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janet/src/core/peg.c

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/*
* Copyright (c) 2019 Calvin Rose
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include <janet/janet.h>
#include <string.h>
#include "util.h"
#include "vector.h"
/*
* Runtime
*/
/* opcodes for peg vm */
typedef enum {
RULE_LITERAL, /* [len, bytes...] */
RULE_NCHAR, /* [n] */
RULE_NOTNCHAR, /* [n] */
RULE_RANGE, /* [lo | hi << 16 (1 word)] */
RULE_SET, /* [bitmap (8 words)] */
RULE_LOOK, /* [offset, rule] */
RULE_CHOICE, /* [len, rules...] */
RULE_SEQUENCE, /* [len, rules...] */
RULE_IF, /* [rule_a, rule_b (b if a)] */
RULE_IFNOT, /* [rule_a, rule_b (b if not a)] */
RULE_NOT, /* [rule] */
RULE_BETWEEN, /* [lo, hi, rule] */
RULE_CAPTURE, /* [rule] */
RULE_POSITION, /* [] */
RULE_ARGUMENT, /* [argument-index] */
RULE_REPINDEX, /* [capture-index] */
RULE_CONSTANT, /* [constant] */
RULE_SUBSTITUTE, /* [rule] */
RULE_GROUP, /* [rule] */
RULE_REPLACE, /* [rule, constant] */
RULE_MATCHTIME, /* [rule, constant] */
RULE_ERROR, /* [rule] */
} Opcode;
/* Hold captured patterns and match state */
typedef struct {
const uint8_t *text_start;
const uint8_t *text_end;
const uint8_t *subst_end;
const uint32_t *bytecode;
const Janet *constants;
JanetArray *captures;
JanetBuffer *scratch;
const Janet *extrav;
int32_t extrac;
int32_t depth;
enum {
PEG_MODE_NORMAL,
PEG_MODE_SUBSTITUTE,
PEG_MODE_NOCAPTURE
} mode;
} PegState;
/* Allow backtrack with captures. We need
* to save state at branches, and then reload
* if one branch fails and try a new branch. */
typedef struct {
const uint8_t *subst_end;
int32_t cap;
int32_t scratch;
} CapState;
/* Save the current capture state */
static CapState cap_save(PegState *s) {
CapState cs;
cs.subst_end = s->subst_end;
cs.scratch = s->scratch->count;
cs.cap = s->captures->count;
return cs;
}
/* Load a saved capture state in the case of failure */
static void cap_load(PegState *s, CapState cs) {
s->subst_end = cs.subst_end;
s->scratch->count = cs.scratch;
s->captures->count = cs.cap;
}
/* Add a capture */
static void pushcap(PegState *s,
Janet capture,
const uint8_t *text,
const uint8_t *result) {
if (s->mode == PEG_MODE_SUBSTITUTE) {
janet_buffer_push_bytes(s->scratch, s->subst_end,
(int32_t)(text - s->subst_end));
janet_to_string_b(s->scratch, capture);
s->subst_end = result;
} else if (s->mode == PEG_MODE_NORMAL) {
janet_array_push(s->captures, capture);
}
}
/* Prevent stack overflow */
#define down1(s) do { \
if (0 == --((s)->depth)) janet_panic("peg/match recursed too deeply"); \
} while (0)
#define up1(s) ((s)->depth++)
/* Evaluate a peg rule */
static const uint8_t *peg_rule(
PegState *s,
const uint32_t *rule,
const uint8_t *text) {
tail:
switch(*rule & 0x1F) {
default:
janet_panic("unexpected opcode");
return NULL;
case RULE_LITERAL:
{
uint32_t len = rule[1];
if (text + len > s->text_end) return NULL;
return memcmp(text, rule + 2, len) ? NULL : text + len;
}
case RULE_NCHAR:
{
uint32_t n = rule[1];
return (text + n > s->text_end) ? NULL : text + n;
}
case RULE_NOTNCHAR:
{
uint32_t n = rule[1];
return (text + n > s->text_end) ? text : NULL;
}
case RULE_RANGE:
{
uint8_t lo = rule[1] & 0xFF;
uint8_t hi = (rule[1] >> 16) & 0xFF;
return (text < s->text_end &&
