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wren.c
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/** @file wren.h
*
* @brief Wren interpreter
*
* @par
* @copyright Copyright (c) 2007 Darius Bacon <[email protected]>
* @copyright Copyright (c) 2018 Doug Currie, Londonderry, NH, USA
* @note See LICENSE file for licensing terms.
*/
#include <assert.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include "wren.h" /* Configuration & API */
/* More Configuration */
enum {
/* Capacity in bytes. */
store_capacity = 4096,
/* True iff voluminous tracing is wanted. */
loud = 0,
};
/* Accessors for unaligned storage in dictionary and code spaces */
#if WREN_UNALIGNED_ACCESS_OK
static inline wIndex fetch_wX (const uint8_t *p)
{
return *(wIndex *)p;
}
static inline int16_t fetch_2i (const uint8_t *p)
{
return *(int16_t *)p;
}
static inline wValue fetch_wV (const uint8_t *p)
{
return *(wValue *)p;
}
static inline apply_t fetch_wP (const uint8_t *p)
{
return *(apply_t *)p;
}
static inline void write_2i (uint8_t *p, const int16_t v)
{
*(int16_t *)p = v;
}
static inline void write_wX (uint8_t *p, const wIndex v)
{
*(wIndex *)p = v;
}
static inline void write_wV (uint8_t *p, const wValue v)
{
*(wValue *)p = v;
}
static inline void write_wP (uint8_t *p, const apply_t v)
{
*(apply_t *)p = v;
}
#else
// Unaligned access is not supported by hardware.
// It looks a little silly using memcpy() here, but it has a big advantage:
// with sufficient optimization, e.g., -Os, the compiler will expand it inline
// using a simple (and hopfully optimal) instruction sequence. Together with
// the union, this code uses no Undefined Behavior as long as the data are
// written and read with the matching pair write_XX and fetch_XX.
static inline wIndex fetch_wX (const uint8_t *p)
{
union { wIndex v; uint8_t b[sizeof(wIndex)]; } u;
memcpy(u.b, p, sizeof(wIndex));
return u.v;
}
static inline int16_t fetch_2i (const uint8_t *p)
{
union { int16_t v; uint8_t b[sizeof(int16_t)]; } u;
memcpy(u.b, p, sizeof(int16_t));
return u.v;
}
static inline wValue fetch_wV (const uint8_t *p)
{
union { wValue v; uint8_t b[sizeof(wValue)]; } u;
memcpy(u.b, p, sizeof(wValue));
return u.v;
}
static inline apply_t fetch_wP (const uint8_t *p)
{
union { apply_t v; uint8_t b[sizeof(apply_t)]; } u;
memcpy(u.b, p, sizeof(apply_t));
return u.v;
}
static inline void write_wX (uint8_t *p, const wIndex v)
{
union { wIndex v; uint8_t b[sizeof(wIndex)]; } u;
u.v = v;
memcpy(p, u.b, sizeof(wIndex));
}
static inline void write_2i (uint8_t *p, const int16_t v)
{
union { int16_t v; uint8_t b[sizeof(int16_t)]; } u;
u.v = v;
memcpy(p, u.b, sizeof(int16_t));
}
static inline void write_wV (uint8_t *p, const wValue v)
{
union { wValue v; uint8_t b[sizeof(wValue)]; } u;
u.v = v;
memcpy(p, u.b, sizeof(wValue));
}
static inline void write_wP (uint8_t *p, const apply_t v)
{
union { apply_t v; uint8_t b[sizeof(apply_t)]; } u;
u.v = v;
memcpy(p, u.b, sizeof(apply_t));
}
#endif
/* Error state */
static const char *complaint = NULL;
static void complain (const char *msg)
{
if (!complaint)
complaint = msg;
}
/* Main data store in RAM
Most of the memory we use is doled out of one block.
From the top, growing downwards, is a dictionary: a stack of
header/name pairs. The header distinguishes the kind of name and
what address it denotes, along with the length of the name.
