lib/ascii: add strlower_buf/strupper_buf (#11)

Restore Hare's two-tier delegation: strlower/strupper alloc a buffer
then delegate to strlower_buf/strupper_buf, which fold ASCII case
into a caller-provided buffer. Too-small buffer returns nomem via the
`let nm: nomem` value form. ref/hare/ascii/string.ha:21,43.

Regen w6c/wwdump/smoke combined.ww — all three embed lib/ascii.

lib/ascii/ascii.ww

@@ -138,15 +138,10 @@ export fn strcasecmp(a: str, b: str) i32 = {
 };
 
 // strlower — ASCII-lowercased copy of s, newly allocated.
-// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
-// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
-// equals Hare's rune fold and is length-preserving.
-// _buf variants deferred — ww has no nomem-value form / static-append
-// builtin; restore Hare's two-tier delegation when they land (#230).
 // ref/hare/ascii/string.ha:11.
 export fn strlower(s: str) (str | nomem) = {
 	// empty bypass: ww alloc([],0) routes through nomem; Hare allocs 0
-	// and zero-loops (ref/hare/ascii/string.ha)
+	// and zero-loops (ref/hare/ascii/string.ha:12).
 	if (s.len == 0) {
 		let r: str;
 		r.ptr = nil;
@@ -154,6 +149,22 @@ export fn strlower(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strlower_buf(s, buf);
+};
+
+// strlower_buf — ASCII-lowercase s into buf (overwrites). nomem if buf
+// too small. ref/hare/ascii/string.ha:21.
+// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
+// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
+// equals Hare's rune fold and is length-preserving.
+// ww uses an explicit `buf.cap < s.len` check + `let nm: nomem` value
+// because it has no static-append builtin; Hare reaches the same
+// nomem-on-too-small via `static append(buf, ...)?` (string.ha:25).
+export fn strlower_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = tolower(s[i]: rune): u8;
@@ -173,6 +184,15 @@ export fn strupper(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strupper_buf(s, buf);
+};
+
+// strupper_buf — see strlower_buf. ref/hare/ascii/string.ha:43.
+export fn strupper_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = toupper(s[i]: rune): u8;

lib/ascii/asciitest.ww

@@ -35,7 +35,45 @@ fn checkfold(in: str, lo: str, up: str) void = {
 	signalled = 105; checkfold("aB1z", "ab1z", "AB1Z");
 };
 
+// checkbuf — strlower_buf/strupper_buf into an exactly-sized buf.
+fn checkbuf(in: str, lo: str, up: str) void = {
+	let lstore: [16]u8; let lbuf: []u8 = lstore[0:16]; lbuf.len = 0;
+	match (ascii.strlower_buf(in, lbuf)) {
+	case let got: str => { if (got != lo) { fail(); }; };
+	case nomem        => { fail(); };
+	};
+	let ustore: [16]u8; let ubuf: []u8 = ustore[0:16]; ubuf.len = 0;
+	match (ascii.strupper_buf(in, ubuf)) {
+	case let got: str => { if (got != up) { fail(); }; };
+	case nomem        => { fail(); };
+	};
+};
+
+@test fn strfold_buf_cases() void = {
+	signalled = 110; checkbuf("ABC", "abc", "ABC");
+	signalled = 111; checkbuf("aB1z", "ab1z", "AB1Z");
+	signalled = 112; checkbuf("", "", "");
+	// non-ASCII pins UTF-8 multibyte passthrough through the _buf path
+	// directly (all bytes >=0x80, untouched by the byte-wise fold).
+	signalled = 113; checkbuf("こ", "こ", "こ");
+	// cap exactly == s.len must succeed — pins the `<` boundary in the
+	// buf.cap check (a `<=` off-by-one would wrongly return nomem here).
+	signalled = 114;
+	let exact: [3]u8; let ebuf: []u8 = exact[0:3]; ebuf.len = 0;
+	match (ascii.strlower_buf("ABC", ebuf)) {
+	case let got: str => { if (got != "abc") { fail(); }; };
+	case nomem        => { fail(); };
+	};
+	signalled = 115;
+	let small: [2]u8; let sbuf: []u8 = small[0:2]; sbuf.len = 0;
+	match (ascii.strlower_buf("ABC", sbuf)) {
+	case let got: str => { fail(); };
+	case nomem        => void;
+	};
+};
+
 export fn main() i32 = {
 	signalled = 1; strfold_cases();
+	signalled = 2; strfold_buf_cases();
 	return 0;
 };

selfhost/cmd/w6c/main.combined.ww

@@ -4477,15 +4477,10 @@ export fn strcasecmp(a: str, b: str) i32 = {
 };
 