text[0] >= lo &&
text[0] <= hi)
? text + 1
: NULL;
}
case RULE_SET:
{
uint32_t word = rule[1 + (text[0] >> 5)];
uint32_t mask = (uint32_t)1 << (text[0] & 0x1F);
return (text < s->text_end && (word & mask))
? text + 1
: NULL;
}
case RULE_LOOK:
{
text += ((int32_t *)rule)[1];
if (text < s->text_start || text > s->text_end) return NULL;
int oldmode = s->mode;
s->mode = PEG_MODE_NOCAPTURE;
down1(s);
const uint8_t *result = peg_rule(s, s->bytecode + rule[2], text);
up1(s);
s->mode = oldmode;
return result ? text : NULL;
}
case RULE_CHOICE:
{
uint32_t len = rule[1];
const uint32_t *args = rule + 2;
if (len == 0) return NULL;
down1(s);
CapState cs = cap_save(s);
for (uint32_t i = 0; i < len - 1; i++) {
const uint8_t *result = peg_rule(s, s->bytecode + args[i], text);
if (result) {
up1(s);
return result;
}
cap_load(s, cs);
}
up1(s);
rule = s->bytecode + args[len - 1];
goto tail;
}
case RULE_SEQUENCE:
{
uint32_t len = rule[1];
const uint32_t *args = rule + 2;
if (len == 0) return text;
down1(s);
for (uint32_t i = 0; text && i < len - 1; i++)
text = peg_rule(s, s->bytecode + args[i], text);
up1(s);
if (!text) return NULL;
rule = s->bytecode + args[len - 1];
goto tail;
}
case RULE_IF:
case RULE_IFNOT:
{
const uint32_t *rule_a = s->bytecode + rule[1];
const uint32_t *rule_b = s->bytecode + rule[2];
int oldmode = s->mode;
s->mode = PEG_MODE_NOCAPTURE;
down1(s);
const uint8_t *result = peg_rule(s, rule_a, text);
up1(s);
s->mode = oldmode;
if (rule[0] == RULE_IF ? !result : !!result) return NULL;
rule = rule_b;
goto tail;
}
case RULE_NOT:
{
const uint32_t *rule_a = s->bytecode + rule[1];
int oldmode = s->mode;
s->mode = PEG_MODE_NOCAPTURE;
down1(s);
const uint8_t *result = peg_rule(s, rule_a, text);
up1(s);
s->mode = oldmode;
return (result) ? NULL : text;
}
case RULE_BETWEEN:
{
uint32_t lo = rule[1];
uint32_t hi = rule[2];
const uint32_t *rule_a = s->bytecode + rule[3];
uint32_t captured = 0;
const uint8_t *next_text;
CapState cs = cap_save(s);
down1(s);
while (captured < hi && (next_text = peg_rule(s, rule_a, text))) {
captured++;
text = next_text;
}
up1(s);
if (captured < lo) {
cap_load(s, cs);
return NULL;
}
return text;
}
case RULE_POSITION:
{
pushcap(s, janet_wrap_number((double)(text - s->text_start)), text, text);
return text;
}
case RULE_ARGUMENT:
{
int32_t index = ((int32_t *)rule)[1];
Janet capture = (index >= s->extrac) ? janet_wrap_nil() : s->extrav[index];
pushcap(s, capture, text, text);
return text;
}
case RULE_REPINDEX:
{
int32_t index = ((int32_t *)rule)[1];
if (index < 0) index += s->captures->count;
if (index >= s->captures->count || index < 0) return NULL;
Janet capture = s->captures->data[index];
pushcap(s, capture, text, text);
return text;
}
case RULE_CONSTANT:
{
pushcap(s, s->constants[rule[1]], text, text);
return text;
}
case RULE_CAPTURE:
{
int oldmode = s->mode;
if (oldmode == PEG_MODE_NOCAPTURE) {
rule = s->bytecode + rule[1];
goto tail;
}
if (oldmode == PEG_MODE_SUBSTITUTE) s->mode = PEG_MODE_NOCAPTURE;
down1(s);
const uint8_t *result = peg_rule(s, s->bytecode + rule[1], text);
up1(s);
s->mode = oldmode;
if (!result) return NULL;
if (oldmode != PEG_MODE_SUBSTITUTE)
pushcap(s, janet_stringv(text, (int32_t)(result - text)), text, result);
return result;
}
case RULE_SUBSTITUTE:
case RULE_GROUP:
case RULE_REPLACE:
