6fdeaac338
* Add some documentation for standard library things. Added a bunch of descriptions for array_list. Added some usage notes for failing_allocator. Documented some of mem.Allocator.
82 lines
2.9 KiB
Zig
82 lines
2.9 KiB
Zig
const std = @import("../std.zig");
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const mem = std.mem;
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/// Allocator that fails after N allocations, useful for making sure out of
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/// memory conditions are handled correctly.
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///
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/// To use this, first initialize it and get an allocator with
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///
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/// `const failing_allocator = &FailingAllocator.init(<allocator>,
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/// <fail_index>).allocator;`
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///
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/// Then use `failing_allocator` anywhere you would have used a
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/// different allocator.
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pub const FailingAllocator = struct {
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allocator: mem.Allocator,
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index: usize,
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fail_index: usize,
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internal_allocator: *mem.Allocator,
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allocated_bytes: usize,
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freed_bytes: usize,
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allocations: usize,
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deallocations: usize,
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/// `fail_index` is the number of successful allocations you can
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/// expect from this allocator. The next allocation will fail.
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/// For example, if this is called with `fail_index` equal to 2,
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/// the following test will pass:
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///
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/// var a = try failing_alloc.create(i32);
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/// var b = try failing_alloc.create(i32);
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/// testing.expectError(error.OutOfMemory, failing_alloc.create(i32));
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pub fn init(allocator: *mem.Allocator, fail_index: usize) FailingAllocator {
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return FailingAllocator{
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.internal_allocator = allocator,
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.fail_index = fail_index,
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.index = 0,
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.allocated_bytes = 0,
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.freed_bytes = 0,
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.allocations = 0,
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.deallocations = 0,
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.allocator = mem.Allocator{
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.reallocFn = realloc,
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.shrinkFn = shrink,
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},
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};
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}
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fn realloc(allocator: *mem.Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) ![]u8 {
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const self = @fieldParentPtr(FailingAllocator, "allocator", allocator);
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if (self.index == self.fail_index) {
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return error.OutOfMemory;
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}
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const result = try self.internal_allocator.reallocFn(
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self.internal_allocator,
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old_mem,
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old_align,
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new_size,
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new_align,
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);
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if (new_size < old_mem.len) {
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self.freed_bytes += old_mem.len - new_size;
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if (new_size == 0)
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self.deallocations += 1;
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} else if (new_size > old_mem.len) {
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self.allocated_bytes += new_size - old_mem.len;
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if (old_mem.len == 0)
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self.allocations += 1;
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}
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self.index += 1;
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return result;
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}
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fn shrink(allocator: *mem.Allocator, old_mem: []u8, old_align: u29, new_size: usize, new_align: u29) []u8 {
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const self = @fieldParentPtr(FailingAllocator, "allocator", allocator);
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const r = self.internal_allocator.shrinkFn(self.internal_allocator, old_mem, old_align, new_size, new_align);
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self.freed_bytes += old_mem.len - r.len;
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if (new_size == 0)
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self.deallocations += 1;
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return r;
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}
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};
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