Hojun-Cho
f3750ae3ce
io.empty (discard+EOF stream, ref/hare/io/empty.ha:4-17) — needed by getopt's two-pass printusage width measurement. Diverges from Hare's `const empty: *stream`: a `let _empty_vt` + `fn empty()` that wires the fn-ptr slots per call, because const-init of a vtable struct with fn-ptr fields is blocked (#118, ruled accept). Co-discovered while making empty() byte-identical across stages: three wwstage-only cgen fixes (cstage was already correct; wwstage aligned down): - #129 sretretsize: consult the same-module pointer-alias before structlookup's any-module struct fallback (io.stream = *vtable was mis-sized as memio's 56B struct -> spurious sret save). - #129 callsretsize: swap curmod to the callee's module before sret-size classification (cross-module callee context). - #130 cgassign global-struct tagged-union field store: add the missing arm (was a 1-word store) mirroring cstage cgen.c:4893-4912. The three are inseparable from io.empty here — splitting them out leaves a divergent-asm intermediate (993/995 red), so they ride one commit per the one-class gate-repair carve-out (#133-expanded precedent). Regenerates the embedded combined.ww; 989_lib_byteid pins bufio + fmt graduated to M_ID. (cgenexpr.ww fix-3 inline comment cites the #129 cluster; narrow to #130 on next touch to avoid a regen for a comment.)
223 lines
7.4 KiB
Plaintext
223 lines
7.4 KiB
Plaintext
// stream — Hare-shaped vtable surface. Project #94 fold-eFinal.
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//
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// The single io stream surface (the fold-eFinal collapse retired the
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// pre-vtable `stream` struct + `closed` tag). Exports:
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//
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// vtable a struct of optional fn-pointer slots — reader/writer/
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// closer per ref/hare/io/stream.ha:36-42. Hare spells the
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// nullable as `nullable *T`; ww parser rejects that
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// spelling (#192), so each slot is a `(*T | void)` tagged
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// union (Plan-9-lean per the Nullable kept ruling; opt-in
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// at optionality boundaries only).
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// stream `*vtable` alias matching Hare's `stream = *vtable`
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// (ref/hare/io/stream.ha:33).
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// read /
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// write /
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// close the three dispatchers per ref/hare/io/stream.ha:44-68.
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// Each `match`es the matching vtable slot, returns
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// `errors.unsupported` (widened twice) when the slot is
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// void, otherwise calls through the fn pointer. Hare keeps
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// these private (`st_read` …) behind a `handle`-typed
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// public `read`/`write`/`close`; ww has no `handle` yet
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// (io fold-2, #5), so the dispatchers ARE the public
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// surface and grow the `handle` match when #5 lands.
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// empty the discard+EOF stream (ref/hare/io/empty.ha:13). Lives
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// here rather than io.ww so that 900_stdlib can compile
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// io.ww standalone (io.ww has no cross-file type refs).
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//
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// Deferrals (drew-signed): `seeker` lands with io fold-2 (#5) once `off`
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// + `whence` plug into the signature. Hare's `?`-propagating `close`
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// body (`c(s)?;`) collapses to a direct `return (*c)(s);` here because
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// the dispatcher's surface stays Hare-shaped; only the internal
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// try-prop is omitted (#173 history, now closed — kept direct for the
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// void-arm fall-through shape).
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package io;
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// Q2 layering (ratified): the file-arm of the handle dispatchers routes
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// to os.{read,write,close,lseek}; ww `os` plays Hare's `sys` role, so
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// `lib/io import os` is the correct direction (os is the import floor).
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import os;
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// ref/hare/io/stream.ha:36-42. Nullable spelling per #192 (ww parser
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// rejects `nullable *T`); each slot is `(*T | void)`. The `seeker` slot
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// (4th) lands with io fold-2 (#5); `copier` stays deferred.
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export type vtable = struct {
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reader: (*reader | void),
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writer: (*writer | void),
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closer: (*closer | void),
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seeker: (*seeker | void),
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};
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// ref/hare/io/stream.ha:33.
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export type stream = *vtable;
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// ref/hare/io/stream.ha:44-51. Private stream-arm body behind the
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// handle-typed [[read]] (#5). The void-arm `return e;` chains two
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// direct widens: `errors.unsupported → error` via #199 α, then
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// `error → (size | eof | error)` via #205. The call-arm spells the
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// fn-ptr call explicitly per #193 (ww requires `(*r)(args)` rather
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// than implicit `r(args)`).
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fn st_read(s: stream, buf: []u8) (size | eof | error) = {
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match (s.reader) {
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case void => {
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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case let r: *reader => return (*r)(s, buf);
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};
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};
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// ref/hare/io/stream.ha:53-60.