From the bottom, growing upwards, are the bindings of the names:
the code, for procedures, or the data cell, for globals. (Locals
denote an offset in a transient stack frame. We'd have interleaved
the dictionary headers with the values, like in Forth, except the
entries for locals would get in the way while we're compiling the
body of a procedure; moving all of the headers out of the way was
the simplest solution.)
At runtime, the stack grows down from the bottom of the dictionary
(but wValue-aligned).
*/
static uint8_t the_store[store_capacity];
#define store_end (the_store + store_capacity)
typedef enum { a_primitive, a_procedure, a_global, a_local, a_cfunction } NameKind;
typedef struct Header Header;
struct Header {
wIndex binding; // or for primintives, uint8_t arity; uint8_t opcode
uint8_t kind_lnm1; // (kind << 4) | (name_length - 1)
uint8_t name[0];
} __attribute__((packed)); /* XXX gcc dependency */
#define PRIM_HEADER(opcode, arity, name_length) \
(uint8_t )(arity), (uint8_t )(opcode), \
(uint8_t )(a_primitive << 4) | (((name_length) - 1u) & 0xfu)
static inline NameKind get_header_kind (const uint8_t *p_header)
{
return (NameKind )((((Header *)p_header)->kind_lnm1) >> 4);
}
static inline uint8_t get_header_name_length (const uint8_t *p_header)
{
return ((((Header *)p_header)->kind_lnm1) & 0xfu) + 1u;
}
static inline wIndex get_header_binding (const uint8_t *p_header)
{
return fetch_wX(p_header);
}
static inline uint8_t get_header_prim_arity (const uint8_t *p_header)
{
return p_header[0];
}
static inline uint8_t get_header_prim_opcode (const uint8_t *p_header)
{
return p_header[1];
}
static inline void set_header_kind_lnm1 (uint8_t *p_header, NameKind kind, int name_length)
{
uint8_t k = (uint8_t )kind;
uint8_t z = (uint8_t )(name_length - 1);
((Header *)p_header)->kind_lnm1 = (k << 4) | (z & 0xfu);
}
static inline void set_header_binding (uint8_t *p_header, const wIndex binding)
{
write_wX(p_header, binding);
}
/* We make code_idx and dict_idx accessible as a global variable to Wren code, located in
* the first two wValue cells of the_store. (See "cp" and "dp" setup in wren_initialize().)
*/
#define code_idx (((wUvalu *)the_store)[0])
#define dict_idx (((wUvalu *)the_store)[1])
#define code_ptr (&the_store[code_idx])
#define dict_ptr (&the_store[dict_idx])
static int available (unsigned amount)
{
if (code_idx + amount <= dict_idx)
return 1;
complain("Store exhausted");
return 0;
}
static const uint8_t *next_header (const uint8_t *header)
{
const Header *h = (const Header *) header;
return h->name + get_header_name_length(header);
}
static Header *bind (const char *name, unsigned length, NameKind kind, unsigned binding)
{
assert(name);
assert((length - 1u) < (1u << 4));
assert(kind <= a_cfunction);
assert(binding <= UINT16_MAX);
if (available(sizeof(Header) + length))
{
dict_idx -= sizeof(Header) + length;
{
Header *h = (Header *)dict_ptr;
set_header_kind_lnm1((uint8_t *)h, kind, (uint8_t )length);
