update

3 files changed, 383 insertions, 0 deletions

diff --git a/src/main.zig b/src/main.zig
new file mode 100644
index 0000000..d40f09a
--- /dev/null
+++ b/src/main.zig
@@ -0,0 +1,73 @@
+//! By convention, main.zig is where your main function lives in the case that
+//! you are building an executable. If you are making a library, the convention
+//! is to delete this file and start with root.zig instead.
+
+const std = @import("std");
+
+/// This imports the separate module containing `root.zig`. Take a look in `build.zig` for details.
+const zisp = @import("zisp_lib");
+
+pub fn main() !void {
+    const T = extern union {
+        bits: u64,
+        double: f64,
+    };
+    var f1: *volatile f64 = undefined;
+    var f2: *volatile f64 = undefined;
+    var x: *volatile T = undefined;
+
+    var _gpa: std.heap.GeneralPurposeAllocator(.{}) = .init;
+    const gpa = _gpa.allocator();
+
+    f1 = try gpa.create(f64);
+    f2 = try gpa.create(f64);
+    x = try gpa.create(T);
+
+    f1.* = 0.0;
+    f2.* = 0.0;
+    x.*.double = f1.* / f2.*;
+    std.debug.print(" 0/0: {x}\n", .{x.*.bits});
+
+    f1.* = -0.0;
+    f2.* = 0.0;
+    x.*.double = f1.* / f2.*;
+    std.debug.print("-0/0: {x}\n", .{x.*.bits});
+
+    // // Prints to stderr (it's a shortcut based on `std.io.getStdErr()`)
+    // std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
+
+    // // stdout is for the actual output of your application, for example if you
+    // // are implementing gzip, then only the compressed bytes should be sent to
+    // // stdout, not any debugging messages.
+    // const stdout_file = std.io.getStdOut().writer();
+    // var bw = std.io.bufferedWriter(stdout_file);
+    // const stdout = bw.writer();
+
+    // try stdout.print("Run `zig build test` to run the tests.\n", .{});
+
+    // try bw.flush(); // Don't forget to flush!
+}
+
+test "simple test" {
+    var list = std.ArrayList(i32).init(std.testing.allocator);
+    defer list.deinit(); // Try commenting this out and see if zig detects the memory leak!
+    try list.append(42);
+    try std.testing.expectEqual(@as(i32, 42), list.pop());
+}
+
+test "use other module" {
+    //try std.testing.expectEqual(@as(i32, 150), lib.add(100, 50));
+}
+
+test "fuzz example" {
+    const Context = struct {
+        fn testOne(context: @This(), input: []const u8) anyerror!void {
+            _ = context;
+            // Try passing `--fuzz` to `zig build test` and see if it manages to fail this test case!
+            try std.testing.expect(!std.mem.eql(u8, "canyoufindme", input));
+        }
+    };
+    try std.testing.fuzz(Context{}, Context.testOne, .{});
+}
+
+test "nan" {}
diff --git a/src/root.zig b/src/root.zig
new file mode 100644
index 0000000..05ad381
--- /dev/null
+++ b/src/root.zig
@@ -0,0 +1,191 @@
+//! By convention, root.zig is the root source file when making a library. If
+//! you are making an executable, the convention is to delete this file and
+//! start with main.zig instead.
+const std = @import("std");
+const builtin = @import("builtin");
+const testing = std.testing;
+
+// Read the following article to understand the NaN-packing strategy:
+//
+// https://tkammer.de/zisp/notes/nan.html
+//
+// Note: Packed structs are least-to-most significant, so the order of fields
+// must be reversed relative to a typical big-endian illustration of the bit
+// patterns of IEEE 754 double-precision floating point numbers.
+
+const Value = packed union {
+    double: f64,
+    nan: packed struct {
+        rest: u51,
+        quiet: u1,
+        exp: u11,
+        sign: u1,
+    },
+    int: packed struct {
+        code: u51,
+        neg: bool,
+        exp: u11,
+        is_int: bool,
+    },
+    pointer: packed struct {
+        value: u48,
+        type: u3,
+        _zo: u1,
+        _qnan: u12,
+    },
+};
+
+// Helpers
+
+inline fn zisp_dump(v: Value) void {
+    std.debug.dumpHex(std.mem.asBytes(&v));
+}
+
+///! Checks for any IEEE 754 NaN.
