From 4c1477737344f42bf6c6e4e37aebdb6ed1ff9bc4 Mon Sep 17 00:00:00 2001
From: r4gus <david@thesugar.de>
Date: Sun, 4 Aug 2024 14:58:51 +0200
Subject: [PATCH] writeFloat and GetFloatN added

---
 src/build.zig | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/cbor.zig  | 45 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 102 insertions(+)

diff --git a/src/build.zig b/src/build.zig
index bb78820..d7c8f78 100644
--- a/src/build.zig
+++ b/src/build.zig
@@ -49,6 +49,23 @@ pub fn writeFalse(writer: anytype) !void {
     try writeSimple(writer, 20);
 }
 
+pub fn writeFloat(writer: anytype, f: anytype) !void {
+    const T = @TypeOf(f);
+    const TInf = @typeInfo(T);
+
+    switch (TInf) {
+        .Float => |float| {
+            switch (float.bits) {
+                16 => try cbor.encode_2(writer, 0xe0, @as(u64, @intCast(@as(u16, @bitCast(f))))),
+                32 => try cbor.encode_4(writer, 0xe0, @as(u64, @intCast(@as(u32, @bitCast(f))))),
+                64 => try cbor.encode_8(writer, 0xe0, @as(u64, @intCast(@as(u64, @bitCast(f))))),
+                else => @compileError("Float must be 16, 32 or 64 Bits wide"),
+            }
+        },
+        else => return error.NotAFloat,
+    }
+}
+
 /// Write the header of an array to `writer`.
 ///
 /// You must write exactly `len` data items to `writer` afterwards.
@@ -451,3 +468,43 @@ test "write true false" {
     try std.testing.expectEqual(@as(u8, 0xf5), arr.items[0]);
     try std.testing.expectEqual(@as(u8, 0xf4), arr.items[1]);
 }
+
+test "write float #1" {
+    const allocator = std.testing.allocator;
+    var arr = std.ArrayList(u8).init(allocator);
+    defer arr.deinit();
+
+    try writeFloat(arr.writer(), @as(f16, @floatCast(0.0)));
+
+    try std.testing.expectEqualSlices(u8, "\xf9\x00\x00", arr.items);
+}
+
+test "write float #2" {
+    const allocator = std.testing.allocator;
+    var arr = std.ArrayList(u8).init(allocator);
+    defer arr.deinit();
+
+    try writeFloat(arr.writer(), @as(f16, @floatCast(-0.0)));
+
+    try std.testing.expectEqualSlices(u8, "\xf9\x80\x00", arr.items);
+}
+
+test "write float #3" {
+    const allocator = std.testing.allocator;
+    var arr = std.ArrayList(u8).init(allocator);
+    defer arr.deinit();
+
+    try writeFloat(arr.writer(), @as(f32, @floatCast(3.4028234663852886e+38)));
+
+    try std.testing.expectEqualSlices(u8, "\xfa\x7f\x7f\xff\xff", arr.items);
+}
+
+test "write float #4" {
+    const allocator = std.testing.allocator;
+    var arr = std.ArrayList(u8).init(allocator);
+    defer arr.deinit();
+
+    try writeFloat(arr.writer(), @as(f64, @floatCast(-4.1)));
+
+    try std.testing.expectEqualSlices(u8, "\xfb\xc0\x10\x66\x66\x66\x66\x66\x66", arr.items);
+}
diff --git a/src/cbor.zig b/src/cbor.zig
index de6a2e3..ab93d7b 100644
--- a/src/cbor.zig
+++ b/src/cbor.zig
@@ -189,6 +189,45 @@ pub const DataItem = struct {
         }
     }
 
+    pub fn isFloat16(self: @This()) bool {
+        if (self.data.len < 3) return false;
+        return self.data[0] == 0xf9;
+    }
+
+    pub fn getFloat16(self: @This()) ?f16 {
+        if (!self.isFloat16()) return null;
+        if (additionalInfo(self.data, null)) |v| {
+            return @floatCast(@as(f16, @bitCast(@as(u16, @intCast(v)))));
+        }
+        return null;
+    }
+
+    pub fn isFloat32(self: @This()) bool {
+        if (self.data.len < 5) return false;
+        return self.data[0] == 0xfa;
+    }
+
+    pub fn getFloat32(self: @This()) ?f32 {
+        if (!self.isFloat32()) return null;
+        if (additionalInfo(self.data, null)) |v| {
+            return @floatCast(@as(f32, @bitCast(@as(u32, @intCast(v)))));
+        }
+        return null;
+    }
+
+    pub fn isFloat64(self: @This()) bool {
+        if (self.data.len < 9) return false;
+        return self.data[0] == 0xfb;
+    }
+
+    pub fn getFloat64(self: @This()) ?f64 {
+        if (!self.isFloat64()) return null;
+        if (additionalInfo(self.data, null)) |v| {
+            return @floatCast(@as(f64, @bitCast(@as(u64, @intCast(v)))));
+        }
+        return null;
+    }
+
     /// Decode the given DataItem into a Tag
     ///
     /// This function will return null if the DataItem
@@ -673,6 +712,12 @@ test "deserialize float" {
     const di4 = try DataItem.new("\xfb\x7e\x37\xe4\x3c\x88\x00\x75\x9c");
     try std.testing.expectEqual(Type.Float, di4.getType());
     try std.testing.expectApproxEqAbs(di4.float().?, 1.0e+300, 0.000000001);
+
+    try std.testing.expectEqual(@as(f16, 0.0), (try DataItem.new("\xf9\x00\x00")).getFloat16().?);
+    try std.testing.expectEqual(@as(f16, -0.0), (try DataItem.new("\xf9\x80\x00")).getFloat16().?);
+    try std.testing.expectEqual(@as(f16, 65504.0), (try DataItem.new("\xf9\x7b\xff")).getFloat16().?);
+    try std.testing.expectEqual(@as(f32, 3.4028234663852886e+38), (try DataItem.new("\xfa\x7f\x7f\xff\xff")).getFloat32().?);
+    try std.testing.expectEqual(@as(f64, -4.1), (try DataItem.new("\xfb\xc0\x10\x66\x66\x66\x66\x66\x66")).getFloat64().?);
 }
 
 test "deserialize tagged" {