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/// A relatively naive bitmap allocator that uses memory offsets against/// a fixed backing buffer so that the backing buffer can be easily moved/// without having to update pointers.////// The chunk size determines the size of each chunk in bytes. This is the/// minimum distributed unit of memory. For example, if you request a/// 1-byte allocation, you'll use a chunk of chunk_size bytes. Likewise,/// if your chunk size is 4, and you request a 5-byte allocation, you'll/// use 2 chunks.////// The allocator is susceptible to fragmentation. If you allocate and free/// memory in a way that leaves small holes in the memory, you may not be/// able to allocate large chunks of memory even if there is enough free/// memory in aggregate. To avoid fragmentation, use a chunk size that is/// large enough to cover most of your allocations.///// Notes for contributors: this is highly contributor friendly part of// the code. If you can improve this, add tests, show benchmarks, then// please do so!pub fn BitmapAllocator(comptime chunk_size: comptime_int) type { return struct { const Self = @This();
comptime { assert(std.math.isPowerOfTwo(chunk_size)); }
pub const base_align: std.mem.Alignment = .fromByteUnits(@alignOf(u64)); pub const bitmap_bit_size = @bitSizeOf(u64);
/// The bitmap of available chunks. Each bit represents a chunk. A /// 1 means the chunk is free and a 0 means it's used. We use 1 /// for free since it makes it very slightly faster to find free /// chunks. bitmap: Offset(u64), bitmap_count: usize,
/// The contiguous buffer of chunks. chunks: Offset(u8),
/// Initialize the allocator map with a given buf and memory layout. pub fn init(buf: OffsetBuf, l: Layout) Self { assert(base_align.check(@intFromPtr(buf.start())));
// Initialize our bitmaps to all 1s to note that all chunks are free. const bitmap = buf.member(u64, l.bitmap_start); const bitmap_ptr = bitmap.ptr(buf); @memset(bitmap_ptr[0..l.bitmap_count], std.math.maxInt(u64));
return .{ .bitmap = bitmap, .bitmap_count = l.bitmap_count, .chunks = buf.member(u8, l.chunks_start), }; }
/// Returns the number of bytes required to allocate n elements of /// type T. This accounts for the chunk size alignment used by the /// bitmap allocator. pub fn bytesRequired(comptime T: type, n: usize) usize { const byte_count = @sizeOf(T) * n; return alignForward(usize, byte_count, chunk_size); }
/// Allocate n elements of type T. This will return error.OutOfMemory /// if there isn't enough space in the backing buffer. /// /// Use (size.zig).getOffset to get the base offset from the backing /// memory for portable storage. pub fn alloc( self: *Self, comptime T: type, base: anytype, n: usize, ) Allocator.Error![]T { // note: we don't handle alignment yet, we just require that all // types are properly aligned. This is a limitation that should be // fixed but we haven't needed it. Contributor friendly: add tests // and fix this. assert(chunk_size % @alignOf(T) == 0); assert(n > 0);
const byte_count = std.math.mul(usize, @sizeOf(T), n) catch return error.OutOfMemory; const chunk_count = std.math.divCeil(usize, byte_count, chunk_size) catch return error.OutOfMemory;
// Find the index of the free chunk. This also marks it as used. const bitmaps = self.bitmap.ptr(base); const idx = findFreeChunks(bitmaps[0..self.bitmap_count], chunk_count) orelse return error.OutOfMemory;
const chunks = self.chunks.ptr(base); const ptr: [*]T = @ptrCast(@alignCast(&chunks[idx * chunk_size])); return ptr[0..n]; }
pub fn free(self: *Self, base: anytype, slice: anytype) void { // Convert the slice of whatever type to a slice of bytes. We // can then use the byte len and chunk size to determine the // number of chunks that were allocated. const bytes = std.mem.sliceAsBytes(slice); const aligned_len = std.mem.alignForward(usize, bytes.len, chunk_size); const chunk_count = @divExact(aligned_len, chunk_size);
// From the pointer, we can calculate the exact index. const chunks = self.chunks.ptr(base); const chunk_idx = @divExact(@intFromPtr(slice.ptr) - @intFromPtr(chunks), chunk_size);