+inline fn zisp_is_nan(v: Value) bool {
+    return v.nan.exp == std.math.maxInt(u11);
+}
+
+///! Checks for a Zisp value packed into a NaN.
+inline fn zisp_is_packed(v: Value) bool {
+    return zisp_is_nan(v) and v.nan.rest != 0;
+}
+
+///! Checks for a regular double including infinity or canonical NaN
+inline fn zisp_is_double(v: Value) bool {
+    return !zisp_is_packed(v);
+}
+
+inline fn zisp_assert_double(v: Value) void {
+    if (!zisp_is_double(v)) {
+        zisp_dump(v);
+        @panic("not double");
+    }
+}
+
+inline fn zisp_is_int(v: Value) bool {
+    return zisp_is_packed(v) and v.int.is_int;
+}
+
+inline fn zisp_assert_int(v: Value) void {
+    if (!zisp_is_int(v)) {
+        zisp_dump(v);
+        @panic("not int");
+    }
+}
+
+// See detailed NaN packing docs for why the +/- 1.
+const zisp_int_min = std.math.minInt(i52) + 1;
+const zisp_int_max = std.math.maxInt(i52) - 1;
+
+inline fn zisp_assert_int_range(int: i64) void {
+    if (int < zisp_int_min) {
+        std.debug.print("int to pack is too small: {}", .{int});
+        @panic("int to pack is too small");
+    }
+    if (int > zisp_int_max) {
+        std.debug.print("int to pack is too large: {}", .{int});
+        @panic("int to pack is too large");
+    }
+}
+
+inline fn zisp_int_pack_neg(int: i64) Value {
+    return @bitCast(int);
+}
+
+inline fn zisp_int_unpack_neg(v: Value) i64 {
+    return @bitCast(v);
+}
+
+const zisp_int_pos_mask: u64 = 0xfff7ffffffffffff;
+
+inline fn zisp_int_pack_pos(int: i64) Value {
+    const uint: u64 = @bitCast(int);
+    return @bitCast(uint ^ zisp_int_pos_mask);
+}
+
+inline fn zisp_int_unpack_pos(v: Value) i64 {
+    const uint: u64 = @bitCast(v);
+    return @bitCast(uint ^ zisp_int_pos_mask);
+}
+
+inline fn zisp_int_pack(int: i64) Value {
+    zisp_assert_int_range(int);
+    if (int < 0) {
+        return zisp_int_pack_neg(int);
+    } else {
+        return zisp_int_pack_pos(int);
+    }
+}
+
+inline fn zisp_int_unpack(v: Value) i64 {
+    zisp_assert_int(v);
+    if (v.int.neg) {
+        return zisp_int_unpack_neg(v);
+    } else {
+        return zisp_int_unpack_pos(v);
+    }
+}
+
+// Doubles
+
+pub fn zisp_double(d: f64) Value {
+    return @bitCast(d);
+}
+
+// pub fn zisp_double_p(v: Value) Value {
+//     return zisp_bool(zisp_is_double(v));
+// }
+
+pub fn zisp_double_get(v: Value) f64 {
+    zisp_assert_double(v);
+    return v.double;
+}
+
+pub fn zisp_double_add(v1: Value, v2: Value) Value {
+    const d1 = zisp_double_get(v1);
+    const d2 = zisp_double_get(v2);
+    return zisp_double(d1 + d2);
+}
+
+// Ints
+
+pub fn zisp_int(int: i64) Value {
+    return zisp_int_pack(int);
+}
+
+// pub fn zisp_int_p(v: Value) Value {
+//     return zisp_bool(zisp_is_int(v));
+// }
+
+pub fn zisp_int_get(v: Value) i64 {
+    return zisp_int_unpack(v);
+}
+
+pub fn zisp_int_add(v1: Value, v2: Value) Value {
+    const int1 = zisp_int_get(v1);
+    const int2 = zisp_int_get(v2);
+    return zisp_int(int1 + int2);
+}
+
+// Tests
+
+test "double add functionality" {
+    const d1: f64 = 0.123456789;
+    const d2: f64 = -0.987654321;
+    const v1 = zisp_double(d1);
+    const v2 = zisp_double(d2);
+    const v3 = zisp_double_add(v1, v2);
