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allow StringOrTinyString to hold 31 bytes (#8134)

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This commit is contained in:
Meghan Denny
2024-01-12 19:43:50 -08:00
committed by GitHub
parent cb6f4b9f4d
commit 943c72c8a1
1 changed files with 31 additions and 18 deletions
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49
src/string_immutable.zig
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@@ -342,24 +342,31 @@ pub fn cat(allocator: std.mem.Allocator, first: string, second: string) !string
return out;
}
// 30 character string or a slice
// 31 character string or a slice
pub const StringOrTinyString = struct {
pub const Max = 30;
pub const Max = 31;
const Buffer = [Max]u8;
remainder_buf: Buffer = undefined,
remainder_len: u7 = 0,
is_tiny_string: u1 = 0,
meta: packed struct {
remainder_len: u7 = 0,
is_tiny_string: u1 = 0,
} = .{},
comptime {
std.debug.assert(@sizeOf(@This()) == 32);
}
pub inline fn slice(this: *const StringOrTinyString) []const u8 {
// This is a switch expression instead of a statement to make sure it uses the faster assembly
return switch (this.is_tiny_string) {
1 => this.remainder_buf[0..this.remainder_len],
return switch (this.meta.is_tiny_string) {
1 => this.remainder_buf[0..this.meta.remainder_len],
0 => @as([*]const u8, @ptrFromInt(std.mem.readInt(usize, this.remainder_buf[0..@sizeOf(usize)], .little)))[0..std.mem.readInt(usize, this.remainder_buf[@sizeOf(usize) .. @sizeOf(usize) * 2], .little)],
};
}
pub fn deinit(this: *StringOrTinyString, _: std.mem.Allocator) void {
if (this.is_tiny_string == 1) return;
if (this.meta.is_tiny_string == 1) return;
// var slice_ = this.slice();
// allocator.free(slice_);
@@ -384,22 +391,25 @@ pub const StringOrTinyString = struct {
pub fn init(stringy: string) StringOrTinyString {
switch (stringy.len) {
0 => {
return StringOrTinyString{ .is_tiny_string = 1, .remainder_len = 0 };
return StringOrTinyString{ .meta = .{
.is_tiny_string = 1,
.remainder_len = 0,
} };
},
1...(@sizeOf(Buffer)) => {
@setRuntimeSafety(false);
var tiny = StringOrTinyString{
var tiny = StringOrTinyString{ .meta = .{
.is_tiny_string = 1,
.remainder_len = @as(u7, @truncate(stringy.len)),
};
@memcpy(tiny.remainder_buf[0..tiny.remainder_len], stringy[0..tiny.remainder_len]);
} };
@memcpy(tiny.remainder_buf[0..tiny.meta.remainder_len], stringy[0..tiny.meta.remainder_len]);
return tiny;
},
else => {
var tiny = StringOrTinyString{
var tiny = StringOrTinyString{ .meta = .{
.is_tiny_string = 0,
.remainder_len = 0,
};
} };
std.mem.writeInt(usize, tiny.remainder_buf[0..@sizeOf(usize)], @intFromPtr(stringy.ptr), .little);
std.mem.writeInt(usize, tiny.remainder_buf[@sizeOf(usize) .. @sizeOf(usize) * 2], stringy.len, .little);
return tiny;
@@ -410,22 +420,25 @@ pub const StringOrTinyString = struct {
pub fn initLowerCase(stringy: string) StringOrTinyString {
switch (stringy.len) {
0 => {
return StringOrTinyString{ .is_tiny_string = 1, .remainder_len = 0 };
return StringOrTinyString{ .meta = .{
.is_tiny_string = 1,
.remainder_len = 0,
} };
},
1...(@sizeOf(Buffer)) => {
@setRuntimeSafety(false);
var tiny = StringOrTinyString{
var tiny = StringOrTinyString{ .meta = .{
.is_tiny_string = 1,
.remainder_len = @as(u7, @truncate(stringy.len)),
};
} };
_ = copyLowercase(stringy, &tiny.remainder_buf);
return tiny;
},
else => {
var tiny = StringOrTinyString{
var tiny = StringOrTinyString{ .meta = .{
.is_tiny_string = 0,
.remainder_len = 0,
};
} };
std.mem.writeInt(usize, tiny.remainder_buf[0..@sizeOf(usize)], @intFromPtr(stringy.ptr), .little);
std.mem.writeInt(usize, tiny.remainder_buf[@sizeOf(usize) .. @sizeOf(usize) * 2], stringy.len, .little);
return tiny;