{
/* In no-capture mode, all captures simply become their matching pattern */
int oldmode = s->mode;
if (oldmode == PEG_MODE_NOCAPTURE) {
rule = s->bytecode + rule[1];
goto tail;
}
/* Save previous state. Will use this to reload state before
* pushing grammar. Each of these rules pushes exactly 1 new
* capture, regardless of the sub rule. */
CapState cs = cap_save(s);
/* Set sub mode as needed. Modes affect how captures are recorded (pushed to stack,
* pushed to byte buffer, or ignored) */
if (rule[0] == RULE_GROUP) s->mode = PEG_MODE_NORMAL;
if (rule[0] == RULE_REPLACE) s->mode = PEG_MODE_NORMAL;
if (rule[0] == RULE_SUBSTITUTE) {
s->mode = PEG_MODE_SUBSTITUTE;
s->subst_end = text;
}
down1(s);
const uint8_t *result = peg_rule(s, s->bytecode + rule[1], text);
up1(s);
s->mode = oldmode;
if (!result) return NULL;
/* The replacement capture */
Janet cap;
/* Figure out what to push based on opcode */
if (rule[0] == RULE_GROUP) {
int32_t num_sub_captures = s->captures->count - cs.cap;
JanetArray *sub_captures = janet_array(num_sub_captures);
memcpy(sub_captures->data,
s->captures->data + cs.cap,
sizeof(Janet) * num_sub_captures);
sub_captures->count = num_sub_captures;
cap = janet_wrap_array(sub_captures);
} else if (rule[0] == RULE_SUBSTITUTE) {
janet_buffer_push_bytes(s->scratch, s->subst_end,
(int32_t)(result - s->subst_end));
cap = janet_stringv(s->scratch->data + cs.scratch,
s->scratch->count - cs.scratch);
} else { /* RULE_REPLACE */
Janet constant = s->constants[rule[2]];
switch (janet_type(constant)) {
default:
cap = constant;
break;
case JANET_STRUCT:
cap = janet_struct_get(janet_unwrap_struct(constant),
s->captures->data[s->captures->count - 1]);
break;
case JANET_TABLE:
cap = janet_table_get(janet_unwrap_table(constant),
s->captures->data[s->captures->count - 1]);
break;
case JANET_CFUNCTION:
cap = janet_unwrap_cfunction(constant)(s->captures->count - cs.cap,
s->captures->data + cs.cap);
break;
case JANET_FUNCTION:
cap = janet_call(janet_unwrap_function(constant),
s->captures->count - cs.cap,
s->captures->data + cs.cap);
break;
}
}
/* Reset old state and then push capture */
cap_load(s, cs);
pushcap(s, cap, text, result);
return result;
}
case RULE_MATCHTIME:
{
int oldmode = s->mode;
CapState cs = cap_save(s);
s->mode = PEG_MODE_NORMAL;
down1(s);
const uint8_t *result = peg_rule(s, s->bytecode + rule[1], text);
up1(s);
s->mode = oldmode;
if (!result) return NULL;
/* Now check captures with provided function */
int32_t argc = s->captures->count - cs.cap;
Janet *argv = s->captures->data + cs.cap;
Janet fval = s->constants[rule[2]];
Janet cap;
if (janet_checktype(fval, JANET_FUNCTION)) {
cap = janet_call(janet_unwrap_function(fval), argc, argv);
} else {
JanetCFunction cfun = janet_unwrap_cfunction(fval);
cap = cfun(argc, argv);
}
cap_load(s, cs);
/* Capture failed */
if (!janet_truthy(cap)) return NULL;
/* Capture worked, so use new capture */
pushcap(s, cap, text, result);
return result;
}
case RULE_ERROR:
{
int oldmode = s->mode;
s->mode = PEG_MODE_NORMAL;
int32_t old_cap = s->captures->count;
down1(s);
const uint8_t *result = peg_rule(s, s->bytecode + rule[1], text);
up1(s);
s->mode = oldmode;
if (!result) return NULL;
if (s->captures->count > old_cap) {
/* Throw last capture */
janet_panicv(s->captures->data[s->captures->count - 1]);
