hare

commit 9244d60cf6ab00f16fd5663f247c7e9f33812762
parent d480082cfec1d2312428784aba7a3d332434e99b
Author: Drew DeVault <sir@cmpwn.com>
Date:   Mon,  1 Feb 2021 19:20:23 -0500

fmt: initial workitude

Diffstat:
A
encoding/utf8/encode.ha
 | 
26
++++++++++++++++++++++++++
M
fmt/fmt.ha
 | 
54
++++++++++++++++++++++++++++++++++++++++++++++++++----

2 files changed, 76 insertions(+), 4 deletions(-)
diff --git a/encoding/utf8/encode.ha b/encoding/utf8/encode.ha
@@ -0,0 +1,26 @@
+// Encodes a rune as UTF-8 and returns the result as a slice. The result is
+// statically allocated; duplicate it if you aren't using it right away.
+export fn encode_rune(r: rune) []u8 = {
+	let ch = r: u32, n = 0z, first = 0u8;
+	if (ch < 0x80u32) {
+		first = 0u8;
+		n = 1z;
+	} else if (ch < 0x800u32) {
+		first = 0xC0u8;
+		n = 2z;
+	} else if (ch < 0x10000u32) {
+		first = 0xE0u8;
+		n = 3z;
+	} else {
+		first = 0xF0u8;
+		n = 4z;
+	};
+
+	static let buf: [6]u8 = [0u8...];
+	for (let i = n - 1z; i > 0z; i -= 1z) {
+		buf[i] = ch: u8 & 0x3Fu8 | 0x80u8;
+		ch >>= 6u32;
+	};
+	buf[0] = ch: u8 | first;
+	return buf[..n];
+};
diff --git a/fmt/fmt.ha b/fmt/fmt.ha
@@ -8,15 +8,61 @@
 // used to specify additional constraints on the format in a type-specific
 // manner: '{0:x} will print a number in hexadecimal.
 //
-// TODO: Document this more I guess
+// TODO: More detail
+use encoding::utf8;
 use io;
+use strings;
+use strconv;
 use types;
 
 // Tagged union of all types which are formattable.
 export type formattable = (...types::numeric | uintptr | str | *void);
 
 // Formats text for printing and writes it to an [io::stream].
-export fn fprintf(s: *io::stream, fmt: str,
-		args: formattable...) (io::error | size) = {
-	return io::unsupported: io::error; // TODO: Blocked on rune picking
+export fn fprintf(
+	s: *io::stream,
+	fmt: str,
+	args: formattable...
+) (io::error | size) = {
+	let n = 0z, i = 0z;
+	let iter = strings::iter(fmt);
+	for (true) {
+		let r: rune = match (strings::next(&iter)) {
+			void => break,
+			r: rune => r,
+		};
+
+		if (r  == '{') {
+			r = match (strings::next(&iter)) {
+				void => abort("Invalid format string (unterminated '{')"),
+				r: rune => r,
+			};
+			assert(r == '}'); // TODO
+			format(s, args[i]);
+			i += 1z;
+			continue;
+		};
+
+		match (io::write(s, utf8::encode_rune(r))) {
+			err: io::error => return err,
+			w: size => {
+				n += w;
+			},
+		};
+	};
+
+	return n;
+};
+
+fn format(out: *io::stream, arg: formattable) void = {
+	match (arg) {
+		// TODO: Use types::numeric (and strconv::numtos) when match is
+		// more fleshed out
+		i: int => {
+			let s = strconv::itos(i);
+			io::write(out, strings::to_utf8(s));
+		},
+		s: str => io::write(out, strings::to_utf8(s)),
+		* => abort("TODO: implement more formattable values"),
+	};
 };