WIP: Add bump allocator

Signed-off-by: Ran Benita <[email protected]>

meson.build

@@ -232,6 +232,8 @@ libxkbcommon_sources = [
     'src/xkbcomp/xkbcomp-priv.h',
     'src/atom.c',
     'src/atom.h',
+    'src/bump.c',
+    'src/bump.h',
     'src/context.c',
     'src/context.h',
     'src/context-priv.c',

src/bump.c

@@ -0,0 +1,81 @@
+#include "config.h"
+
+#include <assert.h>
+#include <stdalign.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "bump.h"
+
+ // Size of initial chunk.
+#define INITIAL_CHUNK_SIZE 4096
+// Factor by which to grow chunk sizes.
+#define GROWTH_FACTOR 2
+
+static struct bump_chunk dummy_chunk = {
+    .size = 0,
+    .ptr = 0,
+    .prev = NULL,
+};
+
+void
+bump_init(struct bump *bump)
+{
+    // Create the first chunk
+    bump->current = &dummy_chunk;
+}
+
+void *
+bump_alloc(struct bump *bump, size_t size)
+{
+    assert(size <= INITIAL_CHUNK_SIZE);
+
+    /* Align size to the max alignemnt. */
+    const size_t max_alignment = alignof(max_align_t);
+    size = (size + max_alignment - 1) & ~(max_alignment - 1);
+
+    struct bump_chunk *chunk = bump->current;
+
+    /* Check if there is enough space in the current chunk. */
+    if ((size_t) (chunk->ptr - chunk->memory) + size > chunk->size) {
+        /* Not enough space, create a new chunk. */
+        size_t new_chunk_size = chunk->size == 0 ? INITIAL_CHUNK_SIZE : chunk->size * GROWTH_FACTOR;
+        struct bump_chunk *new_chunk = aligned_alloc(max_alignment, sizeof(*new_chunk) + new_chunk_size);
+        if (!new_chunk) {
+            return NULL;
+        }
+        new_chunk->size = new_chunk_size;
+        new_chunk->ptr = new_chunk->memory;
+        new_chunk->prev = chunk;
+
+        bump->current = new_chunk;
+        chunk = new_chunk;
+    }
+
+    void *ptr = chunk->ptr;
+    chunk->ptr += size;
+    return ptr;
+}
+
+char *
+bump_strdup(struct bump *bump, const char *s)
+{
+    size_t len = strlen(s) + 1;
+    char *new = bump_alloc(bump, len);
+    if (!new) {
+        return NULL;
+    }
+    memcpy(new, s, len);
+    return new;
+}
+
+void
+bump_uninit(struct bump *bump)
+{
+    struct bump_chunk *chunk = bump->current;
+    while (chunk != &dummy_chunk) {
+        struct bump_chunk *prev = chunk->prev;
+        free(chunk);
+        chunk = prev;
+    }
+}

src/bump.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdalign.h>
+
+struct bump_chunk {
+    // Size of the chunk.
+    size_t size;
+    // Next free address in memory.
+    char *ptr;
+    // Pointer to the previous chunk.
+    struct bump_chunk *prev;
+    // Pointer to the allocated memory.
+    alignas(max_align_t) char memory[0];
+};
+
+struct bump {
+    struct bump_chunk *current;
+};
+
+void
+bump_init(struct bump *bump);
+void
+bump_uninit(struct bump *bump);
+void
+*bump_alloc(struct bump *bump, size_t size);
+char *
+bump_strdup(struct bump *bump, const char *s);