} else {
/* Throw generic error */
int32_t start = (int32_t)(text - s->text_start);
int32_t end = (int32_t)(result - s->text_start);
janet_panicf("match error in range (%d:%d)", start, end);
}
return NULL;
}
}
}
/*
* Compilation
*/
typedef struct {
JanetTable *grammar;
JanetTable *memoized;
Janet *constants;
uint32_t *bytecode;
Janet form;
int depth;
} Builder;
/* Forward declaration to allow recursion */
static uint32_t compile1(Builder *b, Janet peg);
/*
* Emission
*/
static uint32_t emit_constant(Builder *b, Janet c) {
uint32_t cindex = (uint32_t) janet_v_count(b->constants);
janet_v_push(b->constants, c);
return cindex;
}
/* Reserve space in bytecode for a rule. When a special emits a rule,
* it must place that rule immediately on the bytecode stack. This lets
* the compiler know where the rule is going to be before it is complete,
* allowing recursive rules. */
typedef struct {
Builder *builder;
uint32_t index;
int32_t size;
} Reserve;
static Reserve reserve(Builder *b, int32_t size) {
Reserve r;
r.index = janet_v_count(b->bytecode);
r.builder = b;
r.size = size;
for (int32_t i = 0; i < size; i++)
janet_v_push(b->bytecode, 0);
return r;
}
/* Emit a rule in the builder. Returns the index of the new rule */
static void emit_rule(Reserve r, int32_t op, int32_t n, const uint32_t *body) {
janet_assert(r.size == n + 1, "bad reserve");
r.builder->bytecode[r.index] = op;
memcpy(r.builder->bytecode + r.index + 1, body, n * sizeof(uint32_t));
}
/* For RULE_LITERAL */
static void emit_bytes(Builder *b, uint32_t op, int32_t len, const uint8_t *bytes) {
uint32_t next_rule = janet_v_count(b->bytecode);
janet_v_push(b->bytecode, op);
janet_v_push(b->bytecode, len);
int32_t words = ((len + 3) >> 2);
for (int32_t i = 0; i < words; i++)
janet_v_push(b->bytecode, 0);
memcpy(b->bytecode + next_rule + 2, bytes, len);
}
/* For fixed arity rules of arities 1, 2, and 3 */
static void emit_1(Reserve r, uint32_t op, uint32_t arg) {
emit_rule(r, op, 1, &arg);
}
static void emit_2(Reserve r, uint32_t op, uint32_t arg1, uint32_t arg2) {
uint32_t arr[2] = {arg1, arg2};
emit_rule(r, op, 2, arr);
}
static void emit_3(Reserve r, uint32_t op, uint32_t arg1, uint32_t arg2, uint32_t arg3) {
uint32_t arr[3] = {arg1, arg2, arg3};
emit_rule(r, op, 3, arr);
}
/*
* Errors
*/
static void builder_cleanup(Builder *b) {
janet_v_free(b->constants);
janet_v_free(b->bytecode);
}
static void peg_panic(Builder *b, const char *msg) {
builder_cleanup(b);
janet_panicf("grammar error in %p, %s", b->form, msg);
}
#define peg_panicf(b,...) peg_panic((b), (const char *) janet_formatc(__VA_ARGS__))
static void peg_fixarity(Builder *b, int32_t argc, int32_t arity) {
if (argc != arity) {
peg_panicf(b, "expected %d argument%s, got %d%",
arity,
arity == 1 ? "" : "s",
argc);
}
}
static void peg_arity(Builder *b, int32_t arity, int32_t min, int32_t max) {
if (min >= 0 && arity < min)
peg_panicf(b, "arity mismatch, expected at least %d, got %d", min, arity);
if (max >= 0 && arity > max)
peg_panicf(b, "arity mismatch, expected at most %d, got %d", max, arity);
}
static const uint8_t *peg_getset(Builder *b, Janet x) {
if (!janet_checktype(x, JANET_STRING))
peg_panicf(b, "expected string for character set");
const uint8_t *str = janet_unwrap_string(x);
