From fb6067a7678ca1a3f43c8f783a95d6529a4b8381 Mon Sep 17 00:00:00 2001
From: Jeff Ching <chingor@google.com>
Date: Thu, 29 Mar 2018 15:26:14 -0700
Subject: [PATCH 1/3] SpanData now implements stackTraceHashId()

---
 src/Trace/SpanData.php            | 21 +++++++++++++++++++++
 tests/unit/Trace/SpanDataTest.php | 19 +++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/src/Trace/SpanData.php b/src/Trace/SpanData.php
index a0889cac1..db0f3ea4d 100644
--- a/src/Trace/SpanData.php
+++ b/src/Trace/SpanData.php
@@ -136,6 +136,13 @@ class SpanData
      */
     private $kind;
 
+    /**
+     * An optional value to de-dup the stackTrace array.
+     *
+     * @var int
+     */
+    private $stackTraceHashId;
+
     /**
      * Instantiate a new SpanData instance.
      *
@@ -303,6 +310,20 @@ public function stackTrace()
         return $this->stackTrace;
     }
 
+    /**
+     * Return a hash id for this span's stackTrace.
+     *
+     * @return id
+     */
+    public function stackTraceHashId()
+    {
+        if (!isset($this->stackTraceHashId)) {
+            // take the lower 16 digits of the md5 and convert to an int
+            $this->stackTraceHashId = hexdec(substr(md5(serialize($this->stackTrace)), -16));
+        }
+        return $this->stackTraceHashId;
+    }
+
     /**
      * Whether or not this span is in the same process as its parent.
      *
diff --git a/tests/unit/Trace/SpanDataTest.php b/tests/unit/Trace/SpanDataTest.php
index 711cb6b05..e35b66acf 100644
--- a/tests/unit/Trace/SpanDataTest.php
+++ b/tests/unit/Trace/SpanDataTest.php
@@ -70,4 +70,23 @@ public function spanDataOptions()
             ['kind', Span::KIND_SERVER]
         ];
     }
+
+    public function testStackTraceHashIdIsRepeatable()
+    {
+        $stackTrace = debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
+        $startTime = new \DateTime();
+        $endTime = new \DateTime();
+        $spanData = new SpanData('span-name', 'aaa', 'bbb', $startTime, $endTime, [
+            'stackTrace' => $stackTrace
+        ]);
+
+        $spanData2 = new SpanData('span-name2', 'aaa', 'bbb', $startTime, $endTime, [
+            'stackTrace' => $stackTrace
+        ]);
+
+        $hashId = $spanData->stackTraceHashId();
+        $this->assertInternalType('int', $hashId);
+        $this->assertNotEquals(0, $hashId);
+        $this->assertEquals($hashId, $spanData2->stackTraceHashId());
+    }
 }

From cc56d058035861ba6882bfc046a88a2d4662343d Mon Sep 17 00:00:00 2001
From: Jeff Ching <chingor@google.com>
Date: Thu, 29 Mar 2018 15:45:49 -0700
Subject: [PATCH 2/3] Workaround for intsize on 32-bit PHP

---
 src/Trace/SpanData.php | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Trace/SpanData.php b/src/Trace/SpanData.php
index db0f3ea4d..2c4b19624 100644
--- a/src/Trace/SpanData.php
+++ b/src/Trace/SpanData.php
@@ -318,8 +318,11 @@ public function stackTrace()
     public function stackTraceHashId()
     {
         if (!isset($this->stackTraceHashId)) {
-            // take the lower 16 digits of the md5 and convert to an int
-            $this->stackTraceHashId = hexdec(substr(md5(serialize($this->stackTrace)), -16));
+            // take the lower 16 (8 for 32-bit PHP) digits of the md5 and
+            // convert to an int
+            $digits = PHP_INT_SIZE * -2;
+            $md5 = md5(serialize($this->stackTrace));
+            $this->stackTraceHashId = hexdec(substr($md5, $digits));
         }
         return $this->stackTraceHashId;
     }

From 102831b384430c757ed897dfdf5a825be32f0537 Mon Sep 17 00:00:00 2001
From: Jeff Ching <chingor@google.com>
Date: Mon, 2 Apr 2018 10:09:54 -0700
Subject: [PATCH 3/3] Store and return the hashId as a hex string to preserve
 uint64 semantics

---
 src/Trace/SpanData.php            | 15 +++++++--------
 tests/unit/Trace/SpanDataTest.php |  3 +--
 2 files changed, 8 insertions(+), 10 deletions(-)

diff --git a/src/Trace/SpanData.php b/src/Trace/SpanData.php
index 2c4b19624..2f9e9f6d9 100644
--- a/src/Trace/SpanData.php
+++ b/src/Trace/SpanData.php
@@ -137,9 +137,10 @@ class SpanData
     private $kind;
 
     /**
-     * An optional value to de-dup the stackTrace array.
+     * An optional value to de-dup the stackTrace array. Represented as a
+     * hexadecimal string.
      *
-     * @var int
+     * @var string
      */
     private $stackTraceHashId;
 
@@ -311,18 +312,16 @@ public function stackTrace()
     }
 
     /**
-     * Return a hash id for this span's stackTrace.
+     * Return a hash id for this span's stackTrace in hexadecimal
      *
-     * @return id
+     * @return string
      */
     public function stackTraceHashId()
     {
         if (!isset($this->stackTraceHashId)) {
-            // take the lower 16 (8 for 32-bit PHP) digits of the md5 and
-            // convert to an int
-            $digits = PHP_INT_SIZE * -2;
+            // take the lower 16 digits of the md5
             $md5 = md5(serialize($this->stackTrace));
-            $this->stackTraceHashId = hexdec(substr($md5, $digits));
+            $this->stackTraceHashId = substr($md5, 16);
         }
         return $this->stackTraceHashId;
     }
diff --git a/tests/unit/Trace/SpanDataTest.php b/tests/unit/Trace/SpanDataTest.php
index e35b66acf..2ef4f330c 100644
--- a/tests/unit/Trace/SpanDataTest.php
+++ b/tests/unit/Trace/SpanDataTest.php
@@ -85,8 +85,7 @@ public function testStackTraceHashIdIsRepeatable()
         ]);
 
         $hashId = $spanData->stackTraceHashId();
-        $this->assertInternalType('int', $hashId);
-        $this->assertNotEquals(0, $hashId);
+        $this->assertInternalType('string', $hashId);
         $this->assertEquals($hashId, $spanData2->stackTraceHashId());
     }
 }