const bitmaps = self.bitmap.ptr(base);
// Current bitmap index. var i: usize = @divFloor(chunk_idx, 64); // Number of chunks we still have to mark as free. var rem: usize = chunk_count;
// Mark any bits in the starting bitmap that need to be marked. { // Bit index. const bit = chunk_idx % 64; // Number of bits we need to mark in this bitmap. const bits = @min(rem, 64 - bit);
bitmaps[i] |= ~@as(u64, 0) >> @intCast(64 - bits) << @intCast(bit); rem -= bits; }
// Mark any full bitmaps worth of bits that need to be marked. i += 1; while (rem > 64) : (i += 1) { bitmaps[i] = std.math.maxInt(u64); rem -= 64; }
// Mark any bits at the start of this last bitmap if it needs it. if (rem > 0) { bitmaps[i] |= ~@as(u64, 0) >> @intCast(64 - rem); } }
/// Returns the total capacity in bytes. pub fn capacityBytes(self: Self) usize { return self.bitmap_count * bitmap_bit_size * chunk_size; }
/// Returns the number of bytes currently in use. pub fn usedBytes(self: Self, base: anytype) usize { const bitmaps = self.bitmap.ptr(base); var free_chunks: usize = 0; for (bitmaps[0..self.bitmap_count]) |bitmap| free_chunks += @popCount(bitmap); const total_chunks = self.bitmap_count * bitmap_bit_size; return (total_chunks - free_chunks) * chunk_size; }
/// For testing only. fn isAllocated(self: *Self, base: anytype, slice: anytype) bool { comptime assert(@import("builtin").is_test);
const bytes = std.mem.sliceAsBytes(slice); const aligned_len = std.mem.alignForward(usize, bytes.len, chunk_size); const chunk_count = @divExact(aligned_len, chunk_size);
const chunks = self.chunks.ptr(base); const chunk_idx = @divExact(@intFromPtr(slice.ptr) - @intFromPtr(chunks), chunk_size);
const bitmaps = self.bitmap.ptr(base);
for (chunk_idx..chunk_idx + chunk_count) |i| { const bitmap = @divFloor(i, bitmap_bit_size); const bit = i % bitmap_bit_size; if (bitmaps[bitmap] & (@as(u64, 1) << @intCast(bit)) != 0) { return false; } }
return true; }
/// For debugging fn dumpBitmaps(self: *Self, base: anytype) void { const bitmaps = self.bitmap.ptr(base); for (bitmaps[0..self.bitmap_count], 0..) |bitmap, idx| { std.log.warn("bm={b} idx={}", .{ bitmap, idx }); } }
pub const Layout = struct { total_size: usize, bitmap_count: usize, bitmap_start: usize, chunks_start: usize, };
/// Get the layout for the given capacity. The capacity is in /// number of bytes, not chunks. The capacity will likely be /// rounded up to the nearest chunk size and bitmap size so /// everything is perfectly divisible. pub fn layout(cap: usize) Layout { // Align the cap forward to our chunk size so we always have // a full chunk at the end. const aligned_cap = alignForward(usize, cap, chunk_size);
// Calculate the number of bitmaps. We need 1 bitmap per 64 chunks. // We align the chunk count forward so our bitmaps are full so we // don't have to handle the case where we have a partial bitmap. const chunk_count = @divExact(aligned_cap, chunk_size); const aligned_chunk_count = alignForward(usize, chunk_count, 64); const bitmap_count = @divExact(aligned_chunk_count, 64);
const bitmap_start = 0; const bitmap_end = @sizeOf(u64) * bitmap_count; const chunks_start = alignForward(usize, bitmap_end, @alignOf(u8)); const chunks_end = chunks_start + (aligned_cap * chunk_size); const total_size = chunks_end;
return Layout{ .total_size = total_size, .bitmap_count = bitmap_count, .bitmap_start = bitmap_start, .chunks_start = chunks_start, }; } };}
/// Find `n` sequential free chunks in the given bitmaps and return the index/// of the first chunk. If no chunks are found, return `null`. This also updates/// the bitmap to mark the chunks as used.fn findFreeChunks(bitmaps: []u64, n: usize) ?usize { // NOTE: This is a naive implementation that just iterates through the // bitmaps. There is very likely a more efficient way to do this but // I'm not a bit twiddling expert. Perhaps even SIMD could be used here // but unsure. Contributor friendly: let's benchmark and improve this!