return str;
}
static const uint8_t *peg_getrange(Builder *b, Janet x) {
if (!janet_checktype(x, JANET_STRING))
peg_panicf(b, "expected string for character range");
const uint8_t *str = janet_unwrap_string(x);
if (janet_string_length(str) != 2)
peg_panicf(b, "expected string to have length 2, got %v", x);
if (str[1] < str[0])
peg_panicf(b, "range %v is empty", x);
return str;
}
static int32_t peg_getinteger(Builder *b, Janet x) {
if (!janet_checkint(x))
peg_panicf(b, "expected integer, got %v", x);
return janet_unwrap_integer(x);
}
static int32_t peg_getnat(Builder *b, Janet x) {
int32_t i = peg_getinteger(b, x);
if (i < 0)
peg_panicf(b, "expected non-negative integer, got %v", x);
return i;
}
/*
* Specials
*/
static void bitmap_set(uint32_t *bitmap, uint8_t c) {
bitmap[c >> 5] |= ((uint32_t)1) << (c & 0x1F);
}
static void spec_range(Builder *b, int32_t argc, const Janet *argv) {
peg_arity(b, argc, 1, -1);
if (argc == 1) {
Reserve r = reserve(b, 2);
const uint8_t *str = peg_getrange(b, argv[0]);
uint32_t arg = str[0] | (str[1] << 16);
emit_1(r, RULE_RANGE, arg);
} else {
/* Compile as a set */
Reserve r = reserve(b, 9);
uint32_t bitmap[8] = {0};
for (int32_t i = 0; i < argc; i++) {
const uint8_t *str = peg_getrange(b, argv[i]);
for (uint32_t c = str[0]; c <= str[1]; c++)
bitmap_set(bitmap, c);
}
emit_rule(r, RULE_SET, 8, bitmap);
}
}
static void spec_set(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 9);
const uint8_t *str = peg_getset(b, argv[0]);
uint32_t bitmap[8] = {0};
for (int32_t i = 0; i < janet_string_length(str); i++)
bitmap_set(bitmap, str[i]);
emit_rule(r, RULE_SET, 8, bitmap);
}
static void spec_look(Builder *b, int32_t argc, const Janet *argv) {
peg_arity(b, argc, 1, 2);
Reserve r = reserve(b, 3);
int32_t rulearg = argc == 2 ? 1 : 0;
int32_t offset = argc == 2 ? peg_getinteger(b, argv[0]) : 0;
uint32_t subrule = compile1(b, argv[rulearg]);
emit_2(r, RULE_LOOK, (uint32_t) offset, subrule);
}
/* Rule of the form [len, rules...] */
static void spec_variadic(Builder *b, int32_t argc, const Janet *argv, uint32_t op) {
uint32_t rule = janet_v_count(b->bytecode);
janet_v_push(b->bytecode, op);
janet_v_push(b->bytecode, argc);
for (int32_t i = 0; i < argc; i++)
janet_v_push(b->bytecode, 0);
for (int32_t i = 0; i < argc; i++) {
uint32_t rulei = compile1(b, argv[i]);
b->bytecode[rule + 2 + i] = rulei;
}
}
static void spec_choice(Builder *b, int32_t argc, const Janet *argv) {
spec_variadic(b, argc, argv, RULE_CHOICE);
}
static void spec_sequence(Builder *b, int32_t argc, const Janet *argv) {
spec_variadic(b, argc, argv, RULE_SEQUENCE);
}
/* For (if a b) and (if-not a b) */
static void spec_branch(Builder *b, int32_t argc, const Janet *argv, uint32_t rule) {
peg_fixarity(b, argc, 2);
Reserve r = reserve(b, 3);
uint32_t rule_a = compile1(b, argv[0]);
uint32_t rule_b = compile1(b, argv[1]);
emit_2(r, rule, rule_a, rule_b);
}
static void spec_if(Builder *b, int32_t argc, const Janet *argv) {
spec_branch(b, argc, argv, RULE_IF);
}
static void spec_ifnot(Builder *b, int32_t argc, const Janet *argv) {
spec_branch(b, argc, argv, RULE_IFNOT);
}
/* Rule of the form [rule] */
static void spec_onerule(Builder *b, int32_t argc, const Janet *argv, uint32_t op) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 2);
