authorgravatar for johnnymarler@gmail.comJonathan Marler <johnnymarler@gmail.com> 2020-06-28 23:42:42-06:00
committergravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2020-06-29 05:12:30-04:00
log35e8876c23e53c11115c78ff3984effa965a8cca
tree03d4d821bdab44ba48cc9707d5e265362bc69973
parent1eed0cf0f328372ddd8938ad3a95e37cb15ce6fb

Revert "arena_allocator: refactor and use full capacity"

This reverts commit e120b07a524f1accd4975f5206018c61c4be9345.

1 files changed, 25 insertions(+), 23 deletions(-)

lib/std/heap/arena_allocator.zig+25-23
...@@ -15,7 +15,6 @@ pub const ArenaAllocator = struct {...@@ -15,7 +15,6 @@ pub const ArenaAllocator = struct {
15 /// as a memory-saving optimization.15 /// as a memory-saving optimization.
16 pub const State = struct {16 pub const State = struct {
17 buffer_list: std.SinglyLinkedList([]u8) = @as(std.SinglyLinkedList([]u8), .{}),17 buffer_list: std.SinglyLinkedList([]u8) = @as(std.SinglyLinkedList([]u8), .{}),
18 /// The first available index in the front buffer of `buffer_list`
19 end_index: usize = 0,18 end_index: usize = 0,
2019
21 pub fn promote(self: State, child_allocator: *Allocator) ArenaAllocator {20 pub fn promote(self: State, child_allocator: *Allocator) ArenaAllocator {
...@@ -46,36 +45,39 @@ pub const ArenaAllocator = struct {...@@ -46,36 +45,39 @@ pub const ArenaAllocator = struct {
46 }45 }
47 }46 }
4847
49 fn getBufNodeAddr(buf: []u8) usize {48 fn createNode(self: *ArenaAllocator, prev_len: usize, minimum_size: usize) !*BufNode {
50 return mem.alignBackward(@ptrToInt(buf.ptr) + buf.len - @sizeOf(BufNode), @alignOf(BufNode));49 const actual_min_size = minimum_size + (@sizeOf(BufNode) + 16);
51 }50 const big_enough_len = prev_len + actual_min_size;
5251 const len = big_enough_len + big_enough_len / 2;
53 fn allocBuf(self: *ArenaAllocator, len: usize, ptr_align: u29) ![]u8 {52 const buf = try self.child_allocator.alignedAlloc(u8, @alignOf(BufNode), len);
54 const alloc_len = len + @sizeOf(BufNode) + @alignOf(BufNode) - 1;53 const buf_node_slice = mem.bytesAsSlice(BufNode, buf[0..@sizeOf(BufNode)]);
55 const buf = try self.child_allocator.callAllocFn(alloc_len, ptr_align, 1);54 const buf_node = &buf_node_slice[0];
56 const buf_node = @intToPtr(*BufNode, getBufNodeAddr(buf));55 buf_node.* = BufNode{
57 buf_node.* = .{ .data = buf, .next = null };56 .data = buf,
58 assert(@ptrToInt(buf_node) - @ptrToInt(buf.ptr) >= len);57 .next = null,
58 };
59 self.state.buffer_list.prepend(buf_node);59 self.state.buffer_list.prepend(buf_node);
60 self.state.end_index = len;60 self.state.end_index = 0;
61 return buf[0..len];61 return buf_node;
62 }62 }
6363
64 fn alloc(allocator: *Allocator, n: usize, ptr_align: u29, len_align: u29) ![]u8 {64 fn alloc(allocator: *Allocator, n: usize, ptr_align: u29, len_align: u29) ![]u8 {
65 const self = @fieldParentPtr(ArenaAllocator, "allocator", allocator);65 const self = @fieldParentPtr(ArenaAllocator, "allocator", allocator);
6666
67 if (self.state.buffer_list.first) |node_full_buf| {67 var cur_node = if (self.state.buffer_list.first) |first_node| first_node else try self.createNode(0, n + ptr_align);
68 assert(self.state.end_index > 0);68 while (true) {
69 const cur_buf = node_full_buf.data[0..69 const cur_buf = cur_node.data[@sizeOf(BufNode)..];
70 getBufNodeAddr(node_full_buf.data) - @ptrToInt(node_full_buf.data.ptr)];
71 const addr = @ptrToInt(cur_buf.ptr) + self.state.end_index;70 const addr = @ptrToInt(cur_buf.ptr) + self.state.end_index;
72 const aligned_index = self.state.end_index + (mem.alignForward(addr, ptr_align) - addr);71 const adjusted_addr = mem.alignForward(addr, ptr_align);
73 const aligned_end_index = aligned_index + n;72 const adjusted_index = self.state.end_index + (adjusted_addr - addr);
74 if (aligned_end_index <= cur_buf.len) {73 const new_end_index = adjusted_index + n;
75 self.state.end_index = aligned_end_index;74 if (new_end_index > cur_buf.len) {
76 return cur_buf[aligned_index..aligned_end_index];75 cur_node = try self.createNode(cur_buf.len, n + ptr_align);
76 continue;
77 }77 }
78 const result = cur_buf[adjusted_index..new_end_index];
79 self.state.end_index = new_end_index;
80 return result;
78 }81 }
79 return try self.allocBuf(n, ptr_align);
80 }82 }
81};83};