Improve performance of EncodingDetectingInputStream (#2535)

Slightly improves the performance of `EncodingDetectingInputStream` by refactoring the `read()` method and avoiding the additional `byte[]` copy in `readFully()`. Also make sure that `PlainTextParser#parseInputs()` reads the source text before the encoding, since the latter won't be correctly set otherwise.
openrewrite · Dec 17, 2022 · d29ae3a · d29ae3a
1 parent 7df900f
commit d29ae3a
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Showing 2 changed files with 65 additions and 56 deletions.
diff --git a/rewrite-core/src/main/java/org/openrewrite/internal/EncodingDetectingInputStream.java b/rewrite-core/src/main/java/org/openrewrite/internal/EncodingDetectingInputStream.java
@@ -68,78 +68,86 @@ public int read() throws IOException {
 
         // if we haven't yet determined a charset...
         if (charset == null) {
-            if (prev3 == 0xC3 && prev2 == 0xAF && prev == 0xC2) {
-                charsetBomMarked = true;
-                charset = StandardCharsets.UTF_8;
-            } else {
-                if (aByte == -1 || !(prev2 == 0 && prev == 0xC3 || prev3 == 0 && prev2 == 0xC3)) {
-                    if (maybeTwoByteSequence) {
-                        if (aByte == -1 && !utf8SequenceEnd(prev) || aByte != -1 && !(utf8SequenceEnd(aByte))) {
-                            charset = WINDOWS_1252;
-                        } else {
-                            maybeTwoByteSequence = false;
-                            prev2 = -1;
-                            prev = -1;
-                        }
-                    } else if (maybeThreeByteSequence) {
-                        if (aByte == -1 ||
-                                utf8SequenceEnd(prev) && !(utf8SequenceEnd(aByte)) ||
-                                !utf8SequenceEnd(aByte)) {
-                            charset = WINDOWS_1252;
-                        }
-
-                        if (utf8SequenceEnd(prev) && utf8SequenceEnd(aByte)) {
-                            maybeThreeByteSequence = false;
-                            prev2 = -1;
-                            prev = -1;
-                        }
-                    } else if (maybeFourByteSequence) {
-                        if (aByte == -1 ||
-                                utf8SequenceEnd(prev2) && utf8SequenceEnd(prev) && !utf8SequenceEnd(aByte) ||
-                                utf8SequenceEnd(prev) && !utf8SequenceEnd(aByte) ||
-                                !(utf8SequenceEnd(aByte))) {
-                            charset = WINDOWS_1252;
-                        }
-
-                        if (utf8SequenceEnd(prev2) && utf8SequenceEnd(prev) && utf8SequenceEnd(aByte)) {
-                            maybeFourByteSequence = false;
-                            prev2 = -1;
-                            prev = -1;
-                        }
-                    } else if (utf8TwoByteSequence(aByte)) {
-                        maybeTwoByteSequence = true;
-                    } else if (utf8ThreeByteSequence(aByte)) {
-                        maybeThreeByteSequence = true;
-                    } else if (utf8FourByteSequence(aByte)) {
-                        maybeFourByteSequence = true;
-                    } else if (!utf8TwoByteSequence(prev) && utf8SequenceEnd(aByte)) {
+            guessCharset(aByte);
+        }
+        return aByte;
+    }
+
+    private void guessCharset(int aByte) {
+        if (prev3 == 0xC3 && prev2 == 0xAF && prev == 0xC2) {
+            charsetBomMarked = true;
+            charset = StandardCharsets.UTF_8;
+        } else {
+            if (aByte == -1 || !(prev2 == 0 && prev == 0xC3 || prev3 == 0 && prev2 == 0xC3)) {
+                if (maybeTwoByteSequence) {
+                    if (aByte == -1 && !utf8SequenceEnd(prev) || aByte != -1 && !(utf8SequenceEnd(aByte))) {
+                        charset = WINDOWS_1252;
+                    } else {
+                        maybeTwoByteSequence = false;
+                        prev2 = -1;
+                        prev = -1;
+                    }
+                } else if (maybeThreeByteSequence) {
+                    if (aByte == -1 ||
+                            utf8SequenceEnd(prev) && !(utf8SequenceEnd(aByte)) ||
+                            !utf8SequenceEnd(aByte)) {
+                        charset = WINDOWS_1252;
+                    }
+
+                    if (utf8SequenceEnd(prev) && utf8SequenceEnd(aByte)) {
+                        maybeThreeByteSequence = false;
+                        prev2 = -1;
+                        prev = -1;
+                    }
+                } else if (maybeFourByteSequence) {
+                    if (aByte == -1 ||
+                            utf8SequenceEnd(prev2) && utf8SequenceEnd(prev) && !utf8SequenceEnd(aByte) ||
+                            utf8SequenceEnd(prev) && !utf8SequenceEnd(aByte) ||
+                            !(utf8SequenceEnd(aByte))) {
                         charset = WINDOWS_1252;
                     }
-                }
 
-                if (aByte == -1 && charset == null) {
-                    charset = StandardCharsets.UTF_8;
+                    if (utf8SequenceEnd(prev2) && utf8SequenceEnd(prev) && utf8SequenceEnd(aByte)) {
+                        maybeFourByteSequence = false;
+                        prev2 = -1;
+                        prev = -1;
+                    }
+                } else if (utf8TwoByteSequence(aByte)) {
+                    maybeTwoByteSequence = true;
+                } else if (utf8ThreeByteSequence(aByte)) {
+                    maybeThreeByteSequence = true;
+                } else if (utf8FourByteSequence(aByte)) {
+                    maybeFourByteSequence = true;
+                } else if (!utf8TwoByteSequence(prev) && utf8SequenceEnd(aByte)) {
+                    charset = WINDOWS_1252;
                 }
             }
 
-            prev3 = prev2;
-            prev2 = prev;
-            prev = aByte;
+            if (aByte == -1 && charset == null) {
+                charset = StandardCharsets.UTF_8;
+            }
         }
-        return aByte;
+
+        prev3 = prev2;
+        prev2 = prev;
+        prev = aByte;
     }
 
     public String readFully() {
         try (InputStream is = this) {
-            ByteArrayOutputStream bos = new ByteArrayOutputStream();
+            ByteArrayOutputStream bos = new ByteArrayOutputStream() {
+                @Override
+                public synchronized String toString() {
+                    return new String(buf, 0, count, getCharset());
+                }
+            };
             byte[] buffer = new byte[4096];
             int n;
             while ((n = is.read(buffer)) != -1) {
                 bos.write(buffer, 0, n);
             }
 
-            byte[] bytes = bos.toByteArray();
-            return new String(bytes, 0, bytes.length, getCharset());
+            return bos.toString();
         } catch (IOException e) {
             throw new UnsupportedOperationException(e);
         }

diff --git a/rewrite-core/src/main/java/org/openrewrite/text/PlainTextParser.java b/rewrite-core/src/main/java/org/openrewrite/text/PlainTextParser.java
@@ -39,14 +39,15 @@ public List<PlainText> parseInputs(Iterable<Input> sources, @Nullable Path relat
             Path path = source.getRelativePath(relativeTo);
             try {
                 EncodingDetectingInputStream is = source.getSource(ctx);
+                String sourceStr = is.readFully();
                 PlainText plainText = new PlainText(randomId(),
                         path,
                         Markers.EMPTY,
                         is.getCharset().name(),
                         is.isCharsetBomMarked(),
                         source.getFileAttributes(),
                         null,
-                        is.readFully());
+                        sourceStr);
                 plainTexts.add(plainText);
                 parsingListener.parsed(source, plainText);
             } catch (Throwable t) {