Zig 0.17.0-dev (Split by item)

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alloc

BrkAllocator.alloc

fn alloc(ctx: *anyopaque, len: usize, alignment: Alignment, return_address: usize) ?[*]u8

File

lib/std/heap/BrkAllocator.zig:50

Code

fn alloc(ctx: *anyopaque, len: usize, alignment: Alignment, return_address: usize) ?[*]u8 {
    _ = ctx;
    _ = return_address;
    // Make room for the freelist next pointer.
    const actual_len = @max(len +| @sizeOf(usize), alignment.toByteUnits());
    const slot_size = math.ceilPowerOfTwo(usize, actual_len) catch return null;
    const class = math.log2(slot_size) - min_class;
    if (class < size_class_count) {
        const addr = a: {
            const top_free_ptr = global.frees[class];
            if (top_free_ptr != 0) {
                const node: *usize = @ptrFromInt(top_free_ptr + (slot_size - @sizeOf(usize)));
                global.frees[class] = node.*;
                break :a top_free_ptr;
            }

            const next_addr = global.next_addrs[class];
            if (next_addr % bigpage_size == 0) {
                const addr = allocBigPages(1);
                if (addr == 0) return null;
                //std.debug.print("allocated fresh slot_size={d} class={d} addr=0x{x}\n", .{
                //    slot_size, class, addr,
                //});
                global.next_addrs[class] = addr + slot_size;
                break :a addr;
            } else {
                global.next_addrs[class] = next_addr + slot_size;
                break :a next_addr;
            }
        };
        return @ptrFromInt(addr);
    }
    const bigpages_needed = bigPagesNeeded(actual_len);
    return @ptrFromInt(allocBigPages(bigpages_needed));
}