// Large chunks require special handling. if (n > @bitSizeOf(u64)) { var i: usize = 0; search: while (i < bitmaps.len) { // Number of chunks available at the end of this bitmap. const prefix = @clz(~bitmaps[i]);
// If there are no chunks available at the end of this bitmap // then we can't start in it, so we'll try the next one. if (prefix == 0) { i += 1; continue; }
// Starting position if we manage to find the span we need here. const start_bitmap = i; const start_bit = 64 - prefix;
// The remaining number of sequential free chunks we need to find. var rem: usize = n - prefix;
i += 1; while (rem > 64) : (i += 1) { // We ran out of bitmaps, there's no sufficiently large gap. if (i >= bitmaps.len) return null;
// There's more than 64 remaining chunks and this bitmap has // content in it, so we try starting again with this bitmap. if (bitmaps[i] != std.math.maxInt(u64)) continue :search;
// This bitmap is completely free, we can subtract 64 from // our remaining number. rem -= 64; }
// If the number of available chunks at the start of this bitmap // is less than the remaining required, we have to try again. if (@ctz(~bitmaps[i]) < rem) continue;
const suffix = (n - prefix) % 64;
// Found! Mark everything between our start and end as full. bitmaps[start_bitmap] ^= ~@as(u64, 0) >> @intCast(start_bit) << @intCast(start_bit); const full_bitmaps = @divFloor(n - prefix - suffix, 64); for (bitmaps[start_bitmap + 1 ..][0..full_bitmaps]) |*bitmap| { bitmap.* = 0; } if (suffix > 0) bitmaps[i] ^= ~@as(u64, 0) >> @intCast(64 - suffix);
return start_bitmap * 64 + start_bit; }
return null; }
assert(n <= @bitSizeOf(u64)); for (bitmaps, 0..) |*bitmap, idx| { // Shift the bitmap to find `n` sequential free chunks. // EXAMPLE: // n = 4 // shifted = 001111001011110010 // & 000111100101111001 // & 000011110010111100 // & 000001111001011110 // = 000001000000010000 // ^ ^ // In this example there are 2 places with at least 4 sequential 1s. var shifted: u64 = bitmap.*; for (1..n) |i| shifted &= bitmap.* >> @intCast(i);
// If we have zero then we have no matches if (shifted == 0) continue;
// Trailing zeroes gets us the index of the first bit index with at // least `n` sequential 1s. In the example above, that would be `4`. const bit = @ctz(shifted);
// Calculate the mask so we can mark it as used const mask = (@as(u64, std.math.maxInt(u64)) >> @intCast(64 - n)) << @intCast(bit); bitmap.* ^= mask;
return (idx * 64) + bit; }
return null;}
test "findFreeChunks single found" { const testing = std.testing;
var bitmaps = [_]u64{ 0b10000000_00000000_00000000_00000000_00000000_00000000_00001110_00000000, }; const idx = findFreeChunks(&bitmaps, 2).?; try testing.expectEqual(@as(usize, 9), idx); try testing.expectEqual( 0b10000000_00000000_00000000_00000000_00000000_00000000_00001000_00000000, bitmaps[0], );}
test "findFreeChunks single not found" { const testing = std.testing;
var bitmaps = [_]u64{0b10000111_00000000_00000000_00000000_00000000_00000000_00000000_00000000}; const idx = findFreeChunks(&bitmaps, 4); try testing.expect(idx == null);}
test "findFreeChunks multiple found" { const testing = std.testing;
var bitmaps = [_]u64{ 0b10000111_00000000_00000000_00000000_00000000_00000000_00000000_01110000, 0b10000000_00111110_00000000_00000000_00000000_00000000_00111110_00000000, }; const idx = findFreeChunks(&bitmaps, 4).?; try testing.expectEqual(@as(usize, 73), idx); try testing.expectEqual( 0b10000000_00111110_00000000_00000000_00000000_00000000_00100000_00000000, bitmaps[1], );}
test "findFreeChunks exactly 64 chunks" { const testing = std.testing;
var bitmaps = [_]u64{ 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, }; const idx = findFreeChunks(&bitmaps, 64).?; try testing.expectEqual( 0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000, bitmaps[0], ); try testing.expectEqual(@as(usize, 0), idx);}
test "findFreeChunks larger than 64 chunks" { const testing = std.testing;
