1const std = @import("std.zig");
2const StringHashMap = std.StringHashMap;
3const mem = std.mem;
4const Allocator = mem.Allocator;
5const testing = std.testing;
6
7/// BufMap copies keys and values before they go into the map and
8/// frees them when they get removed.
9pub const BufMap = struct {
10 hash_map: BufMapHashMap,
11
12 const BufMapHashMap = StringHashMap([]const u8);
13
14 /// Create a BufMap backed by a specific allocator.
15 /// That allocator will be used for both backing allocations
16 /// and string deduplication.
17 pub fn init(allocator: Allocator) BufMap {
18 return .{ .hash_map = BufMapHashMap.init(allocator) };
19 }
20
21 /// Free the backing storage of the map, as well as all
22 /// of the stored keys and values.
23 pub fn deinit(self: *BufMap) void {
24 var it = self.hash_map.iterator();
25 while (it.next()) |entry| {
26 self.free(entry.key_ptr.*);
27 self.free(entry.value_ptr.*);
28 }
29
30 self.hash_map.deinit();
31 }
32
33 /// Same as `put` but the key and value become owned by the BufMap rather
34 /// than being copied.
35 /// If `putMove` fails, the ownership of key and value does not transfer.
36 pub fn putMove(self: *BufMap, key: []u8, value: []u8) !void {
37 const get_or_put = try self.hash_map.getOrPut(key);
38 if (get_or_put.found_existing) {
39 self.free(get_or_put.key_ptr.*);
40 self.free(get_or_put.value_ptr.*);
41 get_or_put.key_ptr.* = key;
42 }
43 get_or_put.value_ptr.* = value;
44 }
45
46 /// `key` and `value` are copied into the BufMap.
47 pub fn put(self: *BufMap, key: []const u8, value: []const u8) !void {
48 const value_copy = try self.copy(value);
49 errdefer self.free(value_copy);
50 const get_or_put = try self.hash_map.getOrPut(key);
51 if (get_or_put.found_existing) {
52 self.free(get_or_put.value_ptr.*);
53 } else {
54 get_or_put.key_ptr.* = self.copy(key) catch |err| {
55 _ = self.hash_map.remove(key);
56 return err;
57 };
58 }
59 get_or_put.value_ptr.* = value_copy;
60 }
61
62 /// Find the address of the value associated with a key.
63 /// The returned pointer is invalidated if the map resizes.
64 pub fn getPtr(self: BufMap, key: []const u8) ?*[]const u8 {
65 return self.hash_map.getPtr(key);
66 }
67
68 /// Return the map's copy of the value associated with
69 /// a key. The returned string is invalidated if this
70 /// key is removed from the map.
71 pub fn get(self: BufMap, key: []const u8) ?[]const u8 {
72 return self.hash_map.get(key);
73 }
74
75 /// Removes the item from the map and frees its value.
76 /// This invalidates the value returned by get() for this key.
77 pub fn remove(self: *BufMap, key: []const u8) void {
78 const kv = self.hash_map.fetchRemove(key) orelse return;
79 self.free(kv.key);
80 self.free(kv.value);
81 }
82
83 /// Returns the number of KV pairs stored in the map.
84 pub fn count(self: BufMap) BufMapHashMap.Size {
85 return self.hash_map.count();
86 }
87
88 /// Returns an iterator over entries in the map.
89 pub fn iterator(self: *const BufMap) BufMapHashMap.Iterator {
90 return self.hash_map.iterator();
91 }
92
93 fn free(self: BufMap, value: []const u8) void {
94 self.hash_map.allocator.free(value);
95 }
96
97 fn copy(self: BufMap, value: []const u8) ![]u8 {
98 return self.hash_map.allocator.dupe(u8, value);
99 }
100};
101
102test "BufMap" {
103 const allocator = std.testing.allocator;
104 var bufmap = BufMap.init(allocator);
105 defer bufmap.deinit();
106
107 try bufmap.put("x", "1");
108 try testing.expect(mem.eql(u8, bufmap.get("x").?, "1"));
109 try testing.expect(1 == bufmap.count());
110
111 try bufmap.put("x", "2");
112 try testing.expect(mem.eql(u8, bufmap.get("x").?, "2"));
113 try testing.expect(1 == bufmap.count());
114
115 try bufmap.put("x", "3");
116 try testing.expect(mem.eql(u8, bufmap.get("x").?, "3"));
117 try testing.expect(1 == bufmap.count());
118
119 bufmap.remove("x");
120 try testing.expect(0 == bufmap.count());
121
122 try bufmap.putMove(try allocator.dupe(u8, "k"), try allocator.dupe(u8, "v1"));
123 try bufmap.putMove(try allocator.dupe(u8, "k"), try allocator.dupe(u8, "v2"));
124}