set_header_binding((uint8_t *)h, (wIndex )binding);
memcpy(h->name, name, length);
return h;
}
}
return NULL;
}
static const Header *lookup (const uint8_t *dict, const uint8_t *end,
const char *name, unsigned length)
{
for (; dict < end; dict = next_header(dict))
{
const Header *h = (const Header *)dict;
if (get_header_name_length(dict) == length && 0 == memcmp(h->name, name, length))
return h;
}
return NULL;
}
static inline uint8_t get_proc_arity (wIndex binding)
{
// Procedures are compiled with the first byte holding the procedure's arity
return the_store[binding];
}
#ifndef NDEBUG
#if 0
static void dump (const uint8_t *dict, const uint8_t *end)
{
for (; dict < end; dict = next_header(dict))
{
const Header *h = (const Header *)dict;
const uint8_t nlen = get_header_name_length(dict);
const NameKind nknd = get_header_kind(dict);
printf(" %*.*s\t%x %x %x\n",
nlen, nlen, h->name, nknd, h->binding,
(nknd == a_procedure || nknd == a_cfunction)
? get_proc_arity(h->binding)
: nknd == a_primitive ? get_header_prim_arity(dict) : 0u);
}
}
#endif
#endif
/* The virtual machine */
typedef uint8_t Instruc;
enum {
/* 0 */ HALT, PUSH, POP, PUSH_STRING, GLOBAL_FETCH, GLOBAL_STORE, LOCAL_FETCH,
/* 7 */ TCALL, CALL, RETURN, BRANCH, JUMP,
/* 12 */ ADD, SUB, MUL, DIV, MOD, UMUL, UDIV, UMOD, NEGATE,
/* 21 */ EQ, LT, ULT, AND, OR, XOR, SLA, SRA, SRL,
/* 30 */ GETC, PUTC, REFB, REFV, SETV,
/* 35 */ LOCAL_FETCH_0, LOCAL_FETCH_1, PUSHW, PUSHB,
/* 39 */ CCALL, REFX, SETX, SETB,
};
#ifndef NDEBUG
static const char *opcode_names[] = {
"HALT", "PUSH", "POP", "PUSH_STRING", "GLOBAL_FETCH", "GLOBAL_STORE", "LOCAL_FETCH",
"TCALL", "CALL", "RETURN", "BRANCH", "JUMP",
"ADD", "SUB", "MUL", "DIV", "MOD", "UMUL", "UDIV", "UMOD", "NEGATE",
"EQ", "LT", "ULT", "AND", "OR", "XOR", "SLA", "SRA", "SRL",
"GETC", "PUTC", "REFB", "REFV", "SETV",
"LOCAL_FETCH_0", "LOCAL_FETCH_1", "PUSHW", "PUSHB",
"CCALL", "REFX", "SETX", "SETB",
};
#endif
static const uint8_t primitive_dictionary[] =
{
PRIM_HEADER(UMUL, 2, 4), 'u', 'm', 'u', 'l',
PRIM_HEADER(UDIV, 2, 4), 'u', 'd', 'i', 'v',
PRIM_HEADER(UMOD, 2, 4), 'u', 'm', 'o', 'd',
PRIM_HEADER(ULT, 2, 3), 'u', 'l', 't',
PRIM_HEADER(SLA, 2, 3), 's', 'l', 'a',
PRIM_HEADER(SRA, 2, 3), 's', 'r', 'a',
PRIM_HEADER(SRL, 2, 3), 's', 'r', 'l',
PRIM_HEADER(GETC, 0, 4), 'g', 'e', 't', 'c',
PRIM_HEADER(PUTC, 1, 4), 'p', 'u', 't', 'c',
PRIM_HEADER(REFV, 1, 4), 'r', 'e', 'f', 'v',
PRIM_HEADER(SETV, 2, 4), 's', 'e', 't', 'v',
PRIM_HEADER(REFX, 1, 4), 'r', 'e', 'f', 'x',
PRIM_HEADER(SETX, 2, 4), 's', 'e', 't', 'x',
PRIM_HEADER(SETB, 2, 4), 's', 'e', 't', 'b',
};
#ifndef NDEBUG
#if 0
static void dump_dictionary (void)
{
printf("dictionary:\n");
dump(dict_ptr, store_end);
dump(primitive_dictionary,
primitive_dictionary + sizeof primitive_dictionary);
}
#endif
#endif
/* Call to C functions; see bind_c_function and CCALL prim */
static long ccall(apply_t fn, wValue *args, unsigned arity)
{
switch (arity)
{
#define A1 args[0]
#define A2 args[1],A1