+    const result = zisp_double_get(v3);
+    try std.testing.expect(result == d1 + d2);
+}
+
+test "int add functionality" {
+    const int1: i64 = 123456789;
+    const int2: i64 = -987654321;
+    const v1 = zisp_int(int1);
+    const v2 = zisp_int(int2);
+    const v3 = zisp_int_add(v1, v2);
+    const result = zisp_int_get(v3);
+    try std.testing.expect(result == int1 + int2);
+}
diff --git a/src/test.c b/src/test.c
new file mode 100644
index 0000000..0b0917e
--- /dev/null
+++ b/src/test.c
@@ -0,0 +1,119 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <math.h>
+
+union test {
+  double d;
+  uint64_t u;
+};
+
+int main(int argc, char** argv) {
+
+  volatile uint64_t mask;
+  volatile uint64_t min;
+  volatile uint64_t max;
+
+  volatile double d1;
+  volatile double d2;
+
+  volatile uint64_t pd1;
+  volatile uint64_t pd2;
+
+
+  // 0 .. 2^51
+
+  //       SE__________QP__
+  mask = 0b1111111111110111111111111111111111111111111111111111111111111111;
+  min  = 0b1111111111110111111111111111111111111111111111111111111111111111;
+  max  = 0b1111111111110000000000000000000000000000000000000000000000000001;
+
+  memcpy(&d1, &min, 8);
+  memcpy(&d2, &max, 8);
+
+  printf("%lf\n", d1);
+  printf("%lf\n", d2);
+
+  memcpy(&pd1, &d1, 8);
+  memcpy(&pd2, &d2, 8);
+  pd1 ^= mask;
+  pd2 ^= mask;
+
+  printf("%ld\n", pd1);
+  printf("%ld\n", pd2);
+
+  printf("\n");
+
+  // -2^51 + 1 .. -1
+
+  //       SE__________QP__
+  min  = 0b1111111111111000000000000000000000000000000000000000000000000001;
+  max  = 0b1111111111111111111111111111111111111111111111111111111111111111;
+
+  memcpy(&d1, &min, 8);
+  memcpy(&d2, &max, 8);
+
+  printf("%lf\n", d1);
+  printf("%lf\n", d2);
+
+  memcpy(&pd1, &d1, 8);
+  memcpy(&pd2, &d2, 8);
+
+  printf("%ld\n", pd1);
+  printf("%ld\n", pd2);
+
+  printf("\n");
+
+  return 0;
+
+  // -2^50 + 1 .. -1
+
+  //       SE__________QFP__
+  mask = 0b1111111111111100000000000000000000000000000000000000000000000000;
+  min  = 0b0000000000000000000000000000000000000000000000000000000000000001;
+  max  = 0b0000000000000011111111111111111111111111111111111111111111111111;
+
+  printf("%ld\n", (int64_t) (min | mask));
+  printf("%ld\n", (int64_t) (max | mask));
+
+
+  // 0 .. 2^50
+
+  //       SE__________QFP__
+  mask = 0b0000000000000011111111111111111111111111111111111111111111111111;
+  min  = 0b0000000000000100000000000000000000000000000000000000000000000000;
+  max  = 0b0000000000000111111111111111111111111111111111111111111111111111;
+
+  printf("%ld\n", (int64_t) (min & mask));
+  printf("%ld\n", (int64_t) (max & mask));
+
+
+
+
+  /* volatile union test x; */
+  /* volatile double f1; */
+  /* volatile double f2; */
+
+  /* f1 = 0.0; */
+  /* f2 = 0.0; */
+  /* x.d = f1 / f2; */
+  /* printf(" 0/0: %lx\n", x.u); */
+
+  /* f1 = -0.0; */
+  /* f2 = +0.0; */
+  /* x.d = f1 / f2; */
+  /* printf("-0/0: %lx\n", x.u); */
+
+  /* x.d = sqrt(-1); */
+  /* printf("sqrt(-1): %lx\n", x.u); */
+
+
+  /* double nan_value = fabs(sqrt(-1.0));  // Standard way to generate NaN */
+
+  /* uint64_t nan_bits; */
+  /* memcpy(&nan_bits, &nan_value, sizeof(nan_bits)); */
+
+  /* printf("NaN in hex: 0x%016lx\n", nan_bits); */
+    
+  /* return 0; */
+}