Implement istr.

1 files changed, 25 insertions, 5 deletions

diff --git a/src/libzisp/gc.zig b/src/libzisp/gc.zig
index 92b4387..46ac091 100644
--- a/src/libzisp/gc.zig
+++ b/src/libzisp/gc.zig
@@ -5,18 +5,38 @@ const value = @import("value.zig");
 const Value = value.Value;
 const Hval = value.Hval;
 
-var _gpa: std.heap.GeneralPurposeAllocator(.{}) = .init;
+var _gpa = std.heap.GeneralPurposeAllocator(.{}).init;
 const gpa = _gpa.allocator();
 
-var cpool = std.heap.MemoryPool([2]Value).init(gpa);
+// Cons cells
+
+var cons_pool = std.heap.MemoryPool([2]Value).init(gpa);
 
 pub fn cons(v1: Value, v2: Value) *[2]Value {
-    const mem = cpool.create() catch @panic("OOM");
+    const mem = cons_pool.create() catch @panic("OOM");
     mem[0] = v1;
     mem[1] = v2;
     return mem;
 }
 
-pub fn alloc(count: usize) []Hval {
-    return gpa.alloc(Hval, count) catch @panic("OOM");
+// Interned strings
+
+var istr_pool = std.hash_map.StringHashMap(void).init(gpa);
+
+pub fn intern(header: value.seq.Header, str: []const u8) [*]Hval {
+    comptime {
+        std.debug.assert(@sizeOf(value.seq.Header) == 8);
+    }
+    const size = str.len + 8;
+    const copy = gpa.alloc(u8, size) catch @panic("OOM");
+    const header_bytes: [8]u8 = @bitCast(header);
+    @memcpy(copy[0..8], &header_bytes);
+    @memcpy(copy[8..size], str);
+    const entry = istr_pool.getOrPutValue(copy, {}) catch @panic("OOM");
+    return @ptrCast(entry.key_ptr);
+}
+
+pub fn istrHeader(ptr: [*]Hval) *value.seq.Header {
+    const entry_key: *[]u8 = @ptrCast(ptr);
+    return @alignCast(@ptrCast(entry_key.ptr));
 }