Bruce/bp
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
315aedc7cb
bp/match.c

627 lines
22 KiB
C
Raw Blame History

//
// match.c - Code for the BP virtual machine that performs the matching.
//
#include <ctype.h>
#include <err.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "definitions.h"
#include "match.h"
#include "types.h"
#include "utils.h"
#include "utf8.h"
#ifdef DEBUG_HEAP
// Doubly-linked list operations:
#define DLL_PREPEND(head, node) do { (node)->atme = &(head); (node)->next = head; if (head) (head)->atme = &(node)->next; head = node; } while(false)
#define DLL_REMOVE(node) do { *(node)->atme = (node)->next; if ((node)->next) (node)->next->atme = (node)->atme; } while(false)
#endif
// Refcounting ownership-setting macros:
#define ADD_OWNER(owner, m) do { owner = m; ++(m)->refcount; } while(false)
#define REMOVE_OWNERSHIP(owner) do { if (owner) { --(owner)->refcount; recycle_if_unused(&(owner)); owner = NULL; } } while(false)
// New match objects are either recycled from unused match objects or allocated
// from the heap. While it is in use, the match object is stored in the
// `in_use_matches` linked list. Once it is no longer needed, it is moved to
// the `unused_matches` linked list so it can be reused without the need for
// additional calls to malloc/free. Thus, it is an invariant that every match
// object is in one of these two lists:
static match_t *unused_matches = NULL;
#ifdef DEBUG_HEAP
static match_t *in_use_matches = NULL;
#endif
static inline pat_t *deref(def_t *defs, pat_t *pat);
__attribute__((returns_nonnull))
static match_t *new_match(pat_t *pat, const char *start, const char *end, match_t *child);
__attribute__((nonnull))
static const char *match_backref(const char *str, match_t *cap, bool ignorecase);
__attribute__((nonnull))
static match_t *get_capture_by_num(match_t *m, int *n);
__attribute__((nonnull, pure))
static match_t *get_capture_by_name(match_t *m, const char *name);
__attribute__((hot, nonnull(2,3,4)))
static match_t *match(def_t *defs, file_t *f, const char *str, pat_t *pat, bool ignorecase);
//
// If the given pattern is a reference, look it up and return the referenced
// pattern. This is used for an optimization to avoid repeated lookups.
//
static inline pat_t *deref(def_t *defs, pat_t *pat)
{
if (pat && pat->type == BP_REF) {
def_t *def = lookup(defs, pat->args.ref.len, pat->args.ref.name);
if (def) pat = def->pat;
}
return pat;
}
//
// Attempt to match text against a previously captured value.
// Return the character position after the backref has matched, or NULL if no match has occurred.
//
static const char *match_backref(const char *str, match_t *cap, bool ignorecase)
{
if (cap->pat->type == BP_REPLACE) {
const char *text = cap->pat->args.replace.text;
const char *end = &text[cap->pat->args.replace.len];
for (const char *r = text; r < end; ) {
if (*r == '\\') {
++r;
if (*(str++) != unescapechar(r, &r))
return NULL;
} else if (*r != '@') {
if (*(str++) != *r)
return NULL;
++r;
continue;
}
++r;
match_t *value = get_capture(cap, &r);
if (value != NULL) {
str = match_backref(str, value, ignorecase);
if (str == NULL) return NULL;
}
}
} else {
const char *prev = cap->start;
for (match_t *child = cap->child; child; child = child->nextsibling) {
if (child->start > prev) {
size_t len = (size_t)(child->start - prev);
if ((ignorecase ? memicmp : memcmp)(str, prev, len) != 0) {
return NULL;
}
str += len;
prev = child->start;
}
if (child->start < prev) continue;
str = match_backref(str, child, ignorecase);
if (str == NULL) return NULL;
prev = child->end;
}
if (cap->end > prev) {
size_t len = (size_t)(cap->end - prev);
if ((ignorecase ? memicmp : memcmp)(str, prev, len) != 0) {
return NULL;
}
str += len;
}
}
return str;
}
//
// Find the next match after prev (or the first match if prev is NULL)
//
match_t *next_match(def_t *defs, file_t *f, match_t *prev, pat_t *pat, pat_t *skip, bool ignorecase)
{
const char *str;
if (prev) {
str = prev->end > prev->start ? prev->end : prev->end + 1;
recycle_if_unused(&prev);
} else {
str = f->start;
}
bool only_start = pat->type == BP_START_OF_FILE || (pat->type == BP_CHAIN && pat->args.multiple.first->type == BP_START_OF_FILE);
while (str <= f->end) {
match_t *m = match(defs, f, str, pat, ignorecase);
if (m) return m;
if (only_start) return NULL;
match_t *s;
if (skip && (s = match(defs, f, str, skip, ignorecase))) {
str = s->end > str ? s->end : str + 1;
recycle_if_unused(&s);
} else ++str;
}
return NULL;
}
//
// Attempt to match the given pattern against the input string and return a
// match object, or NULL if no match is found.