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fn st_write(s: stream, buf: []u8) (size | error) = {
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match (s.writer) {
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case void => {
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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case let w: *writer => return (*w)(s, buf);
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};
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};
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// ref/hare/io/stream.ha:62-68. Hare propagates the close error via
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// `c(s)?;` then falls through to the void arm; ww collapses to a
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// direct return for the void-arm fall-through shape. The surface
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// (void | error) matches.
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fn st_close(s: stream) (void | error) = {
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match (s.closer) {
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case void => return void;
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case let c: *closer => return (*c)(s);
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};
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};
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// ref/hare/io/stream.ha:70-77. Clone of st_read's slot-dispatch shape
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// over the new `seeker` vtable slot.
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fn st_seek(s: stream, off: off, w: whence) (off | error) = {
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match (s.seeker) {
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case void => {
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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case let sk: *seeker => return (*sk)(s, off, w);
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};
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};
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// ref/hare/io/handle.ha:16-23. The handle-typed public read: the
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// file-arm routes to os.read (Q2 layering), the stream-arm delegates to
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// the unchanged st_read vtable dispatch above.
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export fn read(h: handle, buf: []u8) (size | eof | error) = {
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match (h) {
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case let fd: file => {
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let r: i64 = os.read(fd, buf.ptr, buf.len: u64);
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if (r < 0) {
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// #199b: faithful errno→io.error needs the ...errors.error spread; see lib/io/types.ww:40
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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if (r == 0) {
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let z: eof;
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return z;
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};
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return r: size;
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};
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case let s: stream => return st_read(s, buf);
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};
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};
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// ref/hare/io/handle.ha:27-36.
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export fn write(h: handle, buf: []u8) (size | error) = {
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match (h) {
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case let fd: file => {
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let r: i64 = os.write(fd, buf.ptr, buf.len: u64);
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if (r < 0) {
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// #199b: faithful errno→io.error needs the ...errors.error spread; see lib/io/types.ww:40
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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return r: size;
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};
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case let s: stream => return st_write(s, buf);
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};
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};
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// ref/hare/io/handle.ha:44-51. Hare propagates each arm's error via `?`
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// then falls through; ww returns directly (matching st_close's shape).
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export fn close(h: handle) (void | error) = {
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match (h) {
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case let fd: file => {
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let r: i32 = os.close(fd);
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if (r < 0) {
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// #199b: faithful errno→io.error needs the ...errors.error spread; see lib/io/types.ww:40
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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return void;
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};
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case let s: stream => return st_close(s);
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};
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};
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// ref/hare/io/handle.ha:55-62. The io.whence → os.whence cast bridges
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// the two enum copies (same SET/CUR/END values); os.lseek owns the
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// syscall.
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export fn seek(h: handle, off: off, w: whence) (off | error) = {
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match (h) {
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case let fd: file => {
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let r: i64 = os.lseek(fd, off, w: os.whence);
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if (r < 0) {
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// #199b: faithful errno→io.error needs the ...errors.error spread; see lib/io/types.ww:40
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let u: errors.unsupported;
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let e: error = u;
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return e;
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};
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return r: off;
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};
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case let s: stream => return st_seek(s, off, w);
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};
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};
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// ref/hare/io/handle.ha:65-67.
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export fn tell(h: handle) (off | error) = {
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return seek(h, 0, whence.CUR);
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};
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// ---- empty stream -------------------------------------------------------
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//
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// ref/hare/io/empty.ha:4-17.
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//
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// Hare uses `const _empty_vt: vtable = { ... }` + `const empty: *stream`.
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// ww can't const-init a vtable struct with fn-ptr fields (#118), so the
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// vtable is a module-level `let` and [[empty]] is a function that wires
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// the fn-ptr slots on every call and returns the stream pointer.
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// Single-assignment on the same words: idempotent under re-entry.
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// Lives in stream.ww (not io.ww) so that 900_stdlib can compile io.ww
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// standalone without referencing the cross-file vtable/reader/writer types.
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fn _empty_read(s: stream, buf: []u8) (size | eof | error) = {
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let e: eof;
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return e;
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};
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fn _empty_write(s: stream, buf: []u8) (size | error) = {
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return buf.len: size;
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};
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let _empty_vt: vtable;
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// empty — a stream that discards all writes (returning their size) and
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// returns EOF on every read. Mirrors ref/hare/io/empty.ha:13.
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// #118: const vtable init with fn-ptr fields is unwired (emit_struct_data
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// needs a two-pass reloc extension, node_fnptr_sym reusable). Using a
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// mutable let + per-call wiring until #118 lands.
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export fn empty() stream = {
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_empty_vt.reader = (&_empty_read): *reader;
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_empty_vt.writer = (&_empty_write): *writer;
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return &_empty_vt;
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};
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