root: add rewriteFloatSm

Author: thislight

src/io.zig

@@ -98,6 +98,14 @@ pub fn writeFloat(writer: anytype, value: anytype) !usize {
     return wsize;
 }
 
+pub fn writeFloatSm(writer: anytype, value: anytype) !usize {
+    const T = @TypeOf(value);
+    var buf: BufferForNumber(@TypeOf(value)) = undefined;
+    const bsize = fmt.writeFloatSm(T, &buf, value);
+    const wsize = try writer.write(buf[0..bsize]);
+    return wsize;
+}
+
 pub fn writeArrayPrefix(writer: anytype, length: u32) !usize {
     const prefix = fmt.prefixArray(length);
     const slice = prefix.constSlice();

src/rewriter.zig

@@ -14,7 +14,7 @@ fn rewriteValue(
         .bool => _ = try zigpak.io.writeBool(writer, try values.bool(reader, h)),
         .int => _ = try zigpak.io.writeIntSm(writer, try values.int(reader, i64, h)),
         .uint => _ = try zigpak.io.writeIntSm(writer, try values.int(reader, u64, h)),
-        .float => _ = try zigpak.io.writeFloat(writer, try values.float(reader, f64, h)),
+        .float => _ = try zigpak.io.writeFloatSm(writer, try values.float(reader, f64, h)),
         .str => {
             var strReader = try values.rawReader(reader, h);
             var strbuf: [4096]u8 = undefined;

src/root.zig

@@ -259,6 +259,20 @@ pub fn writeFloat(comptime T: type, dst: []u8, value: T) usize {
     return 1 + roundedBytes;
 }
 
+/// Write the float as the smallest float type,
+/// as long as the precision won't lost.
+///
+/// This may introduce runtime check for certain input types.
+pub inline fn writeFloatSm(comptime T: type, dst: []u8, value: T) usize {
+    const wontLosePrecision = @as(f32, @floatCast(value)) == value;
+
+    if (wontLosePrecision) {
+        return writeFloat(f32, dst, @floatCast(value));
+    } else {
+        return writeFloat(f64, dst, @floatCast(value));
+    }
+}
+
 /// Write nil into the `dst`.
 pub fn writeNil(dst: []u8) usize {
     dst[0] = 0xc0;