From 7d5b4ea151e8df1861f5948f0d45830fee7ca1b4 Mon Sep 17 00:00:00 2001
From: sfja <sfja2004@gmail.com>
Date: Fri, 2 Oct 2026 04:37:30 +0200
Subject: [PATCH] add keymap

---
 collection.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 collection.h | 15 ++++++++
 main.c       | 11 ++++++
 3 files changed, 123 insertions(+)

diff --git a/collection.c b/collection.c
index 94edff4..022091c 100644
--- a/collection.c
+++ b/collection.c
@@ -232,3 +232,100 @@ char* arena_strdup(Arena* a, const char* str)
     strcpy(p, str);
     return p;
 }
+
+struct KeymapEntry {
+    KeymapKey key;
+    unsigned char value[];
+};
+
+void keymap_init(Keymap* m, size_t elem_size)
+{
+    size_t entry_size = sizeof(KeymapEntry) + (elem_size + 7ul & ~7ul);
+
+    *m = (Keymap) {
+        ARRAY_FIELD_INIT(entries),
+        .elem_size = elem_size,
+        .entry_size = entry_size,
+        .temp_entry = malloc(entry_size),
+    };
+}
+
+void keymap_deinit(Keymap* m)
+{
+    if (m->entries)
+        free(m->entries);
+    free(m->temp_entry);
+}
+
+static KeymapEntry* keymap_idx(Keymap* m, size_t idx)
+{
+    return (KeymapEntry*)((unsigned char*)m->entries + m->entry_size * idx);
+}
+
+struct SearchResult {
+    KeymapEntry* entry;
+    size_t idx;
+};
+
+static struct SearchResult keymap_search(
+    Keymap* m, size_t begin, size_t end, KeymapKey key)
+{
+    if (begin == end)
+        return (struct SearchResult) { nullptr, begin };
+
+    size_t middle = (end - begin) / 2 + begin;
+    KeymapEntry* entry = keymap_idx(m, middle);
+
+    if (entry->key == key)
+        return (struct SearchResult) { entry, middle };
+
+    return key < entry->key ? keymap_search(m, begin, middle, key)
+                            : keymap_search(m, middle + 1, end, key);
+}
+
+void keymap_set(Keymap* m, KeymapKey key, void* value)
+{
+    struct SearchResult result = keymap_search(m, 0, m->entries_size, key);
+
+    if (result.entry) {
+        memcpy(result.entry->value, value, m->elem_size);
+        return;
+    }
+
+    printf("index = %ld\n", result.idx);
+
+    if (m->entries_size) {
+        if (keymap_idx(m, result.idx)->key < key) {
+            printf("key is bigger\n");
+        } else {
+            printf("key is smaller\n");
+        }
+    }
+
+    KeymapEntry* entry = m->temp_entry;
+    memset(entry, 0, m->entry_size);
+
+    array_push((void**)&m->entries,
+        &m->entries_cap,
+        &m->entries_size,
+        entry,
+        m->entry_size);
+
+    entry->key = key;
+    memcpy(&entry->value, value, m->elem_size);
+
+    if (result.idx < m->entries_size - 1) {
+        memmove(keymap_idx(m, result.idx + 1),
+            keymap_idx(m, result.idx),
+            (m->entries_size - result.idx - 1) * m->entry_size);
+    }
+
+    memcpy(keymap_idx(m, result.idx), entry, m->entry_size);
+
+    for (size_t i = 0; i < m->entries_size; ++i) {
+        KeymapEntry* entry = keymap_idx(m, i);
+        printf("  %ld -> %d\n", entry->key, *(int*)entry->value);
+    }
+}
+
+void* keymap_get(Keymap* m, KeymapKey key);
diff --git a/collection.h b/collection.h
index c49f389..408952d 100644
--- a/collection.h
+++ b/collection.h
@@ -92,4 +92,19 @@ char* arena_strdup(Arena* a, const char* str);
         (ELEM_PTR),                                                            \
         sizeof(*(ELEM_PTR)))
 
+typedef size_t KeymapKey;
+typedef struct KeymapEntry KeymapEntry;
+
+typedef struct {
+    ARRAY_FIELD(KeymapEntry, entries);
+    size_t elem_size;
+    size_t entry_size;
+    KeymapEntry* temp_entry;
+} Keymap;
+
+void keymap_init(Keymap* m, size_t elem_size);
+void keymap_deinit(Keymap* m);
+void keymap_set(Keymap* m, KeymapKey key, void* value);
+void* keymap_get(Keymap* m, KeymapKey key);
+
 #endif
diff --git a/main.c b/main.c
index 7065576..cea8a8e 100644
--- a/main.c
+++ b/main.c
@@ -100,4 +100,15 @@ int main(int argc, char* argv[])
         arena_deinit(&ast_arena);
         arena_deinit(&sym_arena);
     }
+
+    Keymap map;
+    keymap_init(&map, sizeof(int));
+
+    int a[] = { 3, 1, 4, 1 };
+    keymap_set(&map, 4, &a[3]);
+    keymap_set(&map, 3, &a[2]);
+    keymap_set(&map, 2, &a[1]);
+    keymap_set(&map, 1, &a[0]);
+
+    keymap_deinit(&map);
 }