// The returned value should be free()'d to avoid memory leaking.
//
static match_t *match(def_t *defs, file_t *f, const char *str, pat_t *pat, bool ignorecase)
{
switch (pat->type) {
case BP_LEFTRECURSION: {
// Left recursion occurs when a pattern directly or indirectly
// invokes itself at the same position in the text. It's handled as
// a special case, but if a pattern invokes itself at a later
// point, it can be handled with normal recursion.
// See: left-recursion.md for more details.
if (str == pat->args.leftrec.at) {
++pat->args.leftrec.visits;
return pat->args.leftrec.match;
} else {
return match(defs, f, str, pat->args.leftrec.fallback, ignorecase);
}
}
case BP_ANYCHAR: {
return (str < f->end && *str != '\n') ? new_match(pat, str, next_char(f, str), NULL) : NULL;
}
case BP_START_OF_FILE: {
return (str == f->start) ? new_match(pat, str, str, NULL) : NULL;
}
case BP_START_OF_LINE: {
return (str == f->start || str[-1] == '\n') ? new_match(pat, str, str, NULL) : NULL;
}
case BP_END_OF_FILE: {
return (str == f->end) ? new_match(pat, str, str, NULL) : NULL;
}
case BP_END_OF_LINE: {
return (str == f->end || *str == '\n') ? new_match(pat, str, str, NULL) : NULL;
}
case BP_STRING: {
if (&str[pat->min_matchlen] > f->end) return NULL;
if (pat->min_matchlen > 0 && (ignorecase ? memicmp : memcmp)(str, pat->args.string, pat->min_matchlen) != 0)
return NULL;
return new_match(pat, str, str + pat->min_matchlen, NULL);
}
case BP_RANGE: {
if (str >= f->end) return NULL;
if ((unsigned char)*str < pat->args.range.low || (unsigned char)*str > pat->args.range.high)
return NULL;
return new_match(pat, str, str+1, NULL);
}
case BP_NOT: {
match_t *m = match(defs, f, str, pat->args.pat, ignorecase);
if (m != NULL) {
recycle_if_unused(&m);
return NULL;
}
return new_match(pat, str, str, NULL);
}
case BP_UPTO: {
match_t *m = new_match(pat, str, str, NULL);
pat_t *target = deref(defs, pat->args.multiple.first),
*skip = deref(defs, pat->args.multiple.second);
if (!target && !skip) {
while (str < f->end && *str != '\n') ++str;
m->end = str;
return m;
}
match_t **dest = &m->child;
for (const char *prev = NULL; prev < str; ) {
prev = str;
if (target) {
match_t *p = match(defs, f, str, target, ignorecase);
if (p != NULL) {
recycle_if_unused(&p);
m->end = str;
return m;
}
} else if (str == f->end) {
m->end = str;
return m;
}
if (skip) {
match_t *s = match(defs, f, str, skip, ignorecase);
if (s != NULL) {
ADD_OWNER(*dest, s);
dest = &s->nextsibling;
str = s->end;
continue;
}
}
// This isn't in the for() structure because there needs to
// be at least once chance to match the pattern, even if
// we're at the end of the string already (e.g. "..$").