#define A3 args[2],A2
#define A4 args[3],A3
#define A5 args[4],A4
#define A6 args[5],A5
#define A7 args[6],A6
case 0: return (*fn)();
case 1: return (*fn)(A1);
case 2: return (*fn)(A2);
case 3: return (*fn)(A3);
case 4: return (*fn)(A4);
case 5: return (*fn)(A5);
case 6: return (*fn)(A6);
case 7: return (*fn)(A7);
default: return 0;
}
}
#undef A1
#undef A2
#undef A3
#undef A4
#undef A5
#undef A6
#undef A7
/* Run VM code starting at 'pc', with the stack allocated the space between
'end' and dict_ptr. Return the result on top of the stack. */
static wValue run (Instruc *pc, const Instruc *end)
{
/* Stack pointer and base pointer
Initially just above the first free aligned wValue cell below
the dictionary. */
wValue *sp = (wValue *)(((uintptr_t )dict_ptr) & ~(sizeof(wValue) - 1));
wValue *bp = sp;
#define need(n) \
if (((uint8_t *)sp - ((n) * sizeof(wValue))) < end) goto stack_overflow; else
for (;;)
{
#ifndef NDEBUG
if (loud)
printf("RUN: %"PRVAL"\t%s\n", (wValue )(pc - the_store), opcode_names[*pc]);
#endif
switch (*pc++)
{
case HALT:
return sp[0];
break;
case PUSH:
need(1);
*--sp = fetch_wV(pc);
pc += sizeof(wValue);
break;
case PUSHW:
need(1);
*--sp = fetch_2i(pc);
pc += sizeof(int16_t);
break;
case PUSHB:
need(1);
*--sp = *(int8_t *)pc;
pc += sizeof(int8_t);
break;
case POP:
++sp;
break;
case PUSH_STRING:
need(1);
*--sp = (wValue)(pc - the_store);
/* N.B. this op is slower the longer the string is! */
pc += strlen((const char *)pc) + 1;
break;
case GLOBAL_FETCH:
need(1);
*--sp = fetch_wV(the_store + fetch_wX(pc));
pc += sizeof(wIndex);
break;
case GLOBAL_STORE:
write_wV(the_store + fetch_wX(pc), sp[0]);
pc += sizeof(wIndex);
break;
case LOCAL_FETCH_0:
need(1);
*--sp = bp[0];
break;
case LOCAL_FETCH_1:
need(1);
*--sp = bp[-1];
break;
case LOCAL_FETCH:
need(1);
*--sp = bp[-*pc++];
break;
/* A stack frame looks like this:
bp[0]: leftmost argument
(This is also where the return value will go.)
...
bp[-(n-1)]: rightmost argument (where n is the number of arguments)
bp[-n]: pair of old bp and return address (in two half-words)
...temporaries...
sp[0]: topmost temporary
The bp could be dispensed with, but it simplifies the compiler and VM
interpreter slightly, and ought to make basic debugging support
significantly simpler, and if we were going to make every stack slot be
32 bits wide then we don't even waste any extra space.
By the time we return, there's only one temporary in this frame:
the return value. Thus, &bp[-n] == &sp[1] at this time, and the
RETURN instruction doesn't need to know the value of n. CALL,
otoh, does. It looks like <CALL> <n> <addr-byte-1> <addr-byte-2>.
*/
case TCALL: /* Known tail call. */
{
wIndex binding = fetch_wX(pc);
uint8_t n = get_proc_arity(binding);
/* XXX portability: this assumes two wIndex fit in a wValue */
wValue frame_info = sp[n];
memmove((bp+1-n), sp, n * sizeof(wValue));
sp = bp - n;
sp[0] = frame_info;
pc = the_store + binding + 1u;
}
break;
case CALL:
{
/* Optimize tail calls.
