Merge pull request #819 from jiftechnify/meta-parser-benchmark

Add benchmark for MetaTagsParser

app/src/main/java/com/vitorpamplona/amethyst/service/previews/UrlPreviewUtils.kt

@@ -20,6 +20,8 @@
  */
 package com.vitorpamplona.amethyst.service.previews
 
+import com.vitorpamplona.amethyst.commons.preview.MetaTag
+import com.vitorpamplona.amethyst.commons.preview.MetaTagsParser
 import com.vitorpamplona.amethyst.service.HttpClientManager
 import com.vitorpamplona.amethyst.service.checkNotInMainThread
 import kotlinx.coroutines.Dispatchers

benchmark/src/androidTest/java/com/vitorpamplona/amethyst/benchmark/MetaTagsParserBenchmark.kt

@@ -0,0 +1,55 @@
+/**
+ * Copyright (c) 2024 Vitor Pamplona
+ *
+ * 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.
+ */
+package com.vitorpamplona.amethyst.benchmark
+
+import androidx.benchmark.junit4.BenchmarkRule
+import androidx.benchmark.junit4.measureRepeated
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import androidx.test.platform.app.InstrumentationRegistry.getInstrumentation
+import com.vitorpamplona.amethyst.commons.preview.MetaTagsParser
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Rule
+import org.junit.Test
+import org.junit.runner.RunWith
+import java.nio.charset.Charset
+
+@RunWith(AndroidJUnit4::class)
+class MetaTagsParserBenchmark {
+    private val html =
+        getInstrumentation().context.assets.open("github_amethyst.html")
+            .readBytes().toString(Charset.forName("utf-8"))
+
+    @get:Rule
+    val benchmarkRule = BenchmarkRule()
+
+    @Test
+    fun parseMetaTags() {
+        benchmarkRule.measureRepeated {
+            val metaOgTitle = MetaTagsParser.parse(html).find { it.attr("property") == "og:title" }
+            assertNotNull(metaOgTitle)
+            assertEquals(
+                "GitHub - vitorpamplona/amethyst: Nostr client for Android",
+                metaOgTitle!!.attr("content"),
+            )
+        }
+    }
+}

commons/src/androidTest/java/com/vitorpamplona/amethyst/commons/preview/MetaTagsParserTest.kt

@@ -18,7 +18,7 @@
  * 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.
  */
-package com.vitorpamplona.amethyst.service.previews
+package com.vitorpamplona.amethyst.commons.preview
 
 import org.junit.Assert.assertEquals
 import org.junit.Test

commons/src/main/java/com/vitorpamplona/amethyst/commons/preview/MetaTagsParser.kt

@@ -18,26 +18,30 @@
  * 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.
  */
-package com.vitorpamplona.amethyst.service.previews
+package com.vitorpamplona.amethyst.commons.preview
 
 import kotlinx.collections.immutable.toImmutableMap
-import java.lang.StringBuilder
 
-internal data class MetaTag(private val attrs: Map<String, String>) {
+data class MetaTag(private val attrs: Map<String, String>) {
+    /**
+     * Returns a value of an attribute specified by its name (case insensitive), or empty string if it doesn't exist.
+     */
     fun attr(name: String): String = attrs[name.lowercase()] ?: ""
 }
 
-// parse a partial HTML document and extract meta tags
-internal object MetaTagsParser {
+object MetaTagsParser {
     private val NON_ATTR_NAME_CHARS = setOf(Char(0x0), '"', '\'', '>', '/')
     private val NON_UNQUOTED_ATTR_VALUE_CHARS = setOf('"', '\'', '=', '>', '<', '`')
 
+    /**
+     * Lazily parse a partial HTML document and extract meta tags.
+     */
     fun parse(input: String): Sequence<MetaTag> =
         sequence {
             val s = TagScanner(input)
             while (!s.exhausted()) {
                 val t = s.nextTag() ?: continue
-                if (t.name == "/head") {
+                if (t.name == "head" && t.isEnd) {
                     break
                 }
                 if (t.name == "meta") {
@@ -47,61 +51,45 @@ internal object MetaTagsParser {
             }
         }
 
-    private data class RawTag(val name: String, val attrPart: String)
+    private data class RawTag(val isEnd: Boolean, val name: String, val attrPart: String)
 
     private class TagScanner(private val input: String) {
-        var p = 0
+        private var p = 0
 
         fun exhausted(): Boolean = p >= input.length
 
         private fun peek(): Char = input[p]
 
-        private fun consume(): Char {
-            return input[p++]
-        }
+        private fun consume(): Char = input[p++]
 
-        private fun consumeChar(c: Char): Boolean {
-            if (this.peek() == c) {
+        private fun skipWhile(pred: (Char) -> Boolean) {
+            while (!this.exhausted() && pred(this.peek())) {
                 this.consume()
-                return true
             }
-            return false
         }
 
         private fun skipSpaces() {
-            while (!this.exhausted() && this.peek().isWhitespace()) {
-                this.consume()
-            }
-        }
-
-        private fun skipUntil(c: Char) {
-            while (!this.exhausted() && this.peek() != c) {
-                this.consume()
-            }
-        }
-
-        private fun readWhile(pred: (Char) -> Boolean): String {
-            val sb = StringBuilder()
-            while (!this.exhausted() && pred(this.peek())) {
-                sb.append(this.consume())
-            }
-            return sb.toString()
+            this.skipWhile { it.isWhitespace() }
         }
 
         fun nextTag(): RawTag? {
-            skipUntil('<')
+            skipWhile { it != '<' }
             consume()
 
             // read tag name
-            val name = StringBuilder()
-            if (consumeChar('/')) {
-                name.append('/')
+            val isEnd = peek() == '/'
+            if (isEnd) {
+                consume()
             }
-            val n = readWhile { !it.isWhitespace() && it != '>' }
-            skipSpaces()
+            val nameStart = p
+            skipWhile { !it.isWhitespace() && it != '>' }
+            val nameEnd = p
 
-            // read until end of tag
-            val attrsPart = StringBuilder()
+            // seek to start of attrs part
+            skipSpaces()
+            val attrsStart = p
+
+            // skip until end of tag
             var quote: Char? = null
             while (!exhausted()) {
                 val c = consume()
@@ -124,13 +112,15 @@ internal object MetaTagsParser {
                         quote = null
                     }
                 }
-                attrsPart.append(c)
             }
+            val attrsEnd = p - 1
 
-            if (!n.matches(Regex("""[0-9a-zA-Z]+"""))) {
+            val name = input.slice(nameStart..<nameEnd)
+            if (!name.matches(Regex("""[0-9a-zA-Z]+"""))) {
                 return null
             }
-            return RawTag(name.append(n).toString().lowercase(), attrsPart.toString())
+            val attrsPart = input.slice(attrsStart..<attrsEnd)
+            return RawTag(isEnd, name.lowercase(), attrsPart)
         }
     }