if (str < f->end && *str != '\n')
str = next_char(f, str);
}
recycle_if_unused(&m);
return NULL;
}
case BP_REPEAT: {
match_t *m = new_match(pat, str, str, NULL);
match_t **dest = &m->child;
size_t reps = 0;
ssize_t max = pat->args.repetitions.max;
pat_t *repeating = deref(defs, pat->args.repetitions.repeat_pat);
pat_t *sep = deref(defs, pat->args.repetitions.sep);
for (reps = 0; max == -1 || reps < (size_t)max; ++reps) {
const char *start = str;
// Separator
match_t *msep = NULL;
if (sep != NULL && reps > 0) {
msep = match(defs, f, str, sep, ignorecase);
if (msep == NULL) break;
str = msep->end;
}
match_t *mp = match(defs, f, str, repeating, ignorecase);
if (mp == NULL) {
str = start;
if (msep) recycle_if_unused(&msep);
break;
}
if (mp->end == start && reps > 0) {
// Since no forward progress was made on either `repeating`
// or `sep` and BP does not have mutable state, it's
// guaranteed that no progress will be made on the next
// loop either. We know that this will continue to loop
// until reps==max, so let's just cut to the chase instead
// of looping infinitely.
if (msep) recycle_if_unused(&msep);
recycle_if_unused(&mp);
if (pat->args.repetitions.max == -1)
reps = ~(size_t)0;
else
reps = (size_t)pat->args.repetitions.max;
break;
}
if (msep) {
ADD_OWNER(*dest, msep);
dest = &msep->nextsibling;
}
ADD_OWNER(*dest, mp);
dest = &mp->nextsibling;
str = mp->end;
}
if (reps < (size_t)pat->args.repetitions.min) {
recycle_if_unused(&m);
return NULL;
}
m->end = str;
return m;
}
case BP_AFTER: {
pat_t *back = deref(defs, pat->args.pat);
// We only care about the region from the backtrack pos up to the
// current pos, so mock it out as a file slice.
// TODO: this breaks ^/^^/$/$$, but that can probably be ignored
// because you rarely need to check those in a backtrack.
file_t slice;
slice_file(&slice, f, f->start, str);
for (const char *pos = &str[-(long)back->min_matchlen];
pos >= f->start && (back->max_matchlen == -1 || pos >= &str[-(long)back->max_matchlen]);
pos = prev_char(f, pos)) {
slice.start = (char*)pos;
match_t *m = match(defs, &slice, pos, back, ignorecase);
// Match should not go past str (i.e. (<"AB" "B") should match "ABB", but not "AB")
if (m && m->end != str)
recycle_if_unused(&m);
else if (m)
return new_match(pat, str, str, m);
if (pos == f->start) break;
// To prevent extreme performance degradation, don't keep
// walking backwards endlessly over newlines.
if (back->max_matchlen == -1 && *pos == '\n') break;
}
return NULL;
}
case BP_BEFORE: {
match_t *after = match(defs, f, str, pat->args.pat, ignorecase);
return after ? new_match(pat, str, str, after) : NULL;
}
case BP_CAPTURE: {
match_t *p = match(defs, f, str, pat->args.pat, ignorecase);
return p ? new_match(pat, str, p->end, p) : NULL;
}
case BP_OTHERWISE: {
match_t *m = match(defs, f, str, pat->args.multiple.first, ignorecase);
return m ? m : match(defs, f, str, pat->args.multiple.second, ignorecase);
}
case BP_CHAIN: {
match_t *m1 = match(defs, f, str, pat->args.multiple.first, ignorecase);
if (m1 == NULL) return NULL;
match_t *m2;
{ // Push backrefs and run matching, then cleanup
def_t *defs2 = defs;
if (m1->pat->type == BP_CAPTURE && m1->pat->args.capture.name)
defs2 = with_backref(defs2, f, m1->pat->args.capture.namelen, m1->pat->args.capture.name, m1);
// def_t *defs2 = with_backrefs(defs, f, m1);
m2 = match(defs2, f, m1->end, pat->args.multiple.second, ignorecase);
free_defs(&defs2, defs);
}
if (m2 == NULL) {