uint32_t rule = compile1(b, argv[0]);
emit_1(r, op, rule);
}
static void spec_not(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_NOT);
}
static void spec_capture(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_CAPTURE);
}
static void spec_substitute(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_SUBSTITUTE);
}
static void spec_group(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_GROUP);
}
static void spec_error(Builder *b, int32_t argc, const Janet *argv) {
spec_onerule(b, argc, argv, RULE_ERROR);
}
static void spec_between(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 3);
Reserve r = reserve(b, 4);
int32_t lo = peg_getnat(b, argv[0]);
int32_t hi = peg_getnat(b, argv[1]);
uint32_t subrule = compile1(b, argv[2]);
emit_3(r, RULE_BETWEEN, lo, hi, subrule);
}
static void spec_position(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 0);
Reserve r = reserve(b, 1);
(void) argv;
emit_rule(r, RULE_POSITION, 0, NULL);
}
static void spec_reference(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 2);
int32_t index = peg_getinteger(b, argv[0]);
emit_1(r, RULE_REPINDEX, index);
}
static void spec_argument(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 2);
int32_t index = peg_getnat(b, argv[0]);
emit_1(r, RULE_ARGUMENT, index);
}
static void spec_constant(Builder *b, int32_t argc, const Janet *argv) {
janet_fixarity(argc, 1);
Reserve r = reserve(b, 2);
emit_1(r, RULE_CONSTANT, emit_constant(b, argv[0]));
}
static void spec_replace(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 2);
Reserve r = reserve(b, 3);
uint32_t subrule = compile1(b, argv[0]);
uint32_t constant = emit_constant(b, argv[1]);
emit_2(r, RULE_REPLACE, subrule, constant);
}
static void spec_repeater(Builder *b, int32_t argc, const Janet *argv, int32_t min) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 4);
uint32_t subrule = compile1(b, argv[0]);
emit_3(r, RULE_BETWEEN, min, UINT32_MAX, subrule);
}
static void spec_some(Builder *b, int32_t argc, const Janet *argv) {
spec_repeater(b, argc, argv, 1);
}
static void spec_any(Builder *b, int32_t argc, const Janet *argv) {
spec_repeater(b, argc, argv, 0);
}
static void spec_atleast(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 2);
Reserve r = reserve(b, 4);
int32_t n = peg_getnat(b, argv[0]);
uint32_t subrule = compile1(b, argv[1]);
emit_3(r, RULE_BETWEEN, n, UINT32_MAX, subrule);
}
static void spec_atmost(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 2);
Reserve r = reserve(b, 4);
int32_t n = peg_getnat(b, argv[0]);
uint32_t subrule = compile1(b, argv[1]);
emit_3(r, RULE_BETWEEN, 0, n, subrule);
}
static void spec_opt(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 1);
Reserve r = reserve(b, 4);
uint32_t subrule = compile1(b, argv[0]);
emit_3(r, RULE_BETWEEN, 0, 1, subrule);
}
static void spec_matchtime(Builder *b, int32_t argc, const Janet *argv) {
peg_fixarity(b, argc, 2);
Reserve r = reserve(b, 3);
uint32_t subrule = compile1(b, argv[0]);
Janet fun = argv[1];
if (!janet_checktype(fun, JANET_FUNCTION) &&
!janet_checktype(fun, JANET_CFUNCTION)) {
peg_panicf(b, "expected function|cfunction, got %v", fun);
}
uint32_t cindex = emit_constant(b, fun);
emit_2(r, RULE_MATCHTIME, subrule, cindex);
}
/* Special compiler form */
