Merge pull request #439 from markw65/faster-pos-details

Make peg$computePosDetails a little faster
peggyjs · Dec 9, 2023 · f2c271f · f2c271f
2 parents fe34d94 + 7c1c759
commit f2c271f
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Showing 7 changed files with 19 additions and 12 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,6 +16,7 @@ Released: TBD
 
 ### Minor Changes
 
+- [#439](https://github.com/peggyjs/peggy/pull/439) Make peg$computePosDetails a little faster
 - [#437](https://github.com/peggyjs/peggy/pull/437) Better type checking for visitor
 - [#435](https://github.com/peggyjs/peggy/pull/435) Setup tsconfig to detect use of library functions from es6 or later
 - [#438](https://github.com/peggyjs/peggy/pull/438) Make test build deterministic

diff --git a/docs/js/benchmark-bundle.min.js b/docs/js/benchmark-bundle.min.js
diff --git a/docs/js/examples.js b/docs/js/examples.js
@@ -319,9 +319,11 @@ function peg$parse(input, options) {
     if (details) {
       return details;
     } else {
-      p = pos - 1;
-      while (!peg$posDetailsCache[p]) {
-        p--;
+      if (pos >= peg$posDetailsCache.length) {
+        p = peg$posDetailsCache.length - 1;
+      } else {
+        p = pos;
+        while (!peg$posDetailsCache[--p]) {}
       }
 
       details = peg$posDetailsCache[p];

diff --git a/docs/js/test-bundle.min.js b/docs/js/test-bundle.min.js
diff --git a/docs/vendor/peggy/peggy.min.js b/docs/vendor/peggy/peggy.min.js
diff --git a/lib/compiler/passes/generate-js.js b/lib/compiler/passes/generate-js.js
@@ -1197,9 +1197,11 @@ function generateJS(ast, options) {
       "    if (details) {",
       "      return details;",
       "    } else {",
-      "      p = pos - 1;",
-      "      while (!peg$posDetailsCache[p]) {",
-      "        p--;",
+      "      if (pos >= peg$posDetailsCache.length) {",
+      "        p = peg$posDetailsCache.length - 1;",
+      "      } else {",
+      "        p = pos;",
+      "        while (!peg$posDetailsCache[--p]) {}",
       "      }",
       "",
       "      details = peg$posDetailsCache[p];",

diff --git a/lib/parser.js b/lib/parser.js
@@ -634,9 +634,11 @@ function peg$parse(input, options) {
     if (details) {
       return details;
     } else {
-      p = pos - 1;
-      while (!peg$posDetailsCache[p]) {
-        p--;
+      if (pos >= peg$posDetailsCache.length) {
+        p = peg$posDetailsCache.length - 1;
+      } else {
+        p = pos;
+        while (!peg$posDetailsCache[--p]) {}
       }
 
       details = peg$posDetailsCache[p];