 // strlower — ASCII-lowercased copy of s, newly allocated.
-// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
-// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
-// equals Hare's rune fold and is length-preserving.
-// _buf variants deferred — ww has no nomem-value form / static-append
-// builtin; restore Hare's two-tier delegation when they land (#230).
 // ref/hare/ascii/string.ha:11.
 export fn strlower(s: str) (str | nomem) = {
 	// empty bypass: ww alloc([],0) routes through nomem; Hare allocs 0
-	// and zero-loops (ref/hare/ascii/string.ha)
+	// and zero-loops (ref/hare/ascii/string.ha:12).
 	if (s.len == 0) {
 		let r: str;
 		r.ptr = nil;
@@ -4493,6 +4488,22 @@ export fn strlower(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strlower_buf(s, buf);
+};
+
+// strlower_buf — ASCII-lowercase s into buf (overwrites). nomem if buf
+// too small. ref/hare/ascii/string.ha:21.
+// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
+// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
+// equals Hare's rune fold and is length-preserving.
+// ww uses an explicit `buf.cap < s.len` check + `let nm: nomem` value
+// because it has no static-append builtin; Hare reaches the same
+// nomem-on-too-small via `static append(buf, ...)?` (string.ha:25).
+export fn strlower_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = tolower(s[i]: rune): u8;
@@ -4512,6 +4523,15 @@ export fn strupper(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strupper_buf(s, buf);
+};
+
+// strupper_buf — see strlower_buf. ref/hare/ascii/string.ha:43.
+export fn strupper_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = toupper(s[i]: rune): u8;

selfhost/cmd/wwdump/main.combined.ww

@@ -4477,15 +4477,10 @@ export fn strcasecmp(a: str, b: str) i32 = {
 };
 
 // strlower — ASCII-lowercased copy of s, newly allocated.
-// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
-// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
-// equals Hare's rune fold and is length-preserving.
-// _buf variants deferred — ww has no nomem-value form / static-append
-// builtin; restore Hare's two-tier delegation when they land (#230).
 // ref/hare/ascii/string.ha:11.
 export fn strlower(s: str) (str | nomem) = {
 	// empty bypass: ww alloc([],0) routes through nomem; Hare allocs 0
-	// and zero-loops (ref/hare/ascii/string.ha)
+	// and zero-loops (ref/hare/ascii/string.ha:12).
 	if (s.len == 0) {
 		let r: str;
 		r.ptr = nil;
@@ -4493,6 +4488,22 @@ export fn strlower(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strlower_buf(s, buf);
+};
+
+// strlower_buf — ASCII-lowercase s into buf (overwrites). nomem if buf
+// too small. ref/hare/ascii/string.ha:21.
+// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
+// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
+// equals Hare's rune fold and is length-preserving.
+// ww uses an explicit `buf.cap < s.len` check + `let nm: nomem` value
+// because it has no static-append builtin; Hare reaches the same
+// nomem-on-too-small via `static append(buf, ...)?` (string.ha:25).
+export fn strlower_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = tolower(s[i]: rune): u8;
@@ -4512,6 +4523,15 @@ export fn strupper(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strupper_buf(s, buf);
+};
+
+// strupper_buf — see strlower_buf. ref/hare/ascii/string.ha:43.
+export fn strupper_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = toupper(s[i]: rune): u8;

selfhost/test/smoke.combined.ww

@@ -4477,15 +4477,10 @@ export fn strcasecmp(a: str, b: str) i32 = {
 };
 
 // strlower — ASCII-lowercased copy of s, newly allocated.
-// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
-// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
-// equals Hare's rune fold and is length-preserving.
-// _buf variants deferred — ww has no nomem-value form / static-append
-// builtin; restore Hare's two-tier delegation when they land (#230).
 // ref/hare/ascii/string.ha:11.
 export fn strlower(s: str) (str | nomem) = {
 	// empty bypass: ww alloc([],0) routes through nomem; Hare allocs 0
-	// and zero-loops (ref/hare/ascii/string.ha)
+	// and zero-loops (ref/hare/ascii/string.ha:12).
 	if (s.len == 0) {
 		let r: str;
 		r.ptr = nil;
@@ -4493,6 +4488,22 @@ export fn strlower(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strlower_buf(s, buf);
+};
+
+// strlower_buf — ASCII-lowercase s into buf (overwrites). nomem if buf
+// too small. ref/hare/ascii/string.ha:21.
+// Byte-wise fold: ASCII case-fold only touches bytes <0x80; UTF-8
+// multibyte bytes are >=0x80 and pass through unchanged, so byte-wise
+// equals Hare's rune fold and is length-preserving.
+// ww uses an explicit `buf.cap < s.len` check + `let nm: nomem` value
+// because it has no static-append builtin; Hare reaches the same
+// nomem-on-too-small via `static append(buf, ...)?` (string.ha:25).
+export fn strlower_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = tolower(s[i]: rune): u8;
@@ -4512,6 +4523,15 @@ export fn strupper(s: str) (str | nomem) = {
 		return r;
 	};
 	let buf: []u8 = alloc([], s.len: u64)?;
+	return strupper_buf(s, buf);
+};
+
+// strupper_buf — see strlower_buf. ref/hare/ascii/string.ha:43.
+export fn strupper_buf(s: str, buf: []u8) (str | nomem) = {
+	if (buf.cap < s.len) {
+		let nm: nomem;
+		return nm;
+	};
 	let i: i32 = 0;
 	for (i < s.len) {
 		buf.ptr[i] = toupper(s[i]: rune): u8;