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Miscellaneous fixes: extern memory allocation functions from a DLL, and alignment fixes #5

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Miscellaneous fixes: extern memory allocation functions from a DLL, and alignment fixes #5

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d783162
Use the new @extern field, .is_dll_import, to link the memory allocat…
kcbanner Nov 5, 2024
447a933
- Alignment fixup
kcbanner Jun 28, 2025
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42 changes: 26 additions & 16 deletions src/memory.zig
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
const std = @import("std");
const options = @import("zmesh_options");

pub fn init(alloc: std.mem.Allocator) void {
std.debug.assert(mem_allocator == null and mem_allocations == null);
Expand All @@ -7,10 +8,27 @@ pub fn init(alloc: std.mem.Allocator) void {
mem_allocations = std.AutoHashMap(usize, usize).init(alloc);
mem_allocations.?.ensureTotalCapacity(32) catch unreachable;

zmeshMallocPtr = zmeshMalloc;
zmeshCallocPtr = zmeshCalloc;
zmeshReallocPtr = zmeshRealloc;
zmeshFreePtr = zmeshFree;
const zmeshMallocPtr = @extern(*?*const fn (size: usize) callconv(.C) ?*anyopaque, .{
.name = "zmeshMallocPtr",
.is_dll_import = options.shared,
});
const zmeshCallocPtr = @extern(*?*const fn (num: usize, size: usize) callconv(.C) ?*anyopaque, .{
.name = "zmeshCallocPtr",
.is_dll_import = options.shared,
});
const zmeshReallocPtr = @extern(*?*const fn (ptr: ?*anyopaque, size: usize) callconv(.C) ?*anyopaque, .{
.name = "zmeshReallocPtr",
.is_dll_import = options.shared,
});
const zmeshFreePtr = @extern(*?*const fn (maybe_ptr: ?*anyopaque) callconv(.C) void, .{
.name = "zmeshFreePtr",
.is_dll_import = options.shared,
});

zmeshMallocPtr.* = zmeshMalloc;
zmeshCallocPtr.* = zmeshCalloc;
zmeshReallocPtr.* = zmeshRealloc;
zmeshFreePtr.* = zmeshFree;
meshopt_setAllocator(zmeshMalloc, zmeshFree);
}

Expand All @@ -31,9 +49,7 @@ extern fn meshopt_setAllocator(
var mem_allocator: ?std.mem.Allocator = null;
var mem_allocations: ?std.AutoHashMap(usize, usize) = null;
var mem_mutex: std.Thread.Mutex = .{};
const mem_alignment = 16;

extern var zmeshMallocPtr: ?*const fn (size: usize) callconv(.C) ?*anyopaque;
const mem_alignment: std.mem.Alignment = .@"16";

pub fn zmeshMalloc(size: usize) callconv(.C) ?*anyopaque {
mem_mutex.lock();
Expand All @@ -50,8 +66,6 @@ pub fn zmeshMalloc(size: usize) callconv(.C) ?*anyopaque {
return mem.ptr;
}

extern var zmeshCallocPtr: ?*const fn (num: usize, size: usize) callconv(.C) ?*anyopaque;

fn zmeshCalloc(num: usize, size: usize) callconv(.C) ?*anyopaque {
const ptr = zmeshMalloc(num * size);
if (ptr != null) {
Expand All @@ -66,18 +80,16 @@ pub fn zmeshAllocUser(user: ?*anyopaque, size: usize) callconv(.C) ?*anyopaque {
return zmeshMalloc(size);
}

extern var zmeshReallocPtr: ?*const fn (ptr: ?*anyopaque, size: usize) callconv(.C) ?*anyopaque;

fn zmeshRealloc(ptr: ?*anyopaque, size: usize) callconv(.C) ?*anyopaque {
mem_mutex.lock();
defer mem_mutex.unlock();

const old_size = if (ptr != null) mem_allocations.?.get(@intFromPtr(ptr.?)).? else 0;

const old_mem = if (old_size > 0)
@as([*]align(mem_alignment) u8, @ptrCast(@alignCast(ptr)))[0..old_size]
@as([*]align(mem_alignment.toByteUnits()) u8, @ptrCast(@alignCast(ptr)))[0..old_size]
else
@as([*]align(mem_alignment) u8, undefined)[0..0];
@as([*]align(mem_alignment.toByteUnits()) u8, undefined)[0..0];

const mem = mem_allocator.?.realloc(old_mem, size) catch @panic("zmesh: out of memory");

Expand All @@ -91,15 +103,13 @@ fn zmeshRealloc(ptr: ?*anyopaque, size: usize) callconv(.C) ?*anyopaque {
return mem.ptr;
}

extern var zmeshFreePtr: ?*const fn (maybe_ptr: ?*anyopaque) callconv(.C) void;

fn zmeshFree(maybe_ptr: ?*anyopaque) callconv(.C) void {
if (maybe_ptr) |ptr| {
mem_mutex.lock();
defer mem_mutex.unlock();

const size = mem_allocations.?.fetchRemove(@intFromPtr(ptr)).?.value;
const mem = @as([*]align(mem_alignment) u8, @ptrCast(@alignCast(ptr)))[0..size];
const mem = @as([*]align(mem_alignment.toByteUnits()) u8, @ptrCast(@alignCast(ptr)))[0..size];
mem_allocator.?.free(mem);
}
}
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