typedef void (*Special)(Builder *b, int32_t argc, const Janet *argv);
typedef struct {
const char *name;
Special special;
} SpecialPair;
/* Keep in lexical order (vim :sort works well) */
static const SpecialPair specials[] = {
{"!", spec_not},
{"$", spec_position},
{"%", spec_substitute},
{"*", spec_sequence},
{"+", spec_choice},
{"/", spec_replace},
{"<-", spec_capture},
{">", spec_look},
{"?", spec_opt},
{"any", spec_any},
{"argument", spec_argument},
{"at-least", spec_atleast},
{"at-most", spec_atmost},
{"backref", spec_reference},
{"between", spec_between},
{"capture", spec_capture},
{"choice", spec_choice},
{"cmt", spec_matchtime},
{"constant", spec_constant},
{"error", spec_error},
{"group", spec_group},
{"if", spec_if},
{"if-not", spec_ifnot},
{"look", spec_look},
{"not", spec_not},
{"opt", spec_opt},
{"position", spec_position},
{"range", spec_range},
{"replace", spec_replace},
{"sequence", spec_sequence},
{"set", spec_set},
{"some", spec_some},
{"substitute", spec_substitute},
};
/* Compile a janet value into a rule and return the rule index. */
static uint32_t compile1(Builder *b, Janet peg) {
/* Check for already compiled rules */
Janet check = janet_table_get(b->memoized, peg);
if (!janet_checktype(check, JANET_NIL)) {
uint32_t rule = (uint32_t) janet_unwrap_number(check);
return rule;
}
/* Keep track of the form being compiled for error purposes */
Janet old_form = b->form;
b->form = peg;
/* Check depth */
if (b->depth-- == 0) {
peg_panic(b, "peg grammar recursed too deeply");
}
/* The final rule to return */
uint32_t rule = janet_v_count(b->bytecode);
if (!janet_checktype(peg, JANET_KEYWORD) &&
!janet_checktype(peg, JANET_STRUCT)) {
janet_table_put(b->memoized, peg, janet_wrap_number(rule));
}
switch (janet_type(peg)) {
default:
peg_panicf(b, "unexpected peg source");
return 0;
case JANET_NUMBER:
{
int32_t n = peg_getinteger(b, peg);
Reserve r = reserve(b, 2);
if (n < 0) {
emit_1(r, RULE_NOTNCHAR, -n);
} else {
emit_1(r, RULE_NCHAR, n);
}
break;
}
case JANET_STRING:
{
const uint8_t *str = janet_unwrap_string(peg);
int32_t len = janet_string_length(str);
emit_bytes(b, RULE_LITERAL, len, str);
break;
}
case JANET_KEYWORD:
{
Janet check = janet_table_get(b->grammar, peg);
if (janet_checktype(check, JANET_NIL))
peg_panicf(b, "unknown rule");
rule = compile1(b, check);
break;
}
case JANET_STRUCT:
{
JanetTable *grammar = janet_struct_to_table(janet_unwrap_struct(peg));
grammar->proto = b->grammar;
b->grammar = grammar;
Janet main_rule = janet_table_get(grammar, janet_ckeywordv("main"));
if (janet_checktype(main_rule, JANET_NIL))
peg_panicf(b, "grammar requires :main rule");
rule = compile1(b, main_rule);
b->grammar = grammar->proto;
break;
}
case JANET_TUPLE:
{
const Janet *tup = janet_unwrap_tuple(peg);
int32_t len = janet_tuple_length(tup);
if (len == 0) peg_panic(b, "tuple in grammar must have non-zero length");
if (!janet_checktype(tup[0], JANET_SYMBOL))
peg_panicf(b, "expected grammar command, found %v", tup[0]);
const uint8_t *sym = janet_unwrap_symbol(tup[0]);
const SpecialPair *sp = janet_strbinsearch(
&specials,
sizeof(specials)/sizeof(SpecialPair),
sizeof(SpecialPair),
sym);
if (!sp)
peg_panicf(b, "unknown special %S", sym);
sp->special(b, len - 1, tup + 1);
break;
}
}
/* Increase depth again */
b->depth++;
b->form = old_form;
