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Merge pull request #180 from SamTebbs33/feature/update-allocator-interface

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Update to new allocator interface
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Sam Tebbs 2020-07-01 23:31:57 +01:00 committed by GitHub
commit 7204c422e0
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1 changed files with 25 additions and 34 deletions
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59
src/kernel/heap.zig
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@ -69,43 +69,32 @@ const Heap = struct {
.size = size,
.bitmap = try Bitmap.init(@intCast(u32, size / block_min_size), allocator),
.allocator = Allocator{
.reallocFn = realloc,
.shrinkFn = shrink,
.allocFn = alloc,
.resizeFn = resize,
},
};
}
/// See std/mem.zig for documentation. This function should only be called by the Allocator interface.
fn realloc(allocator: *Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) Allocator.Error![]u8 {
fn alloc(allocator: *Allocator, len: usize, alignment: u29, len_alignment: u29) Allocator.Error![]u8 {
var heap = @fieldParentPtr(Heap, "allocator", allocator);
// If this is a new allocation
if (old_mem.len == 0) {
if (heap.alloc(new_size, new_align)) |addr| {
return @intToPtr([*]u8, addr)[0..new_size];
}
if (heap.alloc_internal(len, alignment)) |addr| {
return @intToPtr([*]u8, addr)[0..len];
}
// Re-allocation to a smaller size/alignment is not currently supported
return Allocator.Error.OutOfMemory;
}
/// See std/mem.zig for documentation. This function should only be called by the Allocator interface.
fn shrink(allocator: *Allocator, old_mem: []u8, old_alignment: u29, new_size: usize, new_alignment: u29) []u8 {
fn resize(allocator: *Allocator, old_mem: []u8, new_len: usize, len_alignment: u29) Allocator.Error!usize {
var heap = @fieldParentPtr(Heap, "allocator", allocator);
if (new_size != old_mem.len) {
// Freeing will error if the pointer was never allocated in the first place, but the Allocator API doesn't allow errors from shrink so use unreachable
if (new_len == 0) {
// Freeing will error if the pointer was never allocated in the first place, but the Allocator API doesn't allow errors to be thrown from resize in this situation, so use unreachable
// It's not nice but is the only thing that can be done. Besides, if the unreachable is ever triggered then a double-free bug has been found
heap.free(@ptrToInt(&old_mem[0]), old_mem.len) catch unreachable;
if (new_size != 0) {
// Try to re-allocate the memory to a better place
// Alloc cannot error here as new_size is guaranteed to be <= old_mem.len and so freeing the old memory guarantees there is space for the new memory
var new = @intToPtr([*]u8, heap.alloc(new_size, new_alignment) orelse unreachable)[0..new_size];
std.mem.copy(u8, new, old_mem[0..new_size]);
return new;
}
return 0;
}
return old_mem[0..new_size];
// Resizing isn't support at the moment
return Allocator.Error.OutOfMemory;
}
///
@ -165,7 +154,7 @@ const Heap = struct {
/// Return: ?usize
/// The starting address of the allocation or null if there wasn't enough free memory.
///
fn alloc(self: *Self, size: usize, alignment: ?u29) ?usize {
fn alloc_internal(self: *Self, size: usize, alignment: ?u29) ?usize {
if (size == 0 or size > self.size)
return null;
@ -306,19 +295,19 @@ test "whole heap can be allocated and freed" {
// Allocate entire heap
while (occupied < heap.size) {
// This allocation should succeed
const result = heap.alloc(heap.block_min_size, null) orelse unreachable;
const result = heap.alloc_internal(heap.block_min_size, 1) orelse unreachable;
testing.expectEqual(occupied, result);
occupied += heap.block_min_size;
}
// No more allocations should be possible
testing.expectEqual(heap.alloc(1, null), null);
testing.expectEqual(heap.alloc_internal(1, 1), null);
// Try freeing all allocations
while (occupied > 0) : (occupied -= heap.block_min_size) {
const addr = occupied - heap.block_min_size;
heap.free(addr, heap.block_min_size) catch unreachable;
// Make sure it can be reallocated
const result = heap.alloc(heap.block_min_size, null) orelse unreachable;
const result = heap.alloc_internal(heap.block_min_size, 1) orelse unreachable;
testing.expectEqual(addr, result);
// Re-free it
heap.free(addr, heap.block_min_size) catch unreachable;
@ -364,10 +353,11 @@ fn testAllocator(allocator: *Allocator) !void {
allocator.destroy(item);
}
slice = allocator.shrink(slice, 50);
testing.expect(slice.len == 50);
slice = allocator.shrink(slice, 25);
testing.expect(slice.len == 25);
// Shrinking is no longer supported
//slice = allocator.shrink(slice, 50);
//testing.expect(slice.len == 50);
//slice = allocator.shrink(slice, 25);
//testing.expect(slice.len == 25);
slice = allocator.shrink(slice, 0);
testing.expect(slice.len == 0);
slice = try allocator.alloc(*i32, 10);
@ -425,15 +415,16 @@ fn testAllocatorLargeAlignment(allocator: *Allocator) Allocator.Error!void {
var slice = try allocator.alignedAlloc(u8, large_align, 500);
testing.expect(@ptrToInt(slice.ptr) & align_mask == @ptrToInt(slice.ptr));
slice = allocator.shrink(slice, 100);
testing.expect(@ptrToInt(slice.ptr) & align_mask == @ptrToInt(slice.ptr));
// Shrinking is no longer supported
//slice = allocator.shrink(slice, 100);
//testing.expect(@ptrToInt(slice.ptr) & align_mask == @ptrToInt(slice.ptr));
// Re-allocating isn't supported yet
//slice = try allocator.realloc(slice, 5000);
//testing.expect(@ptrToInt(slice.ptr) & align_mask == @ptrToInt(slice.ptr));
slice = allocator.shrink(slice, 10);
testing.expect(@ptrToInt(slice.ptr) & align_mask == @ptrToInt(slice.ptr));
//slice = allocator.shrink(slice, 10);
//testing.expect(@ptrToInt(slice.ptr) & align_mask == @ptrToInt(slice.ptr));
// Re-allocating isn't supported yet
//slice = try allocator.realloc(slice, 20000);