var bitmaps = [_]u64{ 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, }; const idx = findFreeChunks(&bitmaps, 65).?; try testing.expectEqual( 0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000, bitmaps[0], ); try testing.expectEqual( 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111110, bitmaps[1], ); try testing.expectEqual(@as(usize, 0), idx);}
test "findFreeChunks larger than 64 chunks not at beginning" { const testing = std.testing;
var bitmaps = [_]u64{ 0b11111111_00000000_00000000_00000000_00000000_00000000_00000000_00000000, 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, }; const idx = findFreeChunks(&bitmaps, 65).?; try testing.expectEqual( 0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000, bitmaps[0], ); try testing.expectEqual( 0b11111110_00000000_00000000_00000000_00000000_00000000_00000000_00000000, bitmaps[1], ); try testing.expectEqual( 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, bitmaps[2], ); try testing.expectEqual(@as(usize, 56), idx);}
test "findFreeChunks larger than 64 chunks exact" { const testing = std.testing;
var bitmaps = [_]u64{ 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, 0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111, }; const idx = findFreeChunks(&bitmaps, 128).?; try testing.expectEqual( 0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000, bitmaps[0], ); try testing.expectEqual( 0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000, bitmaps[1], ); try testing.expectEqual(@as(usize, 0), idx);}
test "BitmapAllocator layout" { const Alloc = BitmapAllocator(4); const cap = 64 * 4;
const testing = std.testing; const layout = Alloc.layout(cap);
// We expect to use one bitmap since the cap is bytes. try testing.expectEqual(@as(usize, 1), layout.bitmap_count);}
test "BitmapAllocator alloc sequentially" { const Alloc = BitmapAllocator(4); const cap = 64;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout); const ptr = try bm.alloc(u8, buf, 1); ptr[0] = 'A';
const ptr2 = try bm.alloc(u8, buf, 1); try testing.expect(@intFromPtr(ptr.ptr) != @intFromPtr(ptr2.ptr));
// Should grab the next chunk try testing.expectEqual(@intFromPtr(ptr.ptr) + 4, @intFromPtr(ptr2.ptr));
// Free ptr and next allocation should be back bm.free(buf, ptr); const ptr3 = try bm.alloc(u8, buf, 1); try testing.expectEqual(@intFromPtr(ptr.ptr), @intFromPtr(ptr3.ptr));}
test "BitmapAllocator alloc non-byte" { const Alloc = BitmapAllocator(4); const cap = 128;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout); const ptr = try bm.alloc(u21, buf, 1); ptr[0] = 'A';
const ptr2 = try bm.alloc(u21, buf, 1); try testing.expect(@intFromPtr(ptr.ptr) != @intFromPtr(ptr2.ptr)); try testing.expectEqual(@intFromPtr(ptr.ptr) + 4, @intFromPtr(ptr2.ptr));
// Free ptr and next allocation should be back bm.free(buf, ptr); const ptr3 = try bm.alloc(u21, buf, 1); try testing.expectEqual(@intFromPtr(ptr.ptr), @intFromPtr(ptr3.ptr));}
test "BitmapAllocator alloc non-byte multi-chunk" { const Alloc = BitmapAllocator(4 * @sizeOf(u21)); const cap = 128;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout); const ptr = try bm.alloc(u21, buf, 6); try testing.expectEqual(@as(usize, 6), ptr.len); for (ptr) |*v| v.* = 'A';
const ptr2 = try bm.alloc(u21, buf, 1); try testing.expect(@intFromPtr(ptr.ptr) != @intFromPtr(ptr2.ptr)); try testing.expectEqual(@intFromPtr(ptr.ptr) + (@sizeOf(u21) * 4 * 2), @intFromPtr(ptr2.ptr));
// Free ptr and next allocation should be back bm.free(buf, ptr); const ptr3 = try bm.alloc(u21, buf, 1); try testing.expectEqual(@intFromPtr(ptr.ptr), @intFromPtr(ptr3.ptr));}
test "BitmapAllocator alloc large" { const Alloc = BitmapAllocator(2); const cap = 256;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout); const ptr = try bm.alloc(u8, buf, 129); ptr[0] = 'A'; bm.free(buf, ptr);}
test "BitmapAllocator alloc and free one bitmap" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate exactly one bitmap worth of bytes. const slice = try bm.alloc(u8, buf, Alloc.bitmap_bit_size); try testing.expectEqual(Alloc.bitmap_bit_size, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([Alloc.bitmap_bit_size]u8, @splat(0x11)), slice, );
