parent
12280219cb
commit
dbfe13af58
4 changed files with 114 additions and 92 deletions
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const std = @import("std"); |
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const Allocator = std.mem.Allocator; |
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const c = @import("./c.zig"); |
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pub var is_setup = false; |
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pub var allocator: Allocator = undefined; |
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pub fn setup(allocator_: Allocator) void { |
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if (is_setup) std.debug.panic("setup must only be called once", .{}); |
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is_setup = true; |
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allocator = allocator_; |
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c.ecs_os_set_api_defaults(); |
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var os_api = c.ecs_os_api; |
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os_api.malloc_ = flecsMalloc; |
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os_api.realloc_ = flecsRealloc; |
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os_api.calloc_ = flecsCalloc; |
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os_api.free_ = flecsFree; |
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c.ecs_os_set_api(&os_api); |
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_ = c.ecs_log_set_level(-1); // No tracing. |
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} |
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fn flecsMalloc(size: i32) callconv(.C) ?*anyopaque { |
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if (size == 0) return null; |
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return allocLengthEncodedSlice(size, null).ptr; |
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} |
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fn flecsRealloc(ptr: ?*anyopaque, size: i32) callconv(.C) ?*anyopaque { |
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if (size == 0) { |
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flecsFree(ptr); |
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return null; |
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} else { |
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const old = if (ptr) |p| sliceFromPtr(p) else null; |
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return allocLengthEncodedSlice(size, old).ptr; |
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} |
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} |
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fn flecsCalloc(size: i32) callconv(.C) ?*anyopaque { |
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if (size == 0) return null; |
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const slice = allocLengthEncodedSlice(size, null); |
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@memset(slice, 0); |
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return slice.ptr; |
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} |
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fn flecsFree(ptr: ?*anyopaque) callconv(.C) void { |
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if (ptr) |p| { |
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const slice = sliceFromPtr(p); |
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allocator.free(slice); |
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} |
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} |
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/// Reserves an additional `@sizeOf(i32)` bytes, which is used to store the |
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/// length so we can use a simple pointer offset to "encode" the full slice |
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/// information (including length) into just a single pointer. |
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/// |
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/// Optionally allows passing a slice to be reallocated into this new slice. |
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/// The `old_slice` must be the full slice as returned by `sliceFromPtr(...)`. |
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/// |
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/// Returns the pointer from the offset where the actual data is stored. |
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/// This allows manipulating the contents, such as zeroing it out. |
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fn allocLengthEncodedSlice(size: i32, old_slice: ?[]align(@sizeOf(i32)) u8) []u8 { |
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const slice_len = @sizeOf(i32) + @as(usize, @intCast(size)); |
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const slice = if (old_slice) |old| |
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allocator.realloc(old, slice_len) catch @panic("OOM") |
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else |
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allocator.allocWithOptions(u8, slice_len, @sizeOf(i32), null) catch @panic("OOM"); |
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@as([*]i32, @ptrCast(slice.ptr))[0] = size; |
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return slice[@sizeOf(i32)..]; |
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} |
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/// Recovers the original slice that was allocated by `allocSlice` to get the |
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/// specified pointer. Returns the full slice including the "encoded" length. |
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fn sliceFromPtr(ptr: *anyopaque) []align(@sizeOf(i32)) u8 { |
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const slice_ptr = @as([*]align(@sizeOf(i32)) u8, @alignCast(@ptrCast(ptr))) - @sizeOf(i32); |
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const slice_len = @as([*]i32, @ptrCast(slice_ptr))[0]; |
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return slice_ptr[0..(@sizeOf(i32) + @as(usize, @intCast(slice_len)))]; |
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} |
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