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std.SegmentedList: cleaner separation of capacity functions

master
Andrew Kelley 2018-05-07 10:34:38 -04:00
parent 78ba3b8485
commit 2f633452bb
1 changed files with 24 additions and 13 deletions
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37
std/segmented_list.zig
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@ -139,22 +139,23 @@ pub fn SegmentedList(comptime T: type, comptime prealloc_item_count: usize) type
pub fn addOne(self: &Self) !&T {
const new_length = self.len + 1;
try self.setCapacity(new_length);
try self.growCapacity(new_length);
const result = self.uncheckedAt(self.len);
self.len = new_length;
return result;
}
/// Grows or shrinks capacity to match usage.
pub fn setCapacity(self: &Self, new_capacity: usize) !void {
if (new_capacity <= prealloc_item_count) {
const len = ShelfIndex(self.dynamic_segments.len);
if (len == 0) return;
self.freeShelves(len, 0);
self.allocator.free(self.dynamic_segments);
self.dynamic_segments = []&T{};
return;
if (new_capacity <= usize(1) << (prealloc_exp + self.dynamic_segments.len)) {
return self.shrinkCapacity(new_capacity);
} else {
return self.growCapacity(new_capacity);
}
}
/// Only grows capacity, or retains current capacity
pub fn growCapacity(self: &Self, new_capacity: usize) !void {
const new_cap_shelf_count = shelfCount(new_capacity);
const old_shelf_count = ShelfIndex(self.dynamic_segments.len);
if (new_cap_shelf_count > old_shelf_count) {
@ -167,20 +168,30 @@ pub fn SegmentedList(comptime T: type, comptime prealloc_item_count: usize) type
while (i < new_cap_shelf_count) : (i += 1) {
self.dynamic_segments[i] = (try self.allocator.alloc(T, shelfSize(i))).ptr;
}
}
}
/// Only shrinks capacity or retains current capacity
pub fn shrinkCapacity(self: &Self, new_capacity: usize) void {
if (new_capacity <= prealloc_item_count) {
const len = ShelfIndex(self.dynamic_segments.len);
self.freeShelves(len, 0);
self.allocator.free(self.dynamic_segments);
self.dynamic_segments = []&T{};
return;
}
const new_cap_shelf_count = shelfCount(new_capacity);
const old_shelf_count = ShelfIndex(self.dynamic_segments.len);
assert(new_cap_shelf_count <= old_shelf_count);
if (new_cap_shelf_count == old_shelf_count) {
return;
}
self.freeShelves(old_shelf_count, new_cap_shelf_count);
self.dynamic_segments = self.allocator.shrink(&T, self.dynamic_segments, new_cap_shelf_count);
}
pub fn shrinkCapacity(self: &Self, new_capacity: usize) void {
assert(new_capacity <= prealloc_item_count or shelfCount(new_capacity) <= self.dynamic_segments.len);
self.setCapacity(new_capacity) catch unreachable;
}
pub fn uncheckedAt(self: &Self, index: usize) &T {
if (index < prealloc_item_count) {
return &self.prealloc_segment[index];