Why doesn't the compiler emit a tail-call instruction instead
of us checking this at runtime? Because I don't see how it
could without some greater expense there: when we finish parsing
a function with lots of if-then-else branches, we may discover
only then that a bunch of calls we've compiled were in tail
position.
(Maybe that expense would be worth incurring, though, for the
sake of smaller compiled code.)
*/
const Instruc *cont = pc + sizeof(wIndex);
while (*cont == JUMP)
{
++cont;
cont += fetch_wX(cont);
}
if (*cont == RETURN)
{
/* This is a tail call. Replace opcode and re-run */
*--pc = TCALL;
}
else
{
wIndex binding = fetch_wX(pc);
uint8_t n = get_proc_arity(binding);
/* This is a non-tail call. Build a new frame. */
need(1);
--sp;
{
/* XXX portability: this assumes two wIndex fit in a wValue
** and they the alignment is natural for both values; seems ok */
wIndex *f = (wIndex *)sp;
f[0] = (uint8_t *)bp - the_store;
f[1] = cont - the_store;
bp = sp + n;
}
pc = the_store + binding + 1u;
}
}
break;
case CCALL:
{
wIndex binding = fetch_wX(pc);
uint8_t n = get_proc_arity(binding);
wValue result = ccall((apply_t )fetch_wP(the_store + binding + 1u), sp, n);
if (n == 0u)
{
need(1);
sp -= 1;
}
else
{
sp += n - 1;
}
sp[0] = result;
pc += sizeof(wIndex);
}
break;
case RETURN:
{
wValue result = sp[0];
wIndex *f = (wIndex *)(sp + 1);
sp = bp;
bp = (wValue *)(the_store + f[0]);
pc = the_store + f[1];
sp[0] = result;
}
break;
case BRANCH:
if (0 == *sp++)
pc += fetch_wX(pc);
else
pc += sizeof(wIndex);
break;
case JUMP:
pc += fetch_wX(pc);
break;
case ADD: sp[1] += sp[0]; ++sp; break;
case SUB: sp[1] -= sp[0]; ++sp; break;
case MUL: sp[1] *= sp[0]; ++sp; break;
case DIV: sp[1] /= sp[0]; ++sp; break;
case MOD: sp[1] %= sp[0]; ++sp; break;
case UMUL: sp[1] = (wUvalu )sp[1] * (wUvalu )sp[0]; ++sp; break;
case UDIV: sp[1] = (wUvalu )sp[1] / (wUvalu )sp[0]; ++sp; break;
case UMOD: sp[1] = (wUvalu )sp[1] % (wUvalu )sp[0]; ++sp; break;
case NEGATE: sp[0] = -sp[0]; break;
case EQ: sp[1] = sp[1] == sp[0]; ++sp; break;
case LT: sp[1] = sp[1] < sp[0]; ++sp; break;
case ULT: sp[1] = (wUvalu )sp[1] < (wUvalu )sp[0]; ++sp; break;
case AND: sp[1] &= sp[0]; ++sp; break;
case OR: sp[1] |= sp[0]; ++sp; break;
case XOR: sp[1] ^= sp[0]; ++sp; break;
case SLA: sp[1] <<= sp[0]; ++sp; break;
case SRA: sp[1] >>= sp[0]; ++sp; break;
case SRL: sp[1] = (wUvalu )sp[1] >> (wUvalu )sp[0]; ++sp; break;
case GETC:
need(1);
*--sp = getc(stdin);
break;
case PUTC:
putc(sp[0], stdout);
break;
case REFB:
{
wUvalu x = (wUvalu )sp[0]; // unsigned for comparison
if (x < (wUvalu )store_capacity)
{
sp[0] = the_store[x];
}
else
{
// Out of Bounds -- XXX ignore!?
