From a989f3edec5864d5de8b217aa595c962d8fc4b0a Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 13 Feb 2018 22:12:36 -0800
Subject: [PATCH] Add hb_blob_copy_writable_or_fail()

New API:
- hb_blob_copy_writable_or_fail()
---
 docs/harfbuzz-sections.txt |  1 +
 src/hb-blob.cc             | 25 +++++++++++++++++++++++++
 src/hb-blob.h              |  3 +++
 3 files changed, 29 insertions(+)

diff --git a/docs/harfbuzz-sections.txt b/docs/harfbuzz-sections.txt
index a9b4d53eb..5df33a816 100644
--- a/docs/harfbuzz-sections.txt
+++ b/docs/harfbuzz-sections.txt
@@ -9,6 +9,7 @@ HB_EXTERN
 <FILE>hb-blob</FILE>
 hb_blob_create
 hb_blob_create_sub_blob
+hb_blob_copy_writable_or_fail
 hb_blob_destroy
 hb_blob_get_data
 hb_blob_get_data_writable
diff --git a/src/hb-blob.cc b/src/hb-blob.cc
index 804601258..b5291f650 100644
--- a/src/hb-blob.cc
+++ b/src/hb-blob.cc
@@ -170,6 +170,31 @@ hb_blob_create_sub_blob (hb_blob_t    *parent,
   return blob;
 }
 
+/**
+ * hb_blob_copy_writable_or_fail:
+ * @blob: A blob.
+ *
+ * Makes a writable copy of @blob.
+ *
+ * Return value: New blob, or nullptr if allocation failed.
+ *
+ * Since: 1.8.0
+ **/
+hb_blob_t *
+hb_blob_copy_writable_or_fail (hb_blob_t *blob)
+{
+  blob = hb_blob_create (blob->data,
+			 blob->length,
+			 HB_MEMORY_MODE_DUPLICATE,
+			 nullptr,
+			 nullptr);
+
+  if (unlikely (blob == hb_blob_get_empty ()))
+    blob = nullptr;
+
+  return blob;
+}
+
 /**
  * hb_blob_get_empty:
  *
diff --git a/src/hb-blob.h b/src/hb-blob.h
index 53682d3eb..fd561f738 100644
--- a/src/hb-blob.h
+++ b/src/hb-blob.h
@@ -82,6 +82,9 @@ hb_blob_create_sub_blob (hb_blob_t    *parent,
 			 unsigned int  offset,
 			 unsigned int  length);
 
+HB_EXTERN hb_blob_t *
+hb_blob_copy_writable_or_fail (hb_blob_t *blob);
+
 HB_EXTERN hb_blob_t *
 hb_blob_get_empty (void);