datastruct: make CircBuf use the assumeCapacity pattern

src/datastruct/circ_buf.zig

@@ -91,15 +91,24 @@ pub fn CircBuf(comptime T: type, comptime default: T) type {
             self.full = self.head == self.tail;
         }
 
-        /// Append a slice to the buffer. If the buffer cannot fit the
-        /// entire slice then an error will be returned. It is up to the
-        /// caller to rotate the circular buffer if they want to overwrite
-        /// the oldest data.
-        pub fn appendSlice(
+        /// Append a single value to the buffer, assuming there is capacity.
+        pub fn appendAssumeCapacity(self: *Self, v: T) void {
+            assert(!self.full);
+            self.storage[self.head] = v;
+            self.head += 1;
+            if (self.head >= self.storage.len) self.head = 0;
+            self.full = self.head == self.tail;
+        }
+
+        /// Append a slice to the buffer.
+        pub fn appendSliceAssumeCapacity(
             self: *Self,
             slice: []const T,
-        ) Allocator.Error!void {
-            const storage = self.getPtrSlice(self.len(), slice.len);
+        ) void {
+            const storage = self.getPtrSlice(
+                self.len(),
+                slice.len,
+            );
             fastmem.copy(T, storage[0], slice[0..storage[0].len]);
             fastmem.copy(T, storage[1], slice[storage[0].len..]);
         }
@@ -456,7 +465,7 @@ test "CircBuf append slice" {
     var buf = try Buf.init(alloc, 5);
     defer buf.deinit(alloc);
 
-    try buf.appendSlice("hello");
+    buf.appendSliceAssumeCapacity("hello");
     {
         var it = buf.iterator(.forward);
         try testing.expect(it.next().?.* == 'h');
@@ -486,7 +495,7 @@ test "CircBuf append slice with wrap" {
     try testing.expect(!buf.full);
     try testing.expectEqual(@as(usize, 2), buf.len());
 
-    try buf.appendSlice("AB");
+    buf.appendSliceAssumeCapacity("AB");
     {
         var it = buf.iterator(.forward);
         try testing.expect(it.next().?.* == 0);

src/terminal/search/sliding_window.zig

@@ -444,8 +444,8 @@ pub const SlidingWindow = struct {
         try self.meta.ensureUnusedCapacity(self.alloc, 1);
 
         // Append our new node to the circular buffer.
-        try self.data.appendSlice(written);
-        try self.meta.append(meta);
+        self.data.appendSliceAssumeCapacity(written);
+        self.meta.appendAssumeCapacity(meta);
 
         self.assertIntegrity();
         return written.len;