sp[0] = 0;
}
break;
}
case REFV:
{
wUvalu x = (wUvalu )sp[0]; // unsigned for comparison
if (x <= (wUvalu )(store_capacity - sizeof(wValue)))
{
sp[0] = fetch_wV(&the_store[x]);
}
else
{
// Out of Bounds -- XXX ignore!?
sp[0] = 0;
}
break;
}
case SETV:
{
wUvalu x = (wUvalu )sp[1]; // unsigned for comparison
if (x <= (wUvalu )(store_capacity - sizeof(wValue)))
{
write_wV(&the_store[x], sp[0]);
}
else
{
// Out of Bounds -- XXX ignore!?
}
++sp; // e: just one value popped
break;
}
case REFX:
{
wUvalu x = (wUvalu )sp[0]; // unsigned for comparison
if (x <= (wUvalu )(store_capacity - sizeof(wIndex)))
{
sp[0] = (wValue )fetch_wX(&the_store[x]);
}
else
{
// Out of Bounds -- XXX ignore!?
sp[0] = 0;
}
break;
}
case SETX:
{
wUvalu x = (wUvalu )sp[1]; // unsigned for comparison
if (x <= (wUvalu )(store_capacity - sizeof(wIndex)))
{
write_wX(&the_store[x], (wIndex )sp[0]);
}
else
{
// Out of Bounds -- XXX ignore!?
}
++sp; // e: just one value popped
break;
}
case SETB:
{
wUvalu x = (wUvalu )sp[1]; // unsigned for comparison
if (x < (wUvalu )store_capacity)
{
the_store[x] = (uint8_t )sp[0];
}
else
{
// Out of Bounds -- XXX ignore!?
}
++sp; // e: just one value popped
break;
}
default: assert(0);
}
}
stack_overflow:
complain("Stack overflow");
return 0;
}
/* The 'assembler' */
static wIndex prev_instruc = 0u;
static void gen (Instruc opcode)
{
#ifndef NDEBUG
if (loud)
printf("ASM: %"PRVAL"\t%s\n", code_idx, opcode_names[opcode]);
#endif
if (available(1))
{
prev_instruc = code_idx;
the_store[code_idx++] = opcode;
}
}
static void gen_ubyte (uint8_t b)
{
if (loud)
printf("ASM: %"PRVAL"\tubyte %u\n", code_idx, b);
if (available(1))
the_store[code_idx++] = b;
}
static void gen_sbyte (int8_t b)
{
if (loud)
printf("ASM: %"PRVAL"\tsbyte %d\n", code_idx, b);
if (available(1))
((int8_t *)the_store)[code_idx++] = b;
}
static void gen_ushort (wIndex u)
{
if (loud)
printf("ASM: %"PRVAL"\tushort %u\n", code_idx, u);
if (available(sizeof u))
{
write_wX(code_ptr, u);
code_idx += sizeof u;
}
}
static void gen_sshort (int16_t u)
{
if (loud)
printf("ASM: %"PRVAL"\tsshort %d\n", code_idx, u);
if (available(sizeof u))
{
write_2i(code_ptr, u);
code_idx += sizeof u;
}
}
static void gen_value (wValue v)
{
if (loud)
printf("ASM: %"PRVAL"\tvalue %"PRVAL"\n", code_idx, v);
if (available(sizeof v))
{
write_wV(code_ptr, v);
code_idx += sizeof v;
}
}
static void gen_pointer (apply_t v)
{
if (loud)
printf("ASM: %"PRVAL"\tvalue %"PRPTR"\n", code_idx, v);
if (available(sizeof v))
{
write_wP(code_ptr, v);
code_idx += sizeof v;
}
}
static wIndex forward_ref (void)
{
wIndex ref = code_idx;
code_idx += sizeof(wIndex);
return ref;
}
static void resolve (wIndex ref)
{
if (loud)
printf("ASM: %"PRIDX"\tresolved: %"PRVAL"\n", ref, code_idx - ref);
write_wX(&the_store[ref], code_idx - ref);
}
static void block_prev (void)
{
prev_instruc = 0u; // The previous instruction isn't really known
}
/* Scanning */
enum { unread = EOF - 1 };
static int input_char = unread;
static int token;
static FILE *in_file;
static wValue token_value;
