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const builtin = @import("builtin");
const std = @import("std");
const endian = builtin.target.cpu.arch.endian();
const min = std.math.minInt(i52) + 1;
const max = std.math.maxInt(i52) - 1;
export fn checkValidRange(int: i64) u8 {
return if (min < int and int < max) 1 else 0;
}
export fn checkValidRange2(int: i64) u8 {
const x: u64 = @bitCast(int);
return if (if (int < 0)
x >> 51 == std.math.maxInt(u13)
else
x >> 51 == 0) 1 else 0;
}
export fn isFixnum(v: u64) u8 {
const expt = v >> 52;
const rest = v << 13;
return if (expt == 0xfff and rest != 0) 1 else 0;
}
export fn isFixnum2(v: u64) u8 {
const hi: u14 = @intCast(v >> 50);
return if (hi == (0xfff << 2 | 0b01)) 1 else 0;
}
export fn sstrLen(x: u64) u8 {
const bytes: @Vector(8, u8) = @bitCast(x);
const nulls: @Vector(8, u8) = @splat(0);
const comps: u8 = @bitCast(bytes == nulls);
// Two bits will always be 0, since the actual short string starts at the
// third byte; third lowest or third highest depending on endianness. So,
// depending on endianness, either cut off the two leading bits and ensure
// that the second-last is set, or ensure that the second highest set, to
// limit the length to 6.
return switch (endian) {
.big => @clz(comps << 2 | 2),
.little => @ctz(comps | 64),
};
}
const positive_mask: u64 = 0xfff7ffffffffffff;
fn unpackNegative(v: u64) i64 {
return @bitCast(v);
}
fn unpackPositive(v: u64) i64 {
const uint: u64 = @bitCast(v);
return @bitCast(uint ^ positive_mask);
}
fn packNegative(int: i64) u64 {
return @bitCast(int);
}
fn packPositive(int: i64) u64 {
const uint: u64 = @bitCast(int);
return @bitCast(uint ^ positive_mask);
}
export fn packFx(int: i64) u64 {
if (int < 0) {
return packNegative(int);
} else {
return packPositive(int);
}
}
export fn packSstr(len: usize, s: [*]const u8) u64 {
var v: u64 = 0xfff3000000000000;
const buf: *[8]u8 = @ptrCast(&v);
@memcpy(buf[0 .. 0 + len], s);
return v;
}
pub fn packSstrTest(buf: [*]const u64, len: usize) ?Value {
if (len > 6) return null;
const v = switch (endian) {
.big => @byteSwap(buf[0]),
.little => buf[0],
};
const shift: u6 = 8 * @as(u6, @intCast(len));
const mask = @as(u64, std.math.maxInt(u64)) << shift;
const s = Value{ .sstr = .{ .bytes = @intCast(v & ~mask) } };
// This effectively checks if there were any NUL bytes:
if (len != value.sstrLen(&s)) return null;
return s;
}
pub fn packSstrStatic(comptime s: []const u8) Value {
var val: u64 = undefined;
const buf: [*]align(8) u8 = @ptrCast(&val);
@memcpy(buf, s);
return pack(@ptrCast(buf), s.len).?;
}
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