return rule;
}
/*
* Post-Compilation
*/
typedef struct {
uint32_t *bytecode;
Janet *constants;
uint32_t main_rule;
uint32_t num_constants;
} Peg;
static int peg_mark(void *p, size_t size) {
(void) size;
Peg *peg = (Peg *)p;
for (uint32_t i = 0; i < peg->num_constants; i++)
janet_mark(peg->constants[i]);
return 0;
}
static JanetAbstractType peg_type = {
"core/peg",
NULL,
peg_mark
};
/* Convert Builder to Peg (Janet Abstract Value) */
static Peg *make_peg(Builder *b, uint32_t main_rule) {
size_t bytecode_size = janet_v_count(b->bytecode) * sizeof(uint32_t);
size_t constants_size = janet_v_count(b->constants) * sizeof(Janet);
size_t total_size = bytecode_size + constants_size + sizeof(Peg);
char *mem = janet_abstract(&peg_type, total_size);
Peg *peg = (Peg *)mem;
peg->bytecode = (uint32_t *)(mem + sizeof(Peg));
peg->constants = (Janet *)(mem + sizeof(Peg) + bytecode_size);
peg->num_constants = janet_v_count(b->constants);
peg->main_rule = main_rule;
memcpy(peg->bytecode, b->bytecode, bytecode_size);
memcpy(peg->constants, b->constants, constants_size);
return peg;
}
/* Compiler entry point */
static Peg *compile_peg(Janet x) {
Builder builder;
builder.grammar = janet_table(0);
builder.memoized = janet_table(0);
builder.constants = NULL;
builder.bytecode = NULL;
builder.form = x;
builder.depth = JANET_RECURSION_GUARD;
uint32_t main_rule = compile1(&builder, x);
Peg *peg = make_peg(&builder, main_rule);
builder_cleanup(&builder);
return peg;
}
/*
* C Functions
*/
static Janet cfun_compile(int32_t argc, Janet *argv) {
janet_fixarity(argc, 1);
Peg *peg = compile_peg(argv[0]);
return janet_wrap_abstract(peg);
}
static Janet cfun_match(int32_t argc, Janet *argv) {
janet_arity(argc, 2, -1);
Peg *peg;
if (janet_checktype(argv[0], JANET_ABSTRACT) &&
janet_abstract_type(janet_unwrap_abstract(argv[0])) == &peg_type) {
peg = janet_unwrap_abstract(argv[0]);
} else {
peg = compile_peg(argv[0]);
}
JanetByteView bytes = janet_getbytes(argv, 1);
int32_t start;
PegState s;
if (argc > 2) {
start = janet_gethalfrange(argv, 2, bytes.len, "offset");
s.extrac = argc - 3;
s.extrav = argv + 3;
} else {
start = 0;
s.extrac = 0;
s.extrav = NULL;
}
s.mode = PEG_MODE_NORMAL;
s.text_start = bytes.bytes;
s.text_end = bytes.bytes + bytes.len;
s.depth = JANET_RECURSION_GUARD;
s.captures = janet_array(0);
s.scratch = janet_buffer(10);
s.constants = peg->constants;
s.bytecode = peg->bytecode;
const uint8_t *result = peg_rule(&s, s.bytecode + peg->main_rule, bytes.bytes + start);
return result ? janet_wrap_array(s.captures) : janet_wrap_nil();
}
static const JanetReg cfuns[] = {
{"peg/compile", cfun_compile,
"(peg/compile peg)\n\n"
"Compiles a peg source data structure into a <core/peg>. This will speed up matching "
"if the same peg will be used multiple times."
},
{"peg/match", cfun_match,
"(peg/match peg text [,start=0])\n\n"
"Match a Parsing Expression Grammar to a byte string and return an array of captured values. "
"Returns nil if text does not match the language defined by peg. The syntax of PEGs are very "
"similar to those defined by LPeg, and have similar capabilities."
},
{NULL, NULL, NULL}
};
/* Load the peg module */
void janet_lib_peg(JanetTable *env) {
janet_cfuns(env, NULL, cfuns);
}
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