static char token_name[17]; // 16 + NUL
static int ch (void)
{
if (input_char == unread)
input_char = getc(in_file);
return input_char;
}
static void next_char (void)
{
if (input_char != EOF)
input_char = unread;
}
static void skip_line (void)
{
while (ch() != '\n' && ch() != EOF)
next_char();
}
static unsigned hex_char_value (char c)
{
return c <= '9' ? c - '0' : toupper(c) - ('A'-10);
}
static void next (void)
{
again:
if (isdigit(ch()))
{
token = PUSH;
token_value = 0;
do {
token_value = 10 * token_value + ch() - '0';
next_char();
if (ch() == 'x' && token_value == 0)
{
unsigned int digit_count = 0;
/* Oh, it's a hex literal, not decimal as we presumed. */
next_char();
for (; isxdigit(ch()); next_char()) {
token_value = 16 * token_value + hex_char_value(ch());
digit_count++;
}
if (digit_count == 0)
complain("Invalid Hex Number");
else if (digit_count > 2*sizeof(wValue)) { // allow all bits used for hex entry
complain("Numeric overflow");
}
break;
}
if (token_value < 0) // overflow
{
complain("Numeric overflow");
break;
}
} while (isdigit(ch()));
}
else if (isalpha(ch()) || ch() == '_')
{
char *n = token_name;
do {
if (token_name + sizeof token_name == n + 1)
{
complain("Identifier too long");
break;
}
*n++ = ch();
next_char();
} while (isalnum(ch()) || ch() == '_');
*n++ = '\0';
if (0 == strcmp(token_name, "then"))
token = 't';
else if (0 == strcmp(token_name, "forget"))
token = 'o';
else if (0 == strcmp(token_name, "let"))
token = 'l';
else if (0 == strcmp(token_name, "if"))
token = 'i';
else if (0 == strcmp(token_name, "fun"))
token = 'f';
else if (0 == strcmp(token_name, "else"))
token = 'e';
else
token = 'a';
}
else
switch (ch())
{
case '\'':
next_char();
{
/* We need to stick this string somewhere; after reaching
the parser, if successfully parsed, it would be compiled
into the instruction stream right after the next opcode.
So just put it there -- but don't yet update code_idx. */
uint8_t *s = code_ptr + 1;
for (; ch() != '\''; next_char())
{
if (ch() == EOF)
{
complain("Unterminated string");
token = EOF;
return;
}
if (!available(s + 2 - code_ptr))
{
token = '\n'; /* XXX need more for error recovery? */
return;
}
*s++ = ch();
}
next_char();
*s = '\0';
token = '\'';
}
break;
case '+':
case '-':
case '*':
case '/':
case '%':
case '<':
case '&':
case '|':
case '^':
case '(':
case ')':
case '=':
case ':':
case ';':
case '\n':
case EOF:
token = ch();
next_char();
break;
case ' ':
case '\t':
case '\r':
next_char();
goto again;
case '#':
skip_line();
goto again;
default:
complain("Lexical error");
token = '\n'; /* XXX need more for error recovery */
break;
}
}
/* Parsing and compiling */
static int expect (uint8_t expected, const char *plaint)
{
if (token == expected)
return 1;
complain(plaint);
return 0;
}
static void skip_newline (void)
{
while (!complaint && token == '\n')
next();
}
static void parse_expr (int precedence);
static void parse_arguments (unsigned arity)
{
unsigned i;
for (i = 0; i < arity; ++i)
parse_expr(20); /* 20 is higher than any operator precedence */
}