elf: make TableSection a generic construct

1 files changed, 65 insertions, 0 deletions

diff --git a/src/link/table_section.zig b/src/link/table_section.zig
new file mode 100644
index 0000000000..4d5838adb9
--- /dev/null
+++ b/src/link/table_section.zig
@@ -0,0 +1,65 @@
+pub fn TableSection(comptime Entry: type) type {
+    return struct {
+        entries: std.ArrayListUnmanaged(Entry) = .{},
+        free_list: std.ArrayListUnmanaged(Index) = .{},
+        lookup: std.AutoHashMapUnmanaged(Entry, Index) = .{},
+
+        pub fn deinit(self: *Self, allocator: Allocator) void {
+            self.entries.deinit(allocator);
+            self.free_list.deinit(allocator);
+            self.lookup.deinit(allocator);
+        }
+
+        pub fn allocateEntry(self: *Self, allocator: Allocator, entry: Entry) Allocator.Error!Index {
+            try self.entries.ensureUnusedCapacity(allocator, 1);
+            const index = blk: {
+                if (self.free_list.popOrNull()) |index| {
+                    log.debug("  (reusing entry index {d})", .{index});
+                    break :blk index;
+                } else {
+                    log.debug("  (allocating entry at index {d})", .{self.entries.items.len});
+                    const index = @intCast(u32, self.entries.items.len);
+                    _ = self.entries.addOneAssumeCapacity();
+                    break :blk index;
+                }
+            };
+            self.entries.items[index] = entry;
+            try self.lookup.putNoClobber(allocator, entry, index);
+            return index;
+        }
+
+        pub fn freeEntry(self: *Self, allocator: Allocator, entry: Entry) void {
+            const index = self.lookup.get(entry) orelse return;
+            self.free_list.append(allocator, index) catch {};
+            self.entries.items[index] = undefined;
+            _ = self.lookup.remove(entry);
+        }
+
+        pub fn count(self: Self) usize {
+            return self.entries.items.len;
+        }
+
+        pub fn format(
+            self: Self,
+            comptime unused_format_string: []const u8,
+            options: std.fmt.FormatOptions,
+            writer: anytype,
+        ) !void {
+            _ = options;
+            comptime assert(unused_format_string.len == 0);
+            try writer.writeAll("SectionTable:\n");
+            for (self.entries.items, 0..) |entry, i| {
+                try writer.print("  {d} => {}\n", .{ i, entry });
+            }
+        }
+
+        const Self = @This();
+        pub const Index = u32;
+    };
+}
+
+const std = @import("std");
+const assert = std.debug.assert;
+const log = std.log.scoped(.link);
+
+const Allocator = std.mem.Allocator;