The Macro Library

Header‑only, zero‑allocation building blocks for high‑performance C.
Generate type‑safe, inlined algorithms without dragging in a runtime or templates. Pick a comparator style once (via macro_cmp.h), then stamp out fast, specialized functions for your types.

• Sort: macro_sort — inlined introsort with early “array shape” checks
• Search: macro_bsearch — binary search family (first/last/lb/ub/floor/ceiling)
• Map: macro_map — intrusive red–black tree maps & multimaps
• Heap: macro_heap — min/max heaps over your arrays
• Test & utils: tiny test harness, time, conversions, bit ops

Why this library?

• Speed without ceremony. Functions are generated for your element type and comparator. The compiler inlines everything; no function‑pointer calls in hot loops.
• Small & portable. Pure headers. No linker tricks. Works in C (and C++ via extern "C").
• One comparator model. macro_cmp.h standardizes signatures (less_*, cmp_*, with or without context), so sort/search/map/heap agree on how to compare.

What’s included (at a glance)

Docs:

• README.macro_sort.md
• README.macro_bsearch.md
• README.macro_map.md
• README.macro_cmp.md
• README.macro_heap.md
• README.macro_test.md
• README.macro_time.md
• README.macro_to.md

Algorithmic highlights (why macro_sort is fast)

macro_sort is introsort with two key tweaks:

1. Early “array shape” check. Before partitioning, it probes first/middle/last (and a few neighbors) to detect already sorted or fully reversed inputs.

   • Sorted → linear verification and return
   • Reversed → linear reverse and return

2. Comparator inlining. Your less/cmp is compiled into the call site; no indirect calls, better branch prediction.

Plus the usual wins: median‑of‑three–style pivoting, tiny partitions via insertion sort, and a heapsort fallback to guarantee O(n log n).

Performance (kept from the original README)

macro_sort vs qsort

macro_sort vs std::sort

macro_sort vs std::sort (dynamic comparator)

Results show large wins on ordered and reversed inputs, and strong performance on random data—especially when the C++ path can’t inline the comparator.

Quick starts

Sort (baked comparator)

#include "the-macro-library/macro_sort.h"

static inline bool int_less(const int *a, const int *b) { return *a < *b; }
macro_sort(sort_ints, int, int_less);   // -> void sort_ints(int *base, size_t n);

int a[] = {5,4,3,1,2};
sort_ints(a, sizeof a / sizeof a[0]);

Binary search (KV)

#include "the-macro-library/macro_bsearch.h"

typedef struct { int key, payload; } Item;
static int kv_cmp(const int *k, const Item *v){ return (*k > v->key) - (*k < v->key); }

macro_bsearch_lower_bound_kv(item_lb, int, Item, kv_cmp);

Item arr[] = { {1,10}, {3,30}, {3,31}, {8,80} };
int k = 3;
Item *lb = item_lb(&k, arr, sizeof arr/sizeof arr[0]);

Intrusive map (red–black tree)

#include "the-macro-library/macro_map.h"
typedef struct Node { macro_map_t link; int key, val; } Node;

static int node_cmp(const Node *a, const Node *b) { return (a->key > b->key) - (a->key < b->key); }
static int kv_cmp  (const int  *k, const Node *n) { return (*k > n->key)  - (*k < n->key); }

macro_map_insert        (map_insert,      Node, node_cmp);
macro_map_find_kv       (map_find_by_key, int,  Node, kv_cmp);

macro_map_t *root = NULL;
Node n = {.key=42,.val=7};
map_insert(&root, &n);
int k=42; Node *hit = map_find_by_key(root, &k);

More examples live in examples/ and each module’s README.

Installation

This library is header‑only; you can vendor the headers and include them.

For convenience (examples, tests, tools):

Dependencies

• A cmake library for the CMake build

Build

git clone https://github.com/andycurtis-public/the-macro-library.git
cd the-macro-library

mkdir -p build && cd build
cmake ..
make            # builds examples and tools
# optional:
make install

Debugging macros (stepping through code)

Macros don’t step nicely in a debugger. Use the included script to materialize generated code:

bin/convert-macros-to-code examples/demo/sort_ints.c > sort_ints_expanded.c
# compile & debug the expanded C file

This preserves readability and removes the dependency on the headers for that TU.

Design notes

• Header‑only: drop into any C project; no runtime library to link.
• Type‑safe generation: you name the function and type; the macro emits a real symbol with a concrete signature.
• Comparator styles: shared across sort/search/map/heap. Choose once (less_no_arg, cmp_no_arg, *_arg, arg_*, operator styles) and reuse everywhere. See README.macro_cmp.md.

License

SPDX-License-Identifier: Apache-2.0
© 2019–2025 Andy Curtis, © 2024–2025 Knode.ai

If something feels rough or surprising, open an issue or read the single headers — they’re meant to be understood.