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alloc

SafeAllocator.alloc

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

File

lib/std/heap/SafeAllocator.zig:1053

Code

fn alloc(ctx: *anyopaque, len: usize, alignment: Alignment, ra: usize) ?[*]u8 {
    assert(len != 0);

    const s: *SafeAllocator = @ptrCast(@alignCast(ctx));
    const t = s.acquireThread();
    defer t.mutex.unlock();

    if (s.isLargeOrOom(len, alignment) catch return null) {
        @branchHint(.unlikely);

        const entry = s.newAllocEntry(t, ra) catch return null;
        const alloc_len = AllocFooter.allocLenLarge(s, len);
        const alloc_align = AllocFooter.allocAlign(alignment);
        const alloc_ptr = s.backing.rawAlloc(alloc_len, alloc_align, ra) orelse {
            freeAllocEntry(t, entry);
            return null;
        };

        const footer = AllocFooter.populate(
            @alignCast(alloc_ptr[0..alloc_len]),
            len,
            alignment,
            ra,
            true,
            false,
            .{ .large_entry = entry },
            s,
        );
        entry.* = .fromLargeAlloc(footer);

        return alloc_ptr;
    }

    if (t.fill_bucket) |bucket| {
        @branchHint(.likely);
        if (s.allocBucket(t, bucket, len, alignment, ra)) |ptr| {
            @branchHint(.likely);
            return ptr;
        }
    }
    t.fill_bucket = null; // In case of OOM below, this bucket will still be unusable for future
    // allocations.

    const entry = s.newAllocEntry(t, ra) catch return null;
    const bucket: *Bucket = @ptrCast(@alignCast(s.backing.rawAlloc(
        s.bucketSize(),
        @fromBackingInt(@intCast(s.bucket_size_log2)),
        ra,
    ) orelse {
        freeAllocEntry(t, entry);
        return null;
    }));
    bucket.* = .{
        .entry = entry,
        // No atomic stores necessary because this thread is the
        // first to atomically update these below in allocBucket.
        .alloc_count = .{ .filling = true, .n = 0 },
        .fill = .{ .at = @sizeOf(Bucket), .last_is_extended = false },
    };
    entry.* = .fromBucket(bucket);

    t.fill_bucket = bucket;
    return s.allocBucket(t, bucket, len, alignment, ra);
}