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/* WebAssembly port of the microcore with streaming input, for the language
server. the host (the vs code extension) feeds the server's input in pieces
and calls wasm_resume after each feed; the server's output comes back one
byte at a time through js_putc, and its diagnostics through js_msg. the
server suspends when it wants input it does not have yet (MICRO_WAIT in
micro_port.h), so a step never blocks the host. build with
src/tools/mklspwasm.sh; nothing here needs libc. */
#include "micro_port.h"
extern void js_putc(int c);
extern void js_msg(int c);
#define CHUNK 65536
#define QCAP (8 << 20)
/* the host copies a piece of input here, then calls wasm_feed with its length */
static unsigned char chunk[CHUNK];
/* the input the server has not read yet: q[qp..qn) */
static unsigned char q[QCAP];
static int qn, qp, closed, polled;
unsigned char *wasm_chunk(void) { return chunk; }
int wasm_chunk_cap(void) { return (int)sizeof chunk; }
/* appends the first n bytes of chunk to the input. 0 on success, -1 when the
input would not fit, which the host must not allow (it drains by running) */
int wasm_feed(int n)
{
int i;
if (n < 0 || n > CHUNK || closed) return -1;
if (qn + n > QCAP) { /* move what is unread to the front */
int live = qn - qp;
if (live + n > QCAP) return -1;
for (i = 0; i < live; i++) q[i] = q[qp + i];
qp = 0; qn = live;
}
for (i = 0; i < n; i++) q[qn++] = chunk[i];
return 0;
}
/* 1 while the server is suspended by a poll rather than by a read: the host should resume it
after the event loop has run, whether or not input came */
int wasm_polling(void) { return polled; }
/* no more input will come: the next read past the end is -1 */
void wasm_close(void) { closed = 1; }
/* the machine's memory: the linear memory above everything the module has in it.
the base is fixed when the first machine is made, and a grow only adds pages on
the top, so the base never moves. */
static unsigned char *mbase;
static UCell mcap; /* bytes of machine memory the module has grown for */
Cell *micro_mem_alloc(UCell words)
{
UCell need, extra, pages;
if (words > ((UCell)-1) / sizeof(Cell)) return 0;
if (!mbase) {
UCell top = (UCell)__builtin_wasm_memory_size(0) * 65536u;
mbase = (unsigned char *)top;
mcap = 0;
}
need = words * sizeof(Cell);
if (need <= mcap) return (Cell *)mbase;
extra = need - mcap;
pages = (extra + 65535u) / 65536u;
if (__builtin_wasm_memory_grow(0, (int)pages) < 0) return 0;
mcap += pages * 65536u; /* wasm zeroes the pages it grows by */
return (Cell *)mbase;
}
int micro_getc(void)
{
if (qp < qn) return q[qp++];
return closed ? -1 : MICRO_WAIT;
}
int micro_eof(void) { return closed && qp >= qn; }
void micro_putc(int c) { js_putc(c & 255); }
void micro_msg(const char *s) { while (*s) js_msg(*s++); }
Cell micro_syscall(Cell *mem, Cell op, Cell a, Cell b, Cell c)
{
switch (op) {
case 9: /* memory: the size of the machine and its heap */
if (a == 0) return micro_mem_words();
if (a == 1) return HEAP_LO;
if (a == 2) return HEAP_HI;
if (a == 3) return (Cell)micro_mem_words() * 8;
return -1;
case 42: /* poll: suspend once so the host can feed what has arrived, then say if input is waiting */
if (!polled) { polled = 1; return MICRO_WAIT; }
polled = 0;
return qp < qn;
case 7: /* exit: the run ends */
return -1;
case 21: /* argc: the server has no command line of its own, so <eval> alone */
return 1;
case 22: /* argv: entry 0 is <eval>, as in zy(1) */
if (a != 0) return -1;
if (!b) return 6;
if (c < 7 || b + 6 >= micro_mem_words()) return -1;
{
static const char lead[] = "<eval>";
int i;
for (i = 0; i < 6; i++) mem[b + i] = (unsigned char)lead[i];
mem[b + 6] = 0;
}
return 6;
case 23: /* envc: the host passes no environment */
return 0;
}
return -1;
}
/* the core multiplies 64 by 64 into 128 bits for the float helpers; wasm has no
such instruction and there is no compiler runtime to link, so this is it */
void __multi3(unsigned long long *r, unsigned long long al, unsigned long long ah, unsigned long long bl, unsigned long long bh)
{
unsigned long long a0 = al & 0xffffffffu, a1 = al >> 32, b0 = bl & 0xffffffffu, b1 = bl >> 32;
unsigned long long p00 = a0 * b0, p01 = a0 * b1, p10 = a1 * b0, p11 = a1 * b1;
unsigned long long mid = (p00 >> 32) + (p01 & 0xffffffffu) + (p10 & 0xffffffffu);
r[0] = (p00 & 0xffffffffu) | (mid << 32);
r[1] = p11 + (p01 >> 32) + (p10 >> 32) + (mid >> 32) + al * bh + ah * bl;
}
/* loads the server and runs it until it halts or waits for input (3) */
int wasm_start(void) { return micro_run(); }
/* goes on after the host fed input: as wasm_start, halt (0), error (2) or wait (3) */
int wasm_resume(void) { return micro_resume(); }
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