Commit 1ba03589c0962849a8a45926f53263867404ef6a
2016-11-07T20:50:11
md_collect_marks: Optimize the function. Use character map for a fast path and minimize count of branches for specially handled characters. When profiling md2html on a larger documents with output redirected to /dev/null to mitigate I/O, this function was quite a bottleneck. It consummed about 33% of CPU cycles on a longer document input, with this patch applied it drops down to 12%.
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diff --git a/md4c/md4c.c b/md4c/md4c.c
index 2c14d63..60c4bed 100644
--- a/md4c/md4c.c
+++ b/md4c/md4c.c
@@ -103,6 +103,8 @@ struct MD_CTX_tag {
unsigned n_marks;
unsigned alloc_marks;
+ char mark_char_map[128];
+
/* For resolving of inline spans. */
MD_MARKCHAIN mark_chains[4];
#define BACKTICK_OPENERS ctx->mark_chains[0]
@@ -1045,6 +1047,37 @@ md_split_mark(MD_CTX* ctx, int mark_index, SZ n)
return mark_index + 1;
}
+static void
+md_build_mark_char_map(MD_CTX* ctx)
+{
+ memset(ctx->mark_char_map, 0, sizeof(ctx->mark_char_map));
+
+ ctx->mark_char_map['\\'] = 1;
+ ctx->mark_char_map['*'] = 1;
+ ctx->mark_char_map['_'] = 1;
+ ctx->mark_char_map['`'] = 1;
+ ctx->mark_char_map['&'] = 1;
+ ctx->mark_char_map[';'] = 1;
+ ctx->mark_char_map['<'] = 1;
+ ctx->mark_char_map['>'] = 1;
+ ctx->mark_char_map['\0'] = 1;
+
+ if(ctx->r.flags & MD_FLAG_PERMISSIVEURLAUTOLINKS)
+ ctx->mark_char_map[':'] = 1;
+
+ if(ctx->r.flags & MD_FLAG_PERMISSIVEEMAILAUTOLINKS)
+ ctx->mark_char_map['@'] = 1;
+
+ if(ctx->r.flags & MD_FLAG_COLLAPSEWHITESPACE) {
+ int i;
+
+ for(i = 0; i < sizeof(ctx->mark_char_map); i++) {
+ if(ISWHITESPACE_(i))
+ ctx->mark_char_map[i] = 1;
+ }
+ }
+}
+
static int
md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
{
@@ -1059,6 +1092,13 @@ md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
while(off < line_end) {
CHAR ch = CH(off);
+
+ /* Optimization: Fast path. */
+ if(ch >= sizeof(ctx->mark_char_map) || !ctx->mark_char_map[(int) ch]) {
+ off++;
+ continue;
+ }
+
/* A backslash escape.
* It can go beyond line->end as it may involve escaped new
* line to form a hard break. */
@@ -1076,20 +1116,6 @@ md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
continue;
}
- /* Turn non-trivial whitespace into single space. */
- if((ctx->r.flags & MD_FLAG_COLLAPSEWHITESPACE) && ISWHITESPACE_(ch)) {
- OFF tmp = off+1;
-
- while(tmp < line_end && ISWHITESPACE(tmp))
- tmp++;
-
- if(tmp - off > 1 || ch != _T(' ')) {
- PUSH_MARK(ch, off, tmp, MD_MARK_RESOLVED);
- off = tmp;
- continue;
- }
- }
-
/* A potential (string) emphasis start/end. */
if(ch == _T('*') || ch == _T('_')) {
OFF tmp = off+1;
@@ -1143,6 +1169,7 @@ md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
}
off = tmp;
+ continue;
}
/* A potential code span start/end. */
@@ -1174,24 +1201,24 @@ md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
/* A potential entity end. */
if(ch == _T(';')) {
/* We surely cannot be entity unless the previous mark is '&'. */
- if(ctx->n_marks > 0 && ctx->marks[ctx->n_marks-1].ch == _T('&')) {
+ if(ctx->n_marks > 0 && ctx->marks[ctx->n_marks-1].ch == _T('&'))
PUSH_MARK(ch, off, off+1, MD_MARK_POTENTIAL_CLOSER);
- off++;
- continue;
- }
+
+ off++;
+ continue;
}
/* A potential autolink or raw HTML start/end. */
if(ch == _T('<') || ch == _T('>')) {
- if(!(ctx->r.flags & MD_FLAG_NOHTMLSPANS)) {
+ if(!(ctx->r.flags & MD_FLAG_NOHTMLSPANS))
PUSH_MARK(ch, off, off+1, (ch == _T('<') ? MD_MARK_POTENTIAL_OPENER : MD_MARK_POTENTIAL_CLOSER));
- off++;
- continue;
- }
+
+ off++;
+ continue;
}
/* A potential permissive URL autolink. */
- if((ctx->r.flags & MD_FLAG_PERMISSIVEURLAUTOLINKS) && ch == _T(':')) {
+ if(ch == _T(':')) {
static struct {
const CHAR* scheme;
SZ scheme_size;
@@ -1223,19 +1250,37 @@ md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines)
continue;
}
}
+
+ off++;
+ continue;
}
/* A potential permissive e-mail autolink. */
- if((ctx->r.flags & MD_FLAG_PERMISSIVEEMAILAUTOLINKS) && ch == _T('@')) {
+ if(ch == _T('@')) {
if(line->beg + 1 <= off && ISALNUM(off-1) &&
off + 3 < line->end && ISALNUM(off+1))
{
PUSH_MARK(ch, off, off+1, MD_MARK_POTENTIAL_OPENER);
/* Push a dummy as a reserve for a closer. */
PUSH_MARK('D', off, off, 0);
- off++;
- continue;
}
+
+ off++;
+ continue;
+ }
+
+ /* Turn non-trivial whitespace into single space. */
+ if(ISWHITESPACE_(ch)) {
+ OFF tmp = off+1;
+
+ while(tmp < line_end && ISWHITESPACE(tmp))
+ tmp++;
+
+ if(tmp - off > 1 || ch != _T(' '))
+ PUSH_MARK(ch, off, tmp, MD_MARK_RESOLVED);
+
+ off = tmp;
+ continue;
}
/* NULL character. */
@@ -2589,6 +2634,8 @@ md_process_doc(MD_CTX *ctx)
OFF off = 0;
int ret = 0;
+ md_build_mark_char_map(ctx);
+
MD_ENTER_BLOCK(MD_BLOCK_DOC, NULL);
while(off < ctx->size) {