// Free it try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free half bitmap" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate exactly half a bitmap worth of bytes. const slice = try bm.alloc(u8, buf, Alloc.bitmap_bit_size / 2); try testing.expectEqual(Alloc.bitmap_bit_size / 2, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([Alloc.bitmap_bit_size / 2]u8, @splat(0x11)), slice, );
// Free it try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free two half bitmaps" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate exactly one bitmap worth of bytes across two allocations. const slice = try bm.alloc(u8, buf, Alloc.bitmap_bit_size / 2); try testing.expectEqual(Alloc.bitmap_bit_size / 2, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([Alloc.bitmap_bit_size / 2]u8, @splat(0x11)), slice, );
const slice2 = try bm.alloc(u8, buf, Alloc.bitmap_bit_size / 2); try testing.expectEqual(Alloc.bitmap_bit_size / 2, slice2.len);
@memset(slice2, 0x22); try testing.expectEqualSlices( u8, &@as([Alloc.bitmap_bit_size / 2]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([Alloc.bitmap_bit_size / 2]u8, @splat(0x11)), slice, );
// Free them try testing.expect(bm.isAllocated(buf, slice2)); bm.free(buf, slice2); try testing.expect(!bm.isAllocated(buf, slice2)); try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free 1.5 bitmaps" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate exactly 1.5 bitmaps worth of bytes. const slice = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 2); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 2, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x11)), slice, );
// Free them try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free two 1.5 bitmaps" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate exactly 3 bitmaps worth of bytes across two allocations. const slice = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 2); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 2, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x11)), slice, );
const slice2 = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 2); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 2, slice2.len);
@memset(slice2, 0x22); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x11)), slice, );
// Free them try testing.expect(bm.isAllocated(buf, slice2)); bm.free(buf, slice2); try testing.expect(!bm.isAllocated(buf, slice2)); try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free 1.5 bitmaps offset by 0.75" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate three quarters of a bitmap first. const slice = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 4); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 4, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
// Then a 1.5 bitmap sized allocation, so that it spans // from 0.75 to 2.25, occupying bits in 3 different bitmaps. const slice2 = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 2); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 2, slice2.len);
@memset(slice2, 0x22); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
// Free them try testing.expect(bm.isAllocated(buf, slice2)); bm.free(buf, slice2); try testing.expect(!bm.isAllocated(buf, slice2)); try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free three 0.75 bitmaps" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 3 bitmaps. const cap = Alloc.bitmap_bit_size * 3;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// Allocate three quarters of a bitmap three times. const slice = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 4); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 4, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
const slice2 = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 4); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 4, slice2.len);
