1 files changed, 86 insertions, 0 deletions
diff --git a/src/web/port_wasm.c b/src/web/port_wasm.c
new file mode 100644
index 0000000..c1e8483
--- /dev/null
+++ b/src/web/port_wasm.c
@@ -0,0 +1,86 @@
+/* WebAssembly port of the microcore. the page hands the program over as
+   bytes, calls run(), and gets output back one byte at a time through the
+   one import. build with src/web/build.sh; nothing here needs libc. */
+#include "micro_port.h"
+
+extern void js_putc(int c);
+extern void js_msg(int c);
+
+static unsigned char inbuf[1 << 20];
+static int inn, inp;
+
+/* where the page writes the program, and how it says how long it is */
+unsigned char *wasm_input(void) { return inbuf; }
+int wasm_input_cap(void) { return (int)sizeof inbuf; }
+void wasm_set_input(int n) { inn = n; inp = 0; }
+
+/* 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) {
+		mbase = (unsigned char *)((UCell)__builtin_wasm_memory_size(0) * 65536u);
+		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) { return inp < inn ? inbuf[inp++] : -1; }
+int micro_eof(void) { return inp >= inn; }
+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 7:		/* exit: the page sees run() return */
+		return -1;
+	case 21:	/* argc: the page has no command line, 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: a page has 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;
+}
+
+int wasm_run(void) { return micro_run(); }