1 files changed, 53 insertions, 0 deletions
diff --git a/lib/std/heap/logging_allocator.zig b/lib/std/heap/logging_allocator.zig
new file mode 100644
index 0000000000..c1f09a1aad
--- /dev/null
+++ b/lib/std/heap/logging_allocator.zig
@@ -0,0 +1,53 @@
+const std = @import("../std.zig");
+const Allocator = std.mem.Allocator;
+
+const AnyErrorOutStream = std.io.OutStream(anyerror);
+
+/// This allocator is used in front of another allocator and logs to the provided stream
+/// on every call to the allocator. Stream errors are ignored.
+/// If https://github.com/ziglang/zig/issues/2586 is implemented, this API can be improved.
+pub const LoggingAllocator = struct {
+    allocator: Allocator,
+    parent_allocator: *Allocator,
+    out_stream: *AnyErrorOutStream,
+
+    const Self = @This();
+
+    pub fn init(parent_allocator: *Allocator, out_stream: *AnyErrorOutStream) Self {
+        return Self{
+            .allocator = Allocator{
+                .reallocFn = realloc,
+                .shrinkFn = shrink,
+            },
+            .parent_allocator = parent_allocator,
+            .out_stream = out_stream,
+        };
+    }
+
+    fn realloc(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) ![]u8 {
+        const self = @fieldParentPtr(Self, "allocator", allocator);
+        if (old_mem.len == 0) {
+            self.out_stream.print("allocation of {} ", new_size) catch {};
+        } else {
+            self.out_stream.print("resize from {} to {} ", old_mem.len, new_size) catch {};
+        }
+        const result = self.parent_allocator.reallocFn(self.parent_allocator, old_mem, old_align, new_size, new_align);
+        if (result) |buff| {
+            self.out_stream.print("success!\n") catch {};
+        } else |err| {
+            self.out_stream.print("failure!\n") catch {};
+        }
+        return result;
+    }
+
+    fn shrink(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 {
+        const self = @fieldParentPtr(Self, "allocator", allocator);
+        const result = self.parent_allocator.shrinkFn(self.parent_allocator, old_mem, old_align, new_size, new_align);
+        if (new_size == 0) {
+            self.out_stream.print("free of {} bytes success!\n", old_mem.len) catch {};
+        } else {
+            self.out_stream.print("shrink from {} bytes to {} bytes success!\n", old_mem.len, new_size) catch {};
+        }
+        return result;
+    }
+};