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package common
import "core:mem"
import "core:runtime"
Scratch_Allocator :: struct {
data: []byte,
curr_offset: int,
prev_allocation: rawptr,
backup_allocator: mem.Allocator,
leaked_allocations: [dynamic][]byte,
}
scratch_allocator_init :: proc (s: ^Scratch_Allocator, size: int, backup_allocator := context.allocator) {
s.data = mem.make_aligned([]byte, size, 2 * align_of(rawptr), backup_allocator);
s.curr_offset = 0;
s.prev_allocation = nil;
s.backup_allocator = backup_allocator;
s.leaked_allocations.allocator = backup_allocator;
}
scratch_allocator_destroy :: proc (s: ^Scratch_Allocator) {
if s == nil {
return;
}
for ptr in s.leaked_allocations {
mem.free_bytes(ptr, s.backup_allocator);
}
delete(s.leaked_allocations);
delete(s.data, s.backup_allocator);
s^ = {};
}
scratch_allocator_proc :: proc (allocator_data: rawptr, mode: mem.Allocator_Mode, size, alignment: int, old_memory: rawptr, old_size: int, loc := #caller_location) -> ([]byte, mem.Allocator_Error) {
s := (^Scratch_Allocator)(allocator_data);
if s.data == nil {
DEFAULT_BACKING_SIZE :: 1 << 22;
if !(context.allocator.procedure != scratch_allocator_proc &&
context.allocator.data != allocator_data) {
panic("cyclic initialization of the scratch allocator with itself");
}
scratch_allocator_init(s, DEFAULT_BACKING_SIZE);
}
size := size;
switch mode {
case .Alloc:
size = mem.align_forward_int(size, alignment);
switch {
case s.curr_offset + size <= len(s.data):
start := uintptr(raw_data(s.data));
ptr := start + uintptr(s.curr_offset);
ptr = mem.align_forward_uintptr(ptr, uintptr(alignment));
mem.zero(rawptr(ptr), size);
s.prev_allocation = rawptr(ptr);
offset := int(ptr - start);
s.curr_offset = offset + size;
return mem.byte_slice(rawptr(ptr), size), nil;
}
a := s.backup_allocator;
if a.procedure == nil {
a = context.allocator;
s.backup_allocator = a;
}
ptr, err := mem.alloc_bytes(size, alignment, a, loc);
if err != nil {
return ptr, err;
}
if s.leaked_allocations == nil {
s.leaked_allocations = make([dynamic][]byte, a);
}
append(&s.leaked_allocations, ptr);
if logger := context.logger; logger.lowest_level <= .Warning {
if logger.procedure != nil {
logger.procedure(logger.data, .Warning, "mem.Scratch_Allocator resorted to backup_allocator" , logger.options, loc);
}
}
return ptr, err;
case .Free:
case .Free_All:
s.curr_offset = 0;
s.prev_allocation = nil;
for ptr in s.leaked_allocations {
mem.free_bytes(ptr, s.backup_allocator);
}
clear(&s.leaked_allocations);
case .Resize:
begin := uintptr(raw_data(s.data));
end := begin + uintptr(len(s.data));
old_ptr := uintptr(old_memory);
data, err := scratch_allocator_proc(allocator_data, .Alloc, size, alignment, old_memory, old_size, loc);
if err != nil {
return data, err;
}
runtime.copy(data, mem.byte_slice(old_memory, old_size));
_, err = scratch_allocator_proc(allocator_data, .Free, 0, alignment, old_memory, old_size, loc);
return data, err;
case .Query_Features:
set := (^mem.Allocator_Mode_Set)(old_memory);
if set != nil {
set^ = {.Alloc, .Free, .Free_All, .Resize, .Query_Features};
}
return nil, nil;
case .Query_Info:
return nil, nil;
}
return nil, nil;
}
scratch_allocator :: proc (allocator: ^Scratch_Allocator) -> mem.Allocator {
return mem.Allocator {
procedure = scratch_allocator_proc,
data = allocator,
};
}
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