recycle_if_unused(&m1);
return NULL;
}
ADD_OWNER(m1->nextsibling, m2);
return new_match(pat, str, m2->end, m1);
}
case BP_MATCH: case BP_NOT_MATCH: {
match_t *m1 = match(defs, f, str, pat->args.multiple.first, ignorecase);
if (m1 == NULL) return NULL;
// <p1>==<p2> matches iff the text of <p1> matches <p2>
// <p1>!=<p2> matches iff the text of <p1> does not match <p2>
file_t slice;
slice_file(&slice, f, m1->start, m1->end);
match_t *m2 = next_match(defs, &slice, NULL, pat->args.multiple.second, NULL, ignorecase);
if ((!m2 && pat->type == BP_MATCH) || (m2 && pat->type == BP_NOT_MATCH)) {
recycle_if_unused(&m2);
recycle_if_unused(&m1);
return NULL;
}
if (pat->type == BP_MATCH) ADD_OWNER(m1->nextsibling, m2);
return new_match(pat, m1->start, m1->end, m1);
}
case BP_REPLACE: {
match_t *p = NULL;
if (pat->args.replace.pat) {
p = match(defs, f, str, pat->args.replace.pat, ignorecase);
if (p == NULL) return NULL;
}
return new_match(pat, str, p ? p->end : str, p);
}
case BP_REF: {
def_t *def = lookup(defs, pat->args.ref.len, pat->args.ref.name);
if (def == NULL)
errx(EXIT_FAILURE, "Unknown identifier: '%.*s'", (int)pat->args.ref.len, pat->args.ref.name);
pat_t *ref = def->pat;
pat_t rec_op = {
.type = BP_LEFTRECURSION,
.start = ref->start,
.end = ref->end,
.min_matchlen = 0,
.max_matchlen = -1,
.args.leftrec = {
.match = NULL,
.visits = 0,
.at = str,
.fallback = ref,
},
};
def_t defs2 = {
.namelen = def->namelen,
.name = def->name,
.pat = &rec_op,
.next = defs,
};
const char *prev = str;
match_t *m = match(&defs2, f, str, ref, ignorecase);
if (m == NULL) return NULL;
while (rec_op.args.leftrec.visits > 0) {
rec_op.args.leftrec.visits = 0;
REMOVE_OWNERSHIP(rec_op.args.leftrec.match);
ADD_OWNER(rec_op.args.leftrec.match, m);
prev = m->end;
match_t *m2 = match(&defs2, f, str, ref, ignorecase);
if (m2 == NULL) break;
if (m2->end <= prev) {
recycle_if_unused(&m2);
break;
}
m = m2;
}
if (rec_op.args.leftrec.match) {
// Ensure that `m` isn't garbage collected right now, but do
// clean up the recursive match result if it's not needed.
++m->refcount;
REMOVE_OWNERSHIP(rec_op.args.leftrec.match);
--m->refcount;
}
if (!m)
errx(EXIT_FAILURE, "Match should be non-null at this point");
// This match wrapper mainly exists for record-keeping purposes and
// does not affect correctness. It also helps with visualization of
// match results.
// OPTIMIZE: remove this if necessary
return new_match(pat, m->start, m->end, m);
}
case BP_BACKREF: {
const char *end = match_backref(str, pat->args.backref, ignorecase);
return end ? new_match(pat, str, end, NULL) : NULL;
}
case BP_NODENT: {
if (*str != '\n') return NULL;
const char *start = str;
size_t linenum = get_line_number(f, str);
const char *p = get_line(f, linenum);
if (p < f->start) p = f->start; // Can happen with recursive matching
// Current indentation:
char denter = *p;
int dents = 0;
if (denter == ' ' || denter == '\t') {
for (; *p == denter && p < f->end; ++p) ++dents;
}
// Subsequent indentation:
while (*str == '\n') ++str;
for (int i = 0; i < dents; i++) {
if (str[i] != denter || &str[i] >= f->end) return NULL;
}
return new_match(pat, start, &str[dents], NULL);
}
case BP_ERROR: {
match_t *p = pat->args.pat ? match(defs, f, str, pat->args.pat, ignorecase) : NULL;
return p ? new_match(pat, str, p->end, p) : NULL;
}
default: {
errx(EXIT_FAILURE, "Unknown pattern type: %d", pat->type);
return NULL;
}
}
}
//
// Get a specific numbered pattern capture.
