Replace a regex-based SMAP parser with a hand-crafted one

Author: jbachorik

dd-java-agent/agent-profiling/profiling-controller-openjdk/src/main/java/com/datadog/profiling/controller/openjdk/events/SimpleParser.java

@@ -0,0 +1,91 @@
+package com.datadog.profiling.controller.openjdk.events;
+
+/**
+ * A simple stateful parser for an smap entry.<br>
+ * The values are delimited by spaces and/or dashes. The parser allows consuming next long/string
+ * value, skipping over the current value, skipping to the next value, and slurping the rest of the
+ * current value.<br>
+ * The implementation is minimalistic with the accent on reducing the number of allocations.
+ */
+final class SimpleParser {
+  private final String line;
+
+  private int pos;
+
+  public SimpleParser(String line) {
+    this.line = line;
+    this.pos = 0;
+  }
+
+  void skipToNextValue(boolean acceptDash) {
+    int limit = line.length();
+    while (pos < limit && isDelimiter(line.charAt(pos), acceptDash)) {
+      pos++;
+    }
+  }
+
+  void skipValue(boolean acceptDash) {
+    int limit = line.length();
+    char c = 0;
+    while (pos < limit && !isDelimiter(line.charAt(pos), acceptDash)) {
+      pos++;
+    }
+  }
+
+  long nextLongValue(int base) {
+    if (base != 10 && base != 16) {
+      throw new UnsupportedOperationException("Unsupported base: " + base);
+    }
+    int limit = line.length();
+    skipToNextValue(true);
+    if (pos == limit) {
+      pos = -1;
+      return -1;
+    }
+    long val = 0;
+    char c = 0;
+    while (pos < limit && !isDelimiter(c = line.charAt(pos), true)) {
+      if (c < '0' || c > '9') {
+        if (base == 10 || (c < 'a' || c > 'f')) {
+          skipValue(true);
+          return -1;
+        }
+      }
+      int digit = c >= 'a' ? 10 + (c - 'a') : (c - '0');
+      val = val * base + digit;
+      pos++;
+    }
+    return val;
+  }
+
+  String nextStringValue() {
+    int limit = line.length();
+    skipToNextValue(false);
+    if (pos == limit) {
+      pos = -1;
+      return null;
+    }
+    long val = 0;
+    StringBuilder sb = new StringBuilder();
+    char c = 0;
+    while (pos < limit && !isDelimiter(c = line.charAt(pos), false)) {
+      sb.append(c);
+      pos++;
+    }
+    return sb.toString();
+  }
+
+  String slurpStringValue() {
+    int limit = line.length();
+    skipToNextValue(false);
+    if (pos == limit) {
+      pos = -1;
+      return null;
+    }
+    return line.substring(pos).trim();
+  }
+
+  private static boolean isDelimiter(char c, boolean acceptDash) {
+    return c == ' ' || (acceptDash && c == '-');
+  }
+}

dd-java-agent/agent-profiling/profiling-controller-openjdk/src/main/java/com/datadog/profiling/controller/openjdk/events/SmapEntryEvent.java

@@ -19,120 +19,120 @@
 public class SmapEntryEvent extends Event {
 
   @Label("Region Start Address")
-  private final long startAddress;
+  long startAddress;
 
   @Label("Region End Address")
-  private final long endAddress;
+  long endAddress;
 
   @Label("Region Permissions")
-  private final String perms;
+  String perms;
 
   @Label("Offset into mapping")
-  private final long offset;
+  long offset;
 
   @Label("Device")
-  private final String dev;
+  String dev;
 
   @Label("INode ID")
-  private final int inodeID;
+  int inodeID;
 
   @Label("Path associated with mapping")
-  private final String pathname;
+  String pathname;
 
   @Label("Mapping Size")
-  private final long size;
+  long size;
 
   @Label("Page Size")
-  private final long kernelPageSize;
+  long kernelPageSize;
 
   @Label("Memory Management Unit Page Size")
-  private final long mmuPageSize;
+  long mmuPageSize;
 
   @Label("Resident Set Size")
   @DataAmount
-  private final long rss;
+  long rss;
 
   @Label("Proportional Set Size")
   @DataAmount
-  private final long pss;
+  long pss;
 
   @Label("Dirty Proportional Set Size")
   @DataAmount
-  private final long pssDirty;
+  long pssDirty;
 
   @Label("Shared Clean Pages")
-  private final long sharedClean;
+  long sharedClean;
 
   @Label("Shared Dirty Pages")
   @DataAmount
-  private final long sharedDirty;
+  long sharedDirty;
 
   @Label("Private Clean Pages")
   @DataAmount
-  private final long privateClean;
+  long privateClean;
 
   @Label("Private Dirty Pages")
   @DataAmount
-  private final long privateDirty;
+  long privateDirty;
 
   @Label("Referenced Memory")
-  private final long referenced;
+  long referenced;
 
   @Label("Anonymous Memory")
   @DataAmount
-  private final long anonymous;
+  long anonymous;
 
   @Label("Kernel Same-page Merging")
   @DataAmount
-  private final long ksm;
+  long ksm;
 
   @Label("Lazily Freed Memory")
   @DataAmount
-  private final long lazyFree;
+  long lazyFree;
 
   @Label("Anon Huge Pages")
   @DataAmount
-  private final long anonHugePages;
+  long anonHugePages;
 
   @Label("Shared Memory Huge Pages")
   @DataAmount
-  private final long shmemPmdMapped;
+  long shmemPmdMapped;
 
   @Label("Page Cache Huge Pages")
   @DataAmount
-  private final long filePmdMapped;
+  long filePmdMapped;
 
   @Label("Shared Huge Pages")
   @DataAmount
-  private final long sharedHugetlb;
+  long sharedHugetlb;
 
   @Label("Private Huge Pages")
   @DataAmount
-  private final long privateHugetlb;
+  long privateHugetlb;
 
   @Label("Swap Size")
   @DataAmount
-  private final long swap;
+  long swap;
 
   @Label("Proportional Swap Size")
   @DataAmount
-  private final long swapPss;
+  long swapPss;
 
   @Label("Locked Memory")
   @DataAmount
-  private final long locked;
+  long locked;
 
   @Label("THP Eligible")
-  private final boolean thpEligible;
+  boolean thpEligible;
 
   @Label("VM Flags")
-  private final String vmFlags;
+  String vmFlags;
 
   @Label("Encountered foreign keys")
-  private final boolean encounteredForeignKeys;
+  boolean encounteredForeignKeys;
 
   @Label("NMT Category")
-  private final String nmtCategory;
+  String nmtCategory;
 
   public SmapEntryEvent() {
     startAddress = 0;