@memset(slice2, 0x22); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
const slice3 = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 4); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 4, slice3.len);
@memset(slice3, 0x33); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x33)), slice3, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
// Free them try testing.expect(bm.isAllocated(buf, slice2)); bm.free(buf, slice2); try testing.expect(!bm.isAllocated(buf, slice2)); try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice)); try testing.expect(bm.isAllocated(buf, slice3)); bm.free(buf, slice3); try testing.expect(!bm.isAllocated(buf, slice3));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([3]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..3], );}
test "BitmapAllocator alloc and free two 1.5 bitmaps offset 0.75" { const Alloc = BitmapAllocator(1); // Capacity such that we'll have 4 bitmaps. const cap = Alloc.bitmap_bit_size * 4;
const testing = std.testing; const alloc = testing.allocator; const layout = Alloc.layout(cap); const buf = try alloc.alignedAlloc(u8, Alloc.base_align, layout.total_size); defer alloc.free(buf);
var bm = Alloc.init(.init(buf), layout);
// First allocate a 0.75 bitmap const slice = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 4); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 4, slice.len);
@memset(slice, 0x11); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
// Then two 1.5 bitmaps const slice2 = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 2); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 2, slice2.len);
@memset(slice2, 0x22); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
const slice3 = try bm.alloc(u8, buf, 3 * Alloc.bitmap_bit_size / 2); try testing.expectEqual(3 * Alloc.bitmap_bit_size / 2, slice3.len);
@memset(slice3, 0x33); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x33)), slice3, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 2]u8, @splat(0x22)), slice2, ); try testing.expectEqualSlices( u8, &@as([3 * Alloc.bitmap_bit_size / 4]u8, @splat(0x11)), slice, );
// Free them try testing.expect(bm.isAllocated(buf, slice2)); bm.free(buf, slice2); try testing.expect(!bm.isAllocated(buf, slice2)); try testing.expect(bm.isAllocated(buf, slice)); bm.free(buf, slice); try testing.expect(!bm.isAllocated(buf, slice)); try testing.expect(bm.isAllocated(buf, slice3)); bm.free(buf, slice3); try testing.expect(!bm.isAllocated(buf, slice3));
// All of our bitmaps should be free. try testing.expectEqualSlices( u64, &@as([4]u64, @splat(~@as(u64, 0))), bm.bitmap.ptr(buf)[0..4], );}
test "BitmapAllocator bytesRequired" { const testing = std.testing;
// Chunk size of 16 bytes (like grapheme_chunk in page.zig) { const Alloc = BitmapAllocator(16);
// Single byte rounds up to chunk size try testing.expectEqual(16, Alloc.bytesRequired(u8, 1)); try testing.expectEqual(16, Alloc.bytesRequired(u8, 16)); try testing.expectEqual(32, Alloc.bytesRequired(u8, 17));
// u21 (4 bytes each) try testing.expectEqual(16, Alloc.bytesRequired(u21, 1)); // 4 bytes -> 16 try testing.expectEqual(16, Alloc.bytesRequired(u21, 4)); // 16 bytes -> 16 try testing.expectEqual(32, Alloc.bytesRequired(u21, 5)); // 20 bytes -> 32 try testing.expectEqual(32, Alloc.bytesRequired(u21, 6)); // 24 bytes -> 32 }
// Chunk size of 4 bytes { const Alloc = BitmapAllocator(4);
try testing.expectEqual(4, Alloc.bytesRequired(u8, 1)); try testing.expectEqual(4, Alloc.bytesRequired(u8, 4)); try testing.expectEqual(8, Alloc.bytesRequired(u8, 5));
// u32 (4 bytes each) - exactly one chunk per element try testing.expectEqual(4, Alloc.bytesRequired(u32, 1)); try testing.expectEqual(8, Alloc.bytesRequired(u32, 2)); }
// Chunk size of 32 bytes (like string_chunk in page.zig) { const Alloc = BitmapAllocator(32);
try testing.expectEqual(32, Alloc.bytesRequired(u8, 1)); try testing.expectEqual(32, Alloc.bytesRequired(u8, 32)); try testing.expectEqual(64, Alloc.bytesRequired(u8, 33)); }}