//
static match_t *get_capture_by_num(match_t *m, int *n)
{
if (*n == 0) return m;
if (m->pat->type == BP_CAPTURE && *n == 1) return m;
if (m->pat->type == BP_CAPTURE) --(*n);
for (match_t *c = m->child; c; c = c->nextsibling) {
match_t *cap = get_capture_by_num(c, n);
if (cap) return cap;
}
return NULL;
}
//
// Get a capture with a specific name.
//
static match_t *get_capture_by_name(match_t *m, const char *name)
{
if (m->pat->type == BP_CAPTURE && m->pat->args.capture.name
&& strncmp(m->pat->args.capture.name, name, m->pat->args.capture.namelen) == 0)
return m;
for (match_t *c = m->child; c; c = c->nextsibling) {
match_t *cap = get_capture_by_name(c, name);
if (cap) return cap;
}
return NULL;
}
//
// Get a capture by identifier (name or number).
// Update *id to point to after the identifier (if found).
//
match_t *get_capture(match_t *m, const char **id)
{
if (isdigit(**id)) {
int n = (int)strtol(*id, (char**)id, 10);
return get_capture_by_num(m->child, &n);
} else {
const char *end = after_name(*id);
if (end == *id) return NULL;
char *name = strndup(*id, (size_t)(end-*id));
match_t *cap = get_capture_by_name(m, name);
xfree(&name);
*id = end;
if (**id == ';') ++(*id);
return cap;
}
}
//
// Return a match object which can be used (may be allocated or recycled).
//
static match_t *new_match(pat_t *pat, const char *start, const char *end, match_t *child)
{
match_t *m;
#ifdef DEBUG_HEAP
if (unused_matches) {
m = unused_matches;
DLL_REMOVE(m);
memset(m, 0, sizeof(match_t));
} else {
m = new(match_t);
}
// Keep track of the object:
DLL_PREPEND(in_use_matches, m);
#else
if (unused_matches) {
m = unused_matches;
unused_matches = unused_matches->next;
(void)memset(m, 0, sizeof(match_t));
} else {
m = new(match_t);
}
#endif
m->pat = pat;
m->start = start;
m->end = end;
if (child) ADD_OWNER(m->child, child);
return m;
}
//
// If the given match is not currently a child member of another match (or
// otherwise reserved) then put it back in the pool of unused match objects.
//
void recycle_if_unused(match_t **at_m)
{
match_t *m = *at_m;
if (m == NULL) return;
if (m->refcount > 0) {
*at_m = NULL;
return;
}
REMOVE_OWNERSHIP(m->child);
REMOVE_OWNERSHIP(m->nextsibling);
#ifdef DEBUG_HEAP
DLL_REMOVE(m); // Remove from in_use_matches
(void)memset(m, 0, sizeof(match_t));
DLL_PREPEND(unused_matches, m);
#else
(void)memset(m, 0, sizeof(match_t));
m->next = unused_matches;
unused_matches = m;
#endif
*at_m = NULL;
}
#ifdef DEBUG_HEAP
//
// Force all match objects into the pool of unused match objects.
//
size_t recycle_all_matches(void)
{
size_t count = 0;
while (in_use_matches) {
match_t *m = in_use_matches;
DLL_REMOVE(m);
DLL_PREPEND(unused_matches, m);
++count;
}
return count;
}
//
// Free all match objects in memory.
//
size_t free_all_matches(void)
{
size_t count = 0;
recycle_all_matches();
while (unused_matches) {
match_t *m = unused_matches;
DLL_REMOVE(m);
free(m);
++count;
}
return count;
}
#endif
// vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1
Reference in New Issue View Git Blame Copy Permalink