
• A##_add add a value
• A##_add_count add a specified number of counts to a value
• A##_del delete a value
• A##_has check if a value exists
• A##_find find position i and j of a value (to access in lookup table: N.buckets[i].items[j])
• A##_free free lookup table
• A##_clear clear lookup table (reset but don't free)
• A##_dump dump everything unsorted (arr is required, counts is optional)
• A##_clear check if table is empty

todo so I don't forget

• A##_join and A##_join_threaded ...