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const std = @import("index.zig");
const debug = std.debug;
const assert = debug.assert;
const mem = std.mem;
const os = std.os;
const builtin = @import("builtin");
const Os = builtin.Os;
const c = std.c;
const Allocator = mem.Allocator;
pub const c_allocator = &c_allocator_state;
var c_allocator_state = Allocator {
.allocFn = cAlloc,
.reallocFn = cRealloc,
.freeFn = cFree,
};
fn cAlloc(self: &Allocator, n: usize, alignment: u29) ![]u8 {
return if (c.malloc(usize(n))) |buf|
@ptrCast(&u8, buf)[0..n]
else
error.OutOfMemory;
}
fn cRealloc(self: &Allocator, old_mem: []u8, new_size: usize, alignment: u29) ![]u8 {
const old_ptr = @ptrCast(&c_void, old_mem.ptr);
if (c.realloc(old_ptr, new_size)) |buf| {
return @ptrCast(&u8, buf)[0..new_size];
} else if (new_size <= old_mem.len) {
return old_mem[0..new_size];
} else {
return error.OutOfMemory;
}
}
fn cFree(self: &Allocator, old_mem: []u8) void {
const old_ptr = @ptrCast(&c_void, old_mem.ptr);
c.free(old_ptr);
}
pub const IncrementingAllocator = struct {
allocator: Allocator,
bytes: []u8,
end_index: usize,
heap_handle: if (builtin.os == Os.windows) os.windows.HANDLE else void,
fn init(capacity: usize) !IncrementingAllocator {
switch (builtin.os) {
Os.linux, Os.macosx, Os.ios => {
const p = os.posix;
const addr = p.mmap(null, capacity, p.PROT_READ|p.PROT_WRITE,
p.MAP_PRIVATE|p.MAP_ANONYMOUS|p.MAP_NORESERVE, -1, 0);
if (addr == p.MAP_FAILED) {
return error.OutOfMemory;
}
return IncrementingAllocator {
.allocator = Allocator {
.allocFn = alloc,
.reallocFn = realloc,
.freeFn = free,
},
.bytes = @intToPtr(&u8, addr)[0..capacity],
.end_index = 0,
.heap_handle = {},
};
},
Os.windows => {
const heap_handle = os.windows.GetProcessHeap() ?? return error.OutOfMemory;
const ptr = os.windows.HeapAlloc(heap_handle, 0, capacity) ?? return error.OutOfMemory;
return IncrementingAllocator {
.allocator = Allocator {
.allocFn = alloc,
.reallocFn = realloc,
.freeFn = free,
},
.bytes = @ptrCast(&u8, ptr)[0..capacity],
.end_index = 0,
.heap_handle = heap_handle,
};
},
else => @compileError("Unsupported OS"),
}
}
fn deinit(self: &IncrementingAllocator) void {
switch (builtin.os) {
Os.linux, Os.macosx, Os.ios => {
_ = os.posix.munmap(self.bytes.ptr, self.bytes.len);
},
Os.windows => {
_ = os.windows.HeapFree(self.heap_handle, 0, @ptrCast(os.windows.LPVOID, self.bytes.ptr));
},
else => @compileError("Unsupported OS"),
}
}
fn reset(self: &IncrementingAllocator) void {
self.end_index = 0;
}
fn bytesLeft(self: &const IncrementingAllocator) usize {
return self.bytes.len - self.end_index;
}
fn alloc(allocator: &Allocator, n: usize, alignment: u29) ![]u8 {
const self = @fieldParentPtr(IncrementingAllocator, "allocator", allocator);
const addr = @ptrToInt(&self.bytes[self.end_index]);
const rem = @rem(addr, alignment);
const march_forward_bytes = if (rem == 0) 0 else (alignment - rem);
const adjusted_index = self.end_index + march_forward_bytes;
const new_end_index = adjusted_index + n;
if (new_end_index > self.bytes.len) {
return error.OutOfMemory;
}
const result = self.bytes[adjusted_index .. new_end_index];
self.end_index = new_end_index;
return result;
}
fn realloc(allocator: &Allocator, old_mem: []u8, new_size: usize, alignment: u29) ![]u8 {
if (new_size <= old_mem.len) {
return old_mem[0..new_size];
} else {
const result = try alloc(allocator, new_size, alignment);
mem.copy(u8, result, old_mem);
return result;
}
}
fn free(allocator: &Allocator, bytes: []u8) void {
// Do nothing. That's the point of an incrementing allocator.
}
};
test "c_allocator" {
if (builtin.link_libc) {
var slice = c_allocator.alloc(u8, 50) catch return;
defer c_allocator.free(slice);
slice = c_allocator.realloc(u8, slice, 100) catch return;
}
}
test "IncrementingAllocator" {
const total_bytes = 100 * 1024 * 1024;
var inc_allocator = try IncrementingAllocator.init(total_bytes);
defer inc_allocator.deinit();
const allocator = &inc_allocator.allocator;
const slice = try allocator.alloc(&i32, 100);
for (slice) |*item, i| {
*item = try allocator.create(i32);
**item = i32(i);
}
assert(inc_allocator.bytesLeft() == total_bytes - @sizeOf(i32) * 100 - @sizeOf(usize) * 100);
inc_allocator.reset();
assert(inc_allocator.